JPH1115033A - Laser beam higher harmonic generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser beam higher harminic generator which is capable of realizing a waveform conversion in which nonlinear optical crystals are used with high efficiency and which is provided with an optical system having a simple constitution. SOLUTION: Nonlinear optical crystals 21, 22 provided with the same wavelength conversion characteristic and condensing lenses 31, 32 corresponding to respective nonlinear optical crystals 21, 22 are combined to be continuously arranged. Moreover, they are used by adjusting the distance between the nonlinear crystals 21, 22 and the inclination of the condensing lens 32 or selecting the condensing lens provided with a proper thickness in order to correct so that the phase difference between a second harmonic and a fourth harminic to be generated by a dispersion due to air filling the gap between the crystal 21 and the crystal 22 and constituting materials of the lenses becomes the integral multiple of 360 degrees.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser light harmonic generator, and more particularly, to a wavelength conversion optical system for generating a laser light harmonic using a nonlinear optical crystal.

[0002]

2. Description of the Related Art In a wavelength conversion optical system that generates harmonics of laser light using a nonlinear optical crystal, the conversion efficiency is proportional to the optical power density of incident laser light. As a conventional technology, in order to improve the power density of the incident laser light, the lens is focused by a lens and one or more nonlinear optical crystals are arranged at the beam waist position. There is an “external resonator method” in which a non-linear optical crystal is placed inside a vessel.
Note that there is also an “internal resonator method” that uses the amplified circulating light power inside the laser resonator, but is excluded here because a case where a wavelength converter is provided outside the laser is considered.

As shown in FIG. 2, in the “lens method”, the incident laser light 11 is condensed by a lens 31 and the nonlinear optical crystal 21 is disposed at the position of the beam waist to improve the incident light power density. This improves the efficiency of conversion to harmonics. When the conversion efficiency is not sufficient with one nonlinear optical crystal, a method of reducing the beam size in the crystal by reducing the focal length of the lens and increasing the power density, or a method of increasing the length of the nonlinear optical crystal are usually used. Was taken. The outgoing laser light 12 contains a harmonic generated by the nonlinear optical crystal 21 and a fundamental wave component which remains without being converted. In addition, a sum frequency generation or a difference frequency generation may be performed using a plurality of wavelengths of laser light as the incident laser light 11.

As shown in FIG. 3, in the "external resonator system", incident laser light 11 is reflected by mirrors 41, 4 facing each other.
2 is incident on the resonator. The end face of the mirror 41 is provided with a coating which partially transmits the laser beam 11 and completely reflects its harmonics. The end face of the mirror 42 is provided with a complete reflection for the laser beam 11 and a partial transmission coating for its harmonics. In order to tune this resonator to the wavelength of the incident laser light 11, it is necessary to use a servo controller (not shown). Inside this resonator, the power of the laser light increases. By arranging the nonlinear optical crystal 21 inside the resonator, the conversion efficiency is improved. The resonator internal laser light 14 contains a mixture of a harmonic generated by the nonlinear optical crystal 21 and a fundamental wave that has not been converted and remains. The laser output light 12 has only harmonics. In addition, the incident laser light 1
As one, a sum frequency generation or a difference frequency generation may be performed using laser light of a plurality of wavelengths.

[0005]

A conventional "lens system"
In such a case, when the conversion efficiency is insufficient with one nonlinear optical crystal due to low laser light power, it is necessary to lengthen the nonlinear optical crystal. However, even in that case, it is meaningless to make the crystal longer than the range in which the beam size is small (referred to as Rayleigh length) due to the focusing of the lens. In addition, the power density is increased by squeezing the beam strongly,
Squeezing strongly means that the length of the converged portion of the laser beam is shortened, and the conversion efficiency is not sufficiently improved.
The strong squeezing may also damage the nonlinear optical crystal.

In the "external resonator system", it is necessary to match the resonance wavelength of the incident laser light with the resonator, and the control system becomes complicated and the cost increases. Further, when the laser light is pulsed light, when there are a plurality of longitudinal modes, or when the spectrum width is wide, there is a difficulty that the resonator cannot be tuned to the laser wavelength.

