JP2008028380A - Laser beam source equipment and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam source equipment and an image display device, which can generate a plurality of wavelengths by switching them, and have a W class high optical output and high reliability. <P>SOLUTION: A fiber laser 22 comprises a laser beam source 28 to emit exciting light, a fiber 26 to which the exciting light is emitted from the laser beam source 28, and first and second fiber gratings 29, 30 having a plurality of reflection peaks. The equipment comprises the fiber laser 22, a wavelength converter 23 which converts the basic wave emitted by the fiber laser 22 to higher harmonics, a reflected wavelength variable part 33 which can shift the reflected wavelength of the reflection peak of the second fiber grating 30, and a controller 34 which controls the oscillating wavelength of the fiber laser 22 by the reflected wavelength variable part 33, and controls the phase matching condition of the wavelength converter 32. The interval of adjacent reflection peaks of the first fiber grating 29 is different from the interval of adjacent reflection peaks of the second fiber grating 30. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser light source device that obtains stable and high-power laser light by combining a fiber laser and a wavelength conversion element, and an image display device using the same.

  A high-power visible light source with strong monochromaticity is required to realize a large display, a high brightness display, and the like. Of the three primary colors of red, green, and blue, red high-power semiconductor lasers used in DVD recorders and the like can be used as compact light sources with high productivity. However, a green or blue light source is difficult to realize with a semiconductor laser or the like, and a compact light source with high productivity is demanded.

  As such a light source, a wavelength conversion device combining a fiber laser and a wavelength conversion element has been realized as a low-power visible light source. Small green and blue light sources using a semiconductor laser as an excitation light source for exciting a fiber laser and using a nonlinear optical crystal as a wavelength conversion element are well known.

  In such a laser display using a high-power laser light source, the light from each of the RGB light sources is monochromatic light. Therefore, by using a laser light source of an appropriate wavelength, color purity is high and a vivid image can be displayed. It becomes possible. Furthermore, since such a laser light source can be downsized by using a laser, and can be easily condensed, the optical system can be downsized, and a palmtop type image display device can be realized. .

  On the other hand, the use of a laser with high coherency causes interference noise called speckle noise in the display image. For this reason, a speckle noise is reduced by using a prism and an optical path difference is provided for each polarization direction (Patent Document 1), or light irradiating the screen by oscillating an optical component and changing the beam path of the light source. The wavefront of the light is made random (Patent Document 2), sidebands are generated in the spectrum using an optical modulator, and the apparent light spectrum is made broader (Patent Document 3), or injection seeding into a solid-state laser A method of removing speckle noise by manipulating the oscillation wavelength using a technique (Patent Document 4) or using a semiconductor laser having a plurality of wavelengths as a module (Patent Document 5) has been proposed.

  On the other hand, a reflective element called a sampled grating which is a diffraction grating having a plurality of reflection wavelengths in order to realize a fiber laser using a Raman fiber (Patent Document 6) and a semiconductor laser capable of simultaneously oscillating multiple wavelengths. A semiconductor laser (Patent Document 7) using the above has been proposed. The configuration of the fiber laser disclosed in Patent Document 6 is shown in FIG. The laser includes a sampled grating 2001, a Raman fiber 2002, and a broadband dielectric mirror 2003. By exciting the Raman fiber 2002 with the excitation light 2004, light of λ1 is generated due to resonance between one reflection peak of the sampled grating 2001 and the broadband dielectric mirror 2003. Further, the generated light of λ1 is used as excitation light, and light of λ2 is generated by resonance between another reflection peak of the sampled grating 2001 and the broadband dielectric mirror 2003. In this way, λ3, λ4 are sequentially generated. Is generated, and finally, the light 2005 of λ4 is extracted.

  The configuration disclosed in Patent Document 7 is shown in FIG. The configuration in which the Raman fiber and the sampled grating shown in FIG. 26B are combined is intended to generate excitation light having a desired wavelength by Raman shift. A light emitting region 2007 and a reflective region 2008 are provided on a semiconductor substrate 2006. The reflective region 2008 has a sampled grating structure, and can oscillate a plurality of wavelengths simultaneously. The reflection area 2008 is provided with a control means (refractive index changing electrode) 2009 for changing the refractive index of the reflection area 2008, and has a structure capable of shifting the wavelength of the reflection area 2008.

  Patent Document 8 shows an example of a semiconductor laser array in which two reflection regions having a sampled grating structure are provided and the oscillation wavelength is switched. Patent Document 9 shows an example in which the configuration of Patent Document 8 is applied to a fiber laser.

On the other hand, the laser light source having a plurality of oscillation wavelengths described above has begun to be used in the medical field. In the medical field, laser beams having different wavelengths are required depending on the treatment, but the wavelengths of laser beams used particularly in ophthalmology are around 530 nm, around 600 nm, and around 1 μm. The vicinity of 530 nm is used for retinal coagulation of the eye, the vicinity of 600 nm is used for hemostasis of fundus hemorrhage, and the vicinity of 1 μm is used for cataract surgery. Currently, laser light sources used for such ophthalmic treatment are being developed, and in particular, there is a need for laser application equipment capable of obtaining multi-wavelength laser light so that a single laser light source can cope with many treatments. Is coming. Patent Document 10 discloses a laser device that enables multi-wavelength oscillation by shifting the oscillation wavelength by a long wavelength using a Raman fiber. In addition, lasers that realize multi-wavelength oscillation by utilizing a plurality of fluorescence peaks of a solid-state laser have been developed.
JP 2004-151133 A JP 2004-138669 A JP 9-121069 A Japanese Patent Laid-Open No. 10-294517 JP 2004-144794 A International Publication No. 01/54238 Pamphlet Japanese Patent No. 3689483 US Pat. No. 6,432,736 US Pat. No. 6,597,711 JP 2006-122081 A

  However, when using the above-described conventional technique in a method of reducing speckle noise by using a broadband light source or using a light source having a plurality of oscillation wavelengths, a plurality of laser light sources are required. There have been problems such as high costs and increased device dimensions. In addition, in the semiconductor laser and the fiber laser light source using the sampled grating, an output that can be used as a light source for laser display has not been obtained, and the oscillation wavelength is determined by controlling the two reflection regions, There has been a problem that the control method for simultaneously controlling the oscillation wavelength and the laser output becomes complicated. Further, there is a problem that the wavelength change due to the control of the reflection region is sensitive to the outside air temperature. Further, regarding the example of the fiber laser light source, in order to obtain a large variable range, it is necessary to apply a large stress to the fiber grating, and there is a possibility that the fiber may break, and there is a problem in the reliability of the fiber. Furthermore, there is a problem that when the wavelength is switched, the wavelength dependence of the gain of the laser medium triggers and the oscillation output changes.

  Furthermore, the above-described multi-wavelength laser device using the Raman fiber, which has begun to be used in the medical field, cannot simultaneously generate light of two wavelengths. Further, the gain of the Raman fiber laser is the largest at a wavelength of 1000 to 1100 nm. Therefore, when light of 1100 to 1200 nm necessary as the wavelength of orange light is generated, it has a broad emission spectrum of 1000 to 1100 nm. Light is also generated. For this reason, there was a problem of destruction of the laser oscillator by pulse oscillation. On the other hand, the above-described laser capable of multi-wavelength oscillation using a solid-state laser needs to switch an optical system for each oscillation wavelength, and there is a problem that it is difficult to instantaneously switch to a desired wavelength. Furthermore, since the characteristics of the laser beam differ greatly depending on the oscillation wavelength, there is a problem that the maximum output that can be obtained is not constant.

  In the configuration of the conventional medical laser light source device, the fundamental wave of the laser beam generated by the laser oscillator is converted into visible light by the wavelength conversion element, and then propagated to the surgical handpiece by a hollow fiber or the like. . However, due to the coupling loss of visible light from the laser oscillator to the hollow fiber and the propagation loss in the fiber, about 30% of the visible light is lost, causing the propagation efficiency to decrease. In addition, there is a problem that handling of the handpiece becomes difficult due to fiber handling.

  In view of the above problems, an object of the present invention is to provide a highly reliable laser light source device and an image display device that can generate light by switching a plurality of wavelengths and has a large W-class light output.

  In order to achieve the above object, a laser light source apparatus according to the present invention includes a laser light source that emits excitation light, a fiber that includes a laser active material, and into which excitation light from the laser light source is incident, and the laser of the fiber A laser resonator having a first fiber grating having a plurality of reflection peaks provided on the light source side, and a second fiber grating having a plurality of reflection peaks provided on the output end side of the fiber; A wavelength conversion unit that converts a fundamental wave emitted from the laser resonator into a harmonic, a reflection wavelength variable unit that can shift a reflection wavelength of a reflection peak of the second fiber grating, and the reflection wavelength variable unit A control unit for controlling an oscillation wavelength of the laser resonator and controlling a phase matching condition of the wavelength conversion unit, the first fiber gray Different from the spacing between adjacent reflection peak of the the spacing of the reflection peak second fiber grating adjacent Ingu to.

  In the above laser light source device, the first and second fiber gratings each have a plurality of reflection peaks, and the interval between the reflection peaks of the first fiber grating and the reflection peak of the second fiber grating is different. Thus, the oscillation wavelength of the laser resonator can be switched by shifting the reflection wavelength of the reflection peak of the second fiber grating.

  The grating length defining each of the reflectances of the plurality of reflection peaks of the second fiber grating prevents the decrease in oscillation efficiency of the fiber due to a decrease in the oscillation wavelength of the laser resonator. It is preferable that the wavelength is increased in order in the direction in which the oscillation wavelength decreases.

  In this case, the oscillation efficiency of the fiber can be maintained even if the oscillation wavelength of the laser resonator is decreased. In particular, when the light in the 1045 to 1070 nm band is oscillated, the decrease in the oscillation efficiency of the fiber accompanying the decrease in the oscillation wavelength of the laser resonator is significant. Therefore, in this case, the output of light in the 1045 to 1070 nm band can be improved.

  The bandwidth of the reflection peak of the first fiber grating is wider than the bandwidth of the reflection peak of the second fiber grating, and the reflectance of the reflection peak of the first fiber grating is the second fiber grating. It is preferable that the reflectance of the reflection peak is larger.

  In this case, since the bandwidth of the reflection peak of the first fiber grating is wider than the bandwidth of the reflection peak of the second fiber grating, the accuracy required for shift control of the reflectance of the reflection peak of the second fiber grating is required. Since the reflectance of the reflection peak of the first fiber grating is larger than the reflectance of the reflection peak of the second fiber grating, the fundamental wave can be efficiently emitted from the second fiber grating. Can do.

  The bandwidth of the reflection peak of the first fiber grating is preferably 0.5 to 2 nm, and the bandwidth of the reflection peak of the second fiber grating is preferably 0.2 nm or less.

  In this case, when shifting the reflectance of the reflection peak of the second fiber grating, the reflection peak of the second fiber grating can be surely matched with the reflection peak of the first fiber grating.

  The reflectance of the reflection peak of the first fiber grating is preferably 95% or more, and the reflectance of the reflection peak of the second fiber grating is preferably 5 to 20%.

  In this case, the laser beam can be emitted efficiently while preventing the excitation laser from being destroyed by the laser beam by the laser resonator.

  The control unit switches the oscillation wavelength of the laser resonator by shifting the reflection wavelength of the reflection peak of the second fiber grating by the reflection wavelength variable unit, and then converts the wavelength according to the switched oscillation wavelength. It is preferable to change the phase matching condition of the part.

  In this case, since the phase matching condition of the wavelength converter is changed in accordance with the switching of the oscillation wavelength of the fundamental wave emitted from the laser resonator, the fundamental wave can be efficiently wavelength-converted into a harmonic.

  The wavelength conversion unit holds a first wavelength conversion element composed of a nonlinear crystal using angular phase matching, the first wavelength conversion element, and an angular phase matching condition of the first wavelength conversion element. A first holding unit that sets an incident angle of a fundamental wave emitted from the laser resonator with respect to the first wavelength conversion element according to an oscillation wavelength of the laser resonator to be established, and the control unit Preferably, the phase matching condition of the wavelength conversion unit is controlled by the first holding unit.

  In this case, when the wavelength conversion element is formed of a nonlinear crystal using angular phase matching, the fundamental wave from the laser resonator can be wavelength-converted efficiently to a harmonic.

  The wavelength conversion unit further holds a second wavelength conversion element composed of a nonlinear crystal using angle phase matching, the second wavelength conversion element, and an angle phase matching condition of the second wavelength conversion element. A second holding unit that sets an incident angle of the fundamental wave emitted from the first wavelength conversion element with respect to the second wavelength conversion element according to the oscillation wavelength of the laser resonator so as to establish The second holding unit is disposed so as to suppress a change in the optical axis caused by the first holding unit, and the control unit is configured to control the wavelength converting unit by the first and second holding units. It is preferable to control the phase matching conditions.

  In this case, even when the wavelength conversion element is formed of a nonlinear crystal using angular phase matching, fluctuations in the optical axis that occur during wavelength conversion can be suppressed.

  The wavelength conversion unit includes a wavelength conversion element composed of a nonlinear crystal using temperature phase matching, holds the wavelength conversion element, and oscillates the laser resonator to satisfy the temperature phase matching condition of the wavelength conversion element. It is preferable that the control unit controls the phase matching condition of the wavelength conversion unit by the holding unit.

