JP3125512B2 - Method for stabilizing output of ultraviolet laser light and ultraviolet laser light generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet laser light output stabilizing method and an ultraviolet laser light generator.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional ultraviolet laser light generator, wherein 1 is a YAG laser oscillator,
The AG laser oscillator 1 outputs a laser beam (Y
A fundamental wave of an AG laser) is oscillated.

[0003] Reference numeral 2 denotes a YAG laser second harmonic generator. The YAG laser second harmonic generator 2 includes the aforementioned YA.
From the fundamental wave of the YAG laser oscillated by the G laser oscillator 1, 1 / λ ₂ = 1 / λ ₁ + 1 / λ ₁ (λ ₁ : wavelength of the fundamental wave, λ ₂ : wavelength of the second harmonic) (Second harmonic generation), the second harmonic generation nonlinear optical crystal 3 that generates a laser beam (the second harmonic of the YAG laser) having a wavelength of 532 nm is provided.

[0004] Reference numeral 4 denotes a YAG laser fourth harmonic generator.
From the second harmonic of the YAG laser generated by the second harmonic generator 2 of the G laser, 1 / λ ₄ = 1 / λ ₂ + 1 / λ ₂ (2) (λ ₂ : wavelength of the second harmonic, λ ₄ : The fourth harmonic generation nonlinear optical crystal 5 that generates an ultraviolet laser beam (YAG laser fourth harmonic) having a wavelength of 266 nm according to the relationship (fourth harmonic generation). I have.

Reference numeral 6 denotes a prism. The prism 6 is converted by the YAG laser fourth harmonic generated by the fourth harmonic generation nonlinear optical crystal 5 and converted by the fourth harmonic generation nonlinear optical crystal 5. The second harmonic of the YAG laser remaining without being separated from the fundamental wave of the YAG laser remaining without being converted by the nonlinear optical crystal 3 for generating the second harmonic and passing through the nonlinear optical crystal 5 for generating the fourth harmonic. It is supposed to.

The above-mentioned nonlinear optical crystal for generating the fourth harmonic 5
Has a BBO (β-BaB ₂ O ₄ ) crystal and a heavy water substitution rate of 95%.
D-KDP (K
D ₂ PO ₄ : D is deuterium) crystal or the like is used.

When an ultraviolet laser is generated by the above-mentioned ultraviolet laser light generator, the nonlinear optical crystal for second harmonic generation 3 and the nonlinear optical crystal for fourth harmonic generation 5 are raised to a predetermined temperature in advance. Heating and changing the inclination of the crystal to change the crystal angle (the angle between the optical axis of the crystal and the incident laser beam)
Is adjusted.

Then, when a YAG laser fundamental wave having a wavelength of 1064 nm is oscillated by the YAG laser oscillator 1, the YAG laser fundamental wave is transmitted to the second harmonic generation nonlinear optical crystal 3 of the YAG laser second harmonic generator 2. Incident on the nonlinear optical crystal for second harmonic generation 3 according to the relationship of the above equation (1) (second harmonic generation), at a wavelength of 532 nm.
The second harmonic of the YAG laser is generated.

The YAG laser second harmonic generated by the second harmonic generation nonlinear optical crystal 3 is the YAG laser fourth harmonic.
The incident light enters the fourth harmonic generation nonlinear optical crystal 5 of the harmonic generator 4, and the fourth harmonic generation crystal 4 has a wavelength of 266 nm according to the relationship of the above equation (2) (fourth harmonic generation).
The fourth harmonic of the YAG laser is generated.

Further, a nonlinear optical crystal for fourth harmonic generation 5
Laser generated by the fourth harmonic and YAG remaining without being converted by the fourth harmonic generation nonlinear optical crystal 5
The laser second harmonic and the YAG laser fundamental wave remaining without being converted by the second harmonic generation nonlinear optical crystal 3 and passing through the fourth harmonic generation nonlinear optical crystal 5 are:
Each is separated by a prism 6.

