JPH07131101A - Laser beam generating device - Google Patents

Abstract

PURPOSE:To stably generate a second harmonic, using an Nd:YVO4 birefringence laser medium, by orienting the c-axis of the medium in the same direction as that of a crystal of a nonlinear optical crystal element. CONSTITUTION:A laser beam is emitted as a pumping beam from a laser diode 11, i.e., a semiconductor laser element as a pumping light source element. This beam is focused by a lens 12 and applied to a laser medium 16 made of Nd: YVO4 through a reflection mirror 14 of a laser resonator 13 and a quarter-wave plate 15. The mirror 14 uses a concave mirror having a concave face inside. The medium 16 generates a fundamental wave of the laser beam in response to the incidence of the excited beam, and this wave passing through a nonlinear optical crystal element 17 using e.g. KTP is reflected by a reflection mirror 18. The c-axis of the Nd:YVO4 of the medium 16 is oriented in the same direction as that of a KTP crystal of the element 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser light generator, and more particularly to a laser light generator having a laser light source for generating high-order harmonic laser light using a nonlinear optical crystal element.

[0002]

2. Description of the Related Art It has hitherto been proposed to efficiently perform wavelength conversion by utilizing a high power density inside a resonator, for example, an external resonance type SHG (second harmonic generation).
Alternatively, SHG and the like using a nonlinear optical element inside the laser resonator have been tried.

As an example of the second harmonic generation type in the laser resonator, there is known one in which a laser medium and a nonlinear optical crystal element are arranged between at least one pair of reflecting mirrors constituting the resonator. In the case of this type of laser light generator, the nonlinear optical crystal element in the resonator is arranged so that the second harmonic laser light is phase-matched with the fundamental laser light, so that the second harmonic laser light is efficiently generated. Can be taken out.

As a method of realizing the above phase matching, a type I or type II phase matching condition is established between the fundamental laser light and the second harmonic laser light. In other words, the principle of type I phase matching is to use the ordinary ray of the fundamental laser light to generate a phenomenon in which two photons polarized in the same direction produce one photon having a frequency doubled. To do. On the other hand, type II phase matching is to make two fundamental polarizations that are orthogonal to each other enter a nonlinear optical crystal element so that the phase matching conditions can be established for each of the two polarizations. The fundamental wave laser light is divided into an ordinary ray and an extraordinary ray inside the nonlinear optical crystal element to cause phase matching with the extraordinary ray of the second harmonic laser light.

However, when the second harmonic laser light is to be generated using the type II phase matching condition, the intrinsic polarization of the fundamental laser light is changed every time the fundamental laser light repeatedly passes through the nonlinear optical crystal element. Since the phase changes, the generation of the second harmonic laser light may not be stably continued.

That is, each time the fundamental laser light generated in the laser medium repeatedly passes through the nonlinear optical crystal element due to the resonance operation, the phases of orthogonal natural vibrations (that is, p-wave component and s-wave component) are shifted. Then, in each part of the resonator, it becomes impossible to obtain a steady state in which the fundamental wave laser lights efficiently reinforce each other, so that a strong resonance state (strong standing wave) cannot be formed.
As a result, the conversion efficiency of the fundamental wave laser light into the second harmonic laser light may be deteriorated, and noise may be generated in the second harmonic laser light.

Therefore, the applicant of the present application filed Japanese Patent Application Laid-Open No. 1-220.
In Japanese Patent Publication No. 879, in a laser light source configured to generate a second harmonic laser beam by a non-linear optical crystal element, a birefringent element such as a quarter-wave plate is inserted in the resonance optical path of a fundamental wave laser beam. By doing so, a laser light source is proposed which stabilizes the second harmonic laser light emitted as the output laser light.

The laser light source disclosed in Japanese Unexamined Patent Publication No. 1-220879 is for exciting a laser medium using a Nd: YAG disposed between a pair of reflecting surfaces constituting a laser resonator from a semiconductor laser. A laser beam is input to generate a fundamental wave laser beam, and the fundamental wave laser beam is passed through a nonlinear optical crystal element made of KTP (KTiOPO ₄ ) provided in the resonator for resonance operation.
II second harmonic laser light is generated, by inserting a quarter-wave plate as a birefringent element into the resonator, the two fundamental polarization modes of the fundamental laser light are orthogonal to each other. Suppresses the coupling due to the sum frequency generation and stabilizes the oscillation. Here, in the quarter-wave plate as the birefringent element, in the plane perpendicular to the light propagation direction, the direction of the extraordinary light direction refractive index n _e is the extraordinary light direction refraction of the nonlinear optical crystal element (KTP). The optical axis position is set so as to be inclined by a predetermined azimuth angle θ (for example, θ = 45 °) with respect to the direction of the rate n _KTPe .