An object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a laser light harmonic generation device including an optical system with a simpler configuration that can realize wavelength conversion using a nonlinear optical crystal with high efficiency.

Another object of the present invention is to provide a laser light harmonic generation device capable of correcting a phase relationship between a fundamental wave and a harmonic wave in the optical system and maximizing the amount of generated light harmonics. To provide.

[0009]

In order to achieve the above object, a harmonic generating apparatus according to the present invention comprises a plurality of nonlinear optical crystals having the same wavelength conversion characteristics and a condensing optical element corresponding to each nonlinear optical crystal. And an optical system configured to be continuously arranged by combining the above.

[0010] In order to achieve the above object, the above-mentioned optical system is provided with a fundamental wave, which is generated by dispersion of a medium such as air which fills a space between nonlinear optical crystals and a constituent material of a condensing optical element such as a lens. Phase correction means is provided for correcting a phase difference between laser beams having a plurality of different wavelengths such as harmonics so as to satisfy a predetermined relative relationship such as the following condition.

[0011] m = at _{(L m / l m) +} (L d / l d) ··· Number 1 wherein, m: integer L _m: length of light path of the portion occupied by the medium between the two nonlinear optical crystals L _d : the distance on the optical path occupied by the optical element arranged between the two nonlinear optical crystals l _m : the phase of the fundamental wave and the harmonic wave in the medium is 360 °
Deviation distance l _d : the fundamental wave and the harmonic wave have a phase of 360 in the optical element.
In addition, if the case where the two non-linear optical crystals are arranged so that the crystal orientation directions thereof are opposite to each other is included, l _m and l _d of the above equation 1 are included.
Is used as the distance in which the phases of the fundamental wave and the harmonic wave are shifted by 180 °. Further, the present invention is not limited to the two laser beams of the fundamental wave and its harmonics, and may be configured to adjust the phase difference between a plurality of laser beams for other purposes.

As the phase correcting means, for example, in the optical system, a mechanism capable of adjusting the interval between nonlinear optical crystals or the inclination of the optical element is provided, or the thickness of the optical element to be used is appropriately selected according to the above conditions. Or by providing a phase compensator.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a laser light harmonic generator according to an embodiment of the present invention will be described with reference to FIG.

In this embodiment, for example, the laser beam 11 having a wavelength of 532 nm is used as the incident laser beam.
In the present invention, the type of the incident laser light is not limited, and any type of laser light or the type of laser light source (CW laser or pulse laser) can be used as long as the following conditions are satisfied.

The laser light is condensed using a condensing lens 31 into a nonlinear optical crystal BB having a thickness of 7 mm in the optical axis direction.
O (β-BaB ₂ O ₄ ) 21, so that
The light is converted to light having a wavelength of 266 nm having twice the frequency. In the laser beam 12 immediately downstream of the nonlinear optical crystal 21, the wavelength 2
In addition to the light of 66 nm, there is light of wavelength 532 nm that is not converted by the nonlinear optical crystal 21. Since the wavelength conversion efficiency is proportional to the incident laser light power, if the power of the laser light 11 is not sufficient, the laser light 12
Of the wavelength 532 nm, which is not converted, in the laser beam.

The wavelength 53 existing in the laser light 12
In order to convert a laser beam of 2 nm into a laser beam of a wavelength of 266 nm, in addition to the optical system having the above-described configuration, a condensing lens 32 and a nonlinear optical crystal BBO (β -BaB ₂ O ₄ ) 22 is continuously arranged downstream.

In order to further improve the conversion efficiency,
Downstream of the non-linear optical crystal 22, a plurality of third, fourth,... Condensing lenses and non-linear optical crystals having the same wavelength conversion characteristics as the above-described non-linear optical crystal may be continuously arranged. .

Here, as the condenser lens, a spherical lens, a cylindrical lens, or a combination thereof is used as necessary. The lens 31 has a wavelength of 532n.
The lens 32 has an anti-reflection coating for wavelengths 532 nm and 266 nm.

If necessary, the nonlinear optical crystal 2
The wavelengths 532n are provided on the laser light incidence surface and the emission surface of the laser light sources 1 and 22.
m, 266 nm.