[0011]

However, when the fourth harmonic of the YAG laser having the wavelength of 266 nm is generated as described above, the phase adjustment is performed by adjusting the angle of the nonlinear optical crystal 5 for generating the fourth harmonic. In order to obtain a practical high output YAG laser fourth harmonic by achieving the above, the following problem occurs.

(1) The fourth harmonic generation nonlinear optical crystal 5 itself, which is a wavelength conversion element, absorbs the fourth harmonic of the YAG laser generated nonlinearly, and the fourth harmonic generation nonlinear optical crystal 5 In the beam path, a self-heating phenomenon occurs in which the temperature rises due to intense heat generation.

(2) When the intense self-heating phenomenon occurs, the phase matching condition of the fourth harmonic generation nonlinear optical crystal 5, that is, the refractive index n = n (λ, T, θ)
(Λ: wavelength, T: crystal temperature, θ: angle between the optical axis of the crystal and the incident laser beam) are destroyed in terms of temperature, and are generated by the fourth harmonic generation nonlinear optical crystal 5. The output of the fourth harmonic of the YAG laser drops rapidly.

(3) For this reason, when generating the fourth harmonic of the YAG laser, the crystal temperature and crystal angle (the angle between the optical axis of the crystal and the incident laser light) of the fourth harmonic generation nonlinear optical crystal 5 are determined in advance. Even in an appropriate state, the phase matching state of the fourth harmonic generation nonlinear optical crystal 5 can be maintained for only a few minutes at most due to the occurrence of the self-heating phenomenon. High output YAG
The laser fourth harmonic cannot be continuously generated for a long time.

(4) Such a problem arises not only when the fourth harmonic generation nonlinear optics 5 described above is used to generate the fourth harmonic of the YAG laser, but also when the wavelength is about 300 nm due to wavelength conversion using a nonlinear optical crystal. This occurs in all cases where the following ultraviolet laser light is generated.

[0016]

[Knowledge based on research results] In order to solve the above problem, the present inventors conducted various experiments on the relationship between the laser temperature and the crystal temperature of the nonlinear optical crystal, and as a result, the following results were obtained. I got the knowledge.

(1) Nonlinear optical crystal (deuterium substitution rate 90%)
When the excitation light (the second harmonic of the YAG laser) is made incident on the D-KDP crystal of the present invention to generate the ultraviolet laser light (the fourth harmonic of the YAG laser), the phase matching condition, that is, the matching condition of the refractive index is satisfied. When the temperature of the nonlinear optical crystal is controlled to rise to a predetermined temperature, the relationship between the output of the ultraviolet laser light generated by the nonlinear optical crystal and the angle θ formed by the optical axis of the crystal and the incident laser light, as indicated by the dashed line in FIG. The crystal angle dependence curve of the output of the ultraviolet laser light, which expresses a double peak type, has two angles (phase matching angles) at which the ultraviolet laser light output is maximized, centered at 90 °.

(2) When the temperature of the nonlinear optical crystal is gradually raised from the state of the above item (1), the phase matching angles (crystal angles for achieving the phase matching) approach 90 °, and the crystal angle dependence curve is obtained. Has a single peak type in which the phase matching angle is 90 °, as shown by the broken line in FIG. 2, and 90 ° phase matching is achieved.

(3) When the crystal temperature is further gradually increased in steps of 0.1 ° C. from the state where the 90 ° phase matching is achieved, the ultraviolet laser light output gradually decreases in response to the increase in the crystal temperature. As a result, as shown by a solid line in FIG. 2, a value of about 70 to 80% when 90 ° phase matching is achieved is exhibited.

(4) At this time, a kind of saturation effect on the temperature of the phase matching condition, that is, the refractive index matching condition caused by exceeding the 90 ° phase matching temperature, and the temperature gradient in the crystal by the heating temperature control (temperature rising control). The effect of smoothing appears, 90
(4) Although it is about 70 to 80% of the maximum output at the time of achieving the phase matching, a practically high output ultraviolet laser beam can be continuously generated for a long time.

