JP2007266537A - Internal resonator-type sum frequency mixing laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To materialize a laser equipment for producing a coherent beam with a wavelength of about 488 nm, and for simultaneously producing two coherent beams with wavelengths of 488 nm and 515 nm by using a semiconductor laser as an induction source in a semiconductor laser pumped solid-state laser to do internal resonator-type sum frequency mixing. <P>SOLUTION: An Nd:YAP crystal 6 and Yb:YAG crystal 7 are arranged in a laser resonator as a gain medium by using a first reflecting mirror 5 and a second reflecting mirror 14, which are excited by a semiconductor laser 1 to obtain laser oscillation with wavelengths of 930 nm and 1,030 nm. By use of a first LBO crystal 9 that is arranged in the laser resonator as a nonlinear optical medium, the sum frequency mixing of the laser beam with a wavelength of 930 nm and that with a wavelength of 1,030 nm is performed to produce a coherent beam with a wavelength of about 488 nm. Further, by use of a second LBO crystal 13, a second higher harmonic wave of the laser beam with the wavelength of 1,030 nm is produced, thus simultaneously producing a coherent beam with a wavelength of 515 nm as well. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention uses a two-type laser medium in a laser for converting the oscillation wavelength of a laser beam using a nonlinear optical crystal, and performs sum frequency mixing of two laser beams that oscillate simultaneously in a resonator. In particular, an internal resonator type sum frequency laser that generates laser light having a wavelength in the visible light region, in particular, laser light having a wavelength substantially equal to or close to the wavelength of 488 nm of an argon laser conventionally used in various fields. The present invention relates to a laser device that generates

An argon laser whose main oscillation wavelength is 488 nm is used in various fields such as a spectroscopic device, a bioanalyzer, a medical device, a printing device, a physics experiment, and a biochemistry experiment. In addition, in some of these applications, an argon laser that generates two wavelengths of 488 nm and 514 nm at the same time instead of a single oscillation wavelength of 488 nm, and an oscillation line of this nearby wavelength in addition to these two wavelengths are used. In addition, an argon laser that simultaneously oscillates at a larger number of wavelengths is also used.
However, since the argon laser is a gas laser that uses the discharge phenomenon, the size and power consumption are significantly larger than those of a semiconductor laser-pumped solid-state laser that generates an internal resonator type second harmonic and has the same power level. There is a problem. Therefore, a solid-state laser that replaces the argon laser has been desired. However, no solid-state laser crystal has an oscillation line of just 976 nm, and until recently there has been no solid-state laser that generates coherent light of 488 nm. However, recently, laser devices that generate coherent light with a wavelength of 488 nm, which is composed of only solid elements, have appeared.

  In Patent Document 1, a semiconductor element in which an active layer using a distributed Bragg reflection layer and a quantum well is formed on a semiconductor substrate, and a laser resonator in which a nonlinear optical medium and a reflecting mirror are arranged in the vertical direction of the element, The semiconductor element is excited by current injection, oscillates at a wavelength in the near-infrared region, generates a second harmonic having a near-infrared light as a fundamental wave in a nonlinear optical medium, and generates visible coherent light. . Although a specific wavelength is not shown in Patent Document 1, a laser device having a wavelength of 488 nm using the technique disclosed in Patent Document 1 is manufactured and sold by the company that applied for this patent. I had been there.

  In Patent Document 2, a semiconductor element having a gain portion by providing a structure in which a plurality of active layers are separated by a spacer layer by epitaxial growth on a semiconductor substrate is optically excited by a semiconductor laser beam from the outside to form a gain medium. A laser resonator that oscillates at a wavelength in the near infrared region between the reflector and the externally arranged mirror, generates second harmonics by a nonlinear optical crystal placed in the resonator, and generates coherent light in the visible light region. Is output. According to the example of Patent Document 2, coherent light having a wavelength of 488 nm is obtained when a semiconductor element is designed so that the wavelength of near-infrared light is 976 nm. The company that is the applicant of this patent manufactures and sells a laser device having a wavelength of 488 nm using the technique disclosed in Patent Document 2.

In Reference Document 1, an Nd: YLF laser having a wavelength of 1047 nm and an Nd: GdVO ₄ laser having a wavelength of 912 nm are excited by one semiconductor laser, and the two lasers are simultaneously oscillated. An example in which a nonlinear optical crystal for performing sum frequency mixing is arranged to generate coherent light having a wavelength of 487 nm has been reported.

