JP2008124178A - LASER LIGHT SOURCE DEVICE AND IMAGE DISPLAY DEVICE EQUIPPED WITH THE LASER LIGHT SOURCE DEVICE - Google Patents

Abstract

Provided are a laser light source device that efficiently suppresses a decrease in power of output light even when temperature changes occur, has high light utilization efficiency, and has a stable output, and an image display device with improved utilization efficiency.
A laser light source device includes a light source that emits light having a first wavelength, a multilayer mirror that selectively reflects light having the first wavelength and directs the light toward the light source, and the light source and the multilayer. A band pass filter 312, a polarization beam splitter 313, a wavelength conversion element 314 that converts light of the first wavelength into a second wavelength, and a separation mirror 316 are placed on the first optical path O 1 formed between the film mirror and the first mirror. The second wavelength light reflected by the multilayer mirror and converted by the wavelength conversion element in the process toward the light source is taken out by the polarization beam splitter and the reflection mirror 320 onto the second optical path O2 and emitted. . The bandpass filter displaces the tilt angle θ based on the output signal of the laser output measuring unit 317 that measures the output of the light separated by the separation mirror.
[Selection] Figure 1

Description

  The present invention relates to a laser light source device that emits laser light, and an image display device including the laser light source 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, in SHG, the oscillation wavelength of the laser light source varies with temperature changes. Or since 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, there is a large amount of light in a wavelength region that is not wavelength-converted, and the conversion efficiency is low.
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 utilization efficiency does not improve dramatically. 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 increases or the number of times of passing through the optical element increases, there is a possibility that light loss may occur. 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.
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, and a laser light source that efficiently suppresses power reduction of output light, has high light utilization efficiency, and has stable output even when a temperature change occurs. An object is to provide an apparatus. Another object of the present invention is to provide an image display 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, mirror means that selectively reflects light of the first wavelength and directs it toward the light source, the light source, and the light source A wavelength for converting the wavelength of a part of the light having the first wavelength incident on the first optical path formed between the mirror means to a second wavelength different from the light having the first wavelength. A conversion element, a bandpass filter formed with a bandpass filter multilayer film having bandpass characteristics in the vicinity of the first wavelength, and the second wavelength in the process of being reflected by the mirror means toward the light source. Folding means for taking out the light converted into the second optical path different from the first optical path, and the first laser light of the second wavelength emitted from the mirror means and the folding means Second of the second wavelength to be emitted A laser light source device that uses laser light as output light, the separation mirror separating a part of the light of the second wavelength emitted from the mirror means, and the second separated by the separation mirror And a laser output measuring unit for measuring the output of light having a wavelength of 80% or more, wherein the mirror means reflects 80% or more of the light of the first wavelength and transmits 80% or more of the light of the second wavelength. The band-pass filter is adjusted in angle so that the tilt angle with respect to the first optical path is displaced based on the output signal of the laser output measurement unit. It is characterized by that.

  According to such a configuration, the wavelength conversion element is provided in the resonance structure constituted by the light source and the multilayer film mirror as the mirror means, and is reflected by the multilayer film mirror and converted by the wavelength conversion element in the process toward the light source. By taking out the light having the wavelength of 2 to the second optical path by the folding means and using it, it is possible to efficiently reduce the power reduction of the output light. In addition, the bandpass filter is provided with a bandpass filter multilayer film having bandpass characteristics near the first wavelength, so that the light transmitted through the bandpass filter is narrowed and laser light having a constant wavelength is always obtained. Can be emitted from the laser light source device.

Further, the bandpass filter is emitted from the light source due to temperature fluctuation or the like by performing angle adjustment for displacing the tilt angle with respect to the first optical path based on the output signal of the laser output measuring unit that measures the output of the laser light. Even when the wavelength of the first wavelength light is changed, it can be adjusted to the conversion wavelength of the wavelength conversion element. Furthermore, the multilayer mirror reflects light of the first wavelength by 80% or more and transmits the laser light of the second wavelength by 80% or more, thereby confining the oscillation light of the light source in the resonance structure. However, 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 the power drop of output light, has high light utilization efficiency, and has stable output.

  A laser light source device according to the present invention includes a light source that emits light of a first wavelength, mirror means that selectively reflects light of the first wavelength and directs it toward the light source, the light source, and the light source A wavelength for converting the wavelength of a part of the light having the first wavelength incident on the first optical path formed between the mirror means to a second wavelength different from the light having the first wavelength. A conversion element, a bandpass filter formed with a bandpass filter multilayer film having bandpass characteristics in the vicinity of the first wavelength, and the second wavelength in the process of being reflected by the mirror means toward the light source. Folding means for taking out the light converted into the second optical path different from the first optical path, and the first laser light of the second wavelength emitted from the mirror means and the folding means Second of the second wavelength to be emitted A laser light source device that uses laser light as output light, the separation mirror separating a part of the light of the second wavelength emitted from the mirror means, and the second separated by the separation mirror A laser output measuring unit that measures the output of light having a wavelength of 80%, and wherein the mirror means reflects 80% or more of the light having the first wavelength provided on the end face on the emission side of the wavelength conversion element. And a dielectric multilayer film having a characteristic of transmitting 80% or more of the light of the second wavelength, and the bandpass filter has a tilt angle displaced with respect to the first optical path based on an output signal of the laser output measurement unit The angle adjustment is performed.

  According to this configuration, the resonant structure is configured by the dielectric multilayer film as the mirror means provided on the light source and the end face on the emission side of the wavelength conversion element, and the wavelength conversion is performed in the process of being reflected by the dielectric multilayer film toward the light source. By taking out the light of the second wavelength converted by the element to the second optical path by the folding means and using it, it becomes possible to efficiently reduce the power drop of the output light, and the dielectric multilayer film By being formed on the surface on the emission side of the wavelength conversion element, the number of components can be reduced, and a laser light source device that is reduced in cost and size can be obtained. In addition, the bandpass filter is provided with a bandpass filter multilayer film having bandpass characteristics near the first wavelength, so that the light transmitted through the bandpass filter is narrowed and laser light having a constant wavelength is always obtained. Can be emitted from the laser light source device.