[0021]

SUMMARY OF THE INVENTION An object of the present invention is to generate a practically high-power ultraviolet laser beam continuously for a long time.

[0022]

In order to achieve the above object, in the method for stabilizing the output of an ultraviolet laser beam according to the present invention, an input laser beam is made incident on a nonlinear optical crystal capable of achieving 90 ° phase matching. When generating the ultraviolet laser light, the temperature of the nonlinear optical crystal is controlled to be slightly higher than the temperature at which the nonlinear optical crystal achieves 90 ° phase matching within a range of 0.1 ° C. to 5.0 ° C. I do.

Also, in the ultraviolet laser light generator of the present invention, an input laser light generator for generating an input laser light can achieve 90 ° phase matching and is generated by the input laser light generator. A nonlinear optical crystal capable of generating an ultraviolet laser beam from an input laser beam, and a nonlinear optical crystal slightly within a range of 0.1 ° C. to 5.0 ° C. within a temperature range at which the nonlinear optical crystal achieves 90 ° phase matching. A temperature control device capable of controlling a temperature rise to a high temperature.

Further, in the ultraviolet laser light generator of the present invention, a YAG laser oscillator for oscillating a fundamental wave of a YAG laser and a second harmonic of the YAG laser are generated from the fundamental wave of the YAG laser oscillated by the YAG laser oscillator. Generating a fourth harmonic of the YAG laser from the second harmonic of the YAG laser which can achieve 90 ° phase matching with the nonlinear optical crystal for second harmonic generation and which is generated by the nonlinear optical crystal for second harmonic generation; A fourth harmonic generation nonlinear optical crystal, and a fourth harmonic generation nonlinear optical crystal that is 0.1 ° C. to 5 ° C. lower than the temperature at which the fourth harmonic generation nonlinear optical crystal achieves 90 ° phase matching. A temperature control device capable of controlling a temperature rise to a slightly higher temperature within a range of 0.0 ° C.

[0025]

In the method for stabilizing the output of an ultraviolet laser beam according to the first aspect of the present invention, an input laser beam is made incident on a nonlinear optical crystal for generating an ultraviolet laser beam capable of 90 ° phase matching.
70-80 when 90 ° phase matching is achieved (when maximum output is achieved)
% So that the nonlinear optical crystal is heated to a temperature slightly higher than the temperature at which 90 ° phase matching is achieved in the range of 0.1 ° C. to 5.0 ° C. so that an ultraviolet laser light output of about% is obtained. Control. As a result, a practically high output ultraviolet laser beam of about 70 to 80% of the time when the 90 ° phase matching is achieved (when the maximum output is achieved) is continuously generated for a long time.

In the ultraviolet laser light generator according to a second aspect of the present invention, the input laser light generated from the input laser light generator is incident on a nonlinear optical crystal for generating an ultraviolet laser light capable of phase matching by 90 °. And controlling the temperature of the nonlinear optical crystal to be slightly higher than the temperature at which the nonlinear optical crystal achieves 90 ° phase matching in the range of 0.1 ° C. to 5.0 ° C. by the temperature controller. As a result, a practical high output ultraviolet laser beam is continuously generated for a long time.

In the ultraviolet laser light generator according to a third aspect of the present invention, the fundamental wave of the YAG laser oscillated from the YAG laser oscillator is converted into the second harmonic of the YAG laser by the second harmonic generation nonlinear optical crystal. And the Y
The second harmonic of the AG laser is incident on the fourth harmonic generation nonlinear optical crystal capable of phase matching by 90 °, and the (non-linear crystal temperature) of the fourth harmonic generation nonlinear optical crystal is subjected to the fourth harmonic generation by a temperature controller. The temperature is controlled so as to be slightly higher than the temperature at which the nonlinear optical crystal for wave generation achieves 90 ° phase matching in the range of 0.1 ° C. to 5.0 ° C., and is continuously used for a long time. , The fourth harmonic of the YAG laser having a high output is generated.