  In this case, when the wavelength conversion element is composed of a nonlinear crystal using temperature phase matching, the fundamental wave from the laser resonator can be wavelength-converted efficiently to a harmonic.

  The wavelength conversion unit is composed of a nonlinear crystal using quasi phase matching, holds a wavelength conversion element having a polarization inversion periodic structure, the wavelength conversion element, and establishes a quasi phase matching condition of the wavelength conversion element A holding unit that causes the fundamental wave emitted from the laser resonator to enter the polarization inversion period region of the wavelength conversion element according to the oscillation wavelength of the laser resonator, and the control unit is configured to It is preferable to control the phase matching condition of the wavelength converter.

  In this case, when the wavelength conversion element is composed of a nonlinear crystal using quasi phase matching, the fundamental wave from the laser resonator can be wavelength-converted efficiently into a harmonic.

  The period of the polarization inversion periodic structure of the wavelength conversion element changes in a direction perpendicular to the incident direction of the fundamental wave emitted from the laser resonator, and the holding unit depends on the oscillation wavelength of the laser resonator. It is preferable to have a moving stage that can move the wavelength conversion element in a direction in which the period of the domain-inverted periodic structure changes.

  In this case, since the period of the polarization inversion periodic structure of the wavelength conversion element can be set to an optimum length, the conversion efficiency from the fundamental wave to the harmonic can be increased.

  It is preferable that the period of the polarization inversion periodic structure of the wavelength conversion element changes along the incident direction of the fundamental wave emitted from the laser resonator.

  In this case, since the fundamental wave can be incident on the polarization inversion period region corresponding to the oscillation wavelength of the laser resonator without moving the wavelength conversion element, the wavelength conversion unit can be realized with a simple configuration. .

  It is preferable that the number of reflection peaks having an overlapping portion between the first fiber grating and the second fiber grating is two, and the range of each reflection wavelength of the two reflection peaks having the overlapping portion is: It is preferable that they are 1000-1090nm and 1100-1180nm.

  In this case, even when light in the wavelength band of 1100 to 1180 nm is generated, it is possible to prevent destruction of the laser resonator due to generation of ASE light by simultaneously generating light in the wavelength band of 1000 to 1090 nm. it can.

  An image display device according to the present invention is connected to the laser light source device and the control unit of the laser light source device, and outputs a selection signal for determining an oscillation wavelength of the laser light source device to the control unit. A luminance signal for determining a luminance of the video signal based on a luminance signal included in a video signal displayed by a circuit and a laser beam emitted from the laser light source device, and outputting the determined luminance to the wavelength determining circuit; Used by the image display device, a projector control circuit having a determination circuit, a video mode switching unit that instructs the wavelength determination circuit to oscillate the oscillation wavelength of the laser light source device input by a user of the image display device A power supply control circuit that determines the type and remaining amount of power to be output and outputs the determined type and remaining amount of power to the wavelength determination circuit.

  In the above image display device, the oscillation wavelength of the laser light emitted from the laser light source device can be switched according to the type of the video signal and the usage status of the power source. For this reason, it is possible to realize an image display device with high brightness, a wide color reproduction range, high image quality, and low power consumption.

  A microscope apparatus according to the present invention includes the laser light source apparatus described above and a microscope unit that enables observation of light emission of the fluorescent sample by excitation of the fluorescent sample by irradiation of laser light emitted from the laser light source apparatus.

  In the above microscope apparatus, since the oscillation wavelength of the laser light emitted from the laser light source apparatus can be switched in accordance with the fluorescent sample, a plurality of fluorescent samples can be excited well.

  A laser light source device according to the present invention includes a laser oscillation device that emits at least two fundamental waves, and converts at least two fundamental waves emitted from the laser oscillation device into harmonics, and the converted harmonics. An irradiable laser beam irradiation unit; and a fiber unit that is disposed between the laser oscillation device and the laser beam irradiation unit and that propagates a fundamental wave emitted from the laser oscillation device to the laser beam irradiation unit. The laser oscillation device includes: a laser light source that emits excitation light; a fiber that includes a laser active material; the excitation light from the laser light source is incident; and at least two provided on the laser light source side of the fiber. A first fiber grating and at least one corresponding to each of the first fiber gratings, provided at the output end side of the fiber; It has two second fiber grating and a laser resonator formed from.

  In the laser light source device described above, the laser oscillation device emits at least two fundamental waves, propagates these fundamental waves to the laser beam irradiation unit through the fiber unit, and the laser beam irradiation unit converts each wavelength of the fundamental wave into a harmonic. Therefore, it is possible to oscillate and emit at least two laser beams having different wavelengths more efficiently than in the past.

  The laser resonator further includes an optical branching unit that branches the outgoing light in accordance with a polarization direction of the outgoing light of the fiber, and the second fiber grating includes a portion of the branched light branched by the optical branching unit. Either is preferably incident.

  In this case, since fundamental waves having different wavelengths are oscillated for each polarization direction of light emitted from the fiber, it is possible to suppress competition between modes that occurs during multi-wavelength oscillation.

  The second fiber grating is configured such that the reflection wavelength of the second fiber grating can be shifted so that the Q value of the resonator formed between the second fiber grating and the corresponding first fiber grating can be varied. Is preferred.

  In this case, since the Q value of the resonator formed between the first and second fiber gratings can be changed by shifting the reflection wavelength of the second fiber grating, it is not necessary for irradiation by the laser beam irradiation unit. The Q value of a resonator having a fundamental wave can be lowered and its oscillation can be stopped.

  The laser light irradiation unit includes at least two wavelength conversion elements that convert a fundamental wave emitted from the laser resonator into a harmonic, and an optical member that reflects a part of the harmonic emitted from the wavelength conversion element. And the harmonics reflected by the optical member are fed back to the laser oscillation device by the fiber unit, and the laser oscillation device is configured to output the harmonics of the laser resonator based on the output intensity of the fed back harmonics. Change the oscillation wavelength.

  In this case, the laser oscillation device changes the oscillation wavelength of the laser resonator in accordance with the harmonic output intensity converted by the laser beam irradiation unit, so that the harmonic output emitted from the laser beam irradiation unit is stabilized. It can be made.

  The reflectance of the optical member is preferably 1 to 10%, and the optical member is preferably a dielectric multilayer film disposed on the emission surface of the wavelength conversion element.

  In this case, the laser oscillation apparatus can accurately detect the output intensity of the harmonic wave whose wavelength has been converted by the laser beam irradiation unit.

  It is preferable that the laser beam irradiation unit further includes a light selection unit that selectively irradiates one of the light emitted from the at least two wavelength conversion elements from the laser beam irradiation unit.

  In this case, the wavelength of the laser light emitted from the laser light irradiation unit can be switched.

  The fiber portion is preferably a double clad fiber.

  In this case, it is possible to efficiently propagate the fundamental wave from the laser oscillation device to the laser beam irradiation unit and the harmonic wave from the laser beam irradiation unit to the laser oscillation device.

  The reflection wavelength of the second fiber grating is preferably shifted by controlling either the temperature of the second fiber grating or the addition of tensile stress.

  In this case, the reflection wavelength of the second fiber grating can be shifted with high accuracy.

  The laser oscillation device further includes a detection unit that detects an output intensity of a harmonic fed back by the fiber unit, and a reflection wavelength of the second fiber grating based on the output intensity of the harmonic detected by the detection unit. And a control unit for controlling the shift amount.

  In this case, the output intensity of the harmonics fed back from the laser beam irradiation unit is detected, and the shift amount of the reflected wavelength of the second fiber grating is controlled based on the detected output intensity of the harmonics. The oscillation wavelength of the laser resonator can be changed according to the output intensity of the harmonic wave converted by the unit. As a result, the output of the harmonics emitted from the laser beam irradiation unit can be stabilized.

  The detection unit is preferably a light receiving element that is disposed in the vicinity of a connection point between the laser resonator and the fiber unit, and that receives the leakage light of the harmonics from the connection point.

  In this case, it is possible to accurately grasp the output intensity of the harmonics fed back from the laser beam irradiation unit.

  The laser oscillation device further includes a switch unit to which an instruction to turn on the laser light source by a user of the laser light source device is input, and the control unit is configured to perform the operation based on the lighting instruction input by the switch unit. A laser light source is turned on to control a shift amount of the reflection wavelength of the second fiber grating so as to stabilize the output intensity of the harmonic detected by the detection unit, and the laser beam irradiation unit further includes the harmonic. It is preferable to have a switch that can irradiate the laser beam irradiation unit with the harmonics emitted from the wavelength conversion element after the output intensity of the laser beam is stabilized.

  In this case, the laser light irradiation unit can be irradiated after the output of the harmonic wave whose wavelength has been converted by the laser light irradiation unit is stabilized, so that it is not necessary to always operate the laser light source. As a result, power consumption by the laser light source can be reduced.

  The control unit converts the wavelength of the fundamental wave emitted from the laser resonator by the wavelength conversion element when the phase matching condition of the wavelength conversion element is not established by controlling the shift amount of the reflection wavelength of the second fiber grating. It is preferable that the light is emitted from the wavelength conversion element without being used.

  In this case, the output of the fundamental wave emitted from the laser beam irradiation unit can be increased.

  The ranges of the oscillation wavelengths of at least two fundamental waves emitted from the laser resonator are preferably 1000 to 1100 nm and 1100 to 1200 nm.

  In this case, even when light in the wavelength band of 1100 to 1200 nm is generated, it is possible to prevent destruction of the laser resonator due to generation of ASE light by simultaneously generating light in the wavelength band of 1000 to 1100 nm. it can.

The wavelength conversion element is made of Mg: LiNbO ₃ crystal by quasi-phase matching, and the half width of the fundamental wave emitted from the laser resonator is preferably 0.06 nm or less.

In this case, when the wavelength conversion element is composed of Mg: LiNbO ₃ crystal by quasi phase matching, the wavelength conversion efficiency from the fundamental wave to the harmonic can be realized by 90% or more of the maximum wavelength conversion efficiency.

  According to the present invention, it is possible to provide a highly reliable laser light source device and an image display device that can be generated by switching a plurality of wavelengths and have a large W-class light output.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same part, and what attached the same code | symbol in drawing may abbreviate | omit description.

(Embodiment 1)
FIG. 1 is a diagram showing a schematic configuration of a laser light source according to Embodiment 1 of the present invention. In FIG. 1, a laser light source 21 according to the present embodiment includes a fiber laser 22, a wavelength conversion unit 23 having a wavelength conversion element 25 that converts a fundamental wave 53 emitted from the fiber laser 22 into a harmonic wave 24, and a control. Part 34.

  The fiber laser 22 includes a fiber 26 containing a laser active substance, a pumping laser 28 that makes the pump 26 incident on the fiber 26 through the fiber 32, and a first laser resonator that forms a laser resonator together with the fiber 26. 1 fiber grating 29 and second fiber grating 30.

  The first fiber grating 29 has a plurality of broadband reflection peaks, and the bandwidth of each reflection peak is 0.5 to 3 nm. The second fiber grating 30 also has a plurality of narrow-band reflection peaks, and the bandwidth of each reflection peak is 0.2 nm or less. The resonator of the fiber laser 22 amplifies and emits the fundamental wave 53 using the reflection peaks selected from the first fiber grating 29 and the second fiber grating 30 as two reflection surfaces. The bandwidth of each reflection peak of the second fiber grating 30 is desirably 0.2 nm or less, and more desirably 0.15 nm or less. This is because the wavelength conversion element 25 can convert the wavelength more efficiently as the bandwidth of the second fiber grating 30 is made narrower from the allowable wavelength width at the time of wavelength conversion by the wavelength conversion element 25. In such a wavelength conversion application technology, the wavelength band of the oscillated fundamental wave 53 needs to be narrow, so the wavelength band of the second fiber grating 30 must be narrowed. Therefore, the bandwidth of the first fiber grating 29 is about 10 times that of the second fiber grating 30, that is, the bandwidth of the first fiber grating 29 is 0.5 to 3 nm, more preferably 0.5 to 2 nm. By doing so, the control of the second fiber grating 30 on the narrow band side can be roughened. If the bandwidth of the first fiber grating 29 is excessively widened, the ripple generated in the top shape of the band becomes large. Therefore, it is preferable to set the bandwidth to 0.5 to 2 nm.

  The second fiber grating 30 is disposed on the reflection wavelength variable unit 33. The reflection wavelength variable unit 33 has a stress applying mechanism that applies tensile stress to the second fiber grating 30. Then, by applying a tensile stress to the second fiber grating 30, the reflection wavelength of the second fiber grating 30 is shifted, and the oscillation wavelength of the fiber laser 22 is changed by the wavelength shift. One end of the second fiber grating 30 is fixed on a base, and the other end is fixed on a uniaxial stage driven by a pulse motor. The movable direction of the stage and the light propagation direction of the second fiber grating 30 are parallel, and a tensile stress can be applied to the second fiber grating 30 by the rotation of the pulse motor. Here, the wavelength variable section 33 is provided with a stress applying mechanism, but the present embodiment is not limited to this. For example, the wavelength control unit 33 may be provided with a temperature control mechanism using a Peltier element, and the reflected wavelength may be shifted by controlling the temperature of the second fiber grating 30.