Further, the bandpass filter is emitted from the light source due to temperature fluctuation or the like by performing angle adjustment for displacing the tilt angle with respect to the first optical path based on the output signal of the laser output measuring unit that measures the output of the laser light. Even when the wavelength of the first wavelength light is changed, it can be adjusted to the conversion wavelength of the wavelength conversion element. Furthermore, the dielectric multilayer film has a characteristic of reflecting 80% or more of the light of the first wavelength and transmitting 80% or more of the light of the second wavelength, so that the oscillation light of the light source is contained in the resonance structure. While confining, the light of 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 the power drop of output light, has high light utilization efficiency, and has stable output.

  In the laser light source device according to the present invention, the multilayer mirror is disposed between the wavelength conversion element and the separation mirror, and the bandpass filter is disposed between the light source and the folding means. It is preferable to adopt a configuration. Alternatively, it is preferable that the band pass filter and the multilayer mirror are arranged in this order from the wavelength conversion element side between the wavelength conversion element and the separation mirror.

  According to such a configuration, a bandpass in which a bandpass filter multilayer film having bandpass characteristics in the vicinity of the first wavelength is provided on the first optical path formed between the light source and the multilayer film mirror as the mirror means. By arranging the filter, the light transmitted through the band-pass filter is narrowed, and laser light having a constant wavelength can always be emitted from the laser light source device. Further, the band-pass filter can be disposed between the light source and the folding means, or between the wavelength conversion element and the separation mirror, and the degree of freedom in designing the optical path in the laser light source device is increased.

  In the laser light source device according to the present invention, the bandpass 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 arranged. The optical film thicknesses are 0.236λH, 0.355λL, 0.207λH, 0.203λL, (0.25λH, 0.25λL) n in order from the light exit side, with the first wavelength being λ. 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 multilayer film is formed by alternately laminating the high refractive index layers H and the low refractive index layers L as described above, thereby having bandpass characteristics in the vicinity of the first wavelength. The light of the first wavelength emitted from the light source can be narrowed. Thereby, the conversion efficiency of wavelength conversion in the wavelength conversion element can be improved.

  Further, in the laser light source device according to the present invention, the folding means includes a polarizing beam splitter provided with a selective reflection film that transmits the light of the first wavelength and reflects the light of the second wavelength; A reflection mirror provided with a reflection film that totally reflects the light of the second wavelength incident from the polarization beam splitter in a direction substantially the same as the traveling direction of the first laser beam. Is preferred.

  According to such a configuration, the folding means has the polarizing beam splitter provided with the selective reflection film, and the light having the second wavelength incident from the polarizing beam splitter is directed in substantially the same direction as the traveling direction of the first laser light. And a reflection mirror provided with a reflective film that totally reflects the second wavelength light reflected by the mirror means and converted by the wavelength conversion element in the process toward the light source. It can be easily taken out to the optical path and used.

In the laser light source device according to the present invention, the first laser light having the second wavelength emitted from the mirror means, and the second laser light having the second wavelength emitted from the folding means, 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 devices 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 beam and the second laser beam 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 or the like, there is an effect that the degree of freedom in optical design is greatly increased.

In the laser light source device according to the present invention, a width of the wavelength conversion element in a direction parallel to a line orthogonal to the first laser light and the second laser light is W1, and the first laser When the distance between the light and the second laser light is W2, it is preferable that W2> W1.
With this configuration, even if the relative position between the first optical path and the folding means 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, it is preferable that the light source includes a plurality of light emitting units arranged in an array.
In the present invention, even if the arrayed light sources are used, the area of the light incident surface and light emission surface of the components of the laser light source device (bandpass filter, wavelength conversion element, separation mirror, folding means, etc.) Need only be expanded to an area corresponding to the array. 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. That is, in the present invention, even when the light sources are arranged in an array, the effect of being able to obtain a laser light source device that efficiently suppresses the power drop of the output light and has high light utilization efficiency and stable output can be maintained. However, an increase in the amount of light due to the array can be effectively linked to a power up of the output light.

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 matching type wavelength conversion element has a 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, it is possible to improve the utilization efficiency of laser light.

  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 bandpass filter 312, a polarizing beam splitter 313, a wavelength conversion element 314, a multilayer mirror 315 as a mirror, a separation mirror 316, a laser output measurement unit 317, a control unit 318, a rotation mechanism 319, A reflection mirror 320. Among these, the band pass filter 312, the polarization beam splitter 313, the wavelength conversion element 314, the multilayer mirror 315, and the separation mirror 316 are on the first optical path O1 formed between the light source 311 and the multilayer mirror 315. They are provided in this order from the light source 311 side.

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 first wavelength when a predetermined amount of current flows from the conduction means. Further, the laser medium 311B allows light of a specific wavelength (first wavelength) to resonate between light of the first wavelength between the mirror layer 311A and the multilayer mirror 315 illustrated in FIG. Amplify. That is, light reflected by the mirror layer 311A and a multilayer film mirror 315 described later is amplified by resonance with light newly emitted by the laser medium 311B, and is reflected from the end surface (light emission surface) of the laser medium 311B. Injected in a direction substantially orthogonal to 311A and the substrate 400.

As shown in FIG. 1, the band-pass filter 312 is disposed on the first optical path O1 formed between the light source 311 and the multilayer mirror 315 so as to face the light source 311 and has a band near the first wavelength. Has path characteristics. 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 specific wavelength of light that selectively passes through the bandpass filter 312 is light having a half-value width of about 0.5 nm at the first wavelength.
In addition, the bandpass filter 312 can be displaced by the rotation mechanism 319 described later with respect to the 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), that is, the inclination angle with respect to the first optical path O1. It is configured.

This band-pass filter 312 has a band-pass multilayer film 312B on one surface (incident surface) of the glass substrate 312A and anti-reflective (AR) for preventing light reflection on the other surface (exit surface). ) Film 312 </ b> C, and the surface on which the bandpass multilayer film 312 </ b> B is formed is disposed on the light source 311 side. The bandpass multilayer film 312B provides the function of the bandpass filter 312 described above.
The band-pass filter 312 may be arranged with the surface on which the AR film 312C is formed facing the light source 311 side.