[0028]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of an ultraviolet laser light generating apparatus according to the present invention. Reference numeral 7 denotes a Q-switched pulse YAG laser oscillator, and the Q-switched pulse YAG laser oscillator 7 has a point suitable for nonlinear wavelength conversion. High head output wavelength 10
A laser beam of 64 nm (YAG laser fundamental wave) is oscillated.

Reference numeral 8 denotes a YAG laser second harmonic generator. The YAG laser second harmonic generator 8 uses the relationship of the above equation (1) from the YAG laser fundamental wave oscillated by the YAG laser oscillator 7. A second harmonic generation nonlinear optical crystal 3 for generating a laser beam having a wavelength of 532 nm (YAG laser second harmonic) by the second harmonic generation;
A crystal temperature controller 9 having a heater for raising the temperature of the nonlinear optical crystal 3 for generating harmonics.

The above-mentioned Q-switched pulse YAG laser oscillator 7 and the second harmonic generation nonlinear optical crystal 3 make
An input laser light generator for generating a YAG laser second harmonic (input laser light) is configured.

Reference numeral 10 denotes a dichroic mirror. The dichroic mirror 10 reflects the second harmonic of the YAG laser generated by the nonlinear optical crystal 3 for generating the second harmonic, and reflects the nonlinear optical crystal for generating the second harmonic. 3, the YAG laser fundamental wave which is not converted is transmitted.

Reference numeral 11 denotes a beam damper. The beam damper 11 blocks a fundamental wave of a YAG laser transmitted through the dichroic mirror 10.

Reference numeral 12 denotes a dichroic mirror. The dichroic mirror 12 reflects the second harmonic of the YAG laser reflected by the dichroic mirror 10 in the direction of a YAG laser fourth harmonic generator 13 to be described later. ing.

Reference numeral 18 denotes a beam damper. The beam damper 18 blocks a small amount of a fundamental wave of a YAG laser beam reflected by the dichroic mirror 10 and transmitted through the dichroic mirror 12.

Reference numeral 13 denotes a YAG laser fourth harmonic generator. The YAG laser fourth harmonic generator 13 converts the YAG laser second harmonic reflected by the dichroic mirror 12 into the above equation (2). According to the relationship (fourth harmonic generation), a fourth harmonic generation nonlinear optical crystal 5 for generating an ultraviolet laser beam (YAG laser fourth harmonic) having a wavelength of 266 nm, and the fourth harmonic generation nonlinear optical crystal 5 And a crystal temperature controller 14 provided with a heater for raising the temperature of the crystal.

The above-mentioned nonlinear optical crystal for fourth harmonic generation 5
Is a 90 ° Y-cut (a cut in which the optical axis of the crystal is parallel to the input / output end face) with a 90% heavy water replacement ratio of DK.
DP (KD ₂ PO ₄ ) crystal is used.

Reference numeral 15 denotes a dichroic mirror. The dichroic mirror 15 reflects the fourth harmonic of the YAG laser generated by the fourth harmonic generation nonlinear optical crystal 5 and generates the fourth harmonic nonlinear optical crystal. 5 allows the second harmonic of the YAG laser remaining without being converted to pass.

Reference numeral 16 denotes a beam damper. The beam damper 16 blocks the second harmonic of the YAG laser transmitted through the dichroic mirror 15.

Reference numeral 17 denotes a dichroic mirror. The dichroic mirror 17 reflects the fourth harmonic of the YAG laser reflected by the dichroic mirror 15 in another direction.

Reference numeral 19 denotes a beam damper. The beam damper 19 blocks a small amount of the second harmonic of the YAG laser reflected by the dichroic mirror 15 and transmitted through the dichroic mirror 17.