US Pat. No. 6,243,407, “High power laser devices”. U.S. Pat. No. 5,991,318, “Intracavity frequency-converted optically-pumped semiconductor laser”.

Reference 1

Conference on Laser and Electro-Optics 2005, Lecture Number CMAA7, “Generation of continuous light by sum-frequency mixing of diodes pumping”

  The techniques of Patent Document 1 and Patent Document 2 have an advantage that a small device that generates coherent light having a wavelength of 488 nm can be realized. However, since an advanced semiconductor device manufacturing process is required to manufacture the most important gain medium, it is not easy to obtain a semiconductor device for manufacturing the semiconductor device. In addition, the manufacturing cost of semiconductor devices is generally reduced when mass-produced, but the demand for lasers with a wavelength of 488 nm is significantly smaller than the quantity generally called mass production generally referred to in the semiconductor industry. It is estimated that the cost for manufacturing the semiconductor elements shown in the literature is very high.

In the technique shown in Reference Document 1, Nd: GdVO ₄ has a stronger oscillation line at a wavelength of 1063 nm as well as an oscillation line with a wavelength of 912 nm. Therefore, an Nd: YLF laser with a wavelength of 1047 nm close to this wavelength is used. While oscillating, it was necessary to suppress the oscillation of Nd: GdVO _{4 at} a wavelength of 1063 nm. For this purpose, an experiment is conducted to generate coherent light having a wavelength of 489 nm by providing an optical path that is not common to the two laser resonators using a large number of reflecting mirrors and arranging a prism therefor for wavelength selection. It was. This method is considered difficult to reduce in size and cost because it requires a large number of reflecting mirrors, requires a wavelength selection element, and has a complicated resonator configuration.

  In the above example, the oscillation wavelength is only 488 nm, and a plurality of wavelengths are not simultaneously generated unlike an argon laser.

  The present invention generates coherent light equivalent to a conventional argon laser having a wavelength of 488 nm by using only those that are technically established such as solid laser crystals, semiconductor lasers for excitation, and nonlinear optical crystals. An object of the present invention is to realize a semiconductor-pumped solid-state laser that can be manufactured with a configuration that is small in size and can reduce production costs.

  As the means, in the semiconductor laser pumped solid-state laser that uses the first laser crystal doped with neodymium as a gain medium and oscillates at a first wavelength between 0.91 μm and 0.95 μm, the semiconductor laser pumped solid-state laser The second laser crystal with ytterbium added inside the resonator is disposed as a gain medium, and the second laser crystal is excited by the laser light of the first wavelength, and the wavelength is 1.02 μm within the laser resonator. First nonlinear optical medium capable of laser oscillation even at a second wavelength in the range of ˜1.05 μm and capable of sum frequency mixing with the laser light of the first wavelength and the second wavelength in the laser resonator The third wavelength coherent light having a wavelength in the range of 0.48 μm to 0.50 μm is output.

Here, if neodymium-doped yttrium aluminum perovskite (structural formula is Nd: YAlO ₃ , also known as neodymium-doped yttrium orthoaluminate, abbreviated as Nd: YAP or Nd: YALO) is used as the first laser crystal. It operates so that the wavelength is 930 nm. Since the wavelength for exciting the laser crystal to which this neodymium is added is often in the range of 0.79 μm to 0.82 μm, a semiconductor laser that has been established technically and can be obtained at a relatively low cost is used. Can be used for excitation.

Next, when ytterbium-doped yttrium aluminum garnet (structural formula Yb: Y ₃ Al ₅ O ₁₂ , abbreviated Yb: YAG) is used for the second laser crystal, the crystal is excited with a laser beam having a wavelength of 930 nm. As a result, laser oscillation with the second wavelength of 1030 nm occurs.

  By performing sum-frequency mixing with a nonlinear optical medium in which these two wavelengths of laser light are arranged in a laser resonator, the third wavelength is a coherent light having a wavelength of about 488 nm, which is substantially the same as one of the main oscillation wavelengths of an argon laser. Can occur.

  Further, in addition to the first nonlinear optical coupling medium for performing the sum frequency mixing of the first wavelength and the second wavelength, a nonlinear medium for generating the second harmonic of the second wavelength is also arranged in the laser resonator. As a result, the third wavelength coherent light can be simultaneously generated with the fourth wavelength generated by the second harmonic generation in the range of 0.51 μm to 0.53 μm.

