JP2008129232A - LASER LIGHT SOURCE DEVICE, IMAGE DISPLAY DEVICE AND MONITOR DEVICE HAVING THE LASER LIGHT SOURCE DEVICE - Google Patents

Abstract

The present invention provides a laser light source device that efficiently suppresses power reduction of output light, has high light utilization efficiency, and has a stable output, an image display device including the laser light source device, and a monitor device.
A laser light source device includes a light source, a wavelength conversion element, and an optical path conversion element. The wavelength conversion element includes a multilayer mirror composed of a dielectric multilayer film having a characteristic of reflecting 80% or more of light of the first wavelength and transmitting 80% or more of light of the second wavelength to the end face on the emission side, and the emission side Is provided with a band-pass filter multilayer film having a band-pass characteristic in the vicinity of the first wavelength, and is provided in the resonance structure. The optical path conversion element includes a selective reflection film 317 for extracting the second laser light LS2 and a reflection surface 316A, and is integrated by the prisms 315 and 316, and the second laser light is extracted to the second optical path O2. The first laser beam LS1 is directed in substantially the same direction as the traveling direction, and is used as output light together with the first laser beam.
[Selection] Figure 1

Description

  The present invention relates to a laser light source device that emits laser light, an image display device including the laser light source device, and a monitor device.

In recent years, laser light source devices are widely used in the field of optoelectronics such as optical communication, applied optical measurement, and optical display.
Such laser light source devices include those that use the wavelength of the fundamental laser as it is, and those that use the wavelength of the fundamental laser after conversion. In the latter laser light source device, a second harmonic generation (SHG) element is known as an element for converting the wavelength of the fundamental laser.

  Here, since the conversion efficiency of SHG is generally about several percent, the power of the light converted by the SHG element is considerably smaller than the power of the output light of the fundamental laser light source. In view of this, a laser light source device as disclosed in Patent Document 1 has been proposed as a configuration that suppresses a decrease in power of output light. In this laser light source device, light emitted from an internal resonance type laser light source and passed through an SHG element is separated into first SHG light whose wavelength is converted and residual fundamental wave light. Then, the remaining fundamental wave light is again passed through the SHG element, thereby taking out the second SHG light whose wavelength has been converted. The second SHG light is combined with the first SHG light in a state in which the second SHG light is converted into polarized light whose polarization direction is 90 ° different from that of the first SHG light. In this way, the laser light source device of Patent Document 1 uses the combined light of the first SHG light and the second SHG light as output light, thereby suppressing the power drop of the output light.

Further, SHG has a problem that the conversion efficiency is low because there is much light in a wavelength region that is not wavelength-converted because the oscillation wavelength width of the light emitted from the laser light source is wider than the allowable width of the conversion wavelength of SHG.
Therefore, in order to stably supply laser light having a narrow wavelength width as output light, a photopolymer volume hologram is provided in an external resonator that resonates laser light emitted from a laser light source, and the photopolymer volume hologram is a laser light source. An external resonant laser device has been proposed that diffracts light emitted from the laser beam so as to enter the optical system in the resonator, and selectively transmits laser light having a predetermined wavelength to be emitted to the outside (for example, Patent Document 2).

JP 59-128525 A JP 2001-284718 A

  However, in the laser light source device described in Patent Document 1, although the second SHG light whose wavelength is converted by passing the remaining fundamental wave light again through the SHG element can be used, it passes through the SHG element again. However, the residual fundamental wave light whose wavelength has not been converted cannot be used. Therefore, the light use efficiency is not dramatically improved. In addition, if such residual fundamental light is returned to the fundamental laser light source as it is, the power of the fundamental laser light source may decrease or become unstable, so the residual fundamental light is returned to the light source. It is essential to have a configuration that does not. Therefore, there is a possibility that the optical system becomes large. Moreover, since the length of the optical path is increased or the number of times of passing through the optical element is increased, there is a possibility that light loss may occur.

Furthermore, in the laser light source device described in Patent Document 1, in order to synthesize the first SHG light and the second SHG light, the polarization directions are different from each other by 90 °, so that the output light has two types. It becomes the combined light of polarized light. Therefore, when considering using the laser light source device described in Patent Document 1 in combination with a polarization control type device (for example, a liquid crystal device) that can use only one type of polarized light, the first SHG light and the second Unless a configuration for aligning the polarization direction of the SHG light is provided, only one SHG light can be used.
That is, in the laser light source device described in Patent Document 1, it is possible to obtain a stable output while suppressing a decrease in the power of the output light to some extent, but the light utilization efficiency does not increase so much. In particular, when used in combination with a polarization control type device, there is a possibility that the light utilization efficiency may not be improved at all.
On the other hand, in the photopolymer volume hologram used in the external resonance laser device described in Patent Document 2, for example, a large number of interference patterns having different refractive indexes are formed in layers in a resin, and laser light having an oscillation wavelength is narrowed. It is a reflective element and is very expensive. Therefore, although the laser device can be configured simply, there is a problem that the manufacturing cost increases.

  Therefore, the present invention has been made in view of such circumstances, efficiently reducing the power reduction of output light, high light utilization efficiency, the polarization direction of the output light is aligned, and the output is An object is to provide a stable laser light source device. It is another object of the present invention to provide an image display device and a monitor device in which the use efficiency of light is improved by using such a laser light source device.

  A laser light source device according to the present invention includes a light source that emits light of a first wavelength, a multilayer mirror that selectively reflects the light of the first wavelength toward the light source, and the light source. Provided on the first optical path formed between the multilayer mirrors and converts the wavelength of a part of the incident first wavelength light to a second wavelength different from the first wavelength. And a light that is reflected by the multilayer mirror and converted to the second wavelength in the process toward the light source, and a wavelength conversion element that performs bandpass characteristics near the first wavelength. An optical path conversion element for taking out a second optical path different from the first optical path, and the first laser light having the second wavelength emitted from the multilayer mirror and the optical path conversion element And a second laser beam having the second wavelength. A selective reflection film that is provided between the light source and the wavelength conversion element, and selectively reflects the light of the second wavelength; and A reflective surface that reflects light reflected by the selective reflection film and directs the light in a direction substantially the same as the traveling direction of the first laser light, and the translucency that integrates the selective reflection film and the reflection surface And the multilayer mirror reflects 80% or more of the light having the first wavelength and 80% or more of the light having the second wavelength, which is formed on the end face on the emission side of the wavelength conversion element. It is characterized by comprising a dielectric multilayer film having a transmitting characteristic.

  According to the present invention, the resonant structure (first optical path) constituted by the light source and the multilayer mirror includes a wavelength conversion element and bandpass filter means having bandpass characteristics in the vicinity of the first wavelength. The wavelength of the light of the first wavelength emitted from is narrowed. Thereby, the conversion efficiency in the wavelength conversion element is improved, and output light of the second wavelength with improved light use efficiency can be obtained. In addition, the second laser beam, which has been reflected by the multilayer mirror and converted in the process toward the light source, is extracted into the second optical path by the optical path conversion element and used, thereby efficiently reducing the power reduction of the output light. Is possible. In the present invention, since the second laser beam only needs to be directed in substantially the same direction as the traveling direction of the first laser beam, output light having substantially the same polarization direction can be obtained. Therefore, even when used in combination with a polarization control type device, the light utilization efficiency can be improved.

Furthermore, the power of the output light is easily influenced by the fluctuations in the positions of the selective reflection film and the reflection surface. In the present invention, however, the selective reflection film and the reflection surface are integrated by the translucent element. Is not necessary, and the position of the selective reflection film and the reflection surface is not shifted, so that a stable output can be obtained.
Furthermore, the multilayer mirror has a characteristic of reflecting 80% or more of light of the first wavelength and transmitting 80% or more of light of the second wavelength, so that the oscillation light of the light source is confined inside the resonance structure. The light having the second wavelength converted by the wavelength conversion element can be efficiently extracted.
That is, according to the present invention, it is possible to obtain a laser light source device that efficiently suppresses power reduction of output light, has high light utilization efficiency, has the same polarization direction of output light, and has a stable output. Become.

  In the laser light source device according to the present invention, the translucent element has a first prism and a second prism, and the first and second prisms have a first surface and a second prism, respectively. The selective reflection film is provided between the second surface of the first prism and the first surface of the second prism, and the light emitted from the light source is The first surface of the first prism is incident on the optical path conversion element, and the second surface of the first prism, the selective reflection film, and the first surface of the second prism are made to pass through the first surface. The light that passes through the second prism and is emitted from the second surface of the second prism toward the wavelength conversion element, reflected by the multilayer mirror, and directed toward the light source is transmitted through the second prism. 2 is incident on the optical path conversion element from the surface 2 and passes through the first surface of the second prism. Of the light that enters the selective reflection film and is reflected by the multilayer mirror and travels toward the light source, the light that passes through the selective reflection film and travels toward the light source is the first light. Of the light that passes through the second surface of the prism, is emitted from the first surface of the first prism toward the light source, is reflected by the multilayer mirror, and travels toward the light source, It is preferable that the light reflected by the selective reflection film is reflected by the reflection surface and emitted from the second surface of the second prism.

