JPH06310794A - Output stabilizing method for ultraviolet laser light and ultraviolet laser light generator - Google Patents

Abstract

PURPOSE:To sustain generation of high output ultraviolet laser light for a long time by controlling the temperature to a level higher by a specific range than the temperature at which a nonlinear optical crystal achieves phase matching of 90 deg.. CONSTITUTION:A crystal temperature controller 30 operates the heater in a crystal temperature conditioner 14 and controls the temperature of a nonlinear optical crystal 5 generating the fourth higher harmonic to a set level based on a crystal temperature set signal 29 from a crystal temperature setter 28 and a crystal temperature detection signal 27 from a crystal temperature detector 26. When laser light is inputted to the optical crystal 5 upon phase matching of 90 deg. to generate ultraviolet laser light, temperature of the optical crystal 5 is controlled to a level higher by a range of 0.1-5.0 deg.C than the temperature at which 90 deg. phase matching is achieved. This constitution allows long time continuous generation of practically high output ultraviolet laser light in the range of 70-80% of maximum output (when 90 deg. phase matching is achieved).

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, in which 1 is a YAG laser oscillator.
The AG laser oscillator 1 uses a laser beam (Y
It is designed to oscillate an AG laser fundamental wave).

Reference numeral 2 is a YAG laser second harmonic generator, and the YAG laser second harmonic generator 2 is the above-mentioned YA.
From the YAG laser fundamental wave oscillated by the G laser oscillator 1, 1 / λ ₂ = 1 / λ ₁ + 1 / λ ₁ (1) (λ _{1 is} the wavelength of the fundamental wave, λ _{2 is} the wavelength of the second harmonic) The second harmonic generation nonlinear optical crystal 3 for generating a laser beam (YAG laser second harmonic) having a wavelength of 532 nm by the above relationship (second harmonic generation).

Reference numeral 4 is a YAG laser fourth harmonic generator, and the YAG laser fourth harmonic generator 4 is the YA
From the YAG laser second harmonic generated by the G laser second harmonic generator 2, 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 for generating the ultraviolet laser light (YAG laser fourth harmonic) having a wavelength of 266 nm by the relationship (fourth harmonic wavelength) (fourth harmonic generation). There is.

Reference numeral 6 is a prism, and the prism 6 is converted by the fourth harmonic generation nonlinear optical crystal 5 generated by the fourth harmonic generation nonlinear optical crystal 5 described above. The YAG laser second harmonic that remains without separation and the YAG laser fundamental wave that remains unconverted by the second harmonic generation nonlinear optical crystal 3 and that passes through the fourth harmonic generation nonlinear optical crystal 5 are separated. It is supposed to do.

Nonlinear optical crystal 5 for generating the above fourth harmonic
Include BBO (β-BaB ₂ O ₄ ) crystals and a heavy water substitution rate of 95.
% Or more or heavy water substitution rate 99% or more of 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-described ultraviolet laser light generator, the second harmonic generation nonlinear optical crystal 3 and the fourth harmonic generation nonlinear optical crystal 5 are heated to a predetermined temperature in advance. Crystallization angle (angle between the optical axis of the crystal and the incident laser beam) by changing the tilt of the crystal after heating
Is adjusted.

Next, when the YAG laser oscillator 1 oscillates a YAG laser fundamental wave having a wavelength of 1064 nm, the YAG laser fundamental wave is transmitted to the second harmonic generation nonlinear optical crystal 3 of the YAG laser second harmonic generator 2. When incident, the wavelength of 532 nm is generated in the nonlinear optical crystal for second harmonic generation 3 by the relationship (second harmonic generation) of the above equation (1).
The second harmonic of the YAG laser is generated.

The second harmonic of the YAG laser generated by the nonlinear optical crystal 3 for generating the second harmonic is the fourth harmonic of the YAG laser.
A wavelength of 266 nm is incident on 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 due to the relation (4th harmonic generation) of the above equation (2).
The fourth harmonic of the YAG laser is generated.

