JP2005109036A - Optical fiber laser device and image display device - Google Patents

Abstract

To obtain laser beams having a plurality of wavelengths, it is necessary to use a plurality of optical fiber lasers, and a plurality of optical fibers and pumping light sources are required. It is an object of the present invention to provide an optical fiber laser device that can generate laser light having a plurality of wavelengths from one optical fiber laser.
In an optical fiber laser device that performs laser oscillation by adding a laser active substance into a core of an optical fiber and absorbing the pumping light into the laser active substance, the optical fiber is composed of an inner clad and an outer clad. A plurality of cores are embedded in the cladding, and excitation light from the excitation light source is incident on the optical fiber. In addition, mirrors are installed on both end faces of a plurality of cores, and the mirrors installed on at least one end face of each core have different characteristics between the cores, and perform laser oscillation with different wavelengths for each core, A plurality of laser beams can be emitted.
[Selection] Figure 1

Description

  The present invention relates to an optical fiber laser device, and more particularly to an optical fiber laser device in the case where laser beams having a plurality of wavelengths are necessary for configuring a system. The present invention also relates to an image display device using an optical fiber laser device.

  Conventionally, as an example of generating a laser beam having a specific wavelength, for example, in Patent Document 1, infrared light of 850 nm is incident as an excitation light on an optical fiber doped with rare earth Pr3 + and Yb3 +, and blue, green, orange, red An example of obtaining laser light is shown.

  Such an optical fiber laser device is configured as shown in FIG. In FIG. 9, 1 is a semiconductor laser used as an excitation light source, 2 is a lens for entering light emitted from the semiconductor laser 1, 3 is an optical fiber doped with rare earth Pr3 + and Yb3 +, and 4 and 5 are specific It is a mirror that reflects light of a wavelength. FIG. 10 is a perspective view showing a main part of the optical fiber 3, and a part thereof is shown in cross section, 6 is a core, and the rare earth is added. Reference numeral 7 denotes an outer cladding.

  In such a configuration, the mirror 4 is designed to transmit, for example, a wavelength of 850 nm from a semiconductor laser and totally reflect all visible light (blue: 490 nm to red: 635 nm), and the mirror 5 has a red wavelength of only 635 nm. Are partially reflected and partially transmitted, and all other wavelengths are transmitted. Thereby, since the red wavelength 635 nm resonates between the mirror 4 and the mirror 5, laser light having a red wavelength of 635 nm can be obtained from the mirror 5. If the mirror 5 is designed to partially reflect and partially transmit only the green wavelength 520 nm and transmit all other wavelengths, a laser beam having a green wavelength of 520 nm can be obtained. Thus, by changing the characteristics of the mirrors 4 and 5, laser beams having various wavelengths can be obtained.

However, when it is desired to obtain laser beams having a plurality of wavelengths at the same time, it is difficult to obtain laser beams having a plurality of wavelengths from one optical fiber, and there is a disadvantage that a plurality of optical fiber lasers are required. It was. Although a multi-core optical fiber including a plurality of cores in a clad is shown in Patent Document 2, this example does not obtain laser light having a plurality of wavelengths.
US Pat. No. 5,805,631 (Fig.1, Fig.7) JP-A-11-95049 (FIG. 1)

  As described above, when it is desired to obtain laser beams having a plurality of wavelengths, it has conventionally been necessary to use a plurality of optical fiber lasers. In this case, a plurality of optical fibers and a plurality of pumping light sources are required, which complicates the system configuration and increases the cost. It is an object of the present invention to provide an optical fiber laser device capable of generating laser light having a plurality of wavelengths from a single optical fiber laser and to provide an image display device using the optical fiber laser device. .