According to such a configuration, since light can be incident on or emitted from the optical path conversion element via the prism surface, the light incident on the optical path conversion element or the optical path conversion element It is easy to control the direction of light emitted from.
In particular, when the first surface of the first prism and the second surface of the second prism are parallel, the light incident on the optical path conversion element and the light emitted from the optical path conversion element The direction of the light can be made the same, and the control of the light direction is further facilitated.

  In this case, the reflection surface can be constituted by the third surface of the second prism, and at this time, the third surface is configured to prevent light incident on the third surface. A smooth surface disposed at an angle satisfying the total reflection condition is preferable. According to such a configuration, since the reflection efficiency of the reflection surface can be almost 100%, it is possible to further improve the light use efficiency.

  In the laser light source device according to the present invention, it is preferable that the bandpass filter means is composed of a bandpass filter multilayer film formed on an end surface on the incident side of the wavelength conversion element.

  According to such a configuration, since the band-pass filter multilayer film and the multilayer mirror as the band-pass filter means are provided on the incident-side end face and the emission-side end face of the wavelength conversion element, the length of the optical path is increased. In addition, the loss of light due to an increase in the number of passes through the optical element can be reduced, and the number of components can be reduced, thereby contributing to cost reduction and downsizing of the laser light source device.

  In the laser light source device according to the present invention, the band-pass filter means includes a band-pass filter provided with a band-pass filter multilayer film, and the laser beam of the light source is interposed between the optical path conversion element and the wavelength conversion element. It is preferable that the tilt angle with respect to the exit surface is configured to be displaceable.

  According to such a configuration, the band-pass filter means comprises a band-pass filter provided with a band-pass filter multilayer film, and the tilt angle of the light source with respect to the laser light exit surface can be displaced between the optical path conversion element and the wavelength conversion element. With this configuration, the wavelength of the first wavelength light emitted from the light source can be narrowed, and the tilt angle can be changed to change the wavelength of the first wavelength light. This makes it possible to adjust the oscillation wavelength even when the wavelength of light emitted from the light source varies due to temperature changes, etc., improving the conversion efficiency of the wavelength conversion element and increasing the light utilization efficiency. Output light can be obtained.

  In the laser light source device according to the present invention, it is preferable that the bandpass filter means is formed of a bandpass filter multilayer film formed on the second surface of the second prism. Or it is preferable to consist of a band pass filter multilayer film formed on the first surface of the first prism.

  According to such a configuration, the bandpass filter multilayer film as the bandpass filter means is a bandpass filter multilayer film formed on the second surface of the second prism, or the first surface of the first prism. The bandpass filter multilayer film formed above reduces the loss of light due to an increase in the length of the optical path and the number of passes through the optical element, and the number of components is reduced. This can contribute to reduction in cost and size of the laser light source device.

  In the laser light source device according to the present invention, the bandpass filter multilayer film has a transmittance of 80% or more with respect to the second wavelength, and the high refractive index layer H and the low refractive index layer L are alternately laminated. Where the first wavelength is λ and the optical film thicknesses are 0.236λH, 0.355λL, 0.207λH, 0.203λL, (0.25λH, 0.25λL) n in order from the wavelength conversion element side. 0.5λH, (0.25λL, 0.25λH) n, 0.266λL, 0.255λH, 0.248λL, 0.301λH, and 0.631λL. However, n is a value in the range of 3 to 10, and indicates the number of repetitions in which the layers in parentheses are repeatedly laminated.

  According to such a configuration, the bandpass filter multilayer film has a transmittance of 80% or more with respect to the second wavelength, and the high refractive index layer H and the low refractive index layer L are alternately laminated as described above. As a result, the first wavelength light having a bandpass characteristic in the vicinity of the first wavelength can be narrowed. This improves the conversion efficiency of the wavelength conversion in the wavelength conversion element, and always emits laser light of a constant wavelength from the laser light source device even if the oscillation wavelength of the laser light source fluctuates due to temperature changes in the usage environment. can do.

In the laser light source device according to the present invention, the first laser light having the second wavelength emitted from the multilayer mirror, and the second laser light having the second wavelength emitted from the optical path conversion element, Are preferably substantially parallel.
The laser light source device according to the present invention is highly likely to be used in combination with other optical elements such as a lens, a filter, a mirror, a diffraction grating, a prism, and a light modulation element. Depending on the angle of incident light, the characteristics may change or the output result may change. Therefore, if the first laser light and the second laser light are made substantially parallel, the design and arrangement of the optical device arranged after the laser light source device is facilitated. Therefore, according to such a configuration, particularly when the laser light source device according to the present invention is applied to an image display device, a monitor device, or the like, there is an effect that the degree of freedom in optical design is greatly increased.

Further, at this time, the width of the wavelength conversion element in a direction parallel to a line orthogonal to the first laser beam and the second laser beam is W1, and the first laser beam and the second laser beam When the distance to the laser beam is W2, it is preferable that W2> W1.
With this configuration, even if the relative position between the first optical path and the wavelength selection film is slightly shifted, the second optical path is not blocked by the wavelength conversion element. Therefore, alignment of the optical path conversion element is relatively easy.

  In the laser light source device according to the present invention, the light source preferably includes a plurality of light emitting units arranged in an array. In the present invention, even when the arrayed light sources are used, the areas of the light incident surface, light exit surface, and reflection surface of the wavelength conversion element and the optical path conversion element may be expanded to an area corresponding to the array. Only. Thus, in the present invention, even if the light sources are arranged in an array, it is possible to cope with a simple configuration without causing an excessive increase in size of the apparatus. Therefore, in the present invention, even when the light source is arrayed, a laser light source that efficiently suppresses the power drop of the output light, has high light utilization efficiency, has a uniform polarization direction of the output light, and has a stable output. It is possible to effectively increase the amount of light due to the array and increase the power of the output light while maintaining the effect that enables the device to be obtained.

  In the laser light source device according to the present invention, it is preferable that the wavelength conversion element is a quasi phase matching type wavelength conversion element. Since the quasi phase control type wavelength conversion element has higher conversion efficiency than other types of wavelength conversion elements, the effect of the present invention can be further enhanced.

An image display device according to the present invention includes the laser light source device as described above and a light modulation element that modulates laser light emitted from the laser light source device according to image information.
Since such an image display device uses the laser light source device as described above, the light use efficiency can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a schematic diagram showing a schematic configuration of the laser light source device according to the first embodiment.
The laser light source device 31 includes a light source 311, a wavelength conversion element 312, and an optical path conversion element 314.

The light source 311 emits light having a first wavelength.
FIG. 2 is a sectional view schematically showing the structure of the light source 311. A light source 311 shown in FIG. 2 is a so-called surface-emitting semiconductor laser, for example, a substrate 400 made of at least a semiconductor wafer, a mirror layer 311A formed on the substrate 400 and having a function as a reflection mirror, and a mirror layer 311A. A laser medium 311B stacked on the surface.

  The mirror layer 311A is formed of a stacked body of a high refractive index dielectric and a low refractive index dielectric formed on the substrate 400 by, for example, CVD (Chemical Vapor Deposition). The thickness of each layer constituting the mirror layer 311A, the material of each layer, and the number of layers are optimized with respect to the wavelength of light emitted from the light source 311 (first wavelength), and the conditions in which reflected light interferes and strengthens each other. Is set to

  The laser medium 311B is formed on the surface of the mirror layer 311A. The laser medium 311B is connected to a conduction means (not shown), and emits light of a predetermined wavelength when a predetermined amount of current flows from the conduction means. Further, the laser medium 311B is specified by the light of the first wavelength resonating between the mirror layer 311A and the mirror multilayer film 312C provided on the emission surface of the wavelength conversion element 312 shown in FIG. The light of the wavelength (first wavelength) is amplified. In other words, the light reflected by the mirror layer 311A and the mirror multilayer film 312C of the wavelength conversion element 312 is amplified by resonance with the light newly emitted by the laser medium 311B, and is reflected from the light emission end face of the laser medium 311B. Injected in a direction substantially orthogonal to 311A and the substrate 400.