In the case of continuous arrangement, it is not necessary to arrange them on a straight line, and as shown in FIG.
A configuration in which the nonlinear optical crystals 21, 22, and 23 are continuously arranged while bending the optical path by using 1, 62, or the like may be adopted.

According to the present embodiment, it is possible to provide a laser light harmonic generator capable of realizing wavelength conversion using a nonlinear optical crystal with high efficiency by an optical system having a simpler configuration. The optical system as shown in FIG. 1 to which the present invention is applied generates a laser beam and converts the wavelength of the laser beam. For example, a wavelength conversion optical system of an ultraviolet laser light source disclosed in Japanese Patent Application Laid-Open No. 8-334803. It can also be used as a system. Further, the present invention can be applied to a wavelength conversion optical system of an exposure machine that performs an exposure process using the laser light whose wavelength has been converted, similarly to the above embodiment.

Hereinafter, another embodiment of the optical system to which the present invention is applied, based on the configuration shown in FIG. 1 will be described.

In the first embodiment, a Gaussian beam (T) having a wavelength of 532 nm (accurately, 532.07 nm), a beam radius of 200 μm at the starting point, and a divergence angle of 0 rad is used as the incident light.
EM00). The fused silica convex lens 31 having a focal length of 40 mm is arranged so that the laser beam incident surface is located at a position 60 mm downstream of the laser beam incident surface, and the laser beam incident surface is located 38 mm downstream from the emission end surface of the fused quartz convex lens 31. The nonlinear crystal 21 is arranged as follows.
As a result, the beam waist and the center position of the nonlinear optical crystal are substantially aligned.

Further, a fused quartz convex lens 32 for condensing the laser light 12 is arranged so that the laser light incident surface is located at about 72 mm downstream from the emission end face of the nonlinear optical crystal 21. 8 downstream from the light exit surface
7 mm long so that the laser beam incident surface is at a position of 4 mm
Of the second harmonic 266 nm having a wavelength of 532 nm (more precisely, 266.
035 nm).

With the above configuration, the center position of the nonlinear optical crystal 22 and the beam waist position of the laser beam 12 match. The laser light converted by the nonlinear optical crystal 22 propagates as the output beam 13. As an actual experimental result, it was possible to obtain 266 nm light having a larger power than the one using the lens 31 and the crystal 21 in almost all cases. Of course, it is possible to adjust the phase difference by the means described in the following embodiments, but it has been experimentally confirmed that the output light power is improved in many cases.

Next, a second embodiment of the optical system according to the present invention will be described.

In order to improve the conversion efficiency of the wavelength 266 nm in the nonlinear crystal 22, the wavelength 532 nm, 266 nm
It is necessary that the laser beams have the same phase. However, due to the dispersion of the air on the optical path and the fused silica which is the material of the convex lens, a laser beam having a wavelength of 532 nm and a wavelength of 266 nm are used.
The phase of the laser light of nm is shifted.

That is, as shown in FIG. 1, L _Air (=
L _Air1 + L _Air2 ) and L _Si are the distances on the optical path of air and the lens, respectively, and l _Air and l _Si are the phases of the second harmonic wave and the fourth harmonic wave respectively in the air and the phase of the fourth harmonic light in the lens. 3
If the distance is shifted by 60 °, it is necessary to satisfy the following conditions from the above equation (1).

M = (L _Air / l _Air ) + (L _Si / l _Si ) (2) where l _Air = λ _4w / (n _{4w, Air−} n _{2w, Air} ) l _Si = λ _4w / (N _{4w, Si} −n _{2w, Si} ) Specifically, in the case of air, the phase of 266 nm light is 36
The distance shifted by 0 ° is l _Air , the wavelength in air is 266 nm,
The refractive index at 532 nm is n _{266 nm, Air} and n _, respectively.
_{Assuming that} the wavelength of light in _{532 nm, air} , and vacuum is λ _{266 nm} , the following equation holds.

[0030] _{l Air (n 266nm, Air -n} 532nm, Air) here × l _Air = λ _266nm ··· number _{3, n 266nm, Air = 1.00029752} n 532nm, by _Air = 1.00027819 above number 3 Is about 13.7 mm, and the light having the wavelengths of 266 nm and 532 nm returns to the same phase when traveling this distance in the air.