  Here, the wavelength of the fourth wavelength of coherent light is 514.5 nm, which is another main oscillation wavelength of the argon laser when Nd: YAP is used for the first laser crystal and Yb: YAG is used for the second laser crystal. Nearly about 515 nm.

  In addition, in the laser device having a configuration capable of simultaneously generating the third wavelength coherent light and the fourth wavelength coherent light, the temperature of the two nonlinear optical media can be controlled independently and the set temperature can be switched. By changing the temperature so that one of the two nonlinear optical media is removed from the phase matching condition for the sum frequency mixing or second harmonic generation, one of the two coherent lights is selected and output. can do.

By the means described above, main parts such as a semiconductor laser having a wavelength of 0.8 μm, a solid-state laser crystal, and a nonlinear optical crystal are equivalent to a conventional argon laser having a wavelength of 488 nm using only technically established parts. A semiconductor-pumped solid-state laser capable of generating coherent light can be realized with a small size and a configuration capable of suppressing production costs.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. First, Embodiment 1 will be described with reference to FIG.

  The semiconductor laser 1 generates laser light 19 having a wavelength of 813 nm, the maximum output is 2 W, and the width of the active region is 100 μm. The semiconductor laser light 19 is condensed at the position of the Nd: YAP crystal 6 by the lens 2, the first cylindrical lens 3, and the second cylindrical lens 4, and the cross section thereof becomes a substantially circular shape having a diameter of about 0.2 mm. The output light of the semiconductor laser 1 excites the Nd: YAP crystal 6 that is the first laser crystal.

As shown in FIG. 1, the first reflecting mirror 5, the Nd: YAP crystal 6, the Yb: YAG crystal 7, the quartz glass plate 8, the first LBO (triboric acid) provided on the incident surface of the Nd: YAP crystal 6. A laser resonator is configured by arranging lithium, LiB ₃ O ₅ ) crystal 9 and second reflecting mirror 10 in a straight line.

  The first reflecting mirror 5 is formed by coating a dielectric multilayer film on the surface of the Nd: YAP crystal 6 on which the semiconductor laser light 19 first enters. The first reflecting mirror has a characteristic that the reflectance is 99.8% or higher at wavelengths of 930 nm and 1030 nm, and the transmittance is 30% or higher at wavelengths of 1079 nm and 1340 nm. Further, this reflecting mirror has a characteristic of low reflection at 813 nm which is the wavelength of the semiconductor laser light 19.

The Nd: YAP crystal 6 has a neodymium concentration of 1 atomic% and a thickness of 1.2 mm. The thickness direction is cut so as to be the same as the c-axis direction of the crystal. The absorption coefficient of the Nd: YAP crystal 6 is about 6 cm ⁻¹ with respect to the wavelength 813 nm of the semiconductor laser light 19. Therefore, Nd: YAP absorbs about 50% of the incident semiconductor laser beam 19.
The Yb: YAG crystal 7 of the second solid-state laser crystal has a length in the optical axis direction of 0.2 mm, and the ytterbium concentration is 0.5 atomic%. According to this concentration and thickness, the absorption rate when a laser beam having a wavelength of 930 nm passes once is about 0.5%.

  The quartz glass plate 8 is a parallel plate made of quartz glass having a thickness of 0.5 mm, and is arranged with an inclination of about 55.4 ° which is a Brewster angle with respect to the optical axis of the resonator. By virtue of this quartz glass plate 8, a reflection loss is given only to the polarization components of light having a wavelength of 930 nm and a wavelength of 1030 nm, which are s-polarized light, and oscillation is performed only with the p-polarized component at both wavelengths.

  The first LBO crystal 9 has a length in the optical axis direction of 8 mm, a cut orientation of φ = 16.9 °, θ = 90 °, and a sum frequency mixing of a laser beam having a wavelength of 930 nm and a laser beam having a wavelength of 1030 nm Phase matching is possible. The LBO crystal is arranged so that its z-axis is in the same direction as the electric fields of both laser beams having a wavelength of 930 nm and a wavelength of 1030 nm. By this sum frequency mixing, coherent light having a wavelength of about 488 nm is generated so that the electric field direction is parallel to the XY plane of the LBO crystal. Then, it is output as 488 nm output light 20.