  The film configuration of the bandpass multilayer film 312B is such that the high refractive index layers H and the low refractive index layers L are alternately stacked, the oscillation wavelength is λ, and the optical film thickness is from the light emission side, that is, the glass substrate 312A side. , 0.236λH, 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 for the high refractive index layer H, one of the materials such as Ta ₂ 0 ₅ , Nb ₂ 0 ₅ , Ti0 ₂ , and Zr0 ₂ that is transparent in the wavelength region to be used and is environmentally friendly is selected, and the low refractive index is low. Similarly, as the material of the rate layer L, one kind is selected from environmentally friendly substances such as SiO ₂ and MgF ₂ .

FIG. 3 is a graph showing an example of spectral transmittance characteristics of the bandpass 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. 3, the bandpass 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 polarizing beam splitter 313 has a selective reflection film 313B on one surface of a glass substrate 313A, and an anti-reflective (AR) film 313C for preventing light reflection on the other surface. Yes. The polarization beam splitter 313 has a function of transmitting light having a first wavelength and reflecting light having a second wavelength converted by a wavelength conversion element 314 described later toward the reflection mirror 320.

The polarization beam splitter 313 is disposed between the band pass filter 312 on the first optical path O1 and the wavelength conversion element 314 at an angle of approximately 45 ° with respect to the first optical path O1.
In consideration of reflection efficiency, the polarization beam splitter 313 is disposed with the surface provided with the selective reflection film 313B facing the wavelength conversion element 314, but the surface provided with the AR film 313C is disposed on the wavelength conversion element 314 side. May be arranged. The AR film 313C is not an essential component for achieving the function of the polarization beam splitter 313, and can be omitted.

  The wavelength conversion element 314 converts the wavelength of the incident light into light having a substantially half wavelength (second wavelength). As shown in FIG. 1, the wavelength conversion element 314 is provided between the polarizing beam splitter 313 and the multilayer mirror 315 on the first optical path O1 formed between the light source 311 and the multilayer mirror 315. .

  FIG. 4 is a sectional view schematically showing the structure of the wavelength conversion element 314. The wavelength conversion element 314 has, for example, a quadrangular prism shape, the wavelength conversion unit 314A, the AR film 314B on the light source 311 side surface (incident side end surface) of the wavelength conversion unit 314A, and the multilayer film mirror 315 side of the wavelength conversion unit 314A. The AR film 314C is provided on the surface (the exit side end face).

  The wavelength conversion unit 314A is a second harmonic generation (SHG) element that generates a second harmonic of incident light. The wavelength conversion unit 314A 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 (first wavelength) of light emitted from the light source 311 is 1064 nm (near infrared), the wavelength conversion unit 314A converts this to a half wavelength (second wavelength) of 532 nm. Produces green light. However, the wavelength conversion efficiency of the wavelength conversion unit 314A is generally about 30 to 40%. 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 314Aa and 314Ab 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 314Aa and 314Ab 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 the light converted in the wavelength conversion element 314 is about 0.3 nm, and varies by about 0.1 nm / ° C. with respect to the change in use environment temperature.

  The AR films 314B and 314C are dielectric films made of at least a single layer or multiple layers, for example, and transmit both the light with the first wavelength and the light with the second wavelength with a transmittance of 98% or more, for example. The AR films 314B and 314C have a characteristic of reducing the loss of the laser light when the laser light is incident on or emitted from the wavelength conversion element 314. However, in order to achieve the function of the wavelength conversion element 314. Since it is not an essential configuration, it can be omitted. That is, the wavelength conversion element 314 can be configured by only the wavelength conversion unit 314A.

  As shown in FIG. 1, the multilayer mirror 315 is arranged to face the emission end face of the wavelength conversion element 314 on the first optical path O1, and selectively reflects the light of the first wavelength toward the light source 311. And has a function of transmitting light of other wavelengths (including the second wavelength). The multilayer mirror 315 also has a function of narrowing the wavelength of the light to be amplified by selectively reflecting the light having the first wavelength.

  The multilayer mirror 315 is provided with a dielectric multilayer film 315B on one surface (incident surface) of a glass substrate 315A as a transparent member, and an antireflection film for preventing light reflection on the other surface (exit surface). 315C is formed. The multilayer mirror 315 is disposed with the dielectric multilayer film 315B facing the wavelength conversion element 314 side.

  The dielectric multilayer film 315B 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 the required characteristics. This dielectric multilayer film 315B provides the function of the multilayer mirror 315 described above. The higher the transmittance of the dielectric multilayer film 315B for the second wavelength light and the higher the reflectance for the first wavelength light, the better, and 80% or more is desirable.

Further, the glass substrate 315A as a transparent member has a transmittance of 80% or more with respect to the laser light of the second wavelength that transmits the glass substrate 315A, and is 20% or less with respect to the light of the first wavelength. It consists of the material which has the transmittance | permeability of. As a result, it is possible to reduce the loss of light having the second wavelength that is transmitted through the multilayer mirror 315.
The AR film 315C is not an essential component for achieving the function of the multilayer mirror 315, and can be omitted. That is, the multilayer mirror 315 can be configured by only the glass substrate 315A and the dielectric multilayer film 315B.

As shown in FIG. 1, the separation mirror 316 is disposed to face the emission side of the multilayer mirror 315, and a part of the second wavelength light emitted from the multilayer mirror 315, for example, 0. It has a function of reflecting about 5% and separating it toward the laser output measuring unit 317.
This separation mirror 316 is provided with at least a separation film 316B made of a dielectric multilayer film on one surface of a glass substrate 316A. The separation film 316B faces the multilayer film mirror 315, for example, in a direction along the first optical path O1. It is arranged with an inclination of about 45 °. The thickness of each layer of the multilayer film constituting the separation membrane 316B, the material of each layer, and the number of layers are optimized according to the required characteristics. Note that the separation mirror 316 may be provided with an AR film on the other surface of the glass substrate 316A.