Similarly, in the case of fused quartz, the distance at which the phase of 266 nm light is shifted by 360 ° is set to l _Si , and the wavelength of 2
The refractive indices of 66 nm and 532 nm are respectively n _{266 nm, Si} ,
If n _{532 nm, Si} , and the wavelength of light in a vacuum are λ _{266 nm} , the following _equation 4 holds.

[0032] _{(n 266nm, Si -n 532nm,} Si) × l Si = λ 266nm ··· number 4 _{where, n 266nm, Si = 1.49968 n} 532nm, Si = 1.46071 l Si by Equation 4 Is about 6.8 μm, and the light of wavelengths 266 nm and 532 nm returns to the same phase when traveling this distance in the fused quartz.

In the first embodiment, assuming that the lens material is fused quartz and the thickness of the lens 32 is 5.3 mm, 266 nm light and 53
The phase difference of 2 nm light is 266 nm (exactly 266.035n
m) Generates only 132.3 ° in terms of light.

In this embodiment, an interval between two nonlinear optical crystals is set so that the above-mentioned phase difference is corrected. It is also possible to provide a mechanism capable of adjusting the interval between the two nonlinear optical crystals, and to correct the phase difference using this mechanism.

Specifically, depending on the thickness of the air on the optical path, 2
A phase difference of 27.7 ° is created and the entire phase difference is 360
° must be. The air thickness required to create such a phase difference is about 8.7 mm. Also,
In air, the phase difference is 36 for every integral multiple of 13.7 mm.
It vibrates at a rate of 0 °, so that must be taken into account.

In the case of the first embodiment, for example, 11 is taken as a multiple, and 8.7 + 13.7 × 11 = 159.
By providing the air gap of 4 mm, the phases of the laser beams having the wavelengths of 532 nm and 266 nm at the position of the second nonlinear optical crystal 22 are aligned. That is, since the air gap between the nonlinear optical crystals 21 and 22 originally located at the position of the beam waist was 156 mm, the nonlinear optical crystal 22 may be shifted by about 3.4 mm in the downstream direction.

According to the above configuration, efficient wavelength conversion is performed in the second nonlinear optical crystal 22. In this case, for example, the position of the beam waist does not coincide with the center arrangement of the nonlinear optical crystal. However, since the change in the beam diameter in this case is small, there is almost no problem.

According to the present embodiment, for example, the laser beam harmonic that can correct the phase relationship between the fundamental wave and the harmonic in the optical system of the first embodiment and maximize the amount of generation of the optical harmonic. A wave generator can be provided.

Here, the second nonlinear optical crystal 22
Is assumed to be parallel to the crystal orientation of the first nonlinear optical crystal 21, but instead of the above configuration, the direction of the crystal orientation of the second nonlinear optical crystal 22 is changed to the first orientation.
And arranged in the opposite direction to the nonlinear optical crystal 21 of
The phase difference between incident 532 nm and 266 nm light is 180
The air spacing may be adjusted so as to be an odd multiple of °.

In this embodiment, the fundamental wave (532n
m) and its second harmonic (266 nm) have been described as examples, but the specific wavelength of the laser light is not limited to these in the present invention, and the laser light of other wavelengths is also applicable to the present invention. The phase difference can be corrected as in the embodiment.

Next, a third embodiment of the optical system according to the present invention will be described.

In this embodiment, a laser beam having a wavelength of 532 nm and a wavelength of 266 nm are used in the basic configuration shown in FIG.
A lens 32 having a thickness necessary to correct the phase shift of the laser beam is used. Hereinafter, a method for obtaining the thickness of the lens 32 required for this correction will be described.

In the first embodiment, the thickness (L _Air ) of the air from the exit of the first nonlinear optical crystal 21 to the entrance of the second nonlinear optical crystal 22 is 156 mm. , At the entrance of the second nonlinear optical crystal 22 to the phase of 532 nm light and 266 nm light.
A shift of 5 ° occurs. In order to correct this phase difference, the thickness of the fused quartz convex lens 32 for setting the phase difference to 0 ° is selected.