As described above, by providing the quarter-wave plate (birefringent element) in the resonator, the longitudinal polarization between orthogonal polarizations is achieved regardless of the residual retardation or the phase delay amount of the nonlinear optical crystal element (KTP). Effective in suppressing mode competition noise. In particular, when the phase delay amount of KTP is 90 °, the intrinsic polarization mode in Nd: YAG (laser medium) becomes circularly polarized light, so that the saturation of the gain becomes uniform, and the longitudinal mode competing noise between the same polarized lights becomes Has the advantage that it is less likely to occur.

[0010]

By the way, in recent years, Nd: YVO ₄ has been used as a laser medium instead of Nd: YAG.
It has been found to have several advantages over the above, in particular a wide pumping absorption band with a high absorption coefficient and a large stimulated emission cross section at 1064.1 nm. It is desired to construct an efficient low noise SHG (second harmonic generation) Nd: YVO ₄ laser light generator by utilizing these advantages.

The present invention has been made in view of the above circumstances, and is to construct an intracavity SHG (second harmonic generation) type laser light generator using Nd: YVO ₄ as a laser medium. With the goal.

[0012]

A laser light generator according to the present invention comprises an excitation light source element and Nd: YV as a laser medium excited by the excitation light from the excitation light source element.
A birefringent laser medium such as O ₄ and a pair of reflecting means arranged before and after the laser medium to form a laser resonator by reflecting the fundamental wave laser light generated by the laser medium, and the laser resonator. The non-linear optical crystal element disposed inside the laser resonator and the non-linear optical crystal element disposed inside the laser resonator are used to perform type II phase matching to reduce mode competition noise when the second harmonic generation is performed. The birefringent laser medium (Nd: Y
The above problem is solved by arranging the c-axis of the crystal (VO ₄ etc.) in the same direction as the c-axis of the crystal of the nonlinear optical crystal element.

Here, the birefringent laser medium is Nd: YVO ₄ (Yttrium OrthoVanadate) or a birefringent laser medium similar to Nd: YVO ₄ , for example, Nd: GdVO ₄ , Nd: YLF, Nd. : SVAP or the like can be used.

Further, as the birefringent element for reducing the mode competing noise, a quarter wave plate of a fundamental wave is used, and its optical axis is equal to that of the nonlinear optical crystal element.
It is preferable to arrange them so as to form 5 °. Further, it is preferable that the laser medium, the nonlinear optical crystal element, and the birefringent element are brought into close contact with each other and sequentially stacked to be integrally formed.

[0015]

[Function] Nd: YV which is an anisotropic crystal (uniaxial crystal) having higher efficiency than Nd: YAG as a laser medium
When a birefringent laser medium such as O ₄ is used, the birefringent element is arranged by arranging the c-axis of the crystal of the birefringent laser medium in the same direction as the c-axis of the crystal of the nonlinear optical crystal element. To prevent the transfer of energy through the generation of the second harmonic between the intrinsic polarizations orthogonal to each other,
Noise due to mode competition is reduced. Therefore, by using a birefringent laser medium such as Nd: YVO _{4 having} good characteristics, stable generation of the type II phase-matched second harmonic can be performed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram showing a schematic structure of an embodiment of a laser beam generator according to the present invention. In FIG. 1, laser light as excitation light is emitted from a laser diode 11 which is a semiconductor laser element as an excitation light source element. This excitation laser light is condensed by the lens 12,
The light is incident on the laser medium 16 using Nd: YVO ₄ (Yttrium Ortho Vanadate) via the reflecting mirror 14 and the quarter-wave plate 15 of the laser resonator 13. As the reflecting mirror 14, a concave mirror whose inside is concave is used. The laser medium 16 generates a fundamental wave laser light in response to incidence of the excitation light, and the fundamental wave laser light is, for example, KTP (KTi).
It is reflected by a reflecting mirror 18 through a nonlinear optical crystal element 17 using OPO ₄ ). Nd: YVO of laser medium 16
The c-axis of the _four crystals is arranged in the same direction as the c-axis of the KTP crystal of the nonlinear optical crystal element 17.