  Next, the plurality of reflection peaks of each of the first fiber grating 29 and the second fiber grating 30 will be specifically described. 2A shows the reflection spectrum of the first fiber grating 29, and FIG. 2B shows the reflection spectrum of the second fiber grating 30. As shown in FIG. In FIG. 2A, the first fiber grating 29 has three central wavelengths of λ1, λ2, and λ3, and has a reflectivity of 98% or more, that is, a high-reflect (HR) mirror. On the other hand, in FIG. 2B, the second fiber grating 30 has three central wavelengths of λ4, λ5, and λ6, and the reflectance is about 12%. The reason why the reflectance of about 12% is required is that the second fiber grating 30 plays a role of returning a part of the oscillation light to the fiber 26. 2A and 2B, the first fiber grating 29 has a bandwidth of 0.5 nm and a center wavelength that is 5 nm apart. On the other hand, the second fiber grating 30 has a bandwidth of 0.06 nm and a center wavelength separated by 4.5 nm. The interval between the center wavelengths of the first fiber grating 29 and the second fiber grating 30 is appropriately set based on the oscillation wavelength required for the fiber laser 22. In FIGS. 2A and 2B, the first fiber grating 29 and the second fiber grating 30 are λ1 = in a state where no tensile stress is applied to the second fiber grating 30 at room temperature (25 degrees). λ4.

  At this time, when two semiconductor lasers having a wavelength of 915 nm and a maximum output of 7 W with a threshold current of 0.45 A are used as the excitation laser 28, 7.2 W is realized as the output of the fundamental wave 53. It was. By using 915 nm as the excitation wavelength, the fundamental wave 53 can be stably output by a simple cooling mechanism using a cooling fin and a blower fan.

  Next, the wavelength selection operation of the laser light source according to the present embodiment will be described. Here, a case will be described in which the first fiber grating 29 and the second fiber grating 30 having the reflection peaks shown in FIGS. 2A and 2B are used. 3A to 3C are diagrams for explaining the wavelength selection operation of the laser light source according to the present embodiment. FIG. 3A is a diagram illustrating the second fiber grating 30 at room temperature. FIG. 3B is a diagram showing a state in which no tensile stress is applied. FIG. 3B shows that the reflection wavelength of the second fiber grating 30 is set to 0. 0 by applying tensile stress to the second fiber grating 30 at room temperature. FIG. 3 (c) is a diagram showing a state shifted by 5 nm, and FIG. 3C shows that the second fiber grating 30 is further applied with tensile stress at room temperature, and the reflected wavelength of the second fiber grating 30 is further shifted by 0.5 nm. It is a figure which shows the state made to do.

  First, in FIG. 3A, the center wavelength λ1 of the first fiber grating 29 and the center wavelength λ4 of the second fiber grating 30 match. For this reason, the fiber laser 22 oscillates at λ1 (= λ4).

  Next, in FIG. 3B, the reflection wavelength of the second fiber grating 30 shifts due to the addition of tensile stress by the reflection wavelength variable unit 33. Thereby, the center wavelength λ2 of the first fiber grating 29 and the center wavelength λ5 of the second fiber grating 30 coincide. For this reason, the fiber laser 22 oscillates at λ2 (= λ5). That is, the oscillation wavelength of the fiber laser 22 can be shifted by 5 nm only by shifting the reflection wavelength of the second fiber grating 30 by only 0.5 nm.

  Further, in FIG. 3C, the reflection wavelength of the second fiber grating 30 is further shifted by the further addition of the tensile stress by the reflection wavelength variable unit 33. Thereby, the center wavelength λ3 of the first fiber grating 29 and the center wavelength λ6 of the second fiber grating 30 coincide. For this reason, the fiber laser 22 oscillates at λ3 (= λ6), and the oscillation wavelength is further shifted by 5 nm from FIG.

  That is, by shifting the reflection wavelength of the second fiber grating 30 by 1 nm, the oscillation wavelength of the fiber laser 22 can be shifted by 10 nm. As described above, in the present embodiment, although it is discrete, the oscillation wavelength of the fiber laser 22 can be switched by 10 nm in total by 5 nm. The shift amount of the oscillation wavelength of the fiber laser 22 can be arbitrarily designed according to the design of the first fiber grating 29 and the second fiber grating 30.

  In this way, by combining the first fiber grating 29 which is a reflector having a high reflectivity and a wide bandwidth and the second fiber grating 30 which is a reflector having a small reflectivity and a narrow bandwidth, Therefore, it is not necessary to finely adjust both reflectors to control the oscillation wavelength of the fiber laser 22, and the oscillation wavelength can be switched only by controlling one of the reflectors. In addition, conventionally, it is necessary to monitor the oscillation wavelength based on the output of the laser, and it has been difficult to distinguish between the change in the oscillation wavelength and the change in the laser output itself. In this embodiment, it is only necessary to control the change of the laser output itself (Auto Power Control: APC) by eliminating the need to monitor the oscillation wavelength. Therefore, the laser output can be easily controlled. Conventionally, since the reflection wavelength of the fiber grating is sensitive to fluctuations in the outside air temperature, the oscillation wavelength may be switched carelessly. In the present embodiment, this problem can also be prevented by expanding the bandwidth of the first fiber grating 29 as compared with the second fiber grating 30.

  By the way, in the fiber laser used for the laser light source according to the present embodiment, it is known that the oscillation efficiency differs for each oscillation wavelength due to absorption of the fiber by addition of Yb which is a laser active substance. FIG. 4 shows the relationship between the oscillation wavelength and loss of a Yb-doped fiber. As shown in FIG. 4, in the range where the oscillation wavelength is 1045 to 1070 nm, the longer the oscillation wavelength, the smaller the loss of the fiber. Therefore, the oscillation efficiency tends to increase as the oscillation wavelength increases. Therefore, when the oscillation wavelength is shortened, it is necessary to prevent a decrease in oscillation efficiency. In the present embodiment, the reflectance of the second fiber grating 30 is increased with respect to the decrease in oscillation efficiency. That is, the oscillation efficiency is prevented from lowering by increasing the oscillation light that is fed back to the fiber 26 by improving the reflectance of the second fiber grating 30. The second fiber grating 30 having a plurality of reflection wavelengths can change the reflectance of each grating by changing the length of the grating corresponding to each reflection wavelength. As each grating length increases, the reflectance of each grating increases. That is, in the case of a short oscillation wavelength (in this embodiment, 1045 nm), the reflectance of each grating is increased, and in the case of a long oscillation wavelength (in this embodiment, 1070 nm), the reflectance is decreased. As a result, it is possible to suppress a decrease in oscillation efficiency. Thereby, an increase in the drive current amount of the excitation laser 28 due to APC can be suppressed. That is, power consumption can be reduced. FIG. 5 shows an example of the relationship between the reflection wavelength and the reflectance of the second fiber grating 30.

  In FIG. 5, when the fiber laser 22 is designed to oscillate in the wavelength range X from 1045 nm to 1070 nm in increments of 5 nm, the largest reflection peak is set to 1045 nm in the second fiber grating 30 and decreases in steps of 5 nm. By assigning the reflection wavelength in this order, a decrease in the oscillation efficiency of the fiber laser 22 can be suppressed, and the output fluctuation of the fundamental wave 53 due to the fluctuation of the oscillation wavelength of the fiber laser 22 can be suppressed to within 5%.

  Next, the wavelength converter 23 that generates the harmonics 24 of the fundamental wave 53 emitted from the fiber laser 22 will be described. As shown in FIG. 1, the wavelength conversion unit 23 includes a wavelength conversion element 25, a condenser lens 31, a beam splitter 8, and a wavelength conversion element holding unit 35. In the present embodiment, the condensing lens 31 is provided in the wavelength converter 23, but may be provided in the fiber laser 22.

  When the laser light of the fundamental wave 53 is output from the fiber laser 22, the light is condensed by the condenser lens 31 and enters the wavelength conversion element 25. When the fundamental wave 53 from the fiber laser 22 becomes an incident wave and is converted by the nonlinear optical effect of the wavelength conversion element 25, the wavelength becomes a harmonic wave 24 that is ½ of the fundamental wave 53. The converted harmonics 24 are partially reflected by the beam splitter 8, while almost all of the transmitted harmonics 24 are emitted as output light of the laser light source 21.

  The harmonic wave 24 partially reflected by the beam splitter 8 is received by the light receiving element 37 and converted into an electric signal and used for monitoring the output light of the wavelength conversion element 25. The control unit 34 adjusts the drive current of the excitation laser 28 with the excitation laser current source 36 so that the intensity of the converted signal becomes an intensity at which a desired output can be obtained by the wavelength conversion element 25. Then, the intensity of the excitation light 27 from the excitation laser 28 is adjusted, the output intensity of the fundamental wave 53 of the fiber laser 22 is adjusted, and as a result, the output intensity of the laser light source 21 is adjusted. As a result, the intensity of the output of the laser light source 21 is kept constant, and so-called auto power control (APC) operates stably. In addition, in order to control the intensity of the output of the laser light source 21 with higher accuracy by the APC operation, a light receiving element can be arranged outside the second fiber grating 30 of the fiber 26. In this way, the fundamental wave 53 slightly leaking without being reflected by the second fiber grating 30 can be detected. Based on this detection data, the control unit 34 adjusts the drive current of the excitation laser 28 with the excitation laser current source 36 by estimating the overall intensity of the excitation light 27 and the fundamental wave 53, and the laser light source 21. APC operation is performed for the output intensity.

  The detection of the fundamental wave 53 is not limited to the configuration in which the light receiving element is disposed outside the second fiber grating 30, and the configuration for detecting the branched light of the fundamental wave 53 emitted from the second fiber grating 30. It may be. Further, a configuration in which the output of the fundamental wave 53 transmitted through the first fiber grating 29 is detected by a light receiving element may be used. Further, the output of the fundamental wave 53 may be controlled by taking out the excitation light 27 of the excitation laser 28 and reflecting it by a mirror and detecting a part of the excitation light 27 with a light receiving element. With these configurations, the output from the laser light source 21 can be more stably obtained by more accurately detecting the output of the excitation light 27 and the fundamental wave 53 and controlling the output of the fundamental wave 53 stably. .

Next, specific configurations of the wavelength conversion element 25 and the wavelength conversion element holding unit 35 of the wavelength conversion unit 23 will be described. In the present embodiment, the oscillation wavelength of the fiber laser 22 that emits the fundamental wave 53 is changed. For this reason, it is necessary to change the phase matching conditions of the nonlinear optical crystal used in the wavelength conversion element 25 of the wavelength conversion unit 23 that generates the harmonic wave 24 in accordance with the oscillation wavelength. In this embodiment, KTiOPO ₄ (KTP) is used as an example of a crystal using angular phase matching, LiB ₃ O ₅ (LBO) is used as an example of a crystal using temperature phase matching, and MgO: LiNbO is used as an example of a crystal using pseudo phase matching. ₃ will be described.

(When using angle phase matching)
FIG. 6A shows the configuration of the wavelength conversion unit 23 when a nonlinear crystal using angular phase matching is used for the wavelength conversion element 25. 6A, the wavelength conversion unit 23 includes a wavelength conversion element 25a, a condenser lens 31, a beam splitter 8, and a wavelength conversion element holding unit 35a. The wavelength conversion element 25a is formed by angular phase matching of a KTP crystal, and the wavelength conversion element holding unit 35a is provided with a rotation stage that rotates the wavelength conversion element 25a in the φ direction on the crystal optical axis.

  The oscillation wavelength of the fiber laser 22 is set to 1055 nm, 1060 nm, 1065 nm, and 1070 nm, and the KTP crystal constituting the wavelength conversion element 25a is type-II phase-matched (angle θ = 90 in the xy plane and between the z axis and the fundamental wave incident direction). ). As each phase matching condition, the phase matching angle φ (angle between the fundamental wave incident direction and the x axis: angle in the crystal) is 35 °, 32.5 °, 28.5 °, and 23.5 °. It was. Note that this phase matching angle φ varies by about ± 0.2 ° depending on the temperature of the crystal.

  FIG. 6B shows another configuration of the wavelength conversion unit 23 when a nonlinear crystal using angular phase matching is used for the wavelength conversion element 25. 6B, the wavelength conversion unit 23 includes a wavelength conversion element 25a, a condenser lens 31, a beam splitter 8, a wavelength conversion element holding unit 35a, a wavelength conversion element 25b, and a wavelength conversion element holding unit 35b. And have. Of course, the wavelength conversion element 25b is formed by angular phase matching of the KTP crystal, and the wavelength conversion element holding unit 35b is provided with a rotation stage that rotates the wavelength conversion element 25b in the φ direction on the crystal optical axis. That is, the configuration of FIG. 6B is obtained by adding a wavelength conversion element 25b and a wavelength conversion element holding unit 35b to the configuration of FIG. 6A. With this configuration, the change of the optical axis caused by the rotation of the wavelength conversion element 25a can be suppressed by the rotation of the wavelength conversion element 25b.