132.3 for a fused quartz having a thickness of 5.3 mm
° phase difference occurs. To correct the phase difference by changing the thickness of the fused quartz so as to be an integral multiple of 360 °, for example, 360 ° − (120.5 ° + 132.3 °) = 10
What is necessary is just to generate a phase difference of 7.2 ° in the convex lens 32. This corresponds to a thickness of 2.0 μm in fused quartz.

Therefore, in the first embodiment, the phase difference can be corrected by increasing the thickness of the convex lens 32 by 2.0 μm. The thickness of the air is reduced by an amount corresponding to the increase in the thickness of the convex lens 32.
The phase difference due to m air can be almost ignored. Also in this case, it is assumed that the crystal orientation of the second nonlinear optical crystal 22 is parallel to the crystal orientation of the first nonlinear optical crystal 21.

Further, instead of the above structure, the direction of the crystal orientation of the second nonlinear optical crystal 22 is arranged so as to be opposite to that of the first nonlinear optical crystal 21, and the incident 532n
A configuration may be adopted in which a lens having a thickness such that the phase difference between m and 266 nm light is an odd multiple of 180 ° is selected.

Further, instead of accurately determining the thickness of the lens in advance, a lens having a thickness substantially matching the optimum value is provided, and a mechanism for moving the lens in a direction orthogonal to the optical path is provided. Thus, the effective thickness of a portion of the lens through which the laser light passes may be changed.

Next, a fourth embodiment of the optical system according to the present invention will be described.

In the present embodiment, the lens 32 is inclined with respect to the optical path in the first embodiment, so that the phase of the laser beam having a wavelength of 532 nm and the phase of the laser beam having a wavelength of 266 nm required to increase the wavelength conversion efficiency are increased. This is to correct the displacement.

In the first embodiment, when the thickness of the air is 156 mm, the phase shift at this portion is 120.5 mm.
° exists. In addition, the thickness of the fused quartz is 5.3 mm,
This corresponds to a phase difference of 132.3 °. Therefore, to increase the conversion efficiency as in the third embodiment, 360
A phase difference of ° − (120.5 ° + 132.3 °) = 107.2 ° is required.
m.

In this embodiment, about 1.6 ° with respect to the optical axis.
By tilting the lens, the optical path length of the fused silica is increased. The thickness of the air is reduced by an amount corresponding to the increase in the optical path length of the fused quartz, but the phase difference due to the air can be almost ignored. Also in this case, it is assumed that the crystal orientation of the second nonlinear optical crystal 22 is parallel to the crystal orientation of the first nonlinear optical crystal.

Further, instead of the above configuration, the second non-linear optical crystal 22 is arranged so that the direction of the crystal orientation is opposite to that of the first non-linear optical crystal 21, and the incident light 532 n
The inclination of the lens 32 is adjusted so that the phase difference between m and 266 nm light is an odd multiple of 180 °.

Next, a fifth embodiment of the optical system according to the present invention will be described with reference to FIG.

In this embodiment, a phase compensating plate 40 as shown in FIG. 4 is arranged as a means for correcting the phase. The phase compensating plate 40 is composed of, for example, two triangular prism-shaped fused silica plates movably arranged on the optical path. The optical path length can be easily changed by moving these fused quartz plates in a direction perpendicular to the optical path (in the direction of the arrow in the figure).

For example, if the constituent material of the lens 32 is fused silica and the thickness of the lens 32 is 5.3 mm, the lens 3
2, the phase difference between 266 nm and 532 nm
It generates 132.3 ° when converted to 266 nm light. In the present embodiment, in order to correct this phase difference, the thickness of the phase compensator 40 on the optical path is adjusted to make the entire phase difference 360 °.

Here, in the fused quartz constituting the phase compensating plate 40, the phase difference becomes 360 for every integral multiple of about 6.8 μm.
It vibrates at a rate of °, so that must be taken into account. Furthermore, since the thickness of the air decreases as the optical path length of the fused quartz increases, this must also be considered.