The present invention according to claim 1 is an optical fiber laser device that performs laser oscillation by adding a laser active material into the core of an optical fiber and absorbing the laser light into the laser active material.
An excitation light source, an inner cladding and an outer cladding, and a plurality of cores are embedded in the inner cladding, and an optical fiber in which excitation light from the excitation light source is incident on the inner cladding, and both end faces of the plurality of cores The mirrors installed on at least one end face of each core have different characteristics among the cores, emit laser beams having different wavelengths for each core, and emit a plurality of laser beams. This is an optical fiber laser device.

According to a sixth aspect of the present invention, there is provided an optical fiber laser device that performs laser oscillation by adding a laser active substance into a core of an optical fiber and absorbing the pumping light into the laser active substance.
A first optical fiber having a pumping light source, an inner cladding and an outer cladding, wherein a plurality of cores are embedded in the inner cladding, and pumping light from the pumping light source is incident on the inner cladding; and both ends of the plurality of cores Each of the cores includes a mirror disposed on the surface, and the characteristics of the mirrors disposed on at least one end surface of each of the cores are made different between the cores, and laser beams having different wavelengths are emitted from the respective cores to emit a plurality of laser beams. A first optical fiber laser that
A core is embedded in the clad, and a second optical fiber in which an arbitrary laser beam emitted from the first optical fiber laser is incident as excitation light is installed on both end faces of the core in the second optical fiber. And a second optical fiber laser that emits laser light by performing laser oscillation of a predetermined wavelength between the mirrors.

  The present invention according to claim 10 is an image display device that displays light emitted from a light source by entering the light from the light source, and projecting the light emitted from the space modulator. The optical fiber laser device according to claim 1 or 6 is used.

  Thereby, in this invention, the laser beam of a several wavelength can be obtained from one optical fiber laser.

  According to the optical fiber laser device of the present invention, it is possible to obtain laser light having a plurality of wavelengths with a single optical fiber, and in particular, with three wavelengths of red, green, and blue as in a projection type image display device. In the case where a laser beam is required, there is an advantage that the system configuration can be greatly simplified, and the cost can be reduced and the size can be reduced.

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

  1 to 4 show a first embodiment of the present invention, and FIG. 1 shows an overall configuration of an optical fiber laser device 10. FIG. In FIG. 1, 11 is a semiconductor laser used as an excitation light source, and the output wavelength is in the range of 830 to 850 nm, for example, 840 nm. A lens 12 condenses light from the semiconductor laser 11 and enters the optical fiber 13. Reference numerals 14, 15, 16, and 17 denote mirrors disposed on the incident side end face and the emission side end face of the optical fiber 13.

  FIG. 2 is a perspective view showing a main part of the optical fiber 13 and a part thereof is shown in cross section. The optical fiber 13 has a double clad structure as shown in FIG. 23, an inner cladding 24 and an outer cladding 25. The inner clad 24 has a rectangular shape so as to uniformly absorb the excitation light, and the cores 21 to 23 are embedded in the inner clad 24, and Pr3 + and Yb3 + are added as rare earth elements.

FIG. 3 shows the end face structure of the optical fiber 13 on the excitation light incident side, and the mirror 14 is the inner cladding 2.
4 is installed so as to cover the entire end face. The mirror 14 is designed to transmit a wavelength of 840 nm from the excitation light source (semiconductor laser 11) and reflect other wavelengths.

  FIG. 4 shows an end face structure on the exit side of the optical fiber 13, and the mirrors 15, 16 and 17 are installed so as to cover the end faces of the cores 21, 22 and 23, respectively. For example, when the core 21 outputs 635 nm laser light, the core 22 outputs 520 nm laser light, and the core 23 outputs 490 nm laser light, the mirror 15 partially reflects and reflects only 635 nm. The mirror 16 is partially transmitted and the other wavelengths are transmitted. The mirror 16 is partially reflected and partially transmitted only at 520 nm, and the other wavelengths are transmitted. The mirror 17 is partially reflected and transmitted only at 490 nm. What is necessary is just to design so that one part permeate | transmits and other wavelengths may permeate | transmit.