Nonlinear optical crystal element 17 such as KTP
Generates the second harmonic laser light (SHG light) having twice the frequency of the fundamental laser light by the type II phase matching. For example, assuming that the wavelength λ of the fundamental laser light is 1064 nm, the wavelength of the second harmonic laser light is λ / 2 532n.
m. The reflecting surface 14R of the reflecting mirror 14 transmits the excitation light (for example, wavelength 808.7 nm), and the laser medium 1
6 has a characteristic of reflecting the fundamental wave laser light, and the reflecting surface 18R of the reflecting mirror 18 has a characteristic of reflecting the fundamental wave laser light and transmitting the second harmonic laser light. ing. These reflecting mirrors 14 and 18 can be formed by so-called dichroic mirrors. Therefore, the fundamental wave laser light generated in the laser medium 16 travels back and forth between the reflecting mirrors 14 and 18 of the laser resonator 13 to oscillate the laser light.

In the example of FIG. 1, a plane mirror is used as the reflecting mirror 18, but a plane mirror may be used as the reflecting mirror 14 and a concave mirror may be used as the reflecting mirror 18. Further, the order of arranging each element is arbitrary, and for example, as shown in FIG. 2, the laser medium 16 of Nd: YVO ₄ crystal, the nonlinear optical crystal element 17 of KTP crystal, and the compound element are sequentially arranged from the side where the excitation light is incident. You may arrange like a quarter wave plate 15 which is a refractive crystal element. Furthermore, instead of providing the above-mentioned reflector separately,
A reflective film may be formed on the outer surface of the outer element by coating. For example, the laser medium (Nd: YVO ₄ ) 16 shown in FIG.
A reflection film 16R that transmits the excitation light having a wavelength of 808.7 nm and reflects the fundamental wave laser light having a wavelength of 1064 nm is formed on the excitation light incident surface side of, and the wavelength of 1064 nm of the SHG light emission surface side of the 1/4 wavelength plate 15 is formed. Reflects the fundamental laser light and has a wavelength of 53
A reflective film 15R that transmits SHG light of 2 nm may be formed, and one of them may be a concave mirror.

These laser media (Nd: YVO ₄ ) 1
6, the optical axes of the crystals of the nonlinear optical crystal element (KTP) 17 and the quarter-wave plate 15 which is a birefringent crystal element are set as shown in FIG.

In FIG. 3, the c-axis of the Nd: YVO ₄ crystal that is the laser medium 16 and the nonlinear optical crystal element 17 are used.
And the c-axis of the KTP crystal is the same direction, and the fast axis (fast) of the quarter-wave plate 15 that is a birefringent crystal element is fast with respect to the c-axis of this crystal. axi
s) F is arranged at an angle of 45 °.

That is, regarding the quarter wave plate 15, the applicant of the present invention has previously described the specification and drawings of Japanese Patent Application Laid-Open No. 1-220879 and Japanese Patent Application No. 2-125854, and Japanese Patent Application No. 3-1.
A birefringent element used based on the technique disclosed in the specification of 7068, drawings, etc., and its optical axis is set in an azimuth angle θ = 45 ° with respect to the optical axis of the nonlinear optical crystal element 17. This is for stabilizing the power of the laser light in each part of the resonator 13 by passing through the ¼ wavelength plate 15 thus formed.

By inserting the quarter-wave plate 15, (i) non-linear coupling between polarization modes due to sum frequency generation is eliminated, and mode competition between polarization modes can be prevented. (Ii) Since the spatial phase difference between the two polarization modes is 90 °, the spatial hole burning effect can be suppressed by oscillation of the two polarization modes, and stable oscillation of two vertical modes (two polarization modes) can be obtained. To be That is, the action and effect can be obtained.

Next, the physical characteristics of Nd: YVO ₄ used as the laser medium 16, in particular, various characteristics of laser operation will be described.