The thickness of the phase compensating plate 40 made of fused quartz is 6.8 × 1000 = 682, where the multiple is 1000.
If it is 6.6 μm, no phase difference occurs due to the phase compensator 40, but the thickness of the air is reduced by 6.8 mm. The phase difference due to the air reduction is -178.6 °, and the phase difference due to the lens 32 is 132.3 °, so that the total is −
A phase difference of 46.3 ° occurs. The amount of increase in the thickness of the fused quartz required to create a phase difference of 46.3 ° is about 0.3.
9 μm.

Therefore, the thickness of the phase compensating plate 40 is set to 68
By setting 26.9 + 0.9 = 6827.5 μm, the wavelength 532n at the position of the second nonlinear optical crystal 22 is obtained.
m, 266 nm. Although the thickness of the air is reduced by the further increase of the optical path length of the fused quartz, the phase difference caused by the air having a thickness of 0.9 μm can be almost ignored.

According to the above configuration, efficient wavelength conversion is performed in the second nonlinear optical crystal 22. In addition,
In the present embodiment, it is assumed that the crystal orientation of the second nonlinear optical crystal is parallel to the crystal orientation of the first nonlinear optical crystal.

Further, instead of the above configuration, the second non-linear optical crystal 22 is arranged so that the direction of the crystal orientation is opposite to that of the first non-linear optical crystal 21, and the incident 532 n
The interval at the phase compensator 40 is adjusted so that the phase difference between m and 266 nm light is an odd multiple of 180 °.

Next, a sixth embodiment of the optical system according to the present invention will be described with reference to FIG.

In this embodiment, the phase compensating plate 50 is
As shown in FIG. 5, two parallel plates made of fused quartz on the optical path are used. The phase compensating plate 50 is realized by arranging the respective parallel plates made of fused silica so as to be able to be inclined with respect to the optical path. By adjusting the inclination, the optical path length can be easily changed. I can do it.

For example, if the constituent material of the lens 32 is fused quartz and the thickness of the lens 32 is 5.3 mm, the lens 3
2, the phase difference between 266 nm and 532 nm
It generates 132.3 ° when converted to 266 nm light. In the present embodiment, in order to correct this phase difference, the inclination of the phase compensator 50 on the optical path is adjusted to make the entire phase difference 360 °.

Here, in the fused quartz constituting the phase compensating plate 50, the phase difference is 360 ° for every integral multiple of 6.8 μm.
It must be taken into account. Furthermore, since the thickness of the air decreases as the optical path length of the fused quartz increases, this must also be considered.

The thickness of the parallel plate is 6.8266 mm (6.
When the thickness of the air is reduced by 6.8 mm, the phase difference is -17.
8.6 °. 132.3 phase difference due to lens 32
°, a phase difference of -46.3 ° is generated in total. The increase in thickness of the fused quartz required to produce a 46.3 ° phase difference is about 0.9 μm.

In the present embodiment, each parallel flat plate is inclined so that the optical path length increases by about 0.9 μm. That is, by inclining one parallel plate in the opposite direction (in the direction of the arrow in the drawing) by about 0.5 °, the phases of the laser beams having the wavelengths of 532 nm and 266 nm at the position of the second nonlinear optical crystal 22 are aligned. Becomes possible.

According to the above configuration, efficient wavelength conversion is performed in the second nonlinear optical crystal. here,
The crystal orientation of the second nonlinear optical crystal is parallel to the crystal orientation of the first nonlinear optical crystal. The thickness of the air is reduced by an amount corresponding to the increase in the optical path length of the fused quartz, but the phase difference due to the air can be almost ignored.

Further, instead of the above configuration, the second non-linear optical crystal 22 is arranged so that the direction of the crystal orientation is opposite to that of the first non-linear optical crystal 21, and the incident 532n
The interval in the phase compensator 50 is adjusted so that the phase difference between m and 266 nm light is an odd multiple of 180 °.

[0069]

According to the present invention, there is provided a laser light harmonic generator capable of easily and efficiently generating harmonics even with a laser light having a small power by wavelength conversion by a nonlinear optical crystal. It becomes possible.

Further, according to the present invention, there is provided a laser light harmonic generator capable of correcting the phase relationship between a fundamental wave and a harmonic in a wavelength conversion optical system and maximizing the amount of generated optical harmonics. It is possible to do.