(When using temperature phase matching)
FIG. 7 shows the configuration of the wavelength converter 23 when a nonlinear crystal using temperature phase matching is used for the wavelength conversion element 25. In FIG. 7, the wavelength conversion unit 23 includes a wavelength conversion element 25c, a condenser lens 31, a beam splitter 8, and a wavelength conversion element holding unit 35c. The wavelength conversion element 25c is composed of an LBO crystal by temperature phase matching, and the wavelength conversion element holding unit 35c is disposed in the gap between the heater 42 that holds the temperature of the wavelength conversion element 25c and the heater 42 and the wavelength conversion element 25c. Spacer 41 is provided. The heater 42 incorporates a cartridge heater in a brass block, and has a space of 5 mm × 5 mm and 25 mm in the longitudinal direction, and a wavelength conversion element made of LBO crystal of 3 mm × 3 mm × 20 mm in the space. 25c is held. An aluminum spacer 41 is disposed in the gap. Here, the phase matching temperature indicates the temperature of a thermocouple for temperature monitoring arranged in the brass block.

  The oscillation wavelength of the fiber laser 22 is set to 1055 nm, 1060 nm, 1065 nm, and 1070 nm, and the non-critical phase matching condition (type-I) of the LBO crystal (θ = 90 °, φ = 0 °: on the x-axis) constituting the wavelength conversion element 25c. ) Were 161 ° C., 155 ° C., 147 ° C. and 136 ° C., respectively. The phase matching temperature changes by about ± 2 ° C. depending on individual differences of crystals and holding conditions in the heater 42.

(When using quasi phase matching)
FIG. 8 shows the configuration of the wavelength conversion unit 23 when a nonlinear crystal using quasi phase matching is used for the wavelength conversion element 25. In FIG. 8, the wavelength conversion unit 23 includes a wavelength conversion element 25d, a condenser lens 31, a beam splitter 8, and a wavelength conversion element holding unit 35d. The wavelength conversion element 25d is composed of a nonlinear optical crystal (MgO: LiNbO ₃ [MgO: LN]) by quasi phase matching. 51 and a moving stage 52 that can move the wavelength conversion element 25d in a predetermined direction. Since the nonlinear optical crystal (MgO: LN) has a polarization inversion period and the maximum nonlinear optical constant d33 of the MgO: LN crystal can be used, highly efficient wavelength conversion is possible. Since the polarization inversion period is defined by the wavelength of the fundamental wave 53, the polarization inversion period formed in the nonlinear optical crystal needs to be switched every time the wavelength of the fundamental wave 53 is switched.

  When the oscillation wavelength of the fiber laser 22 is 1055 nm, 1060 nm, 1065 nm, and 1070 nm, the necessary polarization inversion periods are 6.8 μm, 6.9 μm, 7 μm, and 7.1 μm. FIGS. 9A to 9C show the polarization inversion periods formed in the MgO: LN crystal. In FIG. 9A, the regions A, B, C,... Where the polarization inversion periods are formed are arranged in parallel with respect to the traveling direction of the fundamental wave 53. For example, the polarization inversion period formed in the region A corresponds to the fundamental wave 53 of λ1, the polarization inversion period formed in the region B corresponds to the fundamental wave 53 of λ2, and the polarization inversion period formed in the region C is This corresponds to the fundamental wave 53 of λ3. On the other hand, in FIG. 9B, the polarization inversion period changes linearly. For example, the polarization inversion period at the position D corresponds to the fundamental wave 53 at λ1, and the polarization inversion period at the position E is the fundamental wave at λ2. Corresponds to a fundamental wave 53 having a polarization inversion period at position F of λ3.

  The wavelength conversion element 25d having the polarization inversion period configuration shown in FIGS. 9A and 9B needs to switch the region or position where the fundamental wave 53 is input corresponding to the switching of the wavelength of the fundamental wave 53. is there. Therefore, the wavelength conversion element 25d can be moved by the moving stage 52 of the wavelength conversion element holding part 35d. Further, the drive timing of the moving stage 52 must be synchronized with the drive timing of the reflection wavelength varying unit 33 in FIG. Therefore, the control unit 34 generates a drive signal for driving the moving stage 52 in synchronization with the drive signal for driving the reflection wavelength varying unit 33. Accordingly, the wavelength conversion is efficiently performed by accurately switching the region or position where the fundamental wave 53 of the wavelength conversion element 25d is input in accordance with the shift of the reflection wavelength of the second fiber grating 30 by the reflection wavelength variable unit 33. Can perform well. If the crystal axis of the MgO: LN crystal is taken into consideration, the configuration of FIG.

  On the other hand, in FIG. 9C, regions G, H, I... Where the polarization inversion periods are formed are arranged in order along the traveling direction of the fundamental wave 53. For example, the polarization inversion period formed in the region G corresponds to the fundamental wave 53 of λ1, the polarization inversion period formed in the region H corresponds to the fundamental wave 53 of λ2, and the polarization inversion period formed in the region I is This corresponds to the fundamental wave 53 of λ3. In the configuration of FIG. 9C, since each domain inversion period region is provided along the traveling direction of the fundamental wave 53, it is necessary to move the wavelength conversion element 25 d in conjunction with wavelength switching of the fundamental wave 53. Absent. Accordingly, the moving stage 52 of FIG. 8 is not required, the configuration of the wavelength conversion element holding unit 35d is simplified, and the processing load of the control unit 34 can be reduced. The configuration of FIG. 9C can be realized because the wavelength of the fundamental wave 53 changes discretely. However, since the wavelength-converted region (interaction length) is shortened, the conversion efficiency from the fundamental wave 53 to the harmonic wave 24 decreases. For this reason, when importance is attached to the conversion efficiency, the configuration of FIG.

  Next, a description will be given of a method in which the laser light source 21 in FIG. 1 outputs high-power green laser light (hereinafter referred to as “G light”). In FIG. 1, the core portion of the fiber 26 of the fiber laser 22 is doped with rare earth element Yb as a laser active substance at a concentration of 1200 ppm. As the fiber excitation laser 28, a semiconductor laser having a wavelength of 915 nm, a threshold current of 400 mA, and a maximum optical output of 10 W is used. Excitation light having a wavelength of 915 nm is incident on the fiber 26 and is completely absorbed before reaching the second fiber grating 30. As a result, when the excitation light 27 from the excitation laser 28 is incident on the fiber 26, the excitation light 27 is absorbed by the core portion, and the wavelength of about 1050 to 1065 nm is obtained from the fiber 26 using the Yb level of the core portion. Stimulated release occurs. The stimulated emission light of about 1050 to 1065 nm is amplified by the gain obtained by absorbing the excitation light 27 in the fiber 26 and proceeds to become the fundamental wave 53 of infrared laser light having a wavelength of about 1050 to 1065 nm. . In addition, the fundamental wave 53 mainly has a low reflectivity by moving the first fiber grating 29 and the second fiber grating 30 as a pair of reflecting surfaces of the laser resonator and reciprocating between these reflecting surfaces. The oscillation wavelength is selected by the second fiber grating 30. At this time, the reflection wavelength of the second fiber grating 30 is set to 1050 nm, 1055 nm, 1060 nm, and 1065 nm as described above, and the reflection wavelength bandwidth is set to 0.1 nm. Therefore, the wavelength bandwidth of the fundamental wave 53 is 0.1 nm and is output from the fiber laser 22. The reflectivities of the first fiber grating 29 and the second fiber grating 30 with respect to the oscillation wavelengths of 1050 nm, 1055 nm, 1060 nm, and 1065 nm are set to about 98% and 10%, respectively. Since both the second fiber grating 30 and the second fiber grating 30 are sampled gratings, the reflectivity for each oscillation wavelength can be changed by design. By setting the reflectance of the first fiber grating 29 to 98% or more, it is possible to prevent the oscillation light from returning to the excitation laser 28 and destroying the excitation laser 28. On the other hand, the reflectivity of the second fiber grating 30 is preferably about 5 to 20% because it is sufficient to feed back an amount of light sufficient to lock a desired oscillation wavelength.

  FIG. 10 shows the input / output characteristics of the optical output of the fundamental wave 53 having a wavelength of 1065 nm with respect to the excitation light amount from the excitation laser 28. It can be seen that the output of the fundamental wave 53 increases with good linearity in proportion to the amount of excitation light up to 7 W.

Next, a process in which the fundamental wave 53 emitted from the fiber laser 22 is converted into the harmonic wave 24 by the wavelength conversion element 25 will be described. The fundamental wave 53 (for example, wavelength 1065 nm) output from the fiber laser 22 is incident on the wavelength conversion element 25 via the condenser lens 31. The wavelength conversion element 25 is an element that converts incident light into a harmonic wave 24 and outputs it, and uses, for example, a MgO: LiNbO ₃ crystal having a domain-inverted periodic structure with a length of 20 mm. Hereinafter, the case where MgO: LiNbO ₃ crystal having a domain-inverted periodic structure is used will be described. Here, the wavelength that can be converted into a harmonic by the wavelength conversion element 25 is called a phase matching wavelength, and is set to 1065 nm at 25 ° C. in the present embodiment. Therefore, the wavelength 1065 nm of the fundamental wave 53 of the fiber laser 22 coincides with the phase matching wavelength, and is converted into the harmonic wave 24 by the wavelength conversion element 25 to become a green laser having a wavelength of 532.5 nm which is a half wavelength. Output from the wavelength converter 23 as a harmonic wave 24.

  In general, the wavelength conversion element 25 is temperature-controlled with an accuracy of 0.01 ° C. because the phase matching wavelength changes sensitively depending on the element temperature. In the present embodiment, the wavelength conversion element 25 and the second fiber grating 30 are individually temperature controlled with an accuracy of 0.01 ° C. by attaching a Peltier element. In this way, even if the fundamental wave output of the fiber laser 22 exceeds 5 W and heat generation in the wavelength conversion element 25 and the second fiber grating 30 increases, the harmonics 24 of the W-class green laser can be obtained. it can. A temperature sensor is attached to the Peltier element, and the Peltier element and the temperature sensor are all connected to the control unit 34 to control the temperature signal output and drive of each component or element.

  Therefore, in this embodiment, by adjusting the kind and amount of rare earth element added to the fiber 26 or adjusting the reflection wavelength of the second fiber grating 30 to a short wavelength, a fundamental wave having a shorter wavelength can be obtained. It can output with high output of 5W or more. Therefore, a W-class green laser beam having a shorter wavelength of 526 to 540 nm can be obtained.

  The control unit 34 may be configured to store a previously input table and perform temperature control of the second fiber grating 30 and the wavelength conversion element 25 based on the table. With these configurations, the phase matching condition of the fundamental wave 53 at the wavelength conversion element 25 can be precisely controlled, and more stable output of the harmonic wave 24 can be efficiently obtained from the wavelength conversion element 25.

  The table may be configured by data of a phase matching wavelength change amount in the wavelength conversion element 25 with respect to the output of the fundamental wave 53. Further, the table may be composed of data on the amount of change in the reflected wavelength of the fundamental wave 53 at the second fiber grating 30 with respect to the output of the fundamental wave 53. With these configurations, when the output of the fundamental wave 53 is changed, the phase matching condition of the wavelength conversion element 25 is quickly set to the second output of the fundamental wave 53 and the wavelength based on the data in the table as described above. It is quickly adjusted by temperature control of the fiber grating 30 and the wavelength conversion element 25, and the harmonic output of the wavelength conversion element 25 is maintained more stably.

  Note that by shortening the fiber length of the fiber 26 of the fiber laser 22, green laser light having a short wavelength of 526 to 540 nm can be obtained, and the reproduction color range can be greatly expanded from the conventional SRGB standard. Therefore, the color reproduction range is further expanded when applied to a display or the like.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. FIG. 11 shows a configuration of a laser display (two-dimensional image display device) according to Embodiment 2 of the present invention. The laser display according to the present embodiment is an example of a laser display to which the laser light source according to the first embodiment is applied.

  As light sources, laser light sources 1001a to 1001c of three colors of red (R), green (G), and blue (B) are used. An AlGaInP / GaAs semiconductor laser with a wavelength of 638 nm is used for the red laser light source (R light source) 1001a, and a GaN semiconductor laser with a wavelength of 465 nm is used for the blue laser light source (B light source) 1001c.

  On the other hand, the laser light source according to the first embodiment is used for the green laser light source (G light source) 1001b. The laser light source includes a wavelength conversion element that halves the wavelength of the infrared laser. The laser beams emitted from the R, G, and B light sources 1001a to 1001c are condensed by the condenser lenses 1009a to 1009c, and then scanned on the diffusion plates 1003a to 1003c by the reflective two-dimensional beam scanning means 1002a to 1002c. The The image data is divided into R, G, and B data. The signals are narrowed down by field lenses 1004a to 1004c, input to spatial light modulators 1005a to 1005c, and then combined by dichroic prism 1006. A color image is formed. The combined image is projected onto the screen 1008 by the projection lens 1007. However, a concave lens 1009 for making the spot size of the G light at the spatial modulation element 1005b the same as that of the R light and the B light is inserted in the optical path incident on the spatial light modulation element 1005b from the G light source 1001b.

  In this embodiment, the R light source and the B light source are configured by using one semiconductor laser, but the outputs of a plurality of semiconductor lasers are collected as one fiber by, for example, a bundle fiber. You may comprise R light source and B light source so that it may be obtained. If it does in this way, the width | variety of the wavelength spectrum of R light source or B light source can be enlarged, coherence can be eased, and speckle noise can also be suppressed as a light source. Similarly, for the G light source, speckle noise is suppressed by guiding the G light outputs of a plurality of laser light sources through output fibers, and combining these output fibers as a single fiber by, for example, a bundle fiber. The G light source may be used.