As a method of forming the mirror in FIG. 4, for example, vapor deposition or sputtering is used, masks other than the target core are masked, and a mirror is sequentially formed for each core.
Next, the operation of the optical fiber laser device 10 of FIG. 1 will be described. Light emitted from the semiconductor laser 11 enters the inner cladding 24 of the optical fiber 13 through the lens 12 as excitation light. As the excitation light incident on the inner cladding 24 propagates through the inner cladding 24, it generates light of other wavelengths instead of being absorbed by the rare earth added to the cores 21, 22, and 23. Here, light having a plurality of wavelengths is generated, but light having a wavelength according to the characteristics of the mirrors 15, 16, and 17 installed in each of the cores 21, 22, and 23 is selected to form a resonator. Laser light having a green wavelength of 635 nm, a core wavelength of 520 nm, and a core of 23 having a blue wavelength of 490 nm is obtained, and each laser beam is emitted from the end face side in FIG.

  By such an operation, a plurality of laser beams can be emitted by performing laser oscillation with different wavelengths for each of the cores 21, 22, and 23, and laser beams with a plurality of wavelengths can be obtained from one optical fiber laser. it can. The laser light of each wavelength obtained in this way can be used as, for example, red, green, and blue light sources of a projection display apparatus.

  Next, a second embodiment of the present invention will be described. The second embodiment controls and outputs the output ratio of a plurality of laser beams, and is different from the first embodiment in the configuration of the optical fiber 13. FIG. 5 is a front view showing the incident side end face of the optical fiber 13 in the second embodiment, and the mirror 14 is not shown. Characteristically, the cross-sectional area ratios of the cores 21, 22, and 23 are different. In the example of FIG. 2, the cross-sectional area of the core 21 is the largest, and the cross-sectional area of the core 22 is the smallest. That is, the larger the cross-sectional area, the larger the amount of absorption of the excitation light. Therefore, if the other conditions are constant, the laser beam output is higher than when the larger cross-sectional area is smaller.

  For example, when it is desired to increase the output of the laser light from the core 21 and reduce the output of the laser light from the core 22 as compared with the case where the cross-sectional areas of the cores 21, 22 and 23 are constant, What is necessary is just to enlarge a cross-sectional area and to make the cross-sectional area of the core 22 small. However, since the output of the laser beam is not determined only by the cross-sectional area, but also varies depending on the light density of the excitation light, the reflectance of the mirror, and the wavelength of the laser beam, it is necessary to comprehensively consider the above conditions. By doing so, for example, the output of the red laser light can be increased, the output of the green laser light can be lowered, and the output of the blue laser light can be set to its intermediate intensity.

6 (a) and 6 (b) show a third embodiment of the present invention. In FIG. 6, the same parts as those in FIG. In the first and second embodiments, the case of generating laser light of 635 nm, 520 nm, and 490 nm has been described. When light of these wavelengths is used as a light source for a display as three primary colors of red, green, and blue, respectively, Since the wavelength of 490 nm blue laser light is too long, the color reproduction range becomes narrow. A shorter wavelength is suitable for use as blue laser light. So there
The third embodiment provides a configuration for generating 455 nm blue laser light.

  The optical fiber laser device shown in FIG. 6 includes a first optical fiber laser 30, a second optical fiber laser 40, a lens 50, and a mirror 60. The first optical fiber laser 30 is substantially the same as the optical fiber laser 10 of FIG. 1, but in this embodiment, as shown in FIG. 6B, a mirror 31 provided on the exit side end face of the core 23 is provided. This is a mirror for a wavelength of 695 nm. That is, the mirror 31 is designed so that only a wavelength of 695 nm is partially reflected and partially transmitted, and other wavelengths are transmitted. Thereby, 635 nm, 520 nm, and 695 nm laser light can be obtained from the emission side end face of the optical fiber laser 30.