Since Nd: YVO ₄ is a uniaxial crystal, the absorption coefficient differs between the component in which the polarization direction of pumping light is perpendicular to the c-axis (σ-polarized light) and the component in parallel with it (π-polarized light). FIG. 4 shows absorption spectra of π-polarized light, σ-polarized light, and Nd: YAG, respectively. In FIG. 4, curves a and b respectively show a π-polarized light absorption spectrum (a) and a σ-polarized light absorption spectrum (b) for an a-axis cut Nd: YVO ₄ having an Nd concentration of 1.1 at. c shows an absorption spectrum with an Nd concentration of 0.85 at.%. The curve a (π-polarized light absorption spectrum of Nd: YVO ₄ ) has a high absorption coefficient of 6 mm ⁻¹ and a small absorption depth of 170 μm. Absorption FWHM (Full Width Half Max.) Is about 1.7 nm.

5 and 6 show fluorescence spectra of Nd: YVO ₄ , FIG. 5 shows σ-polarized light, and FIG. 6 shows π-polarized light. In these fluorescence spectra, the σ polarization components are 1062.5 nm, 1064.1 nm, 1064.
8 nm and 1066.4 nm, the π-polarization component is 10
It is at 64.1 nm. The strongest fluorescence line is π-polarized light with a center wavelength of 1064.1 nm, and FWHM is 1.1 n.
m. The stimulated emission cross section at this wavelength is 2.8 x 10
^-18 cm ^2, which is four times larger than σ at the same wavelength.
Further, Nd: YAG having an Nd concentration of 0.85 at.% Is 0.6 × 10 ⁻¹⁸ cm ² , and Nd: YVO ₄ is four times or more larger.

Such Nd: YVO ₄ is used as a laser medium, and the phase matching of type II is achieved by KTP to obtain S.
The reason why the resonance operation is stabilized when the HG laser light is generated will be described below.

This stabilization method uses the short absorption depth of Nd: YVO ₄ to reduce the spatial hole burning, and decouples the polarization mode using a quarter-wave plate in the resonator. It is a combination of points and points.

Here, Nd: Y in the structure of FIG.
The end surface position of the VO ₄ laser medium 16 is P ₁ , and the end surface position of the KTP crystal element 17 is P ₂ . When the polarized light makes one round trip in the resonator, the Jones matrix M1 when the position P ₁ is the starting point and the Jones matrix M2 when the position P ₂ is the starting point are respectively.

[0029]

[Equation 1]

[0030]

[Equation 2]

It becomes In these equations (1) and (2), M _{Nd: YVO4} , M _KTP and M _QWP are Nd: YVO ₄ ,
The polarization state by KTP and QWP (1/4 wavelength plate) is expressed by Jones matrix, and R _{+ QWP} (R _-QWP ) is Q
The polarization state when the WP (1/4 wavelength plate) is rotated by the azimuth angle + α (−α) is represented by the Jones matrix, and C (δ _X ) is the polarization state when the polarized light passes through the optical element X. In addition, the polarization state when the phase is shifted by the phase amount δ due to birefringence is represented by a Jones matrix. Further, i represents an imaginary unit (-1) ^1/2 .

At this time, the electric field vectors of the two eigenpolarizations are at the above position P ₁ ,

[0033]

[Equation 3]

Thus, at the above position P ₂ ,

[0035]

[Equation 4]

It becomes Further, regarding the nonlinear polarization, at the position P ₁ ,

[0037]

[Equation 5]

Then, at the position P ₂ ,

[0039]

[Equation 6]

It becomes Then, the time average of the second harmonic output power is in the position P _1,

[0041]

[Equation 7]

At the above position P ₂ ,

[0043]

[Equation 8]

It becomes Therefore, the two polarization modes are K
Stable oscillation is possible without any coupling due to some loss due to the sum frequency generation in the TP crystal.

Further, N in the configuration of FIG. 2 or FIG.
The d: YVO ₄ laser medium 16, the KTP crystal element 17, and the quarter-wave plate 15 are integrated so as to be brought into close contact with each other in order to reduce the size of the resonator, and together with the pumping laser diode and the lens. It is possible to further reduce the size of the entire structure of the laser light generator by housing it in a small package.