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

[0011]

However, when the YAG laser fourth harmonic of the wavelength of 266 nm is generated as described above, the phase adjustment is performed by adjusting the angle of the fourth harmonic generating nonlinear optical crystal 5. In order to achieve the above and obtain a practically high output value YAG laser fourth harmonic, the following problems occur.

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

(2) When the above-mentioned 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)
The matching condition of (λ: wavelength, T: crystal temperature, θ: angle formed by the optical axis of the crystal and the incident laser beam) is thermally destroyed, and therefore is generated by the fourth harmonic generation nonlinear optical crystal 5. The output of the fourth harmonic of the YAG laser will drop rapidly.

(3) Therefore, when the YAG laser fourth harmonic is generated, the crystal temperature and the crystal angle (the angle between the optical axis of the crystal and the incident laser beam) of the nonlinear optical crystal 5 for generating the fourth harmonic are previously set. 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 the longest 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 is not limited to the case where the YAG laser fourth harmonic is generated by the above-described fourth harmonic generation nonlinear optics 5, and the wavelength is about 300 nm due to the wavelength conversion using the nonlinear optical crystal. It occurs in all cases of generating the following ultraviolet laser light.

[0016]

[Knowledge Based on Research Results] In order to solve the above problems, the inventor conducted various experiments on the relationship between the laser light output value with respect to the crystal temperature and the crystal angle of the nonlinear optical crystal. We have come to the knowledge.

(1) Nonlinear optical crystal (heavy water substitution rate 90%
When the excitation light (YAG laser second harmonic) is incident on the D-KDP crystal of (1) to generate ultraviolet laser light (YAG laser fourth harmonic), the phase matching condition, that is, the refractive index matching condition is satisfied. When the temperature of the non-linear optical crystal is controlled to reach the temperature, the relationship between the output of the ultraviolet laser light generated by the non-linear optical crystal, the optical axis of the crystal, and the angle θ formed by the incident laser light, as shown by the dashed line in FIG. The crystal angle dependence curve of the output of the ultraviolet laser light, which represents, has a double peak type in which there are two angles (phase matching angles) at which the output of the ultraviolet laser light becomes maximum (centering 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 phase matching) approach 90 °, respectively, and the crystal angle dependence curve 2 exhibits a single peak type having a phase matching angle of 90 °, as shown by a broken line in FIG. 2, and 90 ° phase matching is achieved.

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

(4) At this time, a kind of saturation effect on the temperature of the phase matching condition, that is, the refractive index matching condition accompanying the 90 ° phase matching temperature being exceeded, and the temperature gradient in the crystal due to the heating temperature control (heating control). The effect of being smoothed out appears, 90
Although the value is about 70 to 80% of the maximum output when the phase matching is achieved, it is possible to continuously generate a practically high output ultraviolet laser light for a long time.

[0021]

An object of the present invention is to continuously generate a practical high-power ultraviolet laser light for a long time.

[0022]

In order to achieve the above object, in the ultraviolet laser light output stabilizing method of the present invention, an input laser light is made incident on a nonlinear optical crystal capable of achieving 90 ° phase matching. When the ultraviolet laser light is generated, the temperature of the nonlinear optical crystal is controlled to a temperature 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. To do.

Further, in the ultraviolet laser light generator of the present invention, it is possible to achieve 90 ° phase matching with the input laser light generator which generates the input laser light, and it is generated by the above-mentioned input laser light generator. A non-linear optical crystal capable of generating an ultraviolet laser beam from an input laser beam and a non-linear optical crystal slightly within a range of 0.1 ° C. to 5.0 ° C. above the temperature at which the non-linear optical crystal achieves 90 ° phase matching. And a temperature control device capable of controlling the temperature rise to a high temperature.

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

[0025]

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

In the ultraviolet laser light generator according to the second aspect of the present invention, the input laser light generated by the input laser light generator is incident on the nonlinear optical crystal for ultraviolet laser light generation capable of 90 ° phase matching. Then, 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 by a temperature controller within a range of 0.1 ° C to 5.0 ° C. Thus, a practical high-power ultraviolet laser beam is continuously generated for a long time.