The wavelength conversion element 312 has a function of converting the wavelength of incident light into light having a substantially half wavelength (second wavelength). The wavelength conversion element 312 has, for example, a quadrangular prism shape, and includes a wavelength conversion unit 312A and a bandpass filter multilayer film 312B as bandpass filter means provided on the light source 311 side surface (incident side end surface) of the wavelength conversion unit 312A. And a mirror multilayer film 312C as a multilayer mirror provided on the emission side end face of the wavelength conversion section 312A.
As shown in FIG. 1, the wavelength conversion element 312 is disposed on the first optical path O1 formed between the light source 311 and the mirror multilayer film 312C.

FIG. 3 is a cross-sectional view schematically showing the structure of the wavelength conversion element 312.
The wavelength conversion unit 312A is a second harmonic generation (SHG) element that generates a second harmonic of incident light. The wavelength conversion unit 312A has a periodic polarization inversion structure, and the wavelength of incident light is approximately half the wavelength (second wavelength) by wavelength conversion using quasi phase matching (QPM). Convert to For example, when the wavelength of the light emitted from the light source 311 (first wavelength) is 1064 nm (near infrared), the wavelength conversion unit 312A converts this to a half wavelength (second wavelength) of 532 nm. Produces green light. However, as described in the background art, the wavelength conversion efficiency of the wavelength conversion unit 312A is generally about several percent. That is, not all of the light emitted from the light source 311 is converted into light of the second wavelength.

The periodic domain-inverted structure is formed inside a crystal substrate of an inorganic nonlinear optical material such as lithium niobate (LN: LiNbO ₃ ) or lithium tantalate (LT: LiTaO ₃ ). Specifically, the periodic domain-inverted structure has two regions 312Aa and 312Ab in which the directions of polarization are inverted in a direction substantially orthogonal to the light emitted from the light source 311 inside the crystal substrate. Are formed alternately at a predetermined interval. The pitch of these two regions 312Aa and 312Ab is appropriately determined in consideration of the wavelength of incident light and the refractive index dispersion of the crystal substrate.

  In general, laser light oscillated from a semiconductor laser oscillates in a plurality of longitudinal modes within a gain band, and the wavelengths thereof change due to the influence of temperature fluctuations. That is, the allowable width of the wavelength of light converted by the wavelength conversion element 312 is about 0.3 nm, and varies by about 0.1 nm / ° C. with respect to the change in the use environment temperature.

  The bandpass filter multilayer film 312B has a bandpass characteristic in the vicinity of the first wavelength. It selectively transmits only light having a set specific wavelength out of light having a first wavelength emitted from the light source 311 and reflects light having other wavelengths. That is, the light emitted from the light source 311 has a function of narrowing the band. Note that the specific wavelength of light that selectively passes through the bandpass filter multilayer film 312B is light having a half-value width of about 0.5 nm at the first wavelength.

  The film configuration of the bandpass filter multilayer film 312B is such that the high refractive index layers H and the low refractive index layers L are alternately laminated, the oscillation wavelength is λ, and the optical film thickness is 0.236λH in order from the wavelength conversion unit 312A side. , 0.355λL, 0.207λH, 0.203λL, (0.25λH, 0.25λL) n, 0.5λH, (0.25λL, 0.25λH) n, 0.266λL, 0.255λH, 0.248λL , 0.301λH and 0.631λL. However, n is a value in the range of 3 to 10, and indicates the number of repetitions in which the layers in parentheses are repeatedly laminated.

As the material of the high refractive index layer H, one kind selected from materials such as Ta ₂ 0 ₅ , Nb ₂ 0 ₅ , Ti0 ₂ , and Zr0 ₂ which are transparent in the use wavelength region and environmentally friendly is selected. Similarly, as the material of the layer L, one kind is selected from environmentally friendly substances such as SiO ₂ and MgF ₂ .

FIG. 4 is a graph showing an example of the spectral transmittance characteristics of the bandpass filter multilayer film 312B formed in this way. The horizontal axis of the graph indicates the wavelength (nm), and the vertical axis indicates the transmittance (%). This spectral transmittance characteristic indicates a case where the wavelength (first wavelength) of light emitted from the light source 311 is around 1064 nm.
As shown in FIG. 4, the bandpass filter multilayer film 312B has a bandpass characteristic in the vicinity of the first wavelength. Further, it has a transmittance of about 80% or more for the light of the second wavelength, and particularly has a transmittance of nearly 100% for the light near the green light having a wavelength of 532 nm.

  The mirror multilayer film 312C has a function of selectively reflecting light of the first wavelength and directing it toward the light source 311 and transmitting light of other wavelengths (including the second wavelength). The mirror multilayer film 312C also has a function of narrowing the wavelength of the light to be amplified by selectively reflecting the light of the first wavelength.

  The mirror multilayer film 312C is a dielectric multilayer film. The mirror multilayer film 312C can be formed by, for example, CVD, and the thickness of each layer, the material of each layer, and the number of layers constituting the multilayer film are optimized according to required characteristics. The higher the transmittance of the mirror multilayer film 312C for the light of the second wavelength and the reflectance of the light of the first wavelength are, the better, and preferably at least 80% or more.

FIG. 5 is a perspective view of the optical path conversion element 314.
As shown in FIGS. 1 and 5, the optical path conversion element 314 includes a first prism 315 and a second prism 316 as translucent elements, and a selective reflection film 317 provided therebetween. ing.

The first prism 315 is made of optical glass such as BK7, and has an isosceles triangular prism shape. The side surface of the prism 315 includes a surface 315A (first surface) including two sides sandwiching the apex angle of an isosceles triangle, a surface 315B, and a surface (second surface) 315C including a hypotenuse.
The surface 315A of the prism 315 is disposed so as to face the light source 311 as shown in FIG. The surface 315A is disposed so as to be substantially orthogonal to the first optical path O1. Further, the surface 315A and a surface 316C of a prism 316 described later are parallel.

  A selective reflection film 317 is formed on the surface 315C. The selective reflection film 317 is constituted by a dielectric multilayer film, for example. The dielectric multilayer film can be formed, for example, by CVD, and the thickness of each layer, the material of each layer, and the number of layers constituting the multilayer film are optimized according to required characteristics. The selective reflection film 317 is provided between the light source 311 and the wavelength conversion element 312 and has a characteristic of selectively reflecting light of the second wavelength and transmitting light of the first wavelength. The selectivity of the selective reflection film 317 with respect to the light of the first wavelength and the reflectance with respect to the light of the second wavelength are preferably as high as possible, and preferably at least 80% or more.

  Similar to the prism 315, the second prism 316 is made of, for example, optical glass such as BK7 and has an isosceles triangular prism shape. The side surface of the prism 316 includes a surface 316A (reflective surface) including two sides sandwiching the apex angle of an isosceles triangle, a surface 316B (first surface), and a surface (second surface) 316C including a hypotenuse. ing. The length of two sides sandwiching the apex angle of the isosceles triangular prism constituting the prism 316 is substantially the same as the length of the hypotenuse of the isosceles triangular prism constituting the prism 315.

The surface 316B of the prism 316 is bonded to the surface 315C of the prism 315 on which the selective reflection film 317 is formed, for example, with an optical adhesive that is cured by ultraviolet light.
The surface 316C is disposed so that a part thereof faces the wavelength conversion element 312. The surface 316C is disposed so as to be substantially orthogonal to the first optical path O1. The surface 316A as a reflection surface is a surface arranged at an angle satisfying the total reflection condition with respect to incident light IL (see FIG. 1) described later.

  The surface 316B and the selective reflection film 317 are integrated by bonding the prism 315 and the prism 316 together. Note that the prism 315 and the prism 316 may be integrated by a method other than bonding.

  The selective reflection film 317 may be formed not on the surface 315C of the prism 315 but on the surface 316B of the prism 316. In short, the selective reflection film 317 may be provided between the surface 315C of the prism 315 and the surface 316B of the prism 316. Further, an anti-reflective (AR) film may be formed on the surface 315A of the prism 315 and the surface 316C of the prism 316. By forming an AR film on these surfaces, light loss when light enters the optical path conversion element 314 or is emitted from the optical path conversion element 314 through these surfaces is reduced. Is possible.

  Next, a process until output light is obtained from the laser light source device 31 will be described with reference to FIGS.

The light source 311 emits light having a first wavelength when a current is passed through the laser medium 311B.
The light having the first wavelength emitted from the light source 311 enters the optical path conversion element 314 from the surface 315A of the prism 315, and passes through the surface 315C of the prism 315, the selective reflection film 317, and the surface 316B of the prism 316 in this order. Then, the light is emitted from the surface 316C of the prism 316 toward the wavelength conversion element 312.

The light having the first wavelength emitted from the optical path conversion element 314 enters the wavelength conversion element 312.
In the wavelength conversion element 312, the bandpass filter multilayer film 312B transmits light having a wavelength width of about 0.5 nm among the light having the first wavelength, and reflects light having other wavelength widths. That is, the band of the incident first wavelength light is narrowed.