Next, FIG. 7 is a schematic configuration diagram showing another embodiment of the laser light generator according to the present invention. In this embodiment, parts corresponding to those in the embodiment of FIG. 1 are designated by the same reference numerals, and description thereof will be omitted.

FIG. 1 in the embodiment shown in FIG.
The difference from the embodiment shown in FIG. 2 is that the optical path in the laser resonator 13 is refracted by the reflecting mirror 19. That is, a concave reflecting surface 19 is provided between the laser medium 16 of Nd: YVO ₄ crystal and the nonlinear optical crystal element 17 of KTP crystal.
A reflecting mirror 19 having R is arranged. This reflective surface 19
R is the fundamental laser light (for example, wavelength 1064 nm)
Has an optical characteristic of reflecting SHG light and transmitting SHG light (wavelength 532 nm, for example), and the SHG light is extracted via this reflecting mirror 19. The arrangement order and the structure of the other optical elements in the resonator 13 are the same as those in the example of FIG. 2, for example, and the excitation light is introduced into the laser medium 16 of Nd: YVO ₄ crystal through the end face reflection surface 16R. The incident and generated fundamental laser light is reflected by the reflecting mirror 19, passes through the nonlinear optical crystal element 17 of KTP crystal, and is incident on the quarter-wave plate 15 which is a birefringent element. It is reflected at 15R. The reflection and transmission characteristics of the reflection surfaces 16R and 15R are similar to those in the example of FIG.

In the structure of FIG. 7, the laser medium 16
Of the Nd: YVO ₄ crystal is about 1 mm, the KTP of the nonlinear optical crystal element 17 is about 5 mm, and the concave diameter of the reflecting surface 19R of the reflecting mirror 19 is 40 mm.
mm. The quarter wave plate 15 has a wedge of 1 °. According to the resonator having the structure folded by three mirrors in this way, the Nd: YVO ₄ laser medium 16
Gently focused beam (beam diameter about 25
While maintaining 0 μm), the close focusing (beam diameter of about 50 μm) in the KTP crystal element 17 is allowed. N
The distance between the laser medium 16 of d: YVO ₄ crystal and the reflecting mirror 19 is, for example, about 100 mm, and the reflecting mirror 19 and the quarter-wave plate 1
The distance between 5 and 5 is set to about 23 mm, for example. As the laser diode 11, for example, a broad area type laser diode that outputs a laser beam having a wavelength of 808.7 nm and a power of 200 mW is used. Each crystal 16, 17, 1
5 uses the Peltier effect to increase the temperature from 10 ° C to 40 °
It is mounted on a so-called TE (thermoelectric) element controlled during C.

FIG. 8 shows the output power P of the SHG laser light.
₇ is a graph showing out as a function of pumping light (excitation light) power P _LD incident on a laser medium 16 of Nd: YVO ₄ crystal. This power characteristic shows that the KTP crystal element 17
Temperature is 25 ° C, and the temperature of the laser diode 11 is 25 ° C.
It was obtained at ° C. The conversion efficiency from the excitation light having a wavelength of 808.7 nm to the SHG laser light having a wavelength of 532 nm is about 5% when the excitation light power is 160 mW.
Further, the threshold value at which SHG laser light can be obtained is lower than 40 mW, which is a sufficiently low value as compared with the conventional case (when Nd: YAG is used).

FIG. 9 shows the temperature T _{LD of the} laser diode 11.
Output power P _out of the SHG laser light when V is changed
Is shown. This measurement was performed at a temperature of the KTP crystal element 17 of 25 ° C. and an excitation light power of 100 mW.
It was found from the time locus of the output power that a stable SHG laser light output was obtained over the entire measurement period. From the graph of FIG. 9, the temperature of the laser diode 11 is 20 ° C.
SHG even if changed in the range above (Δλ≈5.6 nm)
The fluctuation of the laser light output power can be made smaller than 50%, and the fluctuation of the power is 25% in the range of 15 ° C.
It turns out that it can be suppressed to the following.

FIG. 10 shows the output power P of the SHG laser light.
₁₂ is a graph showing out as a function of the temperature T _KTP of the KTP crystal element 17. Here, the temperature of the laser diode 11 is 25 ° C., and the pumping light power is 100 mW. Since the laser light generator of this specific example has a KTP temperature allowable range of about 10 ° C., the output was kept stable during the measurement. Fluctuation of SHG laser light power is 2
It is smaller than 0%.