The laser output measurement unit 317 includes a light receiving sensor and a measurement circuit (not shown), receives the separated light incident from the separation mirror 316 and converts it into an electrical signal, and obtains a measured value of the laser light output by signal processing. As the light receiving sensor, a semiconductor photodiode or the like can be used.
The output signal of the laser output measurement value obtained by the laser output measurement unit 317 is sent to the control unit 318.

The control unit 318 is configured by a microcomputer including a CPU, a RAM, a ROM, and the like, and controls the rotation mechanism 319 based on the output signal of the laser output measurement value input from the laser output measurement unit 317.
As shown in FIG. 1, the rotation mechanism 319 performs angle adjustment for changing the inclination angle θ of the bandpass filter 312 with respect to the first optical path O <b> 1 based on a control signal input from the control unit 318.

  The inclination angle θ is an inclination angle with respect to the light emission surface of the light source 311 (a surface substantially orthogonal to the first optical path O1). That is, the inclination angle with respect to the first optical path O1. By adjusting the tilt angle θ, the peak wavelength of the laser light (first wavelength) that passes through the bandpass filter 312 is adjusted. The angle of the inclination angle θ is adjusted by using a rotary motion utilizing the lever principle of various rotary motors, actuators, or piezo elements. For example, with the approximate center point RC of the bandpass filter 312 as the center of rotation, As shown in FIG.

The reflection mirror 320 has a function of totally reflecting the reflected light IL reflected from the polarization beam splitter 313.
The reflection mirror 320 has a reflection film 320B on one surface of the glass substrate 320A, and an AR film 320C is provided on the other surface. The reflection mirror 320 is disposed at a position that is plane-symmetric with the polarization beam splitter 313 with respect to the first optical path O1, with the surface on which the reflection film 320B is provided facing the polarization beam splitter 313 side.

  Similar to the selective reflection film 313B provided on the polarization beam splitter 313, the reflection film 320B can be formed of a dielectric multilayer film. At this time, the dielectric multilayer film constituting the reflective film 320B may be a dielectric multilayer film different from the selective reflective film 313B, but may be the same dielectric multilayer film. Further, the reflective film 320B may be formed of a metal film such as aluminum, chromium, or silver.

  In general, the dielectric multilayer film is more excellent in heat resistance than the metal film. In addition, the dielectric multilayer film can improve the reflectivity for light of a specific wavelength by optimizing the thickness of each layer, the material of each layer, and the number of layers constituting the dielectric multilayer film. It is also suitable for efficiently reflecting light with a narrow band and high directivity. On the other hand, the metal film is more advantageous than the dielectric multilayer film in terms of cost.

  The reflecting mirror 320 is arranged with the surface provided with the reflecting film 320B on the polarizing beam splitter 313 side in consideration of the reflection efficiency, but the surface provided with the AR film 320C is arranged on the polarizing beam splitter 313 side. You may do it. The AR film 320C is not an essential component for achieving the function of the reflection mirror 320, and can be omitted.

  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 band pass filter 312.
In the bandpass filter 312, the bandpass 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 having the first wavelength reflected by the band pass filter 312 is emitted toward the light source 311.
The light having the first wavelength emitted toward the light source 311 returns to the light source 311, is reflected by the mirror layer 311 </ b> A, and is emitted from the light source 311 again. As described above, the light having the first wavelength reflected by the bandpass filter 312 reciprocates between the light source 311 and the bandpass filter 312, thereby resonating with light newly oscillated in the laser medium 311 </ b> B. Amplified.

On the other hand, the light having the first wavelength transmitted through the bandpass multilayer film 312B of the bandpass filter 312 is emitted toward the polarization beam splitter 313. Then, the light passes through the polarization beam splitter 313 and enters the wavelength conversion element 314.
In the wavelength conversion element 314, a part of the incident light having the first wavelength is converted into a half wavelength (second wavelength) and emitted toward the multilayer mirror 315.

  In the multilayer mirror 315, the light converted from the wavelength conversion element 314 to the second wavelength is transmitted through the dielectric multilayer 315 </ b> B and emitted toward the separation mirror 316. On the other hand, of the light emitted from the wavelength conversion element 314, light that has not been converted to the second wavelength (light having the first wavelength) is reflected by the dielectric multilayer film 315B and travels toward the light source 311.

  Then, the light having the second wavelength transmitted through the dielectric multilayer film 315B of the multilayer mirror 315 and emitted toward the separation mirror 316 is incident on the separation film 316B of the separation mirror 316. Of this, about 0.5% of the laser output is separated. The separated light is reflected toward the laser output measuring unit 317 as the branched light L3. The other light of the second wavelength passes through the separation film 316B of the separation mirror 316 and is emitted from the separation mirror 316 (laser light source device 31) as the first laser light LS1 (output light). The branched light L3 separated by the separation film 316B is used to adjust the tilt angle θ of the bandpass filter 312. The adjustment of the tilt angle θ will be described later.

On the other hand, the light having the first wavelength reflected by the dielectric multilayer film 315B of the multilayer mirror 315 and directed toward the light source 311 passes through the wavelength conversion element 314 again in the process toward the light source 311. When passing through the wavelength conversion element 314, some of the light is converted to the second wavelength.
Then, the light that has passed through the wavelength conversion element 314 enters the polarization beam splitter 313.

  In the polarization beam splitter 313, the light having the first wavelength among the light incident on the selective reflection film 313B is transmitted through the selective reflection film 313B. Then, the light having the first wavelength transmitted through the selective reflection film 313 </ b> B is emitted 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 newly oscillates in the laser medium 311B by reciprocating the first optical path O1 formed between the light source 311 and the dielectric multilayer film 315B of the multilayer mirror 315. Resonated with the light to be amplified. In other words, the laser light source device 31 includes a resonance structure formed between the mirror layer 311A of the light source 311 and the dielectric multilayer film 315B of the multilayer mirror 315.