The light of the first wavelength reflected by the bandpass filter multilayer film 312B is emitted toward the light source 311.
On the other hand, the first wavelength light transmitted through the bandpass filter multilayer film 312B is incident on the wavelength conversion unit 312A, and the wavelength of some of the first wavelength light is half the wavelength (second Wavelength) and enters the mirror multilayer film 312C.

The mirror multilayer film 312C transmits light that has been converted to the second wavelength out of light incident from the wavelength conversion unit 312A, and reflects light that has not been converted to the second wavelength (light having the first wavelength).
The light having the second wavelength transmitted through the mirror multilayer film 312C is emitted from the wavelength conversion element 312 as the first laser light LS1 (output light). On the other hand, light that has not been converted to the second wavelength reflected by the mirror multilayer film 312C (light having the first wavelength) travels toward the light source 311.

The light that has not been converted to the second wavelength reflected by the mirror multilayer film 312C passes through the wavelength conversion unit 312A again in the process toward the light source 311. At that time, part of the light is converted into the second wavelength and emitted from the wavelength conversion element 312 toward the light source 311.
The light emitted from the wavelength conversion element 312 toward the light source 311 is incident on the optical path conversion element 314 together with the light having the first wavelength reflected by the bandpass filter multilayer film 312B.

In the optical path conversion element 314, the light enters from the surface 316 </ b> C of the prism 316, passes through the surface 316 </ b> B of the prism 316, and enters the selective reflection film 317.
Of the light incident on the selective reflection film 317, the light having the first wavelength is transmitted through the selective reflection film 317.

Then, the light having the first wavelength transmitted through the selective reflection film 317 passes through the surface 315C of the prism 315 and is emitted from the surface 315A of the prism 315 toward the light source 311.
Further, this light returns to the light source 311, is reflected by the mirror layer 311 A, and is emitted from the light source 311 again. As described above, the light of the first wavelength is newly oscillated in the laser medium 311B by reciprocating the first optical path O1 formed between the light source 311 and the mirror multilayer film 312C of the wavelength conversion element 312. Resonates with the light to be amplified. That is, the laser light source device 31 includes a resonance structure formed between the mirror layer 311A of the light source 311 and the mirror multilayer film 312C of the wavelength conversion element 312.

On the other hand, the light reflected by the mirror multilayer film 312C of the wavelength conversion element 312 and converted to the second wavelength by the wavelength conversion element 312 in the process toward the light source 311 is reflected by the selective reflection film 317.
Then, the light is reflected by the surface 316A of the prism 316 and directed in a direction substantially parallel to the traveling direction of the first laser light LS1. Further, the light reflected by the surface 316A is emitted from the surface 316C of the prism 316 as the second laser light LS2.

That is, the optical path conversion element 314 is a second optical path different from the first optical path O1 for the light reflected by the mirror multilayer film 312C of the wavelength conversion element 312 and converted to the second wavelength in the process toward the light source 311. A function to take out to O2 is provided.
The optical path conversion element 314 can also be configured using a prism other than an isosceles triangular prism as long as such a function can be achieved.

  In FIG. 1, L1 indicates light emitted from the light source 311, converted into light of the second wavelength by the wavelength conversion element 312, and emitted from the wavelength conversion element 312 as the first laser light LS1. . The optical path O1 is emitted from the light source 311 and emitted without being converted into the second wavelength by the wavelength conversion unit 312A of the wavelength conversion element 312, and is reflected by the mirror multilayer film 312C and is also directed to the light source 311 in the process of the wavelength conversion unit. Light that is not converted to the second wavelength by 312A but passes through the selective reflection film 317 and returns to the light source 311 is shown, and it can be considered that the first optical path O1 is formed by such light. Further, L2 is emitted from the light source 311 and emitted without being converted to the second wavelength by the wavelength conversion unit 312A of the wavelength conversion element 312, reflected by the mirror multilayer film 312C, and in the process toward the light source 311 The light converted to the second wavelength by the conversion unit 312A and incident on the selective reflection film 317 is shown. In FIG. 1, L1, O1, and L2 are shown at different positions, but for convenience of explanation, these are only shown at different positions, and may be originally located at the same position.

  Finally, the relationship between the distance between the first laser beam LS1 and the second laser beam LS2 and the width of the wavelength conversion element 312 will be described with reference to FIG. In FIG. 1, W1 indicates the width of the wavelength conversion element 312 in a direction parallel to a line (not shown) perpendicular to the first laser light LS1 and the second laser light LS2. W2 indicates the distance between the first laser beam LS1 and the second laser beam LS2. The laser light source device 31 of this embodiment is configured to have a relationship of W2> W1.

The laser light source device 31 according to the present embodiment has the following effects.
(1) The wavelength conversion element 312 is provided in the resonance structure (first optical path O1) formed between the mirror layer 311A of the light source 311 and the mirror multilayer film 312C of the wavelength conversion element 312, and is reflected by the mirror multilayer film 312C. By taking out the second laser light whose wavelength has been converted in the process toward the light source 311 to the second optical path O2 by the optical path conversion element 314 and using it, the power reduction of the output light can be efficiently reduced. Is possible.
In addition, since the second laser light LS2 only needs to be directed in substantially the same direction as the traveling direction of the first laser light LS1, output light having substantially the same polarization direction can be obtained. Therefore, even when used in combination with a polarization control type device, the light utilization efficiency can be improved. Further, the power of the output light is easily influenced by the position change of the selective reflection film 317 and the surface 316A as the reflection surface. However, since these are integrated by the prisms 315 and 316, the selective reflection film 317 is integrated. And the position of the selective reflection film 317 and the surface 316A are not shifted, and a stable output can be obtained.
That is, according to the present embodiment, it is possible to obtain the laser light source device 31 that efficiently suppresses the power reduction of the output light, has high light utilization efficiency, and has a stable output.

  (2) The mirror multilayer film 312C has a characteristic of reflecting 80% or more of light of the first wavelength and transmitting 80% or more of light of the second wavelength, so that the oscillation light of the light source 311 is contained in the resonance structure. While confined, the light having the second wavelength converted by the wavelength conversion unit 312A can be efficiently extracted. Further, the bandpass filter multilayer film 312B has a transmittance of 80% or more with respect to the second wavelength, and is formed by alternately stacking the high refractive index layers H and the low refractive index layers L as described above. As a result, the band having the bandpass characteristic in the vicinity of the first wavelength and the light of the first wavelength emitted from the light source 311 can be narrowed. As a result, the conversion efficiency of the wavelength conversion in the wavelength conversion element 312 is improved, and even if the oscillation wavelength of the light source 311 varies due to the temperature change of the usage environment, the light from the laser light source device 31 always has a constant wavelength. Can be injected.

  (3) Furthermore, since the bandpass filter multilayer film 312B and the mirror multilayer film 312C are provided on the end face on the incident side and the end face on the exit side of the wavelength conversion element 312, the length of the optical path is increased, or the optical element As a result, the loss of light due to an increase in the number of times of passing through the laser beam can be reduced, the number of components can be reduced, and the laser light source device 31 can be reduced in cost and size.

(4) Light can enter the optical path conversion element 314 via the surfaces 315A and 316C of the prisms 315 and 316, and light can be emitted from the optical path conversion element 314. Therefore, the light enters the optical path conversion element 314. It is easy to control the direction of light and light emitted from the optical path conversion element 314.
In the present embodiment, the surface 315A of the first prism 315 and the surface 316C of the second prism 316 are parallel, but they need not be parallel. However, if the surface 315A of the first prism 315 and the surface 316C of the second prism 316 are made parallel as in the present embodiment, the light incident on the optical path conversion element 314 and the light exiting from the optical path conversion element 314 are emitted. Since the direction of the emitted light can be made the same, the control of the direction of the light becomes extremely easy.

(5) Since the surface 316A of the second prism 316 is a smooth surface arranged at an angle that satisfies the total reflection condition with respect to the incident light IL, the reflection efficiency of the reflecting surface can be made almost 100%. It is possible to further improve the light utilization efficiency.
Note that a reflective film may be provided on the surface 316A, and the second laser light LS2 may be directed in substantially the same direction as the traveling direction of the first laser light LS1 by the reflective film. In such a configuration, although there is a possibility that the reflection efficiency is somewhat lowered, the surface 316A does not have to be arranged at an angle satisfying the total reflection condition, so that the degree of freedom in optical path design is increased.