In the ultraviolet laser light generator according to claim 3 of the present invention, the YAG laser fundamental wave oscillated by the YAG laser oscillator is converted into the YAG laser second harmonic wave by the second harmonic generation nonlinear optical crystal. And the Y
The second harmonic of the AG laser is made incident on a nonlinear optical crystal for generating a fourth harmonic capable of 90 ° phase matching, and (the crystal temperature of) the nonlinear optical crystal for generating a fourth harmonic is adjusted to a fourth harmonic by a temperature adjusting device. The temperature is controlled so that the nonlinear optical crystal for wave generation has a temperature slightly higher than the temperature at which 90 ° phase matching is achieved within a range of 0.1 ° C to 5.0 ° C, and is continuously used for a long time. The fourth harmonic of a high output YAG laser is generated.

[0028]

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

FIG. 1 shows one embodiment of the ultraviolet laser light generator of the present invention. Reference numeral 7 is a Q switch pulse YAG laser oscillator, and the Q switch pulse YAG laser oscillator 7 is a peak suitable for nonlinear wavelength conversion. High head output wavelength 10
It oscillates a laser beam of 64 nm (YAG laser fundamental wave).

Reference numeral 8 is a YAG laser second harmonic generator, and the YAG laser second harmonic generator 8 is derived from the relation (1) from the YAG laser fundamental wave oscillated by the YAG laser oscillator 7. A second harmonic generation nonlinear optical crystal 3 for generating laser light (YAG laser second harmonic) having a wavelength of 532 nm by the second harmonic generation);
It has a crystal temperature controller 9 having a heater for heating the nonlinear optical crystal 3 for harmonic generation.

By the Q switch pulse YAG laser oscillator 7 and the second harmonic generation nonlinear optical crystal 3 described above,
An input laser light generator that generates a YAG laser second harmonic (input laser light) is configured.

Reference numeral 10 is a dichroic mirror. The dichroic mirror 10 reflects the YAG laser second harmonic generated by the second harmonic generation nonlinear optical crystal 3 and generates the second harmonic generation nonlinear optical crystal. 3, the YAG laser fundamental wave that remains unconverted is transmitted.

Reference numeral 11 is a beam damper, and the beam damper 11 blocks the YAG laser fundamental wave that passes through the dichroic mirror 10.

Reference numeral 12 is a dichroic mirror. The dichroic mirror 12 reflects the YAG laser second harmonic reflected by the dichroic mirror 10 toward a YAG laser fourth harmonic generator 13 described later. ing.

Reference numeral 18 is a beam damper, and the beam damper 18 blocks a slight amount of the YAG laser fundamental wave which is reflected by the dichroic mirror 10 and which passes through the dichroic mirror 12.

Reference numeral 13 is a YAG laser fourth harmonic generator, and the YAG laser fourth harmonic generator 13 calculates from the YAG laser second harmonic reflected by the dichroic mirror 12 the above formula (2). The fourth harmonic generation nonlinear optical crystal 5 that generates the ultraviolet laser light (YAG laser fourth harmonic) having a wavelength of 266 nm by the relationship (fourth harmonic generation), and the fourth harmonic generation nonlinear optical crystal 5 And a crystal temperature controller 14 having a heater for raising the temperature.

Nonlinear optical crystal 5 for generating the fourth harmonic mentioned above
D-K with 90% Y cut (cut so that the optical axis of the crystal is parallel to the input / output end faces) with a heavy water substitution rate of 90%
DP (KD ₂ PO ₄ ) crystal is used.

Reference numeral 15 is a dichroic mirror. The dichroic mirror 15 reflects the fourth harmonic of the YAG laser generated by the nonlinear optical crystal 5 for generating the fourth harmonic, and the nonlinear optical crystal for generating the fourth harmonic. The second harmonic wave of the YAG laser, which is left unconverted by 5, is transmitted.