  In the laser display of FIG. 11, members such as vibration diffusion plates 1003a to 1003c and field lenses 1004a to 1004c are arranged in front of the spatial light modulation elements 1005a to 1005c. The arrangement of such a member is for removing speckle noise generated by using a coherent laser beam as a light source, and by swinging these speckle noise removing means, Speckle noise seen with eye response time can be reduced.

  In this embodiment, the fundamental light emitted from the fiber laser is incident on the wavelength conversion element using the laser light source of the first embodiment as the G light source 1001b to generate harmonics. The configuration of the laser display according to this embodiment is characterized by the laser light source used for the G light source 1001b.

  Since the laser display of this embodiment uses a laser light source for the R, G, and B light sources, it can be configured to be thin with high brightness. Further, by using the laser light source according to the first embodiment as the G light source 1001b, the reproduction color range can be broadened to, for example, a range of 525 nm from the conventional SRGB standard, and a color expression close to the primary color can be achieved. It becomes possible. That is, the laser display of this embodiment can expand the color reproduction range as compared with the conventional laser display.

  Furthermore, for example, the G light source 1001b can arbitrarily oscillate any light having a wavelength of 525 nm, 527.5 nm, 530 nm, and 532.5 nm. For this reason, speckle noise can be reduced to 20% or less in the case of a single wavelength. Further, by swinging the vibration diffusing plate 1003b, the difference in brightness between speckle noises can be reduced to the extent that speckle noise is not perceived by human eyes (2% or less).

  In the present embodiment, in addition to the two-dimensional image display device having such a configuration, it is possible to adopt a form (rear projection display) in which projection is performed from behind the screen. Further, by making the laser light uniform with the light guide plate, it can also be used as a backlight of a liquid crystal panel.

(Embodiment 3)
Next, a third embodiment of the present invention will be described. In general, it is known that the color reproduction range of an image changes when the oscillation wavelength of green light changes. FIG. 12 shows the relationship between the wavelength of green light and the color reproduction range. Since 532.5 nm has high visibility, a small amount of input power is sufficient to obtain the same brightness, but there is a problem that a “cyan” color necessary for displaying the color of the sea cannot be produced. On the other hand, although “cyan” color can be reproduced at 525 nm, since the visibility is low, there is a problem that input power more than twice that of the case of 532.5 nm is required.

  In order to solve such a problem, the laser light source according to the present embodiment uses the visibility of the human eye by switching the oscillation wavelength of the laser light according to the type of image and usage conditions. Brighter images can be displayed with power consumption. Hereinafter, a case where the laser light source according to the present embodiment is used as a green light source of a laser display will be described.

  FIG. 13 shows a schematic configuration of the laser light source according to the present embodiment. In the laser light source 110 according to the present embodiment, a projector control circuit 1101 including a wavelength determination circuit 1102 and a luminance signal determination circuit 1103 and a video mode switch 1104 are added to the laser light source according to the first embodiment. It has been configured. Also, a video signal (data) 1105 or a video signal (video) 1106 is input to the projector control circuit 1101 from the outside, and a wavelength selection signal 1107 is transmitted to the control unit 34 by the projector control circuit 1101 to select the oscillation wavelength of the laser light. Is done.

  The operation of the projector control circuit 1101 will be described. Usually, a laser display is provided with a plurality of terminals for inputting / outputting video signals, for example, D-sub 15 pin, DVI, RCA pin, S terminal, D terminal, and HDMI. Therefore, first, a case will be described in which the projector control circuit 1101 changes the oscillation wavelength of the laser light by detecting to which of the terminals of the laser display the video signal is input.

  For example, assume that a video signal (data) 1105 is input to the laser display. If the video signal (data) 1105 is input from D-sub15pin or DVI, it can be said that the video signal 1105 is a data signal in which brightness is regarded as important as used for presentation. In this case, the wavelength determination circuit 1102 selects a green light having a high visibility by transmitting a wavelength selection signal 1107 to the control unit 34.

  When a video signal is input from an RCA pin, an S terminal, a D terminal, or an HDMI terminal, the video signal is often a video signal (video) 1106. In this case, the luminance signal determination circuit 1103 determines the brightness of the video source. The luminance signal determination circuit 1103 analyzes the luminance signal in the video so that the input video signal 1106 has many bright scenes such as a general television program (for example, a program recorded in a studio). It is discriminated whether the video signal is not important, or whether the video signal has a dark scene such as a movie but requires a wide color reproduction range. In the former case, increase the ratio of using a green wavelength with high visibility and improve the efficiency, and in the latter case, increase the ratio of using a short wavelength green wavelength such as 526 nm that can expand color reproducibility. It is possible to improve the image quality.

  Also, the video mode change-over switch 1104 allows the user to arbitrarily decide which wavelength to use. For example, if the user prefers a bright image, a green wavelength with high visibility can be specified. On the other hand, if the user always wants to view a high-quality image with wide color reproducibility, a wavelength that can expand the color reproducibility can be specified. . In addition, the oscillation wavelength can be determined by the wavelength selection signal 1107 determined by the luminance signal determination circuit 1103.

  In the laser light source 110 according to the present embodiment, any wavelength of 525 nm, 527.5 nm, 530 nm, or 532.5 nm can be arbitrarily oscillated, and therefore data that requires brightness rather than color reproducibility. When used as a projector, the brightness perceived by the human eye can be improved with the same power consumption by emitting light of 532.5 nm with high visibility. On the other hand, in the case where color reproducibility is required rather than brightness, color reproducibility can be enhanced as 525 nm light emission capable of widening the reproduction color range although the visibility is low.

  The method for changing the above light emission ratio is not limited to the above, and the same effect can be obtained by applying other methods.

  In this embodiment mode, in the case where the battery 1109 can be used as a power source, the wavelength of oscillation is switched depending on whether the AC power source 1108 or the battery 1109 is used or the remaining amount of the battery 1109. The lifetime of 1109 can also be improved. For example, when determining based on whether the AC power source 1108 or the battery 1109 is used, the power source control circuit 1110 determines the power source type and transmits the power source determination signal 1111 to the wavelength determination circuit 1102, so that the wavelength determination circuit 1102 determines the wavelength. Is determined. Further, by determining the oscillation wavelength by determining the remaining amount of the battery 1109 with the power supply control circuit 1110, the efficiency as the fiber laser 22 is improved when the battery 1109 is used or when the remaining amount of the battery is low. By projecting with long-wavelength green light that is high and has high visibility, a bright image can be displayed with less power consumption.

(Embodiment 4)
Next, a fourth embodiment of the present invention will be described. FIG. 14 shows the configuration of a laser fluorescence microscope according to Embodiment 4 of the present invention. The laser fluorescence microscope according to the present embodiment uses the laser light source according to the first embodiment. The laser fluorescence microscope according to the present embodiment observes a fluorescent portion by staining a sample with a fluorescent substance such as rhodamine and exciting with light generated from the laser light source according to the first embodiment. . There are several types of fluorescent materials, and the wavelengths of the excitation light are different. For example, the excitation wavelength of a fluorescent reagent called TRITC is 540 nm, and the reagent called TexasRed is 560 nm, and fluorescent reagents with various excitation wavelengths are commercially available. Visibility can be greatly enhanced because each reagent has different portions that remain in the cell.

  Laser light emitted from the laser light source 21 of the laser fluorescence microscope 1301 according to this embodiment is folded back by mirrors 1302 a and 1302 b and introduced into the microscope 1303. By irradiating the sample 1304 with laser light, the fluorescent sample held in the sample 1304 can be excited and the light emission portion can be confirmed by an image. Conventionally, light from halogen lamps separated by dichroic mirrors or light sources using dye lasers have been used, but with halogen lamps, color separation is not possible, and even dyes that do not want to be excited are excited. There was a problem. In the case of using a dye laser, color separation is possible because it is a tunable laser, but there is a problem that the liquid dye needs to be replaced frequently and the number of times of maintenance is large. In this embodiment, although the wavelength is discretely variable, it is maintenance-free and can be significantly reduced in size as compared with a dye laser.

  As described above, according to the first to fourth embodiments of the present invention, by changing the fiber grating period on the narrow band side of a set of fiber gratings having a plurality of reflection wavelengths, the oscillation wavelength of the laser can be changed. It can be changed discretely. As a result, it is possible to realize a laser light source device that can be used by switching between a plurality of wavelengths with high output. In addition, because the reflectance on the narrow band side and the gain of the laser medium are matched and the wavelength to be oscillated can be arbitrarily selected, W-class visible laser light is more stable than when simultaneously oscillating multiple wavelengths. It is possible to output a green laser beam with high visibility. Furthermore, it is possible to realize a two-dimensional image display device that has high brightness, a wide color reproduction range, high image quality, and low power consumption.

  In the above first to fourth embodiments, as shown in FIG. 15A, when oscillating light of 1100 nm or more such as 1120 nm to obtain harmonics, the fiber laser side has a wavelength range of 1000 to 1100 nm. Amplified spontaneous emission may be generated, destroying the excitation laser. For this reason, as shown in FIG. 15B, the destruction of the excitation laser can be prevented by designing the fiber grating so that it oscillates simultaneously at any wavelength within the wavelength range of 1000 to 1100 nm. And stable output can be obtained.

  In the first to fourth embodiments, the fiber laser doped with Yb as the rare earth element is used. However, at least one rare earth element selected from other rare earth elements such as Nd and Er is used. May be. Further, the doping amount of the rare earth element may be changed or a plurality of rare earth elements may be doped according to the wavelength and output of the wavelength conversion element.

  Furthermore, in Embodiments 1 to 4 above, lasers with wavelengths of 915 nm and 976 nm were used as the fiber laser excitation lasers, but lasers other than these wavelengths can be used as long as the fiber laser can be excited. It may be used.

  Since the laser light source and the two-dimensional image display device according to the first to fourth embodiments have high brightness, a wide color reproduction range, and low power consumption, the display field such as a large display or a high brightness display, or the biochemistry field This is useful for analytical applications.

(Embodiment 5)
Next, a fifth embodiment of the present invention will be described. The present embodiment relates to a medical laser light source apparatus used for surgery or the like using a laser light source that obtains a stable visible light high-power laser.

  FIG. 16 is a diagram showing a schematic configuration of the laser light source apparatus according to the present embodiment. A laser light source device 2100 according to this embodiment includes a laser oscillation device 2101 and a laser light irradiation unit 2102. The laser oscillation device 2101 includes a fiber laser 2103, a power supply unit 2104, and a control unit 2105. The laser beam irradiation unit 2102 includes two wavelength conversion elements 2111 and 2112 and a light selection unit 2113. is doing. In addition, the laser oscillation device 2101 is provided with a lighting switch 2106 that allows the user to determine the timing for emitting the laser light. Laser light emitted from the fiber laser 2103 is propagated to the laser light irradiation unit 2102 through the fiber 2117.

  The fiber laser 2103 includes a fiber 2110 to which rare earth such as Yb is added, a pump laser 2107 that outputs pump light incident on the fiber 2110, and fiber gratings 2108a, 2108b, 2109a, and 2109b that can select the wavelength of the fundamental wave. And the panda coupler 2110a, and the fiber gratings 2108a and 2109a and the fiber 2110 are formed of a double clad polarization maintaining fiber.

  The laser light irradiation unit 2102 feeds back part of the generated visible light to the laser oscillation device 2101 through the fiber 2117. In the laser oscillation device 2101, visible light returning through the fiber 2117 is monitored by photodiodes 2115 and 2116. The control unit 2105 stabilizes the output of the excitation laser 2107 by controlling the power supply unit 2104 that drives the excitation laser 2107 based on the monitoring result. The fiber 2117 is desirably a double-clad polarization maintaining fiber in order to reduce the visible light coupling loss from the laser light irradiation unit 2102 to the fiber 2117 and the visible light propagation loss through the fiber 2117. Further, by configuring the fiber gratings 2108b and 2109b with ordinary polarization maintaining fibers, leakage light is generated at the connection point with the fiber 2117 which is a double clad polarization maintaining fiber. Thereby, visible light for monitoring for the photodiodes 2115 and 2116 can be obtained.

  Next, the operation of the fiber laser 2103 will be described. Excitation light from the excitation laser 2107 enters the fiber 2110. The incident excitation light propagates through the fiber 2110 while being absorbed by the laser active material contained in the fiber 2110. In the state where the excitation light passes through and is absorbed through the fiber 2110 and the gain for amplifying the fundamental wave in the fiber 2110 is uniformly increased, seed light of the fundamental wave is generated inside the fiber 2110. The seed light of the fundamental wave is amplified in the resonators with the fiber gratings 2108a and 2108b as a set of resonators or the fiber gratings 2109a and 2109b as a set of resonators to increase the intensity. Reflected many times and reciprocated, finally laser oscillation.