On the other hand, the light reflected by the dielectric multilayer film 315B of the multilayer mirror 315 and converted to the second wavelength by the wavelength conversion element 314 in the process toward the light source 311 is selectively reflected by the selective reflection film 313B of the polarization beam splitter 313. Is reflected by. The reflected light IL reflected by the polarization beam splitter 313 travels toward the reflection mirror 320.
Then, the reflected light IL enters the reflecting mirror 320 and is reflected by the reflecting film 320B in a direction substantially parallel to the traveling direction of the first laser light LS1. Further, the light reflected by the reflective film 320B is emitted from the laser light source device 31 as the second laser light LS2 (output light).

  That is, the polarization beam splitter 313 and the reflection mirror 320 reflect the light reflected by the dielectric multilayer film 315B of the multilayer mirror 315 and converted into the second wavelength in the process toward the light source 311 with the first optical path O1. Has a function of taking out to a different second optical path O2. The polarization beam splitter 313 and the reflection mirror 320 constitute a folding means.

  In FIG. 1, L1 is emitted from the light source 311, converted into light of the second wavelength by the wavelength conversion element 314, transmitted through the multilayer mirror 315, and emitted from the separation mirror 316 as the first laser light LS <b> 1. Shows the light to be. The first optical path O <b> 1 is emitted from the light source 311, emitted without being converted to the second wavelength by the wavelength conversion element 314, reflected by the dielectric multilayer 315 </ b> B of the multilayer mirror 315, and directed toward the light source 311. In FIG. 4, light that is not converted to the second wavelength but passes through the polarization beam splitter 313 and the bandpass multilayer film 312B and returns to the light source 311 is shown, and it is considered that the first optical path O1 is formed by such light. be able to.

Further, L2 is emitted from the light source 311, emitted without being converted to the second wavelength by the wavelength conversion element 314, reflected by the dielectric multilayer film 315 </ b> B of the multilayer mirror 315, and in the process toward the light source 311. The light converted into the second wavelength by the wavelength conversion element 314 and incident on the polarization beam splitter 313 is shown.
Further, in FIG. 1, L1, O1, and L2 are shown at different positions, but these are only shown at different positions for convenience of explanation, and originally exist at the same position. The same applies to schematic diagrams showing a schematic configuration of a laser light source device described in the following embodiments.

Next, adjustment of the tilt angle θ of the bandpass filter 312 will be described.
In general, laser 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. Also in the wavelength conversion element 314, the wavelength of the laser light subjected to wavelength conversion changes by about 0.1 nm / ° C. with respect to temperature variation.
The angle adjustment by the displacement of the inclination angle θ of the bandpass filter 312 is performed for the purpose of obtaining stable laser light in response to such temperature fluctuations.

The adjustment of the tilt angle θ of the bandpass filter 312 is performed based on the branched light L3 that is separated by the separation film 316B of the separation mirror 316 and incident on the laser output measurement unit 317.
In the laser output measuring unit 317, the split light L3 is received by the light receiving sensor and converted into an electric signal, and a measurement value of the laser light output is obtained in the measurement circuit based on the electric signal.

The output signal of the laser output measurement value obtained by the laser output measurement unit 317 is sent to the control unit 318.
The control unit 318 executes a control program based on the laser output stored in the ROM and the wavelength shift characteristic depending on the tilt angle θ, and the tilt corresponding to the output signal of the laser output measurement value obtained by the laser output measurement unit 317. A control signal for shifting the angle θ is output to the rotation mechanism 319.

In the rotation mechanism 319, the actuator operates based on the control signal input from the control unit 318, and the angle at which the bandpass filter 312 rotates by a predetermined amount about the center point RC as a rotation center and is displaced to a predetermined inclination angle θ. Adjustments are made.
Note that the measurement time interval of the laser output measurement unit 317 and the operating frequency of the rotation mechanism 319 are appropriately determined in consideration of the use environment and the like.

FIG. 5 is a graph showing the shift characteristic of the transmission wavelength 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 (%). FIG. 5 shows a case where the set wavelength of light emitted from the light source 311 is 1064 nm.
A curve a shown in FIG. 5 is a transmittance curve when the bandpass filter 312 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. 5, as the tilt angle θ of the bandpass filter 312 increases from 0 ° toward 5 °, the peak wavelength of light transmitted through the bandpass filter 312 shifts (shifts) in a direction that decreases (increases the frequency). To do.
The adjustment of the inclination angle θ of the bandpass filter 312 may be in the direction of either the right inclination or the left inclination with respect to the light exit surface of the light source 311.

  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 314 will be described with reference to FIG. In FIG. 1, W1 indicates a width in a direction parallel to a line (not shown) orthogonal to the first laser light LS1 and the second laser light LS2 of the wavelength conversion element 314. 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 light emitted from the light source 311 due to temperature variation or the like by the band pass filter 312 performing angle adjustment for displacing the inclination angle θ with respect to the first optical path O1 based on the output signal of the laser output measuring unit 317. Even when the wavelength changes, the wavelength can be adjusted to the conversion wavelength of the wavelength conversion element 314. That is, it is possible to obtain the laser light source device 31 that efficiently suppresses the power drop of the output light, has high light utilization efficiency, and has a stable output.

  (2) Since the wavelength conversion element 314 is provided inside the resonance structure formed between the light source 311 and the dielectric multilayer film 315B of the multilayer mirror 315, the wavelength conversion element 314 converts the wavelength to the second wavelength. The light that has not been reflected is reflected by the dielectric multilayer 315B of the multilayer mirror 315 and converted to the second wavelength in the process toward the light source 311 is turned back (the polarization beam splitter 313 and the reflection mirror 320). By taking out to the second optical path O2 and using it as the second laser light LS2, it is possible to efficiently suppress the power reduction of the output light and increase the light use efficiency.

  (3) The multilayer mirror 315 has a characteristic of reflecting 80% or more of the light of the first wavelength and transmitting 80% or more of the light of the second wavelength, so that the oscillation light of the light source 311 enters the resonance structure. While confined, the light of the second wavelength converted by the wavelength conversion element 314 can be efficiently extracted.