Reference numeral 16 is a beam damper, and the beam damper 16 blocks the second harmonic of the YAG laser transmitted through the dichroic mirror 15.

A dichroic mirror 17 reflects the YAG laser fourth harmonic reflected by the dichroic mirror 15 in another direction.

Reference numeral 19 denotes a beam damper, and the beam damper 19 blocks a slight 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 is a crystal temperature detector, and the crystal temperature detector 20 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 is a crystal temperature setting device, and the crystal temperature setting device 22 outputs a crystal temperature setting signal 23 based on a value set by manual operation.

Reference numeral 24 is a crystal temperature controller. The crystal temperature controller 24 outputs the crystal temperature setting signal 23 output from the crystal temperature setting device 22 and the crystal temperature detection signal output from the crystal temperature detector 20. 21 and crystal temperature controller 9
On the other hand, the crystal temperature adjusting signal 25 for operating the heater of the crystal temperature adjuster 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 setting device 22. ing.

A crystal temperature detector 26 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 is a crystal temperature setting device, and the crystal temperature setting device 28 outputs a crystal temperature setting signal 29 based on a value set by manual operation.

Reference numeral 30 is a crystal temperature controller. The crystal temperature controller 30 outputs a crystal temperature setting signal 29 output from the crystal temperature setting device 28 and a crystal temperature detection signal output from a crystal temperature detecting device 26. 27 and crystal temperature controller 1
4, the crystal temperature adjusting signal 31 for operating the heater of the crystal temperature adjuster 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 setting device 28. Has become.

By the crystal temperature controller 14, the crystal temperature detector 26, the crystal temperature setting device 28, and the crystal temperature controller 30, the nonlinear optical crystal 5 for generating the fourth harmonic wave is moved to the fourth harmonic wave. The temperature adjusting device is capable of controlling the temperature to a slightly higher temperature within the range of 0.1 ° C. to 5.0 ° C. than the temperature at which the generating nonlinear optical crystal 5 achieves 90 ° phase matching.

The operation of the ultraviolet laser light generator shown in FIG. 1 will be described below.

Ultraviolet laser light (YAG laser fourth harmonic)
When generating, 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 (optical axis of the crystal and incident laser The angle formed by the light) is set to 90 °, and the crystal temperature setter 22 is used to generate the second harmonic generation nonlinear optical crystal 3
Of the non-linear optical crystal 5 for generating the fourth harmonic by the crystal temperature setting device 28.
The temperature is set to a value slightly lower than the temperature at which the nonlinear optical crystal for harmonics 5 achieves 90 ° phase matching.

The crystal temperature controller 24 is based on the crystal temperature setting signal 23 output from the crystal temperature setting device 22 and the crystal temperature detection signal 21 output from the crystal temperature detector 20, and the crystal temperature controller 9 On the other hand, a crystal temperature adjusting signal 25 for operating the crystal temperature adjuster 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, and the crystal temperature adjuster is output. 9 keeps the temperature of the second harmonic generation nonlinear optical crystal 3 at a predetermined temperature.

The crystal temperature controller 30 is based on the crystal temperature setting signal 29 output from the crystal temperature setting device 28 and the crystal temperature detection signal 27 output from the crystal temperature detector 26, and the crystal temperature controller 14 is controlled. On the other hand, the crystal temperature adjusting signal 31 for operating the crystal temperature adjuster 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, and the crystal temperature adjuster is output. The temperature of the fourth harmonic generation nonlinear optical crystal 5 is controlled by 14 so that the temperature is slightly lower than the temperature at which the fourth harmonic generation nonlinear optical crystal 5 achieves 90 ° phase matching. .