Reference numeral 20 denotes a crystal temperature detector, which detects the crystal temperature of the nonlinear optical crystal 3 for generating the second harmonic and outputs a crystal temperature detection signal 21. ing.

Reference numeral 22 denotes a crystal temperature setting device, which outputs a crystal temperature setting signal 23 based on a value set by manual operation.

Reference numeral 24 denotes a crystal temperature controller. The crystal temperature controller 24 includes a crystal temperature setting signal 23 output from the crystal temperature setter 22 and a crystal temperature detection signal output from the crystal temperature detector 20. 21 and the crystal temperature controller 9
On the other hand, a crystal temperature adjustment signal 25 for operating the heater of the crystal temperature controller 9 is output so that the crystal temperature of the second harmonic generation nonlinear optical crystal 3 corresponds to the set value of the crystal temperature setter 22. ing.

Reference numeral 26 denotes a crystal temperature detector, which detects the crystal temperature of the nonlinear optical crystal 5 for generating the fourth harmonic and outputs a crystal temperature detection signal 27. ing.

Reference numeral 28 denotes a crystal temperature setting device, which outputs a crystal temperature setting signal 29 based on a value set by manual operation.

Reference numeral 30 denotes a crystal temperature controller. The crystal temperature controller 30 includes a crystal temperature setting signal 29 output from the crystal temperature setter 28 and a crystal temperature detection signal output from the crystal temperature detector 26. 27, the crystal temperature controller 1
In response to Step 4, a crystal temperature adjustment signal 31 for operating the heater of the crystal temperature controller 14 is output so that the crystal temperature of the fourth harmonic generation nonlinear optical crystal 5 corresponds to the set value of the crystal temperature setter 28. Has become.

The above-mentioned crystal temperature controller 14, crystal temperature detector 26, crystal temperature setter 28, and crystal temperature controller 30 control the fourth harmonic generation nonlinear optical crystal 5 to generate the fourth harmonic. The temperature adjusting device is capable of controlling the temperature to be slightly higher than the temperature at which the generating nonlinear optical crystal 5 achieves 90 ° phase matching in the range of 0.1 ° C. to 5.0 ° C.

Hereinafter, the operation of the ultraviolet laser light generator shown in FIG. 1 will be described.

Ultraviolet laser light (YAG laser fourth harmonic)
Is generated, the crystal angle of the second harmonic generation nonlinear optical crystal 3 is set to a predetermined angle, and the crystal angle of the fourth harmonic generation nonlinear optical crystal 5 (the optical axis of the crystal and the incident laser The angle formed by the light) is set to 90 °, and the crystal temperature setting unit 22 further sets the nonlinear optical crystal 3 for second harmonic generation.
The crystal temperature of the fourth harmonic generation nonlinear optical crystal 5 is set to a predetermined temperature by the crystal temperature setting unit 28, and the temperature of the fourth
The temperature is set slightly lower than the temperature at which the nonlinear optical crystal for harmonics 5 achieves 90 ° phase matching.

The crystal temperature controller 24 controls the crystal temperature controller 9 based on the crystal temperature setting signal 23 output from the crystal temperature setter 22 and the crystal temperature detection signal 21 output from the crystal temperature detector 20. The crystal temperature controller 9 outputs a crystal temperature control signal 25 for operating the crystal temperature controller 9 so that the crystal temperature of the second harmonic generation nonlinear optical crystal 3 corresponds to the set value of the crystal temperature controller 22. 9 keeps the temperature of the second harmonic generation nonlinear optical crystal 3 at a predetermined temperature.