According to the above specific example, when the pumping light power incident from the laser diode 11 is 160 mW, the SHG laser light power of 8 mW can be obtained.
The laser power threshold is smaller than 40 mW of the incident excitation light power. The SHG laser light power is kept stable under the conditions that the temperature change range of the excitation laser diode 11 is 20 ° C. or higher and the temperature change range of the KTP crystal element 17 is 10 ° C. This is superior to the case of using Nd: YAG as the laser medium in that it consumes less power and has a wider allowable temperature range.

[0053] The present invention is not limited to the above embodiments, for example, as a birefringent laser medium, Nd: YVO ₄ Besides, the Nd: birefringent laser similar to YVO ₄ Medium, eg Nd: GdVO ₄ ,
Nd: YLF, Nd: SVAP, etc. can be used. The nonlinear crystal element for generating the second harmonic by the type II phase matching is not limited to KTP, but LN, BBO, LBO, etc. can be used.

[0054]

According to the laser light generator of the present invention, a birefringent laser medium (Nd: YVO ₄ etc.) is used in the resonator for generating the type II second harmonic laser light. By arranging the c-axis of the crystal of the birefringent laser medium in the same direction as the c-axis of the nonlinear optical crystal element for generating the second harmonic, the efficiency is higher than that when Nd: YAG is used as the laser medium. High SH with high and low power consumption
G light output power is obtained, and the temperature change range in which stable operation is possible is wide, about 10 ° C. Therefore, the structure for stabilizing the temperature can be simplified to reduce the cost.

Further, by arranging the optical elements in close contact with each other, the entire laser light generator can be constructed in a small size, which contributes to space saving and size reduction when applied to an optical disk device or the like.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a schematic configuration of a basic embodiment of a laser light generator according to the present invention.

FIG. 2 is a schematic configuration diagram showing a modified example in which the arrangement of elements in the laser resonator of the embodiment is changed.

FIG. 3 is a schematic perspective view for explaining the directions of crystal axes of the respective elements in FIG.

FIG. 4 shows that excitation light incident on Nd: YVO ₄ is π-polarized,
It is a graph which shows the absorption spectrum in the case of (sigma) polarization, and the absorption spectrum of Nd: YAG.

FIG. 5 is a graph showing a fluorescence spectrum of σ-polarized light of Nd: YVO ₄ .

FIG. 6 is a graph showing a fluorescence spectrum of π-polarized light of Nd: YVO ₄ .

FIG. 7 is a diagram showing a schematic configuration of another embodiment of the laser light generator according to the present invention.

FIG. 8 shows SHG laser light output power P _out as Nd: YV
6 is a graph represented as a function of pumping light power P _LD incident on O ₄ .

FIG. 9 is a graph showing the output power P _out of SHG laser light when the temperature T _{LD of the} laser diode is changed.

FIG. 10 is a graph showing SHG laser light output power P _out as a function of _KTP temperature T _KTP .

[Explanation of symbols]

11 ... Laser diode 13 ... Laser resonator 14 ... Reflector 15 ... Quarter wave plate 16 ... Laser medium (Nd: YVO ₄ ). 17-Nonlinear optical crystal element (KTP) 18-Reflector

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display H01S 3/136

Claims (3)

[Claims] 1. A second-harmonic laser light is generated by causing a fundamental-wave laser light generated in a laser medium to resonate so as to pass through a nonlinear optical crystal element provided in the resonator, thereby generating the second harmonic laser light. A laser light generating device for reducing noise due to mode competition by inserting a birefringent element in an optical path inside, wherein a birefringent laser medium is used as the laser medium, and a crystal c of the birefringent laser medium is used. A laser light generator having an axis arranged in the same direction as the c-axis of the crystal of the nonlinear optical crystal element. 2. A quarter wave of a fundamental wave as the birefringent element
2. The laser beam generator according to claim 1, wherein a wave plate is used, and its optical axis forms an angle of 45 ° with the optical axis of the nonlinear optical crystal element. 3. The laser light generator according to claim 1, wherein the laser medium, the nonlinear optical crystal element, and the birefringent element are brought into close contact with each other and sequentially stacked so as to be integrally formed.