The temperature of the non-linear optical crystal 3 for generating the second harmonic is a predetermined temperature, and the temperature of the non-linear optical crystal 5 for generating the fourth harmonic is 90 ° in phase with the non-linear optical crystal 5 for the fourth harmonic. When the Q switch pulse YAG laser oscillator 7 oscillates a YAG laser fundamental wave having a wavelength of 1064 nm after the temperature is controlled to be slightly lower than the temperature at which the matching is achieved, the YAG laser fundamental wave becomes the YAG laser second harmonic The second harmonic generation nonlinear optical crystal 3 of the wave generator 8 is incident, and the wavelength 532 is generated in the second harmonic generation nonlinear optical crystal 3 due to the relationship of the formula (1) (second harmonic generation).
The YAG laser second harmonic of nm is generated.

YAG Laser Generated by Second Harmonic Wave Generation Nonlinear Optical Crystal 3 The second harmonic wave and the YAG laser fundamental wave remaining unconverted by the second harmonic wave generation nonlinear optical crystal 3 are incident on the dichroic mirror 10. To do.

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

The second harmonic of the YAG laser reflected by the dichroic mirror 10 is the dichroic mirror 1.
The beam damper 18 cuts off a small amount of the YAG laser fundamental wave which is further reflected by the YAG laser fourth high-frequency generator 13 by 2 and is reflected by the dichroic mirror 10 and transmitted through the dichroic mirror 12. It

The YAG laser second harmonic reflected by the dichroic mirror 12 enters the fourth harmonic generating nonlinear optical crystal 5 of the YAG laser fourth harmonic generator 13, and the fourth harmonic generating nonlinear In the optical crystal 5, a wavelength of 266 is obtained by the relation (formation of the fourth harmonic) of the equation (2).
YAG laser fourth harmonic (ultraviolet laser light) of nm is generated.

While the YAG laser fourth harmonic (ultraviolet laser light) having a wavelength of 266 nm is being generated, the fourth harmonic generating nonlinear optical crystal 5 is 90 ° phase-matched (when maximum output is achieved). To a value of 70 to 80% of the fourth harmonic output (ultraviolet laser light output), which is slightly higher than the temperature at which 90 ° phase matching is achieved within a range of 0.1 ° C to 5.0 ° C. The temperature is further controlled to a high temperature.

The YAG laser fourth harmonic generated by the fourth harmonic generating nonlinear optical crystal 5 and the YAG laser second harmonic remaining unconverted by the fourth harmonic generating nonlinear optical crystal 5 are dichroic mirrors 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 passes through the dichroic mirror 15 and is blocked by the beam damper 16.

The fourth harmonic of the YAG laser reflected by the dichroic mirror 15 is the dichroic mirror 1.
The YAG laser fourth harmonic that is reflected in another direction by 7 and is reflected by the dichroic mirror 17 is output as an ultraviolet laser beam.

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

In the ultraviolet laser light generator described above, YA
Using the non-linear optical crystal 5 capable of achieving 90 ° phase matching in G laser fourth harmonic generation, it is possible to obtain an ultraviolet laser light output of about 70 to 80% when 90 ° phase matching is achieved (when maximum output is achieved). Further, the temperature of the nonlinear optical crystal 5 for generating the fourth harmonic is controlled to be slightly higher than the temperature at which 90 ° phase matching is achieved within a range of 0.1 ° C to 5.0 ° C. .

At this time, a saturation effect with respect to the temperature of the phase matching condition (refractive index matching condition) accompanying the temperature exceeding the 90 ° C. phase matching temperature and an effect of smoothing the temperature gradient in the crystal by heating temperature control are expressed, It is possible to continuously generate a practically high output UV laser beam having a value of 70 to 80% when 90 ° phase matching is achieved (when maximum output is achieved).