[Brief description of the drawings]

FIG. 1 shows a basic embodiment of an optical system according to the invention, and
FIG. 6 is an explanatory diagram for describing a first embodiment to a fourth embodiment.

FIG. 2 is an explanatory diagram illustrating an example in which a pair of a conventional lens and a nonlinear optical crystal is used.

FIG. 3 is an explanatory view showing a conventional external resonator method.

FIG. 4 is an explanatory diagram illustrating a fifth embodiment according to the present invention.

FIG. 5 is an explanatory diagram for explaining a sixth embodiment according to the present invention.

FIG. 6 is an explanatory diagram for explaining another embodiment according to the present invention.

[Explanation of symbols]

Reference Signs List 11 laser light (wavelength 532 nm) 12 laser light (wavelength 532 nm, 266 nm) 13 laser light (wavelength 532 nm, 266 nm) 21 nonlinear optical crystal BBO (β-BaB2O4) 22 nonlinear optical crystal BBO (β-BaB2O4) 31 fused silica convex lens (Focal length 40mm) with non-reflective coating (wavelength 532nm) 32 fused silica convex lens (focal length 40mm) with non-reflective coating (wavelength 532nm, 266n)
m) 40 phase compensator 41 concave mirror complete reflection coating (wavelength 266 nm) partial reflection coating (wavelength 532 nm) 42 concave mirror complete reflection coating (wavelength 266 nm) partial reflection coating (wavelength 532 nm) 50 phase compensator

Claims (8)

[Claims] 1. A laser light harmonic generator comprising a laser light source and an optical system for converting the wavelength of generated laser light, wherein the optical system is condensed by the condensing optical element and the condensing optical element. A plurality of sets of non-linear optical crystals for converting the wavelength of the laser light, which are successively arranged, wherein the plurality of non-linear optical crystals have the same wavelength conversion characteristics. 2. The laser light harmonic generation device according to claim 1, wherein in the optical system, an interval between at least one nonlinear optical crystal of the plurality of nonlinear optical crystals and another nonlinear optical crystal adjacent thereto is provided. Is set to a length necessary to substantially match or shift the phase of the laser light of two predetermined wavelengths at at least one of the positions of the nonlinear optical crystal and the other nonlinear optical crystal by 180 °. A laser light harmonic generator. 3. The laser beam harmonic generation device according to claim 1, wherein the optical system uses a plurality of condensing lenses as the plurality of condensing optical elements, and the plurality of condensing lenses. Thickness of at least one condenser lens among the lenses for
The thickness required to substantially match or shift the phase of the laser light of two predetermined wavelengths at the arrangement position of the nonlinear optical crystal located on the downstream side of the condensing lens is required. Characteristic laser light harmonic generator. 4. The laser beam harmonic generator according to claim 1, wherein the optical system uses a plurality of condensing lenses as the plurality of condensing optical elements, and the plurality of condensing lenses. The inclination of at least one of the condenser lenses is
The inclination required to substantially match or shift the phase of the laser light of two predetermined wavelengths by 180 ° at the arrangement position of the nonlinear optical crystal located downstream of the condensing lens. Characteristic laser light harmonic generator. 5. The laser light harmonic generator according to claim 1, wherein the optical system includes a plurality of nonlinear optical crystals having different wavelengths, which are incident on at least one of the plurality of nonlinear optical crystals. A laser light harmonic generation device, further comprising a phase correction means for adjusting a phase of the laser light so as to satisfy a predetermined relative relationship. 6. The laser light harmonic generation device according to claim 5, wherein the phase correction means is configured to displace the nonlinear optical crystal in the optical axis direction of the optical system, and a nonlinear optical crystal displacement mechanism. A laser light harmonic generator comprising at least one of a condensing optical element displacement mechanism for displacing or tilting the condensing optical element in a direction other than the optical axis direction. 7. The laser beam harmonic generator according to claim 5, wherein said phase correcting means is a phase compensator comprising a pair of prisms. 8. The laser light harmonic generator according to claim 5, wherein said phase correcting means is a phase compensator comprising one or more parallel flat plates. .