  Thus, the laser light emitted from the first optical fiber 30 is collimated by the lens 50 and hits the mirror 60. The mirror 60 has a dichroic mirror structure and is designed to partially reflect and partially transmit a wavelength of 635 nm, transmit a wavelength of 520 nm, and reflect a wavelength of 695 nm. The laser beams having wavelengths of 635 nm and 520 nm transmitted through the mirror 60 are output to the outside as they are.

  On the other hand, light having wavelengths of 635 nm and 695 nm reflected by the mirror 60 is collected by the lens 70 and incident on the optical fiber laser 40 in order to be used as excitation light for the second optical fiber laser 40. The optical fiber laser 40 has a single clad optical fiber 43 in which Tm3 + is added to a core 42 embedded in a clad 41, and mirrors 44 and 45 are disposed on both end faces thereof. The mirror 44 is designed to transmit excitation light having wavelengths of 635 nm and 695 nm and reflect other wavelengths. The mirror 45 is designed to partially reflect and partially transmit the wavelength 455 nm and transmit other wavelengths. With this configuration, the excitation light 635 nm and 695 nm are converted into laser light having a wavelength of 455 nm in the core 42 and output from the end surface opposite to the excitation light input side. As a result, in the embodiment shown in FIG. 6, light having three wavelengths of red: 635 nm, green: 520 nm, and blue: 455 nm can be obtained.

  FIG. 7 shows a fourth embodiment of the present invention. In FIG. 7, the same parts as those of FIG. The fourth embodiment is different from the third embodiment in that an incident optical system of laser beams having wavelengths of 635 nm and 695 nm to the second optical fiber laser 40 is improved.

  In the previous third embodiment, when the laser light of 635 nm and 695 nm is condensed using the lens 70, the imaging pattern is divided into two. Therefore, it is necessary to enlarge the core 42 of the optical fiber 43 for efficient incidence, but the efficiency of conversion to 455 nm laser light is reduced due to the decrease in the light density of the excitation light. Therefore, in the fourth embodiment, wavelength multiplexing is used to combine the imaging patterns of wavelengths 635 nm and 695 nm into one, the core 42 of the optical fiber 43 is made smaller, the light density of the excitation light is increased, and the conversion efficiency to 455 nm is increased. It is an improvement.

  That is, the embodiment of FIG. 7 is characterized in that four mirrors 61, 62, 63, 64 are used in the incident optical system of the second optical fiber laser 40. The mirrors 61, 62, and 64 have a dichroic mirror structure. The operation is the same as that of the third embodiment until laser light having wavelengths of 635 nm, 520 nm, and 695 nm is generated in the first optical fiber laser 30. The laser beam is collimated by the lens 50 and then applied to the mirror 61. The mirror 61 is designed to reflect only the wavelength 695 nm and transmit the wavelengths 635 nm and 520 nm. The 635 nm and 520 nm laser beams transmitted through the mirror 61 strike the mirror 62. The mirror 62 is designed to reflect a part of the wavelength of 635 nm, transmit a part thereof, and transmit the wavelength of 520 nm. The laser beams having wavelengths of 635 nm and 520 nm that have passed through the mirror 62 are output to the outside as they are.

On the other hand, the wavelength 695 nm reflected by the mirror 61 is reflected by the mirror 63 and hits the mirror 64. The laser beam having a wavelength of 635 nm reflected by the mirror 62 also hits the mirror 64. The mirror 64 is designed to reflect the wavelength 695 nm from the mirror 63 and transmit the wavelength 635 nm from the mirror 62. As a result, the wavelengths 635 nm and 693 nm are wavelength-multiplexed and then condensed by the lens 70. Thus, by adjusting the positions of the mirrors 61, 63, 64, the combined pattern condensed by the lens 70 can be unified. The laser beams with wavelengths of 635 nm and 695 nm incident on the second optical fiber laser 40 are processed in the same manner as in the third embodiment, and emit laser beams with a wavelength of 455 nm.