  (6) The laser light source device 31 according to the present embodiment is likely to be used in combination with other optical devices such as a lens, a filter, a mirror, a diffraction grating, a prism, and a light modulation element. Many devices change their characteristics and output results depending on the angle of incident light. However, in the laser light source device 31 according to the present embodiment, the first laser light LS1, the second laser light, and LS2 are substantially parallel, so the design and arrangement of the optical device arranged after the laser light source device 31. Becomes easy. Therefore, when the laser light source device 31 according to the present embodiment is applied to an image display device or the like, there is an effect that the degree of freedom in optical design is greatly increased.

  (7) Since W2> W1, even if the relative position between the first optical path O1 and the selective reflection film 317 is slightly shifted, the second optical path O2 is not blocked by the wavelength conversion element 312. Therefore, the alignment of the optical path conversion element 314 is relatively easy.

  (8) Since the wavelength conversion element 312 is a quasi-phase matching type wavelength conversion element and has higher conversion efficiency than other types of wavelength conversion elements, the effect of (1) can be further enhanced.

[Second Embodiment]
FIG. 6 is a schematic diagram illustrating a schematic configuration of a laser light source device 41 according to the second embodiment.
The laser light source device 41 of the second embodiment is different from the laser light source device 31 of the first embodiment only in the configuration of the wavelength conversion element 412 and the optical path conversion element 414, and is otherwise the same as the first embodiment. is there. Therefore, in FIG. 6, the same members as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified. Further, the process until the output light is obtained from the laser light source device 41 is the same, and detailed description thereof is omitted or simplified.

As shown in FIG. 6, the optical path conversion element 414 is a band pass filter as a band pass filter means on the surface 316C (second surface) of the second prism 316 of the optical path conversion element 314 in the first embodiment. A multilayer film 318 is provided. Similarly, the bandpass filter multilayer film 318 is formed of a multilayer film having the same film configuration as the bandpass filter multilayer film 312B provided on the incident side end face of the wavelength conversion element 312 in the first embodiment.
That is, the optical path conversion element 414 has the same configuration and the same function as the optical path conversion element 314 except that the bandpass filter multilayer film 318 is provided on the surface 316C.

The optical path conversion element 414 is disposed so that the band-pass filter multilayer film 318 provided on the surface 316C faces the incident side end face of the wavelength conversion element 412. The bandpass filter multilayer film 318 (surface 316C) is disposed so as to be substantially orthogonal to the first optical path O1.
The bandpass filter multilayer film 318 provided on the surface 316C of the second prism 316 is provided on the entire surface 316C of the second prism 316 as shown in FIG. What is necessary is just to be provided in the area | region containing the width W1 of the direction parallel to the line orthogonal to the 1st laser beam LS1 of the wavelength conversion element 412 and the 2nd laser beam LS2.

The wavelength conversion element 412 has, for example, a quadrangular prism shape, and includes a wavelength conversion unit 412A, an anti-reflective (AR) film 412B provided on the incident side end face of the wavelength conversion unit 412A, and the emission of the wavelength conversion unit 412A. And a mirror multilayer film 412C as a multilayer film mirror provided on the side end face.
This wavelength conversion element 412 is the same as the wavelength conversion element 312 except that an AR film 412B is provided instead of the bandpass filter multilayer film 312B provided on the incident side end face of the wavelength conversion element 312 in the first embodiment. It has the same configuration and the same function.

  The laser light source device 41 includes such an optical path conversion element 414 and a wavelength conversion element 412, and a first optical path O1 formed between the light source 311 and the mirror multilayer film 412C provided on the emission side end face of the wavelength conversion element 412. Is placed on top.

Next, a process until output light is obtained from the laser light source device 41 will be described with reference to FIG.
The light having the first wavelength emitted from the light source 311 is incident on the optical path conversion element 414 from the surface 315A of the prism 315, and passes through the surface 315C of the prism 315, the selective reflection film 317, and the surfaces 316B and 316C of the prism 316. The light passes through this order and enters the bandpass filter multilayer film 318.

In the bandpass filter multilayer film 318, light having a wavelength width of about 0.5 nm is transmitted among the incident light having the first wavelength, and light having other wavelength widths is reflected. That is, the band of the incident first wavelength light is narrowed.
Then, the light having the first wavelength transmitted through the band pass filter multilayer film 318 enters the wavelength conversion element 412.

In the wavelength conversion element 412, in the wavelength conversion unit 412A, the wavelength of a part of the first wavelength light is converted to a half wavelength (second wavelength) and is incident on the mirror multilayer film 412C. The mirror multilayer film 412C transmits light that has been converted to the second wavelength out of light incident from the wavelength conversion unit 412A, and reflects light that has not been converted to the second wavelength (light having the first wavelength).
Then, the light with the second wavelength transmitted through the mirror multilayer film 412C is emitted from the wavelength conversion element 412 as the first laser light LS1 (output light). On the other hand, the light that has not been converted to the second wavelength reflected by the mirror multilayer film 412C (light having the first wavelength) travels toward the light source 311.

The light of the first wavelength reflected by the mirror multilayer film 412C of the wavelength conversion element 412 passes through the wavelength conversion unit 412A again in the process toward the light source 311. At that time, the wavelength of a part of the light is converted into the second wavelength and emitted toward the optical path conversion element 414.
Then, the light emitted toward the optical path conversion element 414 enters the optical path conversion element 414, passes through the bandpass filter multilayer film 318, the surfaces 316 C and 316 B of the prism 316, and enters the selective reflection film 317. Incident.

In the selective reflection film 317, the light having the first wavelength among the incident light is transmitted through the selective reflection film 317. Then, the light having the first wavelength transmitted through the selective reflection film 317 is emitted from the surface 315A of the prism 315 toward the light source 311 together with the light emitted from the light source 311 and reflected by the band pass filter multilayer film 318. .
Further, this light returns to the light source 311, is reflected by the mirror layer provided therein, and is emitted from the light source 311 again.

  On the other hand, of the light incident on the selective reflection film 317, the light converted to the second wavelength by the wavelength conversion element 412 is reflected by the selective reflection film 317, reflected by the surface 316A of the prism 316, The laser beam LS1 is directed in a direction substantially parallel to the traveling direction of the first laser beam LS1, and is emitted as the second laser beam LS2.

In the laser light source device 41 of the second embodiment, the optical path conversion element 414 can be configured as follows.
FIG. 7 is a schematic diagram showing a modified configuration of the laser light source device of the second embodiment.

  An optical path conversion element 514 shown in FIG. 7 includes a first prism 315 and a second prism 316 as translucent elements, and a selective reflection film 317 provided therebetween. A band-pass filter multilayer film 319 is provided on the surface 315A (first surface). The bandpass filter multilayer film 319 is formed of a multilayer film having the same film configuration as the bandpass filter multilayer film 318 in the laser light source device 41.

  In the laser light source device 51, such an optical path conversion element 514 has the wavelength of the light source 311 and the wavelength on the first optical path O1 formed between the light source 311 and the mirror multilayer film 412C provided on the emission side end face of the wavelength conversion element 412. A band pass filter multilayer film 319 (surface 315 </ b> A) is disposed between the conversion element 412 and the light source 311. In addition, the surface 315A on which the bandpass filter multilayer film 319 is provided is disposed so as to be substantially orthogonal to the first optical path O1.

  Regarding the process and operation until the output light (first laser light LS1 and second laser light LS2) is obtained from the laser light source device 51, the band-pass filter multilayer of the first wavelength light emitted from the light source 311 The incident order in the optical path conversion element 514 including the film 319 and the bandpass filter multilayer film 319 in the process in which the light of the first wavelength reflected by the mirror multilayer film 412C of the wavelength conversion element 412 is directed toward the light source 311. Although the incident order at the optical path conversion element 514 is different, it is basically the same as the laser light source device 41.

According to the laser light source device 41 and the laser light source device 51 of the second embodiment, in addition to the effects (1), (2) and (4) to (8) of the first embodiment, the following effects can be achieved. it can.
A bandpass filter multilayer film 318 is formed on the surface 316C (second surface) of the second prism 316 of the optical path conversion element 414. Alternatively, the band-pass filter multilayer film 319 is formed on the surface 315A (first surface) of the first prism 315 of the optical path conversion element 514, so that the length of the optical path is increased or the optical element is Light loss due to an increase in the number of passes can be reduced, and the number of components can be reduced, contributing to cost reduction and size reduction of the laser light source devices 41 and 51.

[Third Embodiment]
FIG. 8 is a schematic diagram showing a schematic configuration of a laser light source apparatus according to the third embodiment.
The laser light source device 61 of the third embodiment includes a band pass filter 313 instead of the band pass filter multilayer film 312B provided on the incident side end face of the wavelength conversion element 312 of the laser light source device 31 shown in the first embodiment. Only the provided configuration is different from the laser light source device 31 of the first embodiment, and the other configuration is the same as that of the first embodiment. Therefore, the same members as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified. Further, the process until the output light is obtained from the laser light source device 61 is the same, and the detailed description thereof is omitted or simplified.