The crystal temperature controller 30 controls the crystal temperature controller 14 based on the crystal temperature setting signal 29 output from the crystal temperature setter 28 and the crystal temperature detection signal 27 output from the crystal temperature detector 26. In response to this, the crystal temperature controller 14 outputs a crystal temperature control signal 31 for operating the crystal temperature controller 14 so that the crystal temperature of the fourth harmonic generation nonlinear optical crystal 5 corresponds to the set value of the crystal temperature setter 28. 14, the temperature of the fourth harmonic generation nonlinear optical crystal 5 is controlled to be slightly lower than the temperature at which the fourth harmonic generation nonlinear optical crystal 5 achieves 90 ° phase matching. .

The temperature of the second harmonic generation nonlinear optical crystal 3 is set to a predetermined temperature, and the temperature of the fourth harmonic generation nonlinear optical crystal 5 is set to 90 ° phase. After the temperature is controlled to be slightly lower than the temperature at which the matching is achieved, a QAG switch pulse YAG laser oscillator 7 oscillates a YAG laser fundamental wave having a wavelength of 1064 nm. The light is incident on the second-harmonic generation nonlinear optical crystal 3 of the wave generator 8, and the wavelength 532 is obtained in the second-harmonic generation nonlinear optical crystal 3 according to the relationship of the above equation (1) (second-harmonic generation).
nm second harmonic of the YAG laser is generated.

The YAG laser generated by the second harmonic generation nonlinear optical crystal 3 The second harmonic and the YAG laser fundamental wave left unconverted by the second harmonic generation nonlinear optical crystal 3 enter the dichroic mirror 10. I do.

The second harmonic of the YAG laser is reflected by the dichroic mirror 10, and the fundamental wave of the YAG laser is transmitted through the dichroic mirror 10 and cut off by the beam damper 11.

The second harmonic of the YAG laser reflected by the dichroic mirror 10 is reflected by the dichroic mirror 1
2, a small amount of YAG laser fundamental wave reflected by the dichroic mirror 10 and transmitted through the dichroic mirror 12 is blocked by the beam damper 18. You.

The second harmonic of the YAG laser reflected by the dichroic mirror 12 is incident on the nonlinear optical crystal 5 for generating the fourth harmonic of the fourth harmonic generator 13 of the YAG laser, In the optical crystal 5, the wavelength 266 is obtained from the relationship of the above equation (2) (fourth harmonic generation)
The fourth harmonic (ultraviolet laser light) of the YAG laser of nm is generated.

When the fourth harmonic (ultraviolet laser light) of the YAG laser having the wavelength of 266 nm is generated, the nonlinear optical crystal 5 for generating the fourth harmonic is aligned at 90 ° phase (at the time of achieving the maximum output). So that a fourth harmonic output (ultraviolet laser light output) of a value of about 70 to 80% of the temperature within a range of 0.1 ° C. to 5.0 ° C. lower than the temperature at which 90 ° phase matching is achieved. Further raise the temperature to a higher temperature.

The YAG laser fourth harmonic generated by the fourth harmonic generation nonlinear optical crystal 5 and the YAG laser second harmonic remaining without being converted by the fourth harmonic generation nonlinear optical crystal 5 are converted to a dichroic mirror 15. Incident on.

The fourth harmonic of the YAG laser is reflected by the dichroic mirror 15, and the second harmonic of the YAG laser is cut off by the beam damper 16 after passing through the dichroic mirror 15.

The fourth harmonic of the YAG laser reflected by the dichroic mirror 15
The fourth harmonic of the YAG laser reflected by the dichroic mirror 17 is reflected by the dichroic mirror 17 and output as ultraviolet laser light.

A small amount of the second harmonic of the YAG laser reflected by the dichroic mirror 15 and transmitted through the dichroic mirror 17 is cut off by the beam damper 19.

In the above-described ultraviolet laser light generator, YA
Using the nonlinear optical crystal 5 capable of achieving 90 ° phase matching in G laser fourth harmonic generation, an ultraviolet laser light output of about 70 to 80% of that at the time of achieving 90 ° phase matching (at the time of achieving maximum output) can be obtained. In addition, the temperature of the fourth harmonic generation nonlinear optical crystal 5 is controlled to be slightly higher than the temperature at which 90 ° phase matching is achieved in the range of 0.1 ° C. to 5.0 ° C. .