  In the first to fourth embodiments described above, a single-emitter semiconductor laser or a laser array may be used as the semiconductor laser 11 used as the excitation light source. In addition, the lens for coupling the semiconductor laser and the optical fiber laser may not be a single lens but may be composed of a plurality of lenses in order to increase the incident efficiency to the optical fiber laser. The cross-sectional shape of the inner clad need not be rectangular, but may be other than circular in order to achieve uniform absorption.

  FIG. 8 shows a fifth embodiment of the present invention. The fifth embodiment relates to a projection type image display apparatus using the optical fiber laser apparatus of the first to fourth embodiments.

  In FIG. 8, reference numeral 81 denotes a laser light source, which emits red, green, and blue laser light using the optical fiber laser devices shown in the first to fourth embodiments. A laser driving unit 82 drives an excitation light source (semiconductor laser) of the laser light source 81. Laser light from the laser light source 81 propagates through the optical fiber 83 and is supplied to a spatial modulation element (for example, liquid crystal). .

  Reference numeral 84 denotes a lens for collimating laser light, 85 denotes a color filter, 86 denotes a liquid crystal panel, 87 denotes a projection lens, 88 denotes a screen, 89 denotes a video input terminal, and 90 denotes a liquid crystal driving unit. Note that the following optical coupling means may be used for connection between the optical fiber laser used in the laser light source 81 and the optical fiber 83.

  That is, when connecting to the optical fiber lasers 10 of the first and second embodiments, an optical fiber 83 having a core with a cross-sectional area or larger covering the entire plurality of cores of the optical fiber 13 is used, and a bad joint is used. Just connect. Further, when connecting to the optical fiber lasers 30 and 40 of the third and fourth embodiments, 635 nm, 520 nm and 455 nm may be combined by wavelength multiplexing using an optical component and incident on the optical fiber 83. In any case, since the optical density in the optical fiber 83 does not need to be high, it is desirable to design the coupling loss to be small, for example, by making the core of the optical fiber 83 large.

  Next, the operation of the projection type video display apparatus of FIG. 8 will be described. Laser light output from the optical fiber 83 is collimated by the lens 84, separated into red, green, and blue via the color filter 85 and then incident on the liquid crystal panel 86. On the other hand, the video signal is input from the video input terminal 89, and the liquid crystal driver 90 drives the liquid crystal panel 86 according to the video signal. As a result, the light incident on the liquid crystal panel 86 is spatially modulated along the video signal. The spatially modulated light forms an image on the screen 88 via the projection lens 87.

  Note that a dichroic mirror and a microlens may be used instead of the color filter in order to improve the light use efficiency. When using a three-panel liquid crystal panel, the light from the optical fiber 83 is split into red, green, and blue light by a spectroscopic means using a dichroic mirror and is incident on the liquid crystal panel. Driven by the R, G, and B signals, the emitted light from each liquid crystal panel may be combined by a combining prism and projected onto the screen. As the liquid crystal panel, a transmission type or a reflection type can be used.

The block diagram which shows the optical fiber laser apparatus of this invention. (Example 1) The perspective view of the optical fiber used for the optical fiber laser apparatus of FIG. The front view which shows the excitation light incident side end surface of the optical fiber of FIG. The front view which shows the light emission side end surface of the optical fiber of FIG. Front view of an optical fiber used in the optical fiber laser apparatus of the present invention (Example 2) The block diagram which shows the optical fiber laser apparatus of this invention. Example 3 The block diagram which shows the optical fiber laser apparatus of this invention. (Example 4) FIG. 5 is a block diagram showing a projection type image display device of the present invention (Example 5). The block diagram which shows the conventional optical fiber laser apparatus. The perspective view of the optical fiber used for the optical fiber laser apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical fiber laser apparatus 11 Semiconductor laser 13 Optical fiber 14, 15, 16, 17 Mirror 21, 22, 23 Core 24 Inner clad 25 Outer clad 30 First optical fiber laser 31 Mirror 40 Second optical fiber laser 41 Cladding 42 Core 43 Optical fiber 44, 45 Mirror 60-64 Mirror 81 Laser light source 83 Optical fiber 85 Color filter 86 Liquid crystal panel 87 Projection lens 88 Screen 89 Video signal input terminal 90 Liquid crystal drive unit