  (4) The bandpass multilayer film 312B provided in the bandpass filter 312 is formed by alternately laminating the high refractive index layers H and the low refractive index layers L as described above, so that the vicinity of the first wavelength. Thus, the first-wavelength light emitted from the light source 311 can be narrowed. Therefore, the conversion efficiency of wavelength conversion in the wavelength conversion element 314 can be improved.

  (5) Since the wavelength conversion element 314 is a quasi-phase matching type wavelength conversion element and has higher conversion efficiency than other types of wavelength conversion elements, the effects (1) to (3) can be further enhanced. It is.

[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 arrangement position of the bandpass filter 312, and is otherwise the same as the first embodiment. 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 and the adjustment of the inclination angle θ of the bandpass filter 312 are the same, and the detailed description thereof is omitted or simplified.

  In FIG. 6, a laser light source device 41 includes a light source 311, a band pass filter 312, a polarizing beam splitter 313, a wavelength conversion element 314, a multilayer mirror 315 as a mirror, a separation mirror 316, a laser output measurement unit 317, a control unit 318, A rotation mechanism 319 and a reflection mirror 320 are provided. Among these, the polarization beam splitter 313, the wavelength conversion element 314, the bandpass filter 312, the multilayer mirror 315, and the separation mirror 316 are on the first optical path O1 formed between the light source 311 and the multilayer mirror 315 and the first mirror. They are provided in this order from the light source 311 side in the direction along one optical path O1.

Next, a process until output light is obtained from the laser light source device 41 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 is emitted toward the polarization beam splitter 313. Then, the light passes through the polarization beam splitter 313 and enters the wavelength conversion element 314.
In the wavelength conversion element 314, the wavelength of a part of the incident first wavelength light is converted to a half wavelength (second wavelength) and emitted toward the band pass filter 312.

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

The light that has passed through the bandpass filter 312 is emitted toward the multilayer mirror 315 and enters the multilayer mirror 315.
In the multilayer mirror 315, the light having the second wavelength converted by the wavelength conversion element 314 out of the light emitted from the bandpass filter 312 passes through the dielectric multilayer 315B and travels toward the separation mirror 316. It is injected. On the other hand, of the light emitted from the bandpass filter 312, the light that has not been converted to the second wavelength by the wavelength conversion element 314 (light having the first wavelength) is reflected by the dielectric multilayer film 315 </ b> B, and Head towards.

  The second wavelength light emitted from the multilayer mirror 315 toward the separation mirror 316 is 0.5% of the laser output of the incident second wavelength light in the separation film 316B of the separation mirror 316. A degree of light is separated. The separated light is reflected toward the laser output measuring unit 317 as the branched light L3, and the other light having the second wavelength passes through the separation mirror 316 and is separated as the first laser light LS1. It is emitted from (laser light source device 41).

  On the other hand, the light reflected by the dielectric multilayer film 315B of the multilayer mirror 315 and not converted to the second wavelength toward the light source 311 (first wavelength light) is transmitted through the bandpass filter 312. The light reflected by the bandpass multilayer film 312B of the bandpass filter 312 passes through the wavelength conversion element 314 again. When passing through the wavelength conversion element 314, a part of the light is converted into the second wavelength and emitted from the wavelength conversion element 314 toward the polarization beam splitter 313.

Of the incident light, the light having the first wavelength is incident on the polarization beam splitter 313 and passes through the selective reflection film 313B. Then, the light having the first wavelength transmitted through the selective reflection film 313 </ b> B is emitted toward the light source 311.
The subsequent process until the second laser light LS2 (output light) is obtained by the folding means (the polarization beam splitter 313 and the reflection mirror 320) and the bandpass filter 312 based on the branched light L3 separated by the separation mirror 316 The adjustment of the inclination angle θ is the same as that of the laser light source device 31 of the first embodiment.

  According to the laser light source device 41 of the second embodiment described above, the same effects as those of the first embodiment can be obtained.

[Third Embodiment]
FIG. 7 is a schematic diagram showing a schematic configuration of a laser light source apparatus according to the third embodiment.
The laser light source device 51 of the third embodiment is the same as that of the laser light source device 31 of the first embodiment, except that a dielectric multilayer film is provided on the emission side end face of the wavelength conversion element 414 instead of the multilayer mirror 315. This is the same as in 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 51 and the adjustment of the inclination angle θ of the bandpass filter 312 are the same, and detailed description thereof is omitted or simplified.

  In FIG. 7, the laser light source device 51 includes a light source 311, a band pass filter 312, a polarization beam splitter 313, a wavelength conversion element 414, a separation mirror 316, a laser output measurement unit 317, a control unit 318, a rotation mechanism 319, and a reflection mirror 320. I have. Among these, the band pass filter 312, the polarization beam splitter 313, the wavelength conversion element 414, and the separation mirror 316 are dielectric multilayer films 414C as mirror means provided on the light source 311 and the emission side end face of the wavelength conversion element 414 described later. Are provided in this order from the light source 311 side in the direction along the first optical path O1 formed between and the first optical path O1.

  The wavelength conversion element 414 has a quadrangular prism shape, the wavelength conversion unit 414A, the antireflection film 414B on the light source 311 side surface (incident side end surface) of the wavelength conversion unit 414A, and the separation mirror 316 side of the wavelength conversion unit 414A. A dielectric multilayer film 414C is provided on the surface (end surface of the emission side). The film configuration of the dielectric multilayer film 414C is the same as that of the dielectric multilayer film 315B provided on the multilayer film mirror 315 in the first embodiment and the second embodiment.

Next, a process until output light is obtained from the laser light source device 51 will be described with reference to FIG.
The light having the first wavelength emitted from the light source 311 is incident on the bandpass filter 312, and laser light having a wavelength width of about 0.5 nm among the light having the first wavelength is emitted from the bandpass multilayer film 312 </ b> B. While being transmitted, the laser beam having other wavelength width is reflected. That is, the band of the incident first wavelength light is narrowed.