  The second reflecting mirror 10 is a quartz glass concave surface coated with a dielectric multilayer film, and the concave surface has a radius of curvature of −100 mm. The second reflecting mirror 10 has such a characteristic that a high reflectance of 99.8% or more is obtained at both wavelengths 930 nm and 1030 nm, and a transmittance is 30% or more at wavelengths 1079 nm and 1340 nm. Further, the second reflecting mirror 10 has a characteristic of low reflection with respect to the wavelength 488 nm of coherent light generated by sum frequency mixing. And the distance with the 1st reflective mirror 5 is arrange | positioned in the position of about 22 mm.

  The Nd: YAP crystal 6 is excited by the semiconductor laser light 19 emitted from the semiconductor laser 1, and laser oscillation with a wavelength of 930 nm occurs in the laser resonator using the Nd: YAP crystal 6 as a gain medium. Nd: YAP is a laser crystal that can oscillate at wavelengths of 930 nm, 1079 nm, 1340 nm, etc., but can be selected only at a wavelength of 930 nm by providing the first reflecting mirror 5 and the second reflecting mirror 10 with the wavelength characteristics described above. Oscillates.

  Although it is difficult to directly measure the circulating power of the 930 nm laser light inside the laser resonator, when estimated from the power of the 930 nm laser light passing through the second reflecting mirror 10, the output of the semiconductor laser 1 is 2 W, which is the maximum power. Sometimes, the internal power of the resonator with a wavelength of 930 nm is estimated to be about 15 W.

  A part of the Nd: YAP laser light oscillated at a wavelength of 930 nm is absorbed by the Yb: YAG crystal 7 while resonating the laser resonator. Considering the absorptance at this wavelength of the Yb: YAG crystal 7, it is estimated that 150 mW of Nd: YAP laser light having a wavelength of 930 nm is absorbed during one round trip of the laser resonator. Oscillation is started at a wavelength of 1030 nm by using the Yb: YAG crystal 7 as a gain medium by excitation of the light having a wavelength of 930 nm.

  The first LBO crystal 9 converts two laser beams resonating in a laser resonator having a wavelength of 930 nm and a wavelength of 1030 nm into coherent light having a wavelength of about 488 nm by sum frequency mixing. The coherent light having a wavelength of about 488 nm passes through the second reflecting mirror 10 and is extracted as 488 nm output light 20. When the output of the semiconductor laser was 2 W, the optical power of the 488 nm output light 20 was about 20 mW.

  Next, Example 2 will be described with reference to FIG. In FIG. 2, the same reference numerals are given to portions corresponding to those of the above embodiment, and detailed description thereof is omitted. Actually, the components shown in the second embodiment are the same as those shown in the first embodiment except for the dichroic mirror 12 and the second reflecting mirror 11.

  The dichroic mirror 12 is a quartz glass plate 8 coated with a dielectric multilayer film, and designed to be used at an incident angle of about 55.4 °. The dichroic mirror 12 has a reflectivity close to 100% with respect to the s-polarized component of both 930 nm and 1030 nm laser beams, and has a transmittance of 10 for the p-polarized component of the laser beams with both wavelengths. It has the characteristic which becomes more than%. In addition, the coherent light having a wavelength of 488 nm, in particular, has a characteristic that the transmittance becomes high with respect to the p-polarized component.

  Both laser resonators having a wavelength of 930 nm and a wavelength of 1030 nm are configured between the first reflecting mirror 5 and the second reflecting mirror 11 via the dichroic mirror 12. Due to the polarization characteristics of the dichroic mirror, the laser oscillation light of two wavelengths becomes linearly polarized light.

  The second reflecting mirror 11 used in the second embodiment is different from the second reflecting mirror used in the first embodiment in that the second reflecting mirror 11 has a high reflectance at a wavelength of 488 nm. The coherent light having a wavelength of about 488 nm generated by the sum frequency mixing by the first LBO crystal 9 is opposite to the first LBO crystal 9 because the laser oscillation light having a wavelength of 930 nm and a wavelength of 1030 nm reciprocates the laser resonator. Occurs in the direction. The coherent light having a wavelength of about 488 nm generated in the direction of the second reflecting mirror 11 is reflected by the second reflecting mirror 11 and overlaps with the coherent light having a wavelength of about 488 nm generated in the other direction of the dichroic mirror 12. The light passes through the mirror and is output as 488 nm output light 20. The second embodiment has only one component compared to the first embodiment, but has a large number of parts and is difficult to adjust at the time of manufacture because it is a folded resonator. However, coherent light having a wavelength of about 488 nm generated by sum frequency mixing is difficult. Can be taken out more efficiently.