Claims (10)

In an optical fiber laser device that performs laser oscillation by adding a laser active material into the core of an optical fiber and absorbing the excitation light into the laser active material,
An excitation light source;
An optical fiber having an inner cladding and an outer cladding, wherein a plurality of cores are embedded in the inner cladding, and excitation light from the excitation light source is incident on the inner cladding;
A mirror installed on each end face of the plurality of cores,
An optical fiber characterized in that a mirror installed on at least one end face of each core has different characteristics between the cores, and oscillates laser beams having different wavelengths for each core and emits a plurality of laser beams. Laser device. Of the mirrors installed on both end faces of the plurality of cores, the mirror installed on the incident-side end face of the excitation light has characteristics common to the cores, and is provided on the output-side end faces of the plurality of cores. The optical fiber laser device according to claim 1, wherein each core has different characteristics. 3. The optical fiber laser device according to claim 2, wherein the mirrors installed on the incident side end faces of the plurality of cores are constituted by a single mirror common to the cores. 2. The optical fiber laser device according to claim 1, wherein the cross-sectional areas of the plurality of cores are made different, and the intensity of the laser light between the cores is controlled to a predetermined ratio. The core is composed of three cores, laser active substances Pr3 + and Yb3 + are added into each core, the wavelength of the excitation light is set to 830 nm to 850 nm, and the wavelength of the laser beam obtained from each core is set to 635 nm and 520 nm, respectively. 2. The optical fiber laser device according to claim 1, wherein the optical fiber laser device is 490 nm. In an optical fiber laser device that performs laser oscillation by adding a laser active material into the core of an optical fiber and absorbing the excitation light into the laser active material,
An excitation light source;
A first optical fiber having an inner cladding and an outer cladding, wherein a plurality of cores are embedded in the inner cladding, and excitation light from the excitation light source is incident on the inner cladding; and both end faces of the plurality of cores, respectively A first mirror that emits a plurality of laser beams by performing laser oscillation of different wavelengths for each of the cores, and different characteristics of the mirrors installed on at least one end face of each of the cores. Fiber optic laser,
A core is embedded in the clad, and a second optical fiber in which an arbitrary laser beam emitted from the first optical fiber laser is incident as excitation light is installed on both end faces of the core in the second optical fiber. And a second optical fiber laser that emits laser light by performing laser oscillation at a predetermined wavelength between the mirrors. The core of the first optical fiber laser is composed of three cores, laser active substances Pr3 + and Yb3 + are added into each core, the wavelength of the excitation light is set to 830 nm to 850 nm, and the laser light obtained by each core The wavelengths are 635 nm, 695 nm, and 520 nm, respectively.
In the second optical fiber laser, Tm3 + is added into the core of the second optical fiber, and laser light having wavelengths of 635 nm and 695 nm obtained from the first optical fiber laser is used as excitation light. 7. The optical fiber laser device according to claim 6, wherein a laser beam of 455 nm is emitted. An incident optical system is provided, wherein the laser light having the wavelengths of 635 nm and 695 nm emitted from the first optical fiber laser is wavelength-multiplexed and incident as excitation light of the second optical fiber laser. Item 7. The optical fiber laser device according to Item 6. 9. The optical fiber laser device according to claim 8, wherein the incident optical system is configured by combining a mirror and a dichroic mirror. In the video display device that displays the light emitted from the light source by entering the spatial modulation element and projecting the emitted light from the spatial modulation element.
An image display device using the optical fiber laser device according to claim 1 or 6 as the light source.

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