Further, in this embodiment, as the nonlinear optical crystal (the fourth harmonic generation nonlinear optical crystal 5) for generating the ultraviolet laser beam (the fourth harmonic of the YAG laser), D having a heavy water substitution rate of 90% was used. -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 with 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 ultraviolet laser light output stabilizing method and the ultraviolet laser light generator according to the present invention are not limited to the above-described embodiments, but the input laser light may be a laser other than the YAG laser second harmonic. To use light,
A device other than a YAG laser oscillator is used for an input laser light generator that generates an input laser, and a D-KDP crystal is used as a nonlinear optical crystal that generates an ultraviolet laser light corresponding to the wavelength of the ultraviolet laser light that is generated. Other than 90
Use of other non-linear optical crystal capable of achieving phase matching, a non-linear optical crystal temperature holding means other than the method shown in the embodiment, and other factors within the scope 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, the input laser light is made incident on a nonlinear optical crystal capable of achieving 90 ° phase matching, and 90 ° phase matching is performed. 70-at the time of achievement (at the time of maximum output)
In order to obtain an ultraviolet laser light output of about 80%, the nonlinear optical crystal is adjusted to 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) accompanying the 90 ° phase matching temperature being exceeded. And the effect of leveling the temperature gradient in the crystal by the heating temperature control (temperature rise control) appear, and a practically high output of about 70 to 80% of the value when 90 ° phase matching is achieved (when maximum output is achieved). The ultraviolet laser light 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 non-linear optical crystal capable of achieving 90 ° phase matching (non-linear optical crystal for the fourth harmonic). Input laser light is incident on the
In order to obtain an ultraviolet laser light output of about 70 to 80% when the phase matching is achieved (at the time when the maximum output is achieved), the temperature of the nonlinear optical crystal is adjusted by the temperature adjusting device to be 0.1 ° C. or higher than the temperature at which the 90 ° phase matching is achieved. Since the temperature is controlled to be slightly higher in the range of 5.0 ° C, a kind of saturation effect and heating temperature for the temperature of the phase matching condition (refractive index matching condition) accompanying the 90 ° phase matching temperature being exceeded. The effect that the temperature gradient in the crystal is smoothed by the temperature control (temperature control)
A practically high output UV laser light (YAG laser fourth harmonic) having a value of about 70 to 80% when phase matching is achieved (when maximum output is achieved) can be continuously generated for a long time.

(3) In any of the ultraviolet laser light output stabilizing method according to claim 1 of the present invention and the ultraviolet laser light generator according to claims 2 and 3 of the present invention, nonlinear optical Since the ultraviolet laser light is generated when the angle between the optical axis of the crystal and the incident laser light is 90 °, walk-off does not occur due to the different traveling directions of the incident laser light and the generated ultraviolet laser light. Therefore, the crystal length of the nonlinear optical crystal can be increased to improve the wavelength conversion efficiency.

(4) In the ultraviolet laser light generator according to claim 3 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 device is easy, and an ultraviolet laser beam with high output can be obtained.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an embodiment of an ultraviolet laser light generator of 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)

Claims (3)

[Claims] 1. A non-linear optical crystal that achieves 90-degree phase matching when an input laser beam is incident on the non-linear optical crystal capable of achieving 90-degree phase matching to generate ultraviolet laser light. 0.1 ℃ ~ 5.0 than the temperature
A method for stabilizing the output of an ultraviolet laser beam, which comprises controlling the temperature so that the temperature is slightly higher in the range of ° C. 2. An input laser light generator for generating an input laser light and 90 ° phase matching can be achieved, and an ultraviolet laser light can be generated from the input laser light generated by the input laser light generator. The temperature of the nonlinear optical crystal and the nonlinear optical crystal can be 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. An ultraviolet laser light generator comprising a temperature control device. 3. A YAG laser oscillator which oscillates a YAG laser fundamental wave, and a Y which is oscillated by the YAG laser oscillator.
YAG generated by the second harmonic generation nonlinear optical crystal that can achieve 90 ° phase matching with the second harmonic generation nonlinear optical crystal that generates the YAG laser second harmonic from the AG laser fundamental wave. Laser second harmonic to YA
A G-laser fourth harmonic generating nonlinear optical crystal capable of generating a fourth harmonic, and a temperature at which the fourth harmonic generating nonlinear optical crystal achieves 90 ° phase matching with the fourth harmonic generating nonlinear