The laser light source device 61 shown in FIG. 8 includes a light source 311, an optical path conversion element 314, a band pass filter 313, and a wavelength conversion element 412.
As shown in FIG. 8, the bandpass filter 313 is on the first optical path O1 formed between the light source 311 and a mirror multilayer film 412C as a multilayer mirror provided on the emission side end face of the wavelength conversion element 412. Between the optical path conversion element 314 and the wavelength conversion element 412, an inclination angle θ with respect to the light emission surface of the light source 311 (a surface substantially orthogonal to the first optical path O1) is disposed at, for example, approximately 5 °.

The bandpass filter 313 has a bandpass characteristic in the vicinity of the wavelength of the first wavelength light emitted from the light source 311. It selectively transmits only light having a set specific wavelength out of light having a first wavelength emitted from the light source 311 and reflects light having other wavelengths. That is, the light emitted from the light source 311 has a function of narrowing the band. The bandpass filter 313 includes a structure (not shown) that can displace the inclination angle θ with respect to the laser light emission surface of the light source 311, and transmits the first bandpass filter 313 by displacing the inclination angle θ. The wavelength of the wavelength light can be adjusted. This wavelength adjustment will be described later.
Note that the specific wavelength of light that selectively passes through the bandpass filter 313 is light having a half-value width of approximately 0.5 nm at the first wavelength.

  The bandpass filter 313 includes a bandpass filter multilayer film 313B as bandpass filter means on one surface (incident surface) of the glass substrate 313A and an AR for preventing light reflection on the other surface (exit surface). The film 313C is provided, and the surface on which the bandpass filter multilayer film 313B is formed is disposed on the optical path conversion element 314 side. The bandpass filter multilayer film 313B provides the function of the bandpass filter 313 described above.

The film configuration of the bandpass filter multilayer film 313B is the same as that of the bandpass filter multilayer film 312B formed on the incident end face of the wavelength conversion element 312 in the first embodiment.
Further, the band pass filter 313 may be arranged such that the surface on which the AR film 313C is formed faces the light source 311 side. The AR film 313C is not an essential component for achieving the function of the bandpass filter 313, and can be omitted.

Next, a process until output light is obtained from the laser light source device 61 will be described with reference to FIG.
The light source 311 emits light having a first wavelength. The light having the first wavelength emitted from the light source 311 enters the optical path conversion element 314 from the surface 315A of the prism 315, and passes through the surface 315C of the prism 315, the selective reflection film 317, and the surface 316B of the prism 316 in this order. Then, the light is emitted from the surface 316C of the prism 316 toward the bandpass filter 313.

In the band-pass filter 313, light having a wavelength width of about 0.5 nm is transmitted through the band-pass filter multilayer film 313B, and light having other wavelength widths is reflected. That is, the band of the incident first wavelength light is narrowed.
The light having the first wavelength transmitted through the bandpass filter multilayer film 313B is emitted toward the wavelength conversion element 412 and is incident on the wavelength conversion element 412.

  In the wavelength conversion element 412, in the wavelength conversion unit 412A, the wavelength of a part of the first wavelength light is converted to a half wavelength (second wavelength) and is incident on the mirror multilayer film 412C. The mirror multilayer film 412C transmits light that has been converted to the second wavelength out of light incident from the wavelength conversion unit 412A, and reflects light that has not been converted to the second wavelength (light having the first wavelength).

Then, the light with the second wavelength transmitted through the mirror multilayer film 412C is emitted from the wavelength conversion element 412 as the first laser light LS1 (output light).
On the other hand, the light that has not been converted to the second wavelength reflected by the mirror multilayer film 412C (light having the first wavelength) travels toward the light source 311.

The light having the first wavelength reflected by the mirror multilayer film 412C of the wavelength conversion element 412 and directed toward the light source 311 passes through the wavelength conversion unit 412A again in the process toward the light source 311. At that time, the wavelength of a part of the light is converted into the second wavelength and emitted toward the bandpass filter 313.
Then, the light having the first wavelength emitted toward the bandpass filter 313 passes through the bandpass filter 313 and enters the optical path conversion element 314.

In the optical path conversion element 314, the light emitted from the light source 311 and reflected by the bandpass filter multilayer film 313B of the bandpass filter 313 is incident from the surface 316C of the prism 316, passes through the surface 316B of the prism 316, and is selected. The light enters the reflection film 317.
Of the light incident on the selective reflection film 317, the light having the first wavelength is transmitted through the selective reflection film 317.

Then, the light having the first wavelength transmitted through the selective reflection film 317 passes through the surface 315C of the prism 315 and is emitted from the surface 315A of the prism 315 toward the light source 311.
Further, this light returns to the light source 311, is reflected by the mirror layer 311 A, and is emitted from the light source 311 again. As described above, the light of the first wavelength is newly oscillated in the laser medium 311B by reciprocating the first optical path O1 formed between the light source 311 and the mirror multilayer film 412C of the wavelength conversion element 412. Resonates with the light to be amplified. That is, the laser light source device 61 has a resonance structure formed between the mirror layer 311A of the light source 311 and the mirror multilayer film 412C of the wavelength conversion element 412.

  On the other hand, of the light incident on the selective reflection film 317, the light converted to the second wavelength by the wavelength conversion element 412 is reflected by the selective reflection film 317, and is further reflected by the surface 316A (reflection surface) of the prism 316. The light is reflected and directed in a direction substantially parallel to the traveling direction of the first laser light LS1, and is emitted from the surface 316C of the prism 316 as the second laser light LS2.

Next, wavelength adjustment of the first wavelength light transmitted through the bandpass filter 313 will be described.
The wavelength adjustment of the first wavelength light transmitted through the bandpass filter 313 is performed by displacing the tilt angle θ of the bandpass filter 313 with respect to the laser light emission surface of the light source 311.

In general, light oscillated from a semiconductor laser (light source 311) oscillates in a plurality of longitudinal modes within a gain band, and the wavelengths thereof change due to the influence of temperature fluctuations. In the wavelength conversion element 412 as well, the wavelength of the light subjected to wavelength conversion changes by about 0.1 nm / ° C. with respect to temperature variation.
The angle adjustment for displacing the inclination angle θ of the bandpass filter 313 is performed for the purpose of obtaining stable laser light in response to such temperature fluctuations.

FIG. 9 is a graph showing the transmission wavelength shift characteristic due to the displacement of the inclination angle θ. The horizontal axis of the graph indicates the wavelength (nm), and the vertical axis indicates the transmittance (%). The shift characteristics shown in FIG. 9 indicate the case where the set wavelength of light emitted from the light source 311 is 1064 nm.
The curve a shown in FIG. 9 is a transmittance curve when the bandpass filter 313 has an inclination angle θ of 0 °. Similarly, the curve b has an inclination angle θ of 1 °, the curve c has 2 °, and the curve d has 3 °. , Curve e is a transmittance curve at 4 °, and curve f is a transmittance curve at 5 °.

  In FIG. 9, as the tilt angle θ of the bandpass filter 313 increases from 0 ° to 5 °, the peak wavelength of light transmitted through the bandpass filter 313 is shifted (shifted) in the direction of decreasing (increasing frequency). To do.

Accordingly, the bandpass filter 313 adjusts (displaces) the inclination angle θ inclined approximately 5 ° with respect to the laser light exit surface of the light source 311 to be larger than 5 °, thereby transmitting the first bandpass filter 313. The wavelength of the light of the wavelength can be adjusted to be small. In addition, since the bandpass filter 313 is inclined in advance, the first wavelength to be transmitted can be adjusted to be large when the inclination angle θ is in the range of approximately 0 ° to approximately 5 °.
Note that the angle adjustment of the inclination angle θ of the bandpass filter 313 may be performed in either the right inclination or the left inclination with respect to the laser light emission surface of the light source 311.

  According to the laser light source device 61 of the third embodiment described above, the following effects can be obtained in addition to the effects of the first embodiment.