  The panda coupler 2110a is used to change the oscillation wavelength for each polarization direction of the fundamental wave. For example, a fiber grating 2109b with a reflection wavelength of 1064 nm and a reflection band of 0.05 nm is fused in the slow axis direction of the panda coupler 2110a, and a fiber grating 2108b with a reflection wavelength of 1178 nm and a reflection band of 0.05 nm in the fast axis direction. By fusing, the Yb fiber 2110 oscillates at 1064 nm in the slow axis direction and 1178 nm in the fast axis direction. The same effect can be obtained even if the direction of the fast / slow axis by each wavelength is changed as long as the polarization direction at each wavelength is orthogonal.

  Thus, by changing the oscillation wavelength for each polarization direction of the fundamental wave, it is possible to prevent output instability due to inter-mode competition that occurs during multi-wavelength oscillation. When 1178 nm is generated, ASE (Amplitude Spontaneous Emission) light having a wavelength of 1040 to 1090 nm is generated. As a result, not only the efficiency of generation of 1178 nm is lowered, but also inadvertent pulse oscillation occurs, and the fiber laser resonator is destroyed. For this reason, when 1178 nm is generated, 1064 nm is also oscillated simultaneously. By doing so, inadvertent pulse oscillation can be suppressed and the destruction of the fiber laser resonator can be prevented. At this time, if the desired wavelength is 589 nm, which is a harmonic of 1178 nm, the reflection wavelength of the fiber grating 2109b is changed by controlling the temperature or tensile stress of the fiber grating 2109b for generating 1064 nm, so that 1064 nm becomes 1064 nm. The Q value of the generated resonator is reduced. As a result, the energy of the excitation light is used more for generation of 1178 nm by the fiber grating 2108b.

  Thus, it is essential that the fiber gratings 2108a, 2109a and the fiber 2110 are double clad polarization maintaining fibers. On the other hand, the panda coupler 2110a and the fiber gratings 2108b and 2109b are desirably ordinary polarization maintaining fibers having no double clad structure. The ends of the polarization-maintaining fibers on which the fiber gratings 2108b and 2109b are formed, that is, the exit of the fundamental wave, are fused and connected to a fiber 2117 that propagates the fundamental laser beam to the laser beam emitting unit 2102. In the vicinity of the fusion splicing point, photodiodes 2115 and 2116 for monitoring the return light of visible light generated by the wavelength conversion elements 2111 and 2112 disposed in the laser light irradiation unit 2102 are disposed, respectively. Yes. However, since infrared light also leaks together at the connection point, it is desirable that an infrared filter be attached to the photodiodes 2115 and 2116. In the case of the present embodiment, a dielectric multilayer film for returning to the incident direction by 8% of visible light generated by wavelength conversion is formed on the emission surfaces of the wavelength conversion elements 2111 and 2112. The visible light reflected in the incident direction is again coupled to the fiber 2117. At this time, since the fiber 2117 is a double clad fiber, the efficiency of coupling visible light to the fiber 2117 is improved, and more visible light can be propagated to the connection point. As a result, the photodiodes 2115 and 2116 can monitor the visible light more accurately. It should be noted that the amount of visible light reflected on the respective exit surfaces of the wavelength conversion elements 2111 and 2112 is preferably in the range of 1 to 10% depending on the length of the fiber 2117.

  The laser light source apparatus 2100 according to the present embodiment controls the phase matching conditions of the wavelength conversion elements 2111 and 2112 by changing the oscillation wavelength of the fiber laser 2103. Hereinafter, control of this phase matching condition will be described.

  In FIG. 16, as described above, visible light reflected by the emission end faces of the wavelength conversion elements 2111 and 2112 of the laser light irradiation unit 2102 is propagated to the laser oscillation device 2101 through the fiber 2117 and is reflected by the photodiodes 2115 and 2116. Is being monitored. The control unit 2105 acquires the output intensity of each visible light of the wavelength conversion elements 2111 and 2112 based on the monitoring results of the photodiodes 2115 and 2116. The control unit 2105 changes the oscillation wavelength of the fiber laser 2103 by shifting the reflection wavelength of the fiber gratings 2108b and 2109b based on the output intensity of each visible light of the wavelength conversion elements 2111 and 2112. By changing the oscillation wavelength of the fiber laser 2103, the phase matching conditions of the wavelength conversion elements 2111 and 2112 are controlled.

  The setting of the shift amount of the reflection wavelength of the fiber gratings 2108b and 2109b is realized, for example, by temperature control using a Peltier element. The control unit 2105 changes the oscillation wavelength of the fiber laser 2103 by controlling the temperature of the fiber gratings 2108b and 2109b when the output intensity fluctuates due to the failure of the phase matching condition of the wavelength conversion elements 2111 and 2112. The phase matching conditions 2111 and 2112 are established again. The setting of the shift amount of the reflection wavelength of the fiber gratings 2108b and 2109b may be controlled by applying a tensile stress to the fiber gratings 2108b and 2109b as in the first embodiment.

  Next, temperature control of the fiber gratings 2108b and 2109b by the control unit 2105 will be specifically described. In addition, since the same processing is performed for both temperature control of the fiber gratings 2108b and 2109b, a case where the temperature control of the fiber grating 2108b will be described below. FIG. 17A is a schematic diagram showing a change in the phase matching wavelength when the temperature of the wavelength conversion element 2112 is lowered, and FIG. 17B is a diagram of the phase matching wavelength when the temperature of the wavelength conversion element 2112 is increased. It is a schematic diagram showing a change. The fiber grating 2108b is temperature-controlled by a Peltier element so as to have a predetermined standby temperature in advance. As the standby temperature, for example, a temperature that is 85 to 95% of the phase matching temperature at which the output intensity of the wavelength conversion element 2112 peaks and is lower than the phase matching temperature can be used.

  First, in FIG. 17A, when the temperature of the wavelength conversion element 2112 decreases, the output of the wavelength conversion element 2112 increases as indicated by an arrow A1 in the figure. At this time, the characteristic curve of the phase matching wavelength shifts to the short wavelength side as indicated by an arrow A2 in the figure. Therefore, the control unit 2105 decreases the temperature of the fiber grating 2108b and shifts the oscillation wavelength of the fundamental wave emitted from the fiber laser 2103 to the short wavelength side. As a result, as indicated by an arrow A3 in the figure, the output of the wavelength conversion element 2112 decreases, and the output of the wavelength conversion element 2112 at the standby temperature is restored.

  On the other hand, in FIG. 17B, when the temperature of the wavelength conversion element 2112 increases, the output of the wavelength conversion element 2112 decreases as indicated by an arrow B1 in the figure. At this time, the characteristic curve of the phase matching wavelength shifts to the long wavelength side as indicated by an arrow B2 in the figure. Therefore, the control unit 2105 raises the temperature of the fiber grating 2108b to shift the oscillation wavelength of the fundamental wave emitted from the fiber laser 2103 to the longer wavelength side. Thereby, as indicated by an arrow B3 in the figure, the output of the wavelength conversion element 2112 rises and recovers to the output of the wavelength conversion element 2112 at the standby temperature.

  FIG. 18 is a flowchart showing a processing procedure for temperature control of the fiber grating 2108b by the control unit 2105 described above. First, the control unit 2105 acquires the monitoring result of the output intensity of the return light from the wavelength conversion element 2112 by the photodiode 2116 (step S101), and the output of the wavelength conversion element 2112 is increased or decreased. Is determined (step S102).

  Next, when it is determined in step S102 that the output of the wavelength conversion element 2112 is increasing, the control unit 2105 decreases the average current flowing in the Peltier element of the fiber grating 2108b (step S103). . Thereby, the temperature of the fiber grating 2108b is lowered by lowering the temperature of the Peltier element, and the oscillation wavelength of the fundamental wave emitted from the fiber laser 2103 is shifted to the short wavelength side (see FIG. 17A).

  Next, the control unit 2105 confirms that the drive current value of the excitation laser 2107 supplied by the power supply unit 2104 is within a predetermined setting range, and confirms the output intensity of the wavelength conversion element 2112 (step S104). ). Then, the drive current value from the power supply unit 2104 is compared with the initial current value, and if the difference between the two is within a predetermined setting range (YES in step S105), the process ends, and if it is out of the predetermined setting range ( Step S105 NO), the above steps S101 to 105 are repeated again.

  On the other hand, when it is determined in step S102 that the output of the wavelength conversion element 2112 has decreased, the control unit 2105 increases the average current flowing in the Peltier element of the fiber grating 2108b (step S106). Thus, the temperature of the fiber grating 2108b is raised by raising the temperature of the Peltier element, and the oscillation wavelength of the fundamental wave emitted from the fiber laser 2103 is shifted to the longer wavelength side (see FIG. 17B). And it progresses to said step S105.

  In this way, the temperature control processing of the fiber grating 2108b by the control unit 2105 described above is performed.

  In this embodiment, the bandwidth of the reflection wavelength of the fiber gratings 2108a and 2109a is preferably 1 nm or more in order to correspond to the shift amount of the reflection wavelength of the fiber gratings 2108b and 2109b. Further, in order to suppress the change in the oscillation efficiency of the resonator due to the shift of the reflection wavelength of the fiber gratings 2108b and 2109b, the top shape of the reflection wavelength band of the fiber gratings 2108a and 2109a is a shape with suppressed ripples, that is, as flat as possible. It is desirable.

  In this embodiment, the temperatures of the fiber gratings 2108b and 2109b are controlled. However, the temperature of the fiber gratings 2108a and 2108b and the fiber gratings 2109a and 2109b are controlled together as one set. Also good. Each set may be enclosed in a temperature compensation package. By doing so, the same effect as described above can be obtained even when the reflection wavelength band of the fiber gratings 2108a and 2109a is set to 0.2 to 1 nm.

  In this way, by controlling the output intensity of the visible light that has been wavelength-converted by the oscillation wavelength of the fiber laser 2103, the wiring from the laser oscillation device 2101 to the laser light irradiation unit 2102 can be reduced, and the laser irradiation unit 2102 can be reduced. The degree of freedom of design is improved. In addition, the number of wirings and the like that become obstacles when actually holding the laser beam irradiation unit 2102 by hand is reduced, and the user-friendliness of the laser beam irradiation unit 2102 can be improved.

  Next, the wavelength change of the emitted light by the operation of the laser light irradiation unit 2102 will be described. FIGS. 19A to 19C show a schematic configuration of the laser light irradiation unit 2102.

  As illustrated in FIGS. 19A to 19C, the laser light irradiation unit 2102 includes two wavelength conversion elements 2111 and 2112 and a light selection unit 2113, and the light selection unit 2113 is illustrated in FIG. A pedestal 2401 movable in the direction indicated by the arrow in the middle, a first dielectric multilayer mirror 2402 disposed on the pedestal 2401 and reflecting only infrared light, and adjacent to the first dielectric multilayer mirror 2402 The second dielectric multilayer mirror 2403 is arranged on the pedestal 2401 and reflects only visible light.

  FIG. 19A shows a state where the second dielectric multilayer mirror 2403 is positioned so as to face the emission surface of the wavelength conversion element 2111 that emits the green light 2111a. In this case, since the second dielectric multilayer mirror 2403 that reflects only visible light is in front of the emission surface of the wavelength conversion element 2111, the green light 2111a is emitted to the outside of the laser light irradiation unit 2102.

  FIG. 19B shows a state where the second dielectric multilayer mirror 2403 is positioned so as to face the emission surface of the wavelength conversion element 2112 that emits the orange light 2112a. In this case, since the second dielectric multilayer mirror 2403 that reflects only visible light is in front of the emission surface of the wavelength conversion element 2112, the orange light 2112 a is emitted outside the laser light irradiation unit 2102.

  FIG. 19C shows a state where the first dielectric multilayer mirror 2402 is positioned so as to face the emission surface of the wavelength conversion element 2111 that emits the infrared light 2111b. In this case, since the first dielectric multilayer mirror 2402 that reflects only infrared light is in front of the emission surface of the wavelength conversion element 2111, unconverted infrared light out of the fundamental wave incident on the wavelength conversion element 2111. The light 2111b is emitted to the outside of the laser light irradiation unit 2102.

  In this manner, the wavelength of the emitted light can be changed by operating the laser light irradiation unit 2102.

  In this embodiment mode, the oscillation efficiency of the fiber laser 2103 can be optimized by controlling the fiber laser 2103 of the laser oscillation device 2101 in accordance with the wavelength of the emitted light of the laser light irradiation unit 2102. Hereinafter, optimization of the oscillation efficiency will be described.

  For example, in the state of FIG. 19A, the emitted light from the laser light irradiation unit 2102 is green light 2111a. Therefore, the fundamental wave to be emitted from the laser oscillation device 2101 is 1064 nm light that is the fundamental wave of the green light 2111a emitted from the wavelength conversion element 2111, and the fundamental wave of orange light emitted from the wavelength conversion element 2112 This 1178 nm light becomes unnecessary. Therefore, at this time, the control unit 2105 performs temperature control and tensile stress addition control of the fiber grating 2108b so that the reflection wavelength band of the fiber grating 2108b that oscillates 1178 nm light is out of the reflection wavelength band of the fiber grating 2108a. . In this way, the oscillation of the 1178 nm light can be stopped, and all of the excitation energy of the excitation laser 2107 can be used for the 1064 nm light oscillation by the fiber grating 2109b. For this reason, the oscillation efficiency of 1064 nm light by the fiber grating 2109b can be improved.