The light having the first wavelength reflected by the bandpass filter 312 is emitted toward the light source 311, returns to the light source 311, is reflected by the mirror layer 311 </ b> A (see FIG. 2), and is emitted from the light source 311 again.
On the other hand, the light having the first wavelength transmitted through the bandpass multilayer film 312B of the bandpass filter 312 is emitted toward the polarization beam splitter 313. Then, the light passes through the polarization beam splitter 313 and enters the wavelength conversion element 414.

  In the wavelength conversion element 414, the wavelength of a part of the first wavelength light incident on the wavelength conversion unit 414A is converted to a half wavelength (second wavelength). The laser light converted to the second wavelength passes through the dielectric multilayer film 414C, is emitted toward the separation mirror 316, and is not converted to the second wavelength (light having the first wavelength). Is reflected by the dielectric multilayer film 414C and travels toward the light source 311.

  Then, the light converted to the second wavelength emitted toward the separation mirror 316 has a laser output of 0. 0 of the second wavelength light incident on the separation mirror 316 in the separation film 316B of the separation mirror 316. About 5% of light is separated. The separated light is reflected toward the laser output measuring unit 317 as the branched light L3. The other light of the second wavelength passes through the separation film 316B of the separation mirror 316 and is emitted from the separation mirror 316 (laser light source device 51) as the first laser light LS1.

  On the other hand, the light of the first wavelength reflected by the dielectric multilayer film 414C of the wavelength conversion element 414 and traveling toward the light source 311 passes through the wavelength conversion element 414 again in the process toward the light source 311. When passing through the wavelength conversion element 414, a part of the light is converted into the second wavelength. Then, the light that has passed through the wavelength conversion element 414 enters the polarization beam splitter 313.

In the polarization beam splitter 313, the light converted into the second wavelength of the incident light is reflected by the selective reflection film 313B toward the reflection mirror 320, and is not converted into the second wavelength (first light). 1 wavelength light) passes through the selective reflection film 313B and travels toward the band-pass filter 312.
Then, the reflected light IL reflected by the selective reflection film 313 </ b> B and directed toward the reflection mirror 320 is incident on the reflection mirror 320. In the reflection mirror 320, the reflection film 320B reflects the light in the direction substantially parallel to the traveling direction of the first laser light LS1. Further, the light reflected by the reflective film 320B is emitted from the laser light source device 51 as the second laser light LS2 (output light).

  On the other hand, light that has not been converted to the second wavelength (light having the first wavelength) that has passed through the selective reflection film 313 </ b> B of the polarization beam splitter 313 passes through the bandpass filter 312 and returns to 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 resonates between the light source 311 and the dielectric multilayer film 414C of the wavelength conversion element 414, thereby amplifying by resonating with the light newly oscillated in the laser medium 311B. Is done. That is, the laser light source device 51 includes a resonance structure formed between the mirror layer 311A of the light source 311 and the dielectric multilayer film 414C of the wavelength conversion element 414.

  The adjustment of the inclination angle θ of the bandpass filter 312 based on the branched light L3 separated by the separation mirror 316 is the same as that of the laser light source device 31 of the first embodiment.

According to the laser light source device 51 of the third embodiment, in addition to the effects (1) to (5) of the first embodiment, the following effects can be achieved.
By providing the dielectric multilayer film 414C on the end face on the emission side of the wavelength conversion element 414, it is possible to reduce the number of components and contribute to cost reduction and size reduction of the laser light source device.

[Modification of Embodiment]
The present invention is not limited to the first and 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.

Although the polarization beam splitter 313 has been described as being disposed on the first optical path O1 at an angle of approximately 45 ° with respect to the first optical path O1, it is not limited to 45 °. In that case, in response to the tilt angle of the polarization beam splitter 313, the reflection mirror 320 directs the reflected light IL reflected by the polarization beam splitter 313 in a direction substantially parallel to the traveling direction of the first laser light LS1. And may be arranged so as to reflect.
Similarly, although the separation mirror 316 has been described in the case where the separation mirror 316 is disposed with an inclination of approximately 45 ° with respect to the direction along the first optical path O1, it is not limited to 45 °.

  In addition to the surface emitting semiconductor laser, a so-called edge emitting semiconductor laser or a semiconductor excitation solid-state laser can be used as the light source 311. When an edge-emitting semiconductor laser is used, it is preferable to provide a lens for collimating the light emitted from the light source 311 between the light source 311 and the wavelength conversion elements 314 and 414.

  Furthermore, the light source 311 can include a plurality of light emitting units arranged in an array. FIG. 8A and FIG. 8B are schematic views each showing a light source in which light emitting units are arrayed. In the light source 321 in FIG. 8A, a plurality of light emitting portions 322 are arranged in a line. In addition, in the light source 323 of FIG. 8B, 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, and 51 described above, even if a light source in which the light emitting units are arrayed in this way is used, the bandpass filter 312, the polarization beam splitter 313, the wavelength conversion elements 314 and 414, and the multilayer mirror 315 are used. It is only necessary to expand the area of the light incident surface and the exit surface of the separation mirror 316 and the reflection mirror 320 to an area corresponding to the array.

  As described above, in the laser light source devices 31, 41, and 51 described above, even if the light sources 311 are arrayed, the device is not excessively large and can be handled with a simple configuration. Therefore, in the laser light source devices 31, 41, and 51 described above, even if the light source 311 is arrayed, a reduction in power of output light is efficiently suppressed, and a laser light source device with high light utilization efficiency and stable output is obtained. Thus, 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 can be achieved.

Furthermore, LN (LiNbO ₃ ) and LT (LiTaO ₃ ) have been exemplified as the nonlinear optical material constituting the wavelength conversion elements 314 and 414, but other than this, KNbO ₃ and BNN (Ba ₂ NaNb ₅ ) are also exemplified. 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.

  Further, as the wavelength conversion elements 314 and 414, 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 as described above to an image display device or the like, it is possible to improve the light use efficiency in these devices. An application example to an image display device will be described below.

  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. 9 is a schematic diagram showing an outline of the optical system of the projector 3.