According to the laser light source device 61 of the third embodiment, in addition to the effects (1), (2) and (4) to (8) of the first embodiment, the following effects can be achieved.
A wavelength conversion element 412 is arranged inside a resonance structure (first optical path O1) formed between the mirror layer 311A of the light source 311 and the mirror multilayer film 412C of the wavelength conversion element 412. The wavelength conversion element 412 and the light source 311 And a band pass filter 313 provided with a band pass filter multilayer film 313B having a band pass characteristic in the vicinity of the first wavelength, and the band pass filter 313 has an inclination angle θ with respect to the laser light emission surface of the light source 311. Is configured to be displaceable, the wavelength of the first wavelength light emitted from the light source 311 is narrowed, and the oscillation wavelength of the light emitted from the light source 311 with the tilt angle θ displaced ( The first wavelength can be changed. As a result, even if the oscillation wavelength fluctuates due to a temperature change or the like, the oscillation wavelength can be adjusted, the conversion efficiency in the wavelength conversion element 412 is improved, and output light with improved light utilization efficiency can be obtained. Can do.
In addition, the wavelength conversion element 412 and the bandpass filter 313 can be individually adjusted for various characteristics, and improvement in oscillation efficiency and yield can be expected.

[Modification of Embodiment]
The present invention is not limited to the first to third embodiments described above, but includes modifications and improvements as long as the object of the present invention can be achieved. Even if it is a form which is mentioned as a modification below, the same effect as the above-mentioned embodiment can be acquired.

  (1) As the light source 311, in addition to the surface emitting semiconductor laser, a so-called edge emitting semiconductor laser or semiconductor pumped solid state laser can be used. In the case of using an edge emitting semiconductor laser, it is preferable to provide a lens for collimating the light emitted from the light source 311 between the light source 311 and the optical path conversion elements 314 and 414.

  (2) The light source 311 may include a plurality of light emitting units arranged in an array. FIG. 10A and FIG. 10B are schematic views showing a light source in which light emitting units are arrayed. In the light source 321 in FIG. 10A, a plurality of light emitting portions 322 are arranged in a line. In addition, in the light source 323 of FIG. 10B, a plurality of light emitting portions 322 are arranged in two rows. Note that the number of light emitting units and the number of columns are not limited to those shown in FIGS. In the laser light source devices 31, 41, 51, 61 described above, even if a light source in which the light emitting units are arrayed in this way is used, light incident on each component (wavelength conversion element, optical path conversion element, or bandpass filter) It is only necessary to expand the area of the surface, the light emission surface, and the reflection surface to an area corresponding to the array.

  As described above, in the laser light source devices 31, 41, 51, 61 described above, even if the light sources are arranged in an array, the device is not excessively large and can be handled with a simple configuration. . Therefore, in the laser light source devices 31, 41, 51, 61 described above, even if the light sources are arrayed, the power reduction of the output light is efficiently suppressed, the light use efficiency is high, and the polarization direction of the output light is aligned. In addition, it is possible to effectively increase the power of the output light by effectively increasing the amount of light due to the array while maintaining the effect that it is possible to obtain a laser light source device with stable output.

  (3) The case where the mirror multilayer films 312C and 412C are provided on the emission side end faces of the wavelength conversion elements 312 and 412 has been described. However, instead of the mirror multilayer films 312C and 412C, the output side of the wavelength conversion elements 312 and 412 For example, a configuration may be adopted in which a multilayer mirror including mirror multilayer films 312C and 412C on one surface of the glass substrate is disposed on the first optical path O1. In this case, the wavelength conversion elements 312 and 412 and the multilayer mirror can be individually adjusted for various characteristics, and improvement in oscillation efficiency and yield can be expected.

(4) As the nonlinear optical material constituting the wavelength conversion elements 312 and 412, LN (LiNbO ₃ ) and LT (LiTaO ₃ ) are exemplified previously, but other than this, KNbO ₃ , BNN (Ba ₂ NaNb _5). Inorganic nonlinear optical materials such as O ₁₅ ), KTP (KTiOPO ₄ ), KTA (KTiOAsO ₄ ), BBO (β-BaB ₂ O ₄ ), and LBO (LiB ₃ O ₇ ) may be used. Also, low molecular weight compounds such as metanitroaniline, 2-methyl-4-nitroaniline, chalcone, dicyanovinylanisole, 3,5-dimethyl-1- (4-nitrophenyl) pyrazole, N-methoxymethyl-4-nitroaniline An organic material or an organic nonlinear optical material such as a poled polymer may be used.

  (5) As the wavelength conversion elements 312 and 412, a third harmonic generation element may be used instead of the SHG element described above.

[Application example of laser light source device]
By applying the laser light source devices 31, 41, 51, 61 as described above to the image display device, it is possible to improve the light use efficiency in these devices. Hereinafter, application examples to the image display device and the monitor device will be described.

[Application Example 1: Projector]
A configuration of the projector 3 will be described as an example of an image display device to which the laser light source device 31 according to the first embodiment is applied. FIG. 11 is a schematic diagram showing an outline of the optical system of the projector 3.
11, the projector 3 includes a laser light source device 31, a liquid crystal panel 32 as a light modulation device, an incident side polarizing plate 331, an emission side polarizing plate 332, a cross dichroic prism 34, a projection lens 35, and the like. The liquid crystal light valve 33 is configured by the liquid crystal panel 32, the incident side polarizing plate 331 provided on the light incident side, and the emission side polarizing plate 332 provided on the light emission side.

  The laser light source device 31 includes a red light source device 31R that emits red laser light, a blue light source device 31B that emits blue laser light, and a green light source device 31G that emits green laser light. . These laser light source devices 31 (31R, G, B) are disposed so as to face the three side surfaces of the cross dichroic prism 34, respectively. In FIG. 12, the light source device for red light 31R and the light source device for blue light 31B are opposed to each other, and the projection lens 35 and the light source device for green light 31G are opposed to each other across the cross dichroic prism. These positions can be switched as appropriate.

  The liquid crystal panel 32 uses, for example, a polysilicon TFT (Thin Film Transistor) as a switching element. Color light emitted from the laser light source device 31 (31R, G, B) is incident on the liquid crystal panel 32 via the incident-side polarizing plate 331. The light incident on the liquid crystal panel 32 is modulated according to the image information and emitted from the liquid crystal panel 32. Of the light modulated by the liquid crystal panel 32, only specific linearly polarized light passes through the exit-side polarizing plate 332 and travels toward the cross dichroic prism 34.

  In addition, since the light emitted from the laser light source device 31 is light having a well-aligned polarization direction, in principle, the incident-side polarizing plate 331 can be omitted. However, in practice, the light emitted from the laser light source device 31 is rarely used as illumination light as it is, and an optical element for processing the light emitted from the laser light source device 31 into light suitable for illumination light (for example, In many cases, a diffraction grating, a lens, a rod integrator, and the like) are provided between the laser light source device 31 and the liquid crystal panel 32. And passing through such an optical element may cause some disturbance in polarization. If the light whose polarization is disturbed is incident on the liquid crystal panel 32 as it is, the contrast of the projected image may be lowered, or the projected image may be uneven in color. Therefore, if the incident-side polarizing plate 331 is provided on the incident side of the liquid crystal panel 32 so as to align the direction of polarized light incident on the liquid crystal panel 32, the reduction in the contrast of the projected image and the occurrence of color unevenness can be reduced. Therefore, it is possible to obtain a higher quality image.

  The cross dichroic prism 34 is an optical element that combines color lights modulated by the liquid crystal panels 32 to form a color image. The cross dichroic prism 34 has a substantially square shape in plan view in which four right-angle prisms are bonded. Two kinds of dielectric multilayer films are provided in an X shape at the interface of these four right-angle prisms. These dielectric multilayer films reflect the color lights emitted from the liquid crystal panels 32 facing each other and transmit the color lights emitted from the liquid crystal panel 32 opposed to the projection lens 35. In this way, the color lights modulated by the liquid crystal panels 32 are combined to form a color image.

  The projection lens 35 is configured as a combined lens in which a plurality of lenses are combined. The projection lens 35 enlarges and projects a color image.

In this application example, the laser light source device 31 (31R, G, B) according to the first embodiment is used, but some or all of these are used as the laser light source device 41 according to other embodiments. 51 and 61 may be substituted.
Furthermore, a part of the laser light source device 31 (31R, G, B) may be replaced with a laser light source device that uses the wavelength of the fundamental laser as it is.

In this application example, an example of a projector using three light modulation elements has been described. However, the laser light source devices 31, 41, 51, 61 of the first to third embodiments have one light modulation device and two light modulation devices. Alternatively, it can be applied to a projector using four or more projectors.
In this application example, the transmissive projector has been described. However, the laser light source devices 31, 41, 51, and 61 of the first to third embodiments can be applied to a reflective projector. Here, “transmission type” means that the light modulation element is a type that transmits light, and “reflection type” means that the light modulation element is a type that reflects light. ing.

Further, the light modulation element is not limited to the liquid crystal panel 32, and may be a device using a micromirror, for example.
Furthermore, as a projector, there are a front type that projects an image from the direction of observing the projection surface and a rear type that projects an image from the side opposite to the direction of observing the projection surface. The laser light source devices 31, 41, 51, and 61 are applicable to any type.