  FIG. 20A shows the relationship of the reflection wavelength bands of the fiber gratings 2108 a, 2108 b, 2109 a, and 2109 b with respect to the oscillation wavelength of the fiber laser 2103. As described above, at the oscillation wavelength of 1178 nm, the reflection wavelength band of the fiber grating 2108b deviates from the reflection wavelength band of the fiber grating 2108a. At the oscillation wavelength of 1064 nm, the reflection wavelength band of the fiber grating 2109b is the reflection wavelength of the fiber grating 2109a. Located in the band.

  Next, in the state of FIG. 19B, the emitted light from the laser light irradiation unit 2102 is orange light 2112a. Accordingly, the fundamental wave to be emitted from the laser oscillation device 2101 is 1178 nm light that is the fundamental wave of the orange light 2112a emitted from the wavelength conversion element 2112. The fundamental wave of green light emitted from the wavelength conversion element 2111 is This 1064 nm light is basically unnecessary. However, at this time, similarly to the generation of the green light, when the oscillation of the 1064 nm light is completely stopped, the fiber laser 2103 is destroyed by the generation of the ASE light giant pulse. Therefore, the control unit 2105 performs temperature control and tensile stress addition control of the fiber grating 2109b so that the reflection wavelength band of the fiber grating 2109b that oscillates 1064 nm light is applied to the edge of the reflection wavelength band of the fiber grating 2109a. . By doing so, it becomes possible to oscillate the 1064 nm light weakly and to prevent the ASE giant pulse. Therefore, most of the excitation energy of the excitation laser 2107 can be used for oscillation of 1178 nm light by the fiber grating 2108b. Therefore, the oscillation efficiency of 1178 nm light by the fiber grating 2108b can be improved without generating ASE.

  FIG. 20B shows the relationship of the reflection wavelength bands of the fiber gratings 2108 a, 2108 b, 2109 a, and 2109 b with respect to the oscillation wavelength of the fiber laser 2103. As described above, at the oscillation wavelength of 1064 nm, the reflection wavelength band of the fiber grating 2109b is on the edge of the reflection wavelength band of the fiber grating 2109a, and at the oscillation wavelength of 1178 nm, the reflection wavelength band of the fiber grating 2108b is the fiber grating. 2108a is located within the reflection wavelength band.

  Next, in the state of FIG. 19C, the emitted light from the laser light irradiation unit 2102 is infrared light 2111 b that is a fundamental wave incident on the wavelength conversion element 2111. Therefore, the fundamental wave to be emitted from the laser oscillation device 2101 is 1064 nm light that is the fundamental wave of the green light 2111a emitted from the wavelength conversion element 2111, and the fundamental wave of orange light emitted from the wavelength conversion element 2112 This 1178 nm light becomes unnecessary. Therefore, at this time, the control unit 2105 performs temperature control and tensile stress addition control of the fiber grating 2108b so that the reflection wavelength band of the fiber grating 2108b that oscillates 1178 nm light is out of the reflection wavelength band of the fiber grating 2108a. . In this way, the oscillation of the 1178 nm light can be stopped, and all of the excitation energy of the excitation laser 2107 can be used for the 1064 nm light oscillation by the fiber grating 2109b. For this reason, the oscillation efficiency of 1064 nm light by the fiber grating 2109b can be improved. In addition, by not satisfying the phase matching condition of the wavelength conversion element 2111, the wavelength conversion efficiency by the wavelength conversion element 2111 can be reduced, and thereby the extraction amount of unconverted infrared light 2111b can be increased.

  Further, in this embodiment, by using the lighting switch 2106 of the laser oscillation device 2101 and the shutter 2114 of the laser light irradiation unit 2102, the timing for emitting the laser light can be determined by the user, whereby consumption by the fiber laser 2103 is performed. Electric power can be reduced. Hereinafter, this reduction in power consumption will be described.

  FIG. 21 is a flowchart showing a processing procedure of the emission operation of the laser light irradiation unit 2102 by the lighting switch 2106 and the laser light irradiation unit 2102. First, when the lighting switch 2106 is turned ON by the user of the laser light source device 2100 (step S201), a lighting command is notified from the lighting switch 2106 to the control unit 2105 (step S202).

  The control unit 2105 controls the power supply unit 2104 based on the lighting command from the lighting switch 2106 to turn on the excitation laser 2107 with a predetermined drive current (step S203). The control unit 2105 monitors the return light of the visible light emitted from the wavelength conversion elements 2111 and 2112 generated by turning on the excitation laser 2107 with the photodiodes 2115 and 2116. Then, by using the monitoring result, the oscillation wavelength of the fiber laser 2103 is changed by controlling the reflection wavelength of the fiber gratings 2108b and 2109b so that the output intensity of the wavelength conversion elements 2111 and 2112 is maximized (step S204). . Here, the control of the reflection wavelengths of the fiber gratings 2108b and 2109b may be performed by temperature control as described above, or by tensile stress addition control.

  Next, the controller 2105 opens the shutter 2114 of the laser light irradiation unit 2102 when the outputs of the wavelength conversion elements 2111 and 2112 are stabilized (step S205 YES), and outputs the wavelength conversion elements 2111 and 2112 from the laser light irradiation unit 2102. Irradiation is performed (step S206). On the other hand, if the output is not stable in step S205 (step S205 NO), steps S204 and 205 are repeated.

  In this manner, the emission operation of the laser light irradiation unit 2102 by the lighting switch 2106 and the laser light irradiation unit 2102 is performed.

  In this embodiment, as a method for satisfying the phase matching conditions of the wavelength conversion elements 2111 and 2112, the operation from the operation of the lighting switch 2106 to the emission of visible laser light is adopted by changing the oscillation wavelength of the fiber laser 2103. It can be executed in 200 μs or less.

  As described above, when the phase matching condition is satisfied by the temperature control of the wavelength conversion elements 2111 and 2112, it is desirable that the wavelength conversion elements 2111 and 2112 have a small heat capacity. This is because by using a wavelength conversion element having a small heat capacity, it is possible to reduce the time constant during temperature control and satisfy the phase matching condition in a short time.

  Thus, by shortening the time from the operation of the lighting switch 2106 to the light emission from the laser light irradiation unit 2102, it is not necessary to make the fiber laser 2103 stand by in an operating state, thereby realizing a significant reduction in power consumption. be able to.

  In this embodiment, when using a different laser beam irradiation unit 2102 for each oscillation wavelength, the irradiation range of the laser beam irradiation unit 2102 can be determined by adding a probe to the tip of the laser beam irradiation unit 2102. it can. FIG. 22 shows a schematic configuration in which a probe is added to the emission surface of the laser light irradiation unit 2102.

  As shown in FIG. 22, a probe 2701 is provided on the emission surface of the laser light irradiation unit 2102. A reflection mirror 2702 having a reflectivity of, for example, about 10% with respect to the light emitted from the wavelength conversion element 2111 is disposed inside the probe 2701. A part of the light emitted from the wavelength conversion element 2111 is reflected by the reflection mirror 2702, and the reflected light passes through the wavelength conversion element 2111 again and is monitored by the photodiode 2115 of the laser oscillation device 2101 through the fiber 2117. . By doing so, it is possible to detect whether the probe is mounted or not based on the presence or absence of the reflected light, and misuse of the laser light irradiation unit 2102 can be prevented. In addition, when the type of probe to be used differs depending on the wavelength range of the emitted light, it is possible to prevent erroneous use of the probe for the wavelength used by providing a reflective mirror suitable for reflecting light in the wavelength range suitable for each probe can do.

  In this embodiment mode, by calibrating the excitation energy of the excitation laser 2107, a stable visible laser beam having a desired output can be obtained from the start of the laser. For example, a calibration mode for calibrating the monitoring results by the photodiodes 2115 and 2116 of the laser oscillation device 2101 and the actual output intensity of the wavelength conversion elements 2111 and 2112 may be provided. By directly taking the light emitted from the laser light irradiation unit 2102 into the laser oscillation device 2101, an operation for obtaining a correlation between the actual output intensity and the monitor result is performed from the actual output intensity and the monitor results of the photodiodes 2115 and 2116. . The correlation data is stored as correction data in a storage medium such as a register in the control unit 2105. By this operation, a stable visible laser beam having a desired output can be obtained from the time when the excitation laser 2107 is started up.

Conventionally, as shown in FIG. 23, as the output of the fiber laser 2103 increases, the fiber gratings 2108b and 2109b are heated by the oscillation light, causing non-uniform thermal expansion and widening the bandwidth of the reflected wavelength. was there. For example, in FIG. 24, when the wavelength conversion elements 2111 and 2112 are formed of a Mg: LiNbO ₃ crystal having a polarization inversion period length of 25 mm by quasi phase matching, the half width of the fundamental wave of the laser beam of the fiber laser 2103 and the fundamental wave The relationship with the wavelength conversion efficiency (standardized wavelength conversion efficiency) from a to a harmonic is shown. As shown in FIG. 24, the bandwidths of the reflected wavelengths of the fiber gratings 2108b and 2109b are widened. As a result, the half-value width of the fundamental wave emitted from the fiber laser 2103 is widened, and the wavelength conversion efficiency by the wavelength conversion elements 2111 and 2112 is reduced. There is a problem of doing. Normally, the maximum wavelength conversion efficiency of a wavelength conversion element using Mg: LiNbO ₃ crystal is about 6.5% / W, but it becomes difficult to maximize the wavelength conversion efficiency as the half-width of the fundamental wave increases. End up. Therefore, in order to use the wavelength conversion element at 90% or more of the maximum wavelength conversion efficiency, it is desirable that the half width of the fundamental wave of the laser light of the fiber laser 2103 is 0.06 nm or less. In the present embodiment, partial thermal expansion can be made uniform by fixing the fiber gratings 2108b and 2109b while applying tensile stress to this problem. Therefore, as shown in FIG. 25, even when the output of the fiber laser 2103 is increased, the expansion of the bandwidth of the fundamental wave is suppressed, and a decrease in the wavelength conversion efficiency from the fundamental wave to visible light can be prevented. .

  In this embodiment mode, a laser having a wavelength of 915 nm and a wavelength of 976 nm is generally used for the excitation laser light source 2107 of the fiber laser 2103, but any other wavelength can be used as long as it can excite the fiber laser 2103. The laser light source may be used.

The wavelength conversion elements 2111 and 2112 are made of MgO: LiNbO ₃ having a domain-inverted periodic structure. However, wavelength conversion elements having other materials and structures such as potassium titanyl phosphate (KTP) and Mg having a domain-inverted periodic structure are used. : LiTaO ₃ may be used.

  Note that the range of the oscillation wavelength of the fundamental wave of the laser light of the fiber laser 2103 is 1028 to 1064 nm and 1120 to 1200 nm in relation to the absorption spectrum of hemoglobin contained in blood, particularly in the field of medical devices. It is desirable that

  As described above, according to the fifth embodiment of the present invention, the power consumption of the entire apparatus can be reduced by reducing the optical loss of the laser beam. Further, by making the polarization directions of different wavelengths orthogonal to each other, it is possible to prevent competition between modes and obtain a stable laser light output. Furthermore, by making the Q value of the laser resonator variable according to the oscillation wavelength, it is possible to prevent inadvertent pulse oscillation of the laser light while suppressing a decrease in the efficiency of the laser oscillator. Thereby, the reliability of the apparatus can be improved.

  Since the laser light source device according to the fifth embodiment has high brightness and low power consumption, it is useful in the field of medical devices used in ophthalmology and the like, and can also be applied as a display device such as a laser display. It is.

  Since the laser light source device and the image display device of the present invention have high brightness, a wide color reproduction range and low power consumption, they are used in display fields such as large displays and high brightness displays, analysis applications in the biochemical field, ophthalmology, etc. Useful in the field of medical devices.

It is a schematic diagram which shows schematic structure of the laser light source which concerns on Embodiment 1 of this invention. (A) is a figure which shows the reflection spectrum of a 1st fiber grating, (b) is a figure which shows the reflection spectrum of a 2nd fiber grating. It is a figure for demonstrating the wavelength selection operation | movement of the laser light source which concerns on Embodiment 1 of this invention. It is a figure which shows the relationship between the oscillation wavelength of a Yb addition fiber, and a loss. It is a figure which shows the relationship between the reflective wavelength of a 2nd fiber grating, and a reflectance. It is the schematic which shows the structure of a wavelength conversion part. It is the schematic which shows the other structure of a wavelength conversion part. It is the schematic which shows the other structure of a wavelength conversion part. It is a schematic diagram which shows the structure of the polarization inversion period of the nonlinear optical crystal which comprises a wavelength conversion element. It is a figure which shows the input-output characteristic of the fundamental wave of an excitation laser. It is a schematic diagram which shows schematic structure of the two-dimensional image display apparatus which concerns on Embodiment 2 of this invention. It is a chromaticity diagram showing the relationship between the wavelength of green light and the color reproduction range. It is a schematic diagram which shows schematic structure of the laser light source which concerns on Embodiment 3 of this invention. It is a schematic diagram which shows schematic structure of the laser fluorescence microscope which concerns on Embodiment 4 of this invention. (A) is a figure which shows the oscillation spectrum of the fiber laser at the time of ASE generation | occurrence | production, (b) is a figure which shows the oscillation spectrum of the fiber laser at the time of ASE countermeasures. It is a schematic diagram which shows schematic structure of the laser light source apparatus which concerns on Embodiment 5 of this invention. It is a figure which shows the change of the characteristic curve of the phase matching wavelength of a wavelength conversion element. It is a flowchart which shows the process sequence of the temperature control of a fiber grating. It is a schematic diagram which shows schematic structure of a laser beam irradiation part. It is a figure which shows the relationship of the zone | band of the reflection wavelength of a fiber grating with respect to the oscillation wavelength of a fiber laser. It is a flowchart which shows the process sequence of the emission operation | movement of a laser beam irradiation part. It is a schematic diagram which shows schematic structure which added the probe to the output surface of the laser beam irradiation part. It is a figure which shows the relationship between the fundamental wave output of a fiber laser, and an oscillation wavelength bandwidth. It is a figure which shows the relationship between the fundamental wave half width of a fiber laser, and conversion efficiency. It is a figure which shows the other relationship between the fundamental wave output of a fiber laser, and an oscillation wavelength bandwidth. (A) is a schematic diagram which shows schematic structure of the conventional fiber laser, (b) is sectional drawing which shows schematic structure of the conventional semiconductor laser.