  Next, Example 3 will be described with reference to FIG. In FIG. 3, the same reference numerals are given to portions corresponding to those in the above embodiment, and detailed description thereof is omitted. Among the components of the embodiment shown in FIG. 3, except for the second LBO crystal 13 and the second reflecting mirror 14, they are the same as those used in the first embodiment.

The second LBO crystal 13 is made of LiB ₃ O ₅ which is the same material as the first LBO crystal 9 and has a length of 8 mm. However, φ = 13.9 ° and θ = 90 ° capable of generating a second harmonic wave whose cut direction is fundamental light having a wavelength of 1030 nm. The second reflecting mirror 14 has the reflection characteristics of the second reflecting mirror 10 used in the first embodiment, and also has a characteristic of low reflection with respect to a wavelength of 515 nm.

  Similar to the first embodiment, the Nd: YAP crystal 6 is excited by the semiconductor laser light 19, and the Nd: YAP crystal 6 is gain medium by the laser resonator formed between the first reflecting mirror 5 and the second reflecting mirror 14. As a result, laser oscillation with a wavelength of 930 nm occurs. Next, a Yb: YAG crystal 7 is excited by a laser beam having a wavelength of 930 nm circulating in the laser resonator, and is configured between the first reflecting mirror 5 and the second reflecting mirror 14. Laser oscillation with a wavelength of 1030 nm occurs using the YAG crystal 7 as a gain medium.

  The laser light having a wavelength of 930 nm and a wavelength of 1030 nm of the two lasers that oscillate simultaneously is sum-frequency mixed by the first LBO crystal 9 disposed in the laser resonator to generate coherent light having a wavelength of about 488 nm. As taken out. The laser light with a wavelength of 1030 nm is used for this sum frequency mixing, while it is converted by the second LBO crystal 13 into coherent light with a wavelength of 515 nm, which is the second harmonic, and the converted coherent light is 515 nm output light 21. Is output as

  In Example 3, two LBO crystals were used. In addition, a third LBO crystal capable of generating a second harmonic having a fundamental wavelength of 930 nm of the first wavelength is disposed in the laser resonator. Thus, when coherent light having a wavelength of 465 nm is generated, it can be easily estimated that a laser apparatus capable of simultaneously outputting three wavelengths of coherent light together with the above two wavelengths of output light is obtained.

  Next, Example 4 will be described with reference to FIG. In FIG. 2, the same reference numerals are given to portions corresponding to those of the above embodiment, and detailed description thereof is omitted. Among the components of the embodiment shown in FIG. 4, the components excluding the first electronic cooling element 15, the second electronic cooling element 16, the first temperature controller 17, and the second temperature controller 18 are as follows. This is the same as the third embodiment described with reference to FIG.

  The first electronic cooling element 15 and the second electronic cooling element 16 are elements that utilize the Peltier effect, and can switch between a heating operation and a cooling operation by changing the direction of the supplied current. The first temperature controller 17 and the second temperature controller 18 can drive both the electronic cooling element for heating and cooling. The first electronic cooling element 15 is driven by a first temperature controller 17 to control the temperature of the first LBO crystal 9 for sum frequency mixing. The second electronic cooling element 16 is driven by the second temperature controller 18 to control the temperature of the second LBO crystal 13 for generating the second harmonic. The temperature of the two LBO crystals can be controlled independently by these electronic cooling elements and the temperature controller.

  The angle at which the first LBO crystal 9 and the second LBO crystal 13 are arranged so as to achieve phase matching when the temperature is set to about 25 ° C. is adjusted. When the temperatures of both LBO crystals are set to 25 ° C., as in Example 3, both coherent light having a third wavelength of about 488 nm and coherent light having a fourth wavelength of 515 nm are generated, and a 488 nm output is obtained. Both light 20 and 515 nm output light 21 are output simultaneously.

  When the temperature of the first LBO crystal 9 is increased by about 17 ° C. to about 42 ° C. while the temperature of the second LBO crystal 13 is maintained at about 25 ° C., the phase matching of sum frequency mixing cannot be achieved and the wavelength of 488 nm. Generation of the coherent light is stopped, and only the output light 21 having a wavelength of 515 nm is output. Conversely, when the temperature of the second LBO crystal 13 is increased by about 17 ° C. to about 42 ° C. while the temperature of the first LBO crystal 9 is maintained at about 25 °, the phase of the second harmonic generation occurs. Matching is lost and the generation of coherent light with a wavelength of 515 nm stops, and only the 488 nm output light 20 is output.