At this time, a saturation effect on the temperature of the phase matching condition (refractive index matching condition) caused by exceeding the phase matching temperature of 90 ° C. and an effect of smoothing the temperature gradient in the crystal by the heating temperature control appear. It is possible to continuously generate a practically high output ultraviolet laser beam having a value of 70 to 80% of that at the time of achieving 90 ° phase matching (at the time of achieving the maximum output) for a long time.

In this embodiment, a nonlinear optical crystal (fourth harmonic generation nonlinear optical crystal 5) for generating an ultraviolet laser beam (fourth harmonic of a YAG laser) has a D-water ratio of 90%. -KDP (KD ₂ PO _4: D is deuterium) was used crystal, depending on the wavelength of the ultraviolet laser beam to be generated, it is also possible to use a respective non-linear optical crystal below that can achieve 90 ° phase matched.

D-KDP crystal having a heavy water substitution rate of 90% or less (for example, 80%) BBO (β-BaB ₂ O ₄ ) crystal KDP (KH ₂ PO ₄ ) crystal D-ADP (NH ₄ D ₂ PO ₄ ) crystal ADP (NH ₄ H ₂ PO ₄ ) crystal RDP (RbH ₂ PO ₄ ) crystal D-RDP (RbD ₂ PO ₄ ) crystal LBO (LiB ₃ O ₅ ) crystal KN (KNbO ₃ ) crystal

The method for stabilizing the output of an ultraviolet laser beam and the apparatus for generating an ultraviolet laser beam according to the present invention are not limited to the above-described embodiment, and the input laser light may be a laser other than the second harmonic of the YAG laser. Using light,
A device other than a YAG laser oscillator is used for an input laser light generator for generating an input laser, and a D-KDP crystal is used as a nonlinear optical crystal for generating an ultraviolet laser light so as to correspond to the wavelength of the ultraviolet laser light to be generated. Other than 90
こ と Use another nonlinear optical crystal that can achieve phase matching, use a non-linear optical crystal temperature holding means other than the method shown in the embodiment, and otherwise do not depart from the gist of the present invention. It goes without saying that various changes can be made in.

[0068]

As described above, according to the ultraviolet laser light output stabilizing method and the ultraviolet laser light generator of the present invention, the following various excellent effects can be obtained.

(1) In the ultraviolet laser light output stabilizing method according to the first aspect of the present invention, input laser light is made incident on a nonlinear optical crystal capable of achieving 90 ° phase matching, and 90 ° phase matching is performed. 70 (when maximum output is achieved)
In order to obtain an ultraviolet laser light output of about 80%, the nonlinear optical crystal is set at a temperature lower than the temperature at which 90 ° phase matching is achieved by a temperature of 0.
Since the temperature is controlled to be slightly higher in the range of 1 ° C. to 5.0 ° C., a kind of saturation effect on the temperature of the phase matching condition (refractive index matching condition) caused by exceeding the 90 ° phase matching temperature. And the effect of smoothing the temperature gradient in the crystal by heating temperature control (heating control), and a practically high output of about 70 to 80% of the time when 90 ° phase matching is achieved (when the maximum output is achieved). Can be continuously generated for a long time.

(2) In any of the ultraviolet laser light generators according to the second and third aspects of the present invention, a nonlinear optical crystal (nonlinear optical crystal for fourth harmonic) capable of achieving 90 ° phase matching. Input laser light is incident on the
In order to obtain about 70 to 80% of the ultraviolet laser light output at the time of achieving the phase matching (at the time of achieving the maximum output), the non-linear optical crystal is shifted by 0.1 ° C. Since the temperature is controlled to rise to a slightly higher temperature within the range of 5.0 ° C., a kind of saturation effect on the temperature of the phase matching condition (refractive index matching condition) due to exceeding the 90 ° phase matching temperature and the heating temperature The effect of smoothing the temperature gradient in the crystal by controlling the temperature (controlling the temperature rise) is exhibited.
° Ultraviolet laser light (the fourth harmonic of the YAG laser) having a practically high output of about 70 to 80% of the value at the time of achieving the phase matching (at the time of achieving the maximum output) can be continuously generated for a long time.