Explanation of symbols

8 Beam splitter 21, 110 Laser light source 22 Fiber laser 23 Wavelength conversion unit 24 Harmonic 25, 25a, 25b, 25c, 25d, 2111, 1122 Wavelength conversion element 26, 32, 2110, 2117 Fiber 27, 2004 Excitation light 28, 2107 Excitation laser 29, 30, 2108a, 2108b, 2109a, 2109b Fiber grating 31, 1009a, 1009b, 1009c Condensing lens 33 Reflection wavelength variable section 34, 2105 Control section (controller)
35, 35a, 35b, 35c, 35d Wavelength conversion element holding unit 36 Excitation laser current source 37 Light receiving element 41 Spacer 42 Heater 51 Peltier element controller 52 Moving stage 53 Fundamental wave 1001a Red laser light source (R light source)
1001b Green laser light source (G light source)
1001c Blue laser light source (B light source)
1002a, 1002b, 1002c Two-dimensional beam scanning means 1003a, 1003b, 1003c Diffuser plate 1004a, 1004b, 1004c Field lens 1005a, 1005b, 1005c Spatial light modulation element 1006 Dichroic prism 1007 Projection lens 1008 Screen 1009 Concave lens 1101 Projector control circuit 1 Circuit 1103 Luminance signal determination circuit 1104 Video mode switch 1105 Video signal (data)
1106 Video signal (video)
DESCRIPTION OF SYMBOLS 1107 Wavelength selection signal 1108 AC power supply 1109 Battery 1110 Power supply control circuit 1111 Power supply determination signal 1301 Laser fluorescence microscope 1302a, 1302b Mirror 1303 Microscope 1304 Sample 2001 Sampled grating 2002 Raman fiber 2003 Broadband dielectric mirror 2005 Light of λ4 2006 Semiconductor substrate 2007 Light emission Region 2008 Reflection region 2009 Control means (refractive index changing electrode)
2100 Laser light source device 2101 Laser oscillation device 2102 Laser light irradiation unit 2103 Fiber laser 2104 Power supply unit 2106 Lighting switch 2110a Panda coupler 2113 Light selection unit 2114 Shutter 2115, 2116 Photodiode 2401 Base 2402, 2403 Dielectric multilayer mirror 2111a Green light 2112a Orange light 2111b Infrared light 2701 Probe 2702 Reflection mirror

Claims (31)

A laser light source that emits excitation light;
A fiber containing a laser active material and receiving excitation light from the laser light source; a first fiber grating having a plurality of reflection peaks provided on the laser light source side of the fiber; and an emission end side of the fiber A second fiber grating having a plurality of reflection peaks, and a laser resonator comprising:
A wavelength converter that converts the fundamental wave emitted from the laser resonator into a harmonic; and
A reflection wavelength variable portion capable of shifting the reflection wavelength of the reflection peak of the second fiber grating;
A control unit for controlling the oscillation wavelength of the laser resonator by the reflection wavelength variable unit, and for controlling a phase matching condition of the wavelength conversion unit,
The laser light source device, wherein an interval between adjacent reflection peaks of the first fiber grating is different from an interval between adjacent reflection peaks of the second fiber grating.   The grating length defining each of the reflectances of the plurality of reflection peaks of the second fiber grating prevents the decrease in oscillation efficiency of the fiber due to a decrease in the oscillation wavelength of the laser resonator. 2. The laser light source device according to claim 1, wherein the laser light source device is configured to become longer in the direction in which the oscillation wavelength decreases. The bandwidth of the reflection peak of the first fiber grating is wider than the bandwidth of the reflection peak of the second fiber grating,
3. The laser light source device according to claim 1, wherein the reflectance of the reflection peak of the first fiber grating is larger than the reflectance of the reflection peak of the second fiber grating. 4.   The bandwidth of the reflection peak of the first fiber grating is 0.5 to 2 nm, and the bandwidth of the reflection peak of the second fiber grating is 0.2 nm or less. The laser light source device according to any one of the above.   The reflectance of the reflection peak of the first fiber grating is 95% or more, and the reflectance of the reflection peak of the second fiber grating is 5 to 20%. The laser light source device according to claim 1.   The control unit switches the oscillation wavelength of the laser resonator by shifting the reflection wavelength of the reflection peak of the second fiber grating by the reflection wavelength variable unit, and then converts the wavelength according to the switched oscillation wavelength. The laser light source device according to claim 1, wherein the phase matching condition of the part is changed. The wavelength converter is
A first wavelength converting element composed of a nonlinear crystal using angular phase matching;
The laser resonator for the first wavelength conversion element according to the oscillation wavelength of the laser resonator to hold the first wavelength conversion element and to satisfy the angle phase matching condition of the first wavelength conversion element A first holding unit for setting the incident angle of the fundamental wave emitted from
The laser light source device according to claim 6, wherein the control unit controls a phase matching condition of the wavelength conversion unit by the first holding unit. The wavelength converter further includes
A second wavelength conversion element composed of a nonlinear crystal using angular phase matching;
While holding the second wavelength conversion element, the first wavelength conversion element corresponding to the second wavelength conversion element according to the oscillation wavelength of the laser resonator to satisfy the angle phase matching condition of the second wavelength conversion element A second holding unit for setting the incident angle of the fundamental wave emitted from the wavelength conversion element,
The second holding unit is arranged to suppress a change in the optical axis caused by the first holding unit,
The laser light source device according to claim 7, wherein the control unit controls a phase matching condition of the wavelength conversion unit by the first and second holding units. The wavelength converter is
A wavelength conversion element composed of a nonlinear crystal using temperature phase matching;
Holding the wavelength conversion element, and having a holding unit for setting the temperature of the wavelength conversion element according to the oscillation wavelength of the laser resonator so as to establish the temperature phase matching condition of the wavelength conversion element,
The laser light source device according to claim 6, wherein the control unit controls a phase matching condition of the wavelength conversion unit by the holding unit. The wavelength converter is
A wavelength conversion element composed of a nonlinear crystal using quasi-phase matching and having a domain-inverted periodic structure;
The wavelength conversion element is held and emitted from the laser resonator to the polarization inversion period region of the wavelength conversion element according to the oscillation wavelength of the laser resonator to satisfy the quasi phase matching condition of the wavelength conversion element A holding part for making the fundamental wave incident,
The laser light source device according to claim 6, wherein the control unit controls a phase matching condition of the wavelength conversion unit by the holding unit. The period of the polarization inversion periodic structure of the wavelength conversion element changes in a direction perpendicular to the incident direction of the fundamental wave emitted from the laser resonator,
The said holding | maintenance part has a moving stage which can move the said wavelength conversion element in the direction in which the period of the said polarization inversion periodic structure changes according to the oscillation wavelength of the said laser resonator. Laser light source device.   11. The laser light source device according to claim 10, wherein a period of the polarization inversion periodic structure of the wavelength conversion element changes along an incident direction of a fundamental wave emitted from the laser resonator.   The laser light source device according to any one of claims 1 to 12, wherein there are two reflection peaks having an overlapping portion between the first fiber grating and the second fiber grating. .   The laser light source device according to claim 13, wherein ranges of reflection wavelengths of the two reflection peaks having the overlapping portion are 1000 to 1090 nm and 1100 to 1180 nm. An image display device,
The laser light source device according to any one of claims 1 to 14,
A wavelength determination circuit that is connected to the control unit of the laser light source device and outputs a selection signal for determining the oscillation wavelength of the laser light source device to the control unit, and is displayed by laser light emitted from the laser light source device. A luminance signal determination circuit that determines the luminance of the video signal based on a luminance signal included in the video signal and outputs the determined luminance to the wavelength determination circuit;
A video mode switching unit for instructing the wavelength determination circuit to oscillate wavelengths of the laser light source device input by a user of the image display device;
An image display device comprising: a power supply control circuit that determines a type and remaining amount of a power source used by the image display device and outputs the determined power source type and remaining amount to the wavelength determination circuit. . The laser light source device according to any one of claims 1 to 14,
A microscope unit comprising: a microscope unit capable of observing light emission of the fluorescent sample by excitation of the fluorescent sample by irradiation of laser light emitted from the laser light source device A laser oscillation device that emits at least two fundamental waves;
A laser beam irradiation unit capable of converting at least two fundamental waves emitted from the laser oscillation device into harmonics and irradiating the converted harmonics;
A fiber unit disposed between the laser oscillation device and the laser light irradiation unit and propagating a fundamental wave emitted from the laser oscillation device to the laser light irradiation unit;
The laser oscillation device includes:
A laser light source that emits excitation light;
A fiber containing a laser active material and receiving excitation light from the laser light source; at least two first fiber gratings provided on the laser light source side of the fiber; and provided on an emission end side of the fiber. A laser light source device comprising: at least two second fiber gratings corresponding to the first fiber gratings on a one-to-one basis, and laser resonators. The laser resonator further includes an optical branching unit that branches the outgoing light according to a polarization direction of the outgoing light of the fiber,
18. The laser light source device according to claim 17, wherein the second fiber grating receives one of the branched lights branched by the light branching unit.   The second fiber grating is configured such that the reflection wavelength of the second fiber grating can be shifted so that the Q value of the resonator formed between the second fiber grating and the corresponding first fiber grating can be varied. The laser light source device according to claim 17 or 18, characterized in that: The laser beam irradiation unit is
At least two wavelength conversion elements for converting a fundamental wave emitted from the laser resonator into a harmonic;
An optical member that reflects part of the harmonics emitted from the wavelength conversion element;
The harmonics reflected by the optical member are fed back to the laser oscillation device by the fiber part,
The laser light source device according to any one of claims 17 to 19, wherein the laser oscillation device changes an oscillation wavelength of the laser resonator based on an output intensity of the fed back harmonic.   The laser light source device according to claim 20, wherein the reflectance of the optical member is 1 to 10%.   The laser light source device according to claim 20 or 21, wherein the optical member is a dielectric multilayer film disposed on an emission surface of the wavelength conversion element.   21. The laser beam irradiation unit further includes a light selection unit that selectively irradiates one of light emitted from the at least two wavelength conversion elements from the laser beam irradiation unit. The laser light source device according to any one of ˜22.   The laser light source device according to any one of claims 17 to 23, wherein the fiber portion is a double clad fiber.   25. The reflection wavelength of the second fiber grating is shifted by controlling either the temperature of the second fiber grating or the addition of tensile stress. Laser light source device. The laser oscillation device further includes
A detection unit for detecting the output intensity of the harmonics fed back by the fiber unit;
The control unit according to any one of claims 17 to 25, further comprising: a control unit that controls a shift amount of a reflection wavelength of the second fiber grating based on an output intensity of a harmonic detected by the detection unit. The laser light source device according to 1.   The detection unit is a light receiving element that is disposed in the vicinity of a connection point between the laser resonator and the fiber unit, and that receives the harmonic leakage light from the connection point. Laser light source device. The laser oscillation device further includes a switch unit to which an instruction to turn on the laser light source is input by a user of the laser light source device,
The control unit turns on the laser light source based on a lighting command input by the switch unit, and reflects the reflected wavelength of the second fiber grating so as to stabilize the output intensity of the harmonic detected by the detection unit. Control the shift amount of
The laser light irradiation unit further includes a switch that allows the laser light irradiation unit to irradiate the harmonics emitted from the wavelength conversion element after the output intensity of the harmonics is stabilized by the control unit. 28. The laser light source device according to claim 26, wherein the laser light source device is provided.   The control unit converts the wavelength of the fundamental wave emitted from the laser resonator by the wavelength conversion element when the phase matching condition of the wavelength conversion element is not established by controlling the shift amount of the reflection wavelength of the second fiber grating. The laser light source device according to any one of claims 26 to 28, wherein the laser light source device emits light from the wavelength conversion element without being transmitted.   30. The laser light source device according to any one of claims 17 to 29, wherein the ranges of oscillation wavelengths of at least two fundamental waves emitted from the laser resonator are 1000 to 1100 nm and 1100 to 1200 nm. . The wavelength conversion element is composed of Mg: LiNbO ₃ crystal by quasi phase matching,
The laser light source device according to any one of claims 20 to 23, wherein a half width of a fundamental wave emitted from the laser resonator is 0.06 nm or less.

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