  In this way, a state in which only one of these coherent lights is output is a state in which only one of the 488 nm output light 20 and the 515 nm output light is output by changing the temperatures of the two LBO crystals. Can be switched.

In Examples 1 to 4, Nd: YAP is used as the first laser crystal, but Nd: YAG, Nd: YVO ₄ , Nd: GdVO ₄ , Nd: GGG (Nd: Gd ₃ Ga ₅ O ₁₂ ) The same applies to a laser crystal added with Nd ions such as Nd: YLF (Nd: LiYF ₄ ), which can oscillate at a wavelength of 0.91 μm to 0.95 μm and does not absorb at 1.00 μm to 1.05 μm. The effect is obtained. Even if these crystals are not single crystals but polycrystals called ceramic crystals, the same effect can be obtained.

In Examples 1 to 4, Yb: YAG was used for the second laser crystal, but Yb: YVO ₄ , Yb: GdVO ₄ , Yb: GGG (Yb: Gd ₃ Ga ₅ O ₁₂ ), Yb: YLF. The same effect can be obtained with a laser crystal to which Yb ions such as (Yb: LiYF ₄ ) can be oscillated at a wavelength of 1.02 μm to 1.05 μm and can be excited at a wavelength of 0.91 m to 0.95 μm. can get. Even if these crystals are not single crystals but polycrystals called ceramic crystals, the same effect can be obtained.

Further, in Examples 1 to 4, LBO is used as a nonlinear optical medium for performing sum frequency mixing and second harmonic generation. However, KTiOPO ₄ , KNbO ₃ , BiB ₃ O _6, and others that can perform phase matching are used. The same effect can be obtained by using a non-linear optical crystal having a large nonlinear optical constant, such as LiNbO ₃ or LiTaO _3, and an element having an artificially periodically poled structure for quasi-phase matching.

It is explanatory drawing which shows Example 1 of this invention. It is explanatory drawing which shows Example 2 of this invention. It is explanatory drawing which shows Example 3 of this invention. It is explanatory drawing which shows Example 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2 Lens 3 1st cylindrical lens 4 2nd cylindrical lens 5 1st reflective mirror 6 Nd: YAP crystal 7 Yb: YAG crystal 8 Quartz glass plate 9 1st LBO crystal 10 2nd reflective mirror 11 2nd reflective mirror 12 dichroic mirror 13 second LBO crystal 14 second reflecting mirror 15 first electronic cooling element 16 second electronic cooling element 17 first temperature controller 18 second temperature controller 19 semiconductor laser light 20 488 nm output light 21 515nm output light

Claims (5)

An internal resonator type sum frequency mixing laser,
A laser resonator composed of first and second reflectors;
A first laser crystal, which is disposed in the laser resonator as a gain medium, to which is added neodymium that oscillates at a first wavelength between 0.91 μm and 0.95 μm, and
A laser energy source for exciting the first laser crystal;
A second medium added with ytterbium, which is disposed in the laser resonator as a gain medium excited by the laser beam having the first wavelength and oscillates at a second wavelength between 1.02 μm and 1.05 μm, is added. A laser crystal;
By having a first nonlinear optical medium disposed in the laser resonator for performing sum frequency mixing on the laser light of the first wavelength and the second wavelength,
An internal resonator type sum frequency mixed laser characterized in that coherent light having a third wavelength in the range of 0.48 μm to 0.50 μm is output.   A second nonlinear optical medium disposed in the laser resonator to enable generation of the second harmonic of the laser light having the second wavelength, and having a wavelength in the range of 0.51 μm to 0.53 μm; 2. The internal resonator type sum frequency mixed laser according to claim 1, wherein coherent light having a fourth wavelength is also generated.   The apparatus further includes means for independently controlling the temperatures of the first nonlinear optical medium and the second nonlinear optical medium, and by controlling the temperature of the nonlinear optical medium, the coherent light of the third wavelength and the fourth 3. The internal resonator type sum frequency mixed laser according to claim 2, wherein either one of the coherent lights having wavelengths can be selectively extracted.   The first laser crystal includes neodymium-doped yttrium aluminum perovskite, the second laser crystal includes ytterbium-doped yttrium aluminum garnet, and the means for exciting the first laser crystal is a semiconductor laser. The internal resonator type sum frequency mixing laser according to any one of claims 1 to 3.   5. The internal resonator type sum frequency mixed laser according to claim 1, wherein at least one of the first nonlinear optical medium and the second nonlinear medium contains lithium triborate. 6. .

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