  Furthermore, in this application example, as an example of an image display device to which the laser light source device 31 is applied, a projector including a projection lens 35 for enlarging and projecting an image is introduced, but the laser according to the first to third embodiments. The light source devices 31, 41, 51, 61 can also be applied to an image display device that does not use the projection lens 35.

[Application Example 2: Monitor Device]
Next, a configuration example of the monitor device 40 to which the laser light source device 31 according to the first embodiment is applied will be described. FIG. 12 is a schematic diagram showing an outline of the monitor device. The monitor device 400 includes a device main body 410 and an optical transmission unit 420. The apparatus main body 410 includes the laser light source apparatus 31 of the first embodiment described above.

  The light transmission unit 420 includes two light guides 421 and 422 on the light sending side and the light receiving side. Each of the light guides 421 and 422 is a bundle of a large number of optical fibers, and can send laser light to a distant place. A laser light source device 31 is disposed on the incident side of the light guide 421 on the light transmission side, and a diffusion plate 423 is disposed on the emission side thereof. The laser light emitted from the laser light source device 31 is transmitted to the diffusion plate 423 provided at the tip of the light transmission unit 420 through the light guide 421, and is diffused by the diffusion plate 423 to irradiate the subject.

  An imaging lens 424 is also provided at the tip of the light transmission unit 420, and reflected light from the subject can be received by the imaging lens 424. The received reflected light travels through the light guide 422 on the receiving side and is sent to a camera 411 as an imaging means provided in the apparatus main body 410. As a result, the camera 411 can capture an image based on the reflected light obtained by irradiating the subject with the laser light emitted from the laser light source device 31.

  According to the monitor device 40 configured as described above, the subject can be irradiated by the high-power laser light source device 31, so that the brightness of the captured image obtained by the camera 411 can be increased.

  In this application example, the laser light source device 31 according to the first embodiment is used. However, this may be replaced with the laser light source devices 41, 51, 61 according to other embodiments.

The schematic diagram which shows schematic structure of the laser light source apparatus which concerns on 1st Embodiment. Sectional drawing which shows the structure of a light source typically. Sectional drawing which shows the structure of a wavelength conversion element typically. The graph which shows an example of the spectral transmittance characteristic of a band pass filter multilayer film. The perspective view of an optical path conversion element. The schematic diagram which shows schematic structure of the laser light source apparatus which concerns on 2nd Embodiment. The schematic diagram which shows the deformation | transformation structure in the laser light source apparatus of 2nd Embodiment. The schematic diagram which shows schematic structure of the laser light source apparatus which concerns on 3rd Embodiment. The graph showing the shift characteristic of the transmission wavelength by the displacement of the inclination angle of a band pass filter. The schematic diagram which shows the light source by which the light emission part was arrayed. FIG. 2 is a schematic diagram showing an outline of an optical system of a projector. The schematic diagram which shows the outline of a monitor apparatus.

Explanation of symbols

  31, 41, 51, 61 ... Laser light source device, 31B ... Blue light source device, 31G ... Green light source device, 31R ... Red light source device, 32 ... Liquid crystal panel, 33 ... Polarizer, 34 ... Cross dichroic Prism, 35 ... projection lens, 311 ... light source, 311A ... mirror layer, 311B ... laser medium, 400 ... substrate, 312, 412 ... wavelength converter, 312A, 412A ... wavelength converter, 312B, 313B, 318, 319 ... band Pass filter multilayer film, 312C, 412C ... mirror multilayer film, 313 ... band pass filter, 314, 414, 514 ... optical path conversion element, 315 ... first prism, 316 ... second prism, 317 ... selective reflection film, LS1: first laser beam, LS2: second laser beam.

Claims (15)

A light source that emits light of a first wavelength;
A multilayer mirror that selectively reflects the light of the first wavelength toward the light source;
A second light beam is provided on a first optical path formed between the light source and the multilayer film mirror, and a part of the incident light having the first wavelength is different from the first wavelength. A wavelength conversion element for converting into a wavelength, and bandpass filter means having bandpass characteristics in the vicinity of the first wavelength;
An optical path conversion element for extracting the light reflected by the multilayer mirror and converted to the second wavelength in the process of traveling toward the light source into a second optical path different from the first optical path;
With
A laser light source device that uses, as output light, the first laser light having the second wavelength emitted from the multilayer mirror and the second laser light having the second wavelength emitted from the optical path conversion element. Because
The optical path conversion element is provided between the light source and the wavelength conversion element, and selectively reflects the light having the second wavelength.
A reflecting surface that reflects the light reflected by the selective reflection film and directs the light in a direction substantially the same as the traveling direction of the first laser light;
A translucent element that integrates the selective reflective film and the reflective surface;
The multilayer mirror has a characteristic of reflecting 80% or more of the light having the first wavelength and transmitting 80% or more of the light having the second wavelength, which is formed on the end face on the emission side of the wavelength conversion element. A laser light source device comprising a multi-layer film. The laser light source device according to claim 1,
The translucent element has a first prism and a second prism,
The first and second prisms each have a first surface and a second surface;
The selective reflection film is provided between the second surface of the first prism and the first surface of the second prism,
The light emitted from the light source is incident on the optical path conversion element from the first surface of the first prism, and the second surface of the first prism, the selective reflection film, and the second It passes through the first surface of the prism in this order, is emitted from the second surface of the second prism toward the wavelength conversion element,
Light that is reflected by the multilayer mirror and travels toward the light source enters the optical path conversion element from the second surface of the second prism and passes through the first surface of the second prism. Incident on the selective reflection film,
Of the light that is reflected by the multilayer mirror and travels toward the light source, the light that passes through the selective reflection film and travels toward the light source passes through the second surface of the first prism. , Emitted from the first surface of the first prism toward the light source,
Of the light that is reflected by the multilayer mirror and travels toward the light source, the light that is reflected by the selective reflection film is reflected by the reflection surface and is emitted from the second surface of the second prism. A laser light source device. The laser light source device according to claim 1 or 2,
The laser light source device according to claim 1, wherein the band-pass filter means is formed of a band-pass filter multilayer film formed on an incident-side end face of the wavelength conversion element. The laser light source device according to claim 1 or 2,
The bandpass filter means includes
It consists of a bandpass filter provided with a bandpass filter multilayer film,
A laser light source device, wherein an inclination angle of the light source with respect to a laser light emission surface is displaceable between the optical path conversion element and the wavelength conversion element. The laser light source device according to claim 2,
The laser light source device, wherein the band-pass filter means comprises a band-pass filter multilayer film formed on the second surface of the second prism. The laser light source device according to claim 2,
The laser light source device, wherein the band-pass filter means comprises a band-pass filter multilayer film formed on the first surface of the first prism. The laser light source device according to claim 2,
The laser light source device, wherein the first surface of the first prism and the second surface of the second prism are parallel to each other. The laser light source device according to claim 2,
The reflective surface is a third surface of the second prism;
The laser light source device, wherein the third surface is a surface disposed at an angle satisfying a total reflection condition with respect to light incident on the third surface. In the laser light source device according to any one of claims 3 to 8,
The bandpass filter multilayer film has a transmittance of 80% or more with respect to the second wavelength, and a high refractive index layer H and a low refractive index layer L are alternately stacked, and the first wavelength is changed to λ. The optical film thicknesses are 0.236λH, 0.355λL, 0.207λH, 0.203λL, (0.25λH, 0.25λL) n, 0.5λH, (0.25λL) in this order from the wavelength conversion element side. , 0.25λH) n, 0.266λL, 0.255λH, 0.248λL, 0.301λH, 0.631λL.
However, n is a value in the range of 3 to 10, and indicates the number of repetitions in which the layers in parentheses are repeatedly laminated. In the laser light source device according to any one of claims 1 to 9,
The first laser beam having the second wavelength emitted from the multilayer mirror and the second laser beam having the second wavelength emitted from the optical path conversion element are substantially parallel to each other. A laser light source device. The laser light source device according to claim 10,
The width of the wavelength conversion element in a direction parallel to a line perpendicular to the first laser beam and the second laser beam is W1,
When the distance between the first laser beam and the second laser beam is W2,
W2> W1, wherein the laser light source device. In the laser light source device according to any one of claims 1 to 11,
The light source includes a plurality of light emitting units arranged in an array. In the laser light source device according to any one of claims 1 to 12,
The laser light source device, wherein the wavelength conversion element is a quasi phase matching type wavelength conversion element. A laser light source device according to any one of claims 1 to 13,
A light modulation element that modulates laser light emitted from the laser light source device according to image information;
An image display device comprising: A laser light source device according to any one of claims 1 to 13,
Imaging means for imaging a subject irradiated by the laser light source device;
A monitor device comprising:

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