(3) In the ultraviolet laser light output stabilizing method according to the first aspect of the present invention and the ultraviolet laser light generating apparatus according to the second and third aspects of the present invention, the nonlinear optical system is used. Since the ultraviolet laser light is generated when the angle between the optical axis of the crystal and the incident laser light is 90 °, no walk-off occurs due to the different traveling directions of the incident laser light and the generated ultraviolet laser light, Therefore, the wavelength conversion efficiency can be improved by increasing the crystal length of the nonlinear optical crystal.

(4) In the ultraviolet laser light generator according to the third aspect of the present invention, the YAG laser fundamental wave oscillated by the YAG laser oscillator is sequentially converted to generate the YAG laser fourth harmonic. Therefore, maintenance and inspection of the apparatus are easy and an ultraviolet laser beam having a high output can be obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an embodiment of an ultraviolet laser light generator according to the present invention.

FIG. 2 is a graph showing a relationship between a crystal angle of a nonlinear optical crystal and an ultraviolet laser light output.

FIG. 3 is a conceptual diagram showing an example of a conventional ultraviolet laser light generator.

[Explanation of symbols]

3 Nonlinear optical crystal for second harmonic generation (input laser generator) 5 Nonlinear optical crystal for fourth harmonic generation (nonlinear optical crystal) 7 Q switch pulse YAG laser oscillator (input laser generator) 14 Crystal temperature controller ( Temperature control device) 28 Crystal temperature setting device (Temperature control device) 30 Crystal temperature controller (Temperature control device)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-52-55494 (JP, A) JP-A-49-102366 (JP, A) JP-A-3-252186 (JP, A) JP-A-3-252186 283686 (JP, A) JP-A-5-11300 (JP, A) JP-A-5-204011 (JP, A) JP-A-3-145777 (JP, A) JP-A-62-162375 (JP, A) JP-A-51-959 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01S 3/00-3/30 G02F 1/37 JICST file (JOIS)

Claims (3)

(57) [Claims] When an input laser beam is incident on a nonlinear optical crystal capable of achieving 90 ° phase matching to generate an ultraviolet laser beam, the nonlinear optical crystal achieves 90 ° phase matching. 0.1 ° C to 5.0
A method for stabilizing the output of an ultraviolet laser beam, wherein the temperature is controlled so as to be slightly higher in the range of ° C. 2. An input laser light generating device for generating an input laser light, capable of achieving 90 ° phase matching and generating an ultraviolet laser light from the input laser light generated by the input laser light generating device. The nonlinear optical crystal and the temperature of the nonlinear optical crystal can be controlled to be slightly higher than the temperature at which the nonlinear optical crystal achieves 90 ° phase matching in the range of 0.1 ° C. to 5.0 ° C. An ultraviolet laser light generator comprising a temperature controller. 3. A YAG laser oscillator for oscillating a fundamental wave of a YAG laser, and a YAG laser oscillated by the YAG laser oscillator.
A second harmonic generation nonlinear optical crystal for generating a YAG laser second harmonic from an AG laser fundamental wave, and a YAG generated by the second harmonic generation nonlinear optical crystal capable of achieving 90 ° phase matching. Laser second harmonic to YA
A fourth harmonic generation nonlinear optical crystal capable of generating a G laser fourth harmonic, and a temperature at which the fourth harmonic generation nonlinear optical crystal achieves 90 ° phase matching. An ultraviolet laser light generator comprising: a temperature control device capable of controlling the temperature to be slightly higher in the range of 0.1 ° C. to 5.0 ° C.