  In FIG. 9, 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 and an emitting-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. 9, the red light source device 31 </ b> R and the blue light source device 31 </ b> B face each other across the cross dichroic prism 34, and the projection lens 35 and the green light source device 31 </ b> G face each other. 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. The color light emitted from the laser light source device 31 enters 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. Further, by passing through such an optical element, there is a possibility that some disturbance occurs in the 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.

  Since the projector 3 configured as described above uses the laser light source device 31, a projector with improved light utilization efficiency can be obtained.

In this application example, the laser light source device 31 (31R, 31G, 31B) according to the first embodiment is used, but some or all of these are used as the laser light source device 41 according to the other embodiments. It may be replaced with 51.
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, and 51 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, and 51 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 of the embodiment can be applied 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 that magnifies and projects an image is introduced, but the first to third embodiments are introduced. The laser light source devices 31, 41, and 51 can be applied to an image display device that does not use the projection lens 35.

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. The graph which shows an example of the spectral transmittance characteristic of a band pass multilayer film. Sectional drawing which shows the structure of a wavelength conversion element typically. 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 schematic structure of the laser light source apparatus which concerns on 2nd Embodiment. The schematic diagram which shows schematic structure of the laser light source apparatus which concerns on 3rd Embodiment. 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.

Explanation of symbols

  3 ... projector as an image display device, 31, 41, 51 ... laser light source device, 31B ... light source device for blue light, 31G ... light source device for green light, 31R ... light source device for red light, 32 ... liquid crystal panel, 33 ... Liquid crystal light valve, 34: Cross dichroic prism, 35: Projection lens, 311, 321, 323 ... Light source, 322 ... Light emitting unit, 311A ... Mirror layer, 311B ... Laser medium, 312 ... Bandpass filter, 312B ... Bandpass multilayer film 313 ... Polarizing beam splitter, 313B ... Selective reflecting film, 314, 414 ... Wavelength conversion element, 314A, 414A ... Wavelength conversion section, 315 ... Multilayer film mirror, 314B, 414C ... Dielectric multilayer film, 316 ... Separation mirror, 316B ... Separation membrane, 317 ... Laser output measuring unit, 318 ... Control unit, 319 ... Rotating mechanism, 320 Reflection mirror, 320B ... reflective film, 400 ... substrate.

Claims (11)

A light source that emits light of a first wavelength;
Mirror means for selectively reflecting the light of the first wavelength toward the light source;
On the first optical path formed between the light source and the mirror means,
A wavelength conversion element for converting the wavelength of a part of the incident first wavelength light into a second wavelength different from the first wavelength;
A bandpass filter in which a bandpass filter multilayer film having a bandpass characteristic in the vicinity of the first wavelength is formed;
A folding means for extracting the light reflected by the mirror means and converted into the second wavelength in the process toward the light source into a second optical path different from the first optical path;
With
A laser light source device that uses the first laser light having the second wavelength emitted from the mirror means and the second laser light having the second wavelength emitted from the folding means as output light. And
A separation mirror for separating a part of the light of the second wavelength emitted from the mirror means;
A laser output measurement unit that measures the output of the light of the second wavelength separated by the separation mirror;
The mirror means comprises a multilayer mirror provided with 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,
The laser light source apparatus according to claim 1, wherein the band-pass filter is subjected to angle adjustment such that an inclination angle with respect to the first optical path is displaced based on an output signal of the laser output measuring unit. A light source that emits light of a first wavelength;
Mirror means for selectively reflecting the light of the first wavelength toward the light source;
On the first optical path formed between the light source and the mirror means,
A wavelength conversion element that converts the wavelength of some of the incident first wavelength light to a second wavelength different from the first wavelength;
A bandpass filter in which a bandpass filter multilayer film having a bandpass characteristic in the vicinity of the first wavelength is formed;
A folding means for extracting the light reflected by the mirror means and converted into the second wavelength in the process toward the light source into a second optical path different from the first optical path;
With
A laser light source device that uses the first laser light having the second wavelength emitted from the mirror means and the second laser light having the second wavelength emitted from the folding means as output light. And
A separation mirror for separating a part of the light of the second wavelength emitted from the mirror means;
A laser output measurement unit that measures the output of the light of the second wavelength separated by the separation mirror;
The mirror means is a dielectric having 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 provided on an end face on the emission side of the wavelength conversion element. It consists of a multilayer film,
The laser light source apparatus according to claim 1, wherein the band-pass filter is adjusted so that an inclination angle with respect to the first optical path is displaced based on an output signal of the laser output measuring unit. The laser light source device according to claim 1,
The multilayer mirror is disposed between the wavelength conversion element and the separation mirror;
The laser light source device, wherein the band pass filter is disposed between the light source and the folding means. The laser light source device according to claim 1,
The laser light source device, wherein the band pass filter and the multilayer mirror are arranged in order from the wavelength conversion element side between the wavelength conversion element and the separation mirror. In the laser light source device according to any one of claims 1 to 4,
The bandpass 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 λ. The optical film thicknesses are 0.236λH, 0.355λL, 0.207λH, 0.203λL, (0.25λH, 0.25λL) n, 0.5λH, (0.25λL, 0) in this order from the light exit side. .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. In the laser light source device according to any one of claims 1 to 5,
The folding means is
A polarizing beam splitter provided with a selective reflection film that transmits light of the first wavelength and reflects light of the second wavelength;
A reflection mirror provided with a reflection film that totally reflects the light of the second wavelength incident from the polarization beam splitter in a direction substantially the same as the traveling direction of the first laser beam;
A laser light source device comprising: In the laser light source device according to any one of claims 1 to 6,
The first laser light having the second wavelength emitted from the mirror means and the second laser light having the second wavelength emitted from the folding means are substantially parallel to each other. Laser light source device. In the laser light source device according to any one of claims 1 to 7,
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 8,
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 9,
The laser light source device, wherein the wavelength conversion element is a quasi phase matching type wavelength conversion element. The laser light source device according to any one of claims 1 to 10,
A light modulation element that modulates laser light emitted from the laser light source device according to image information;
An image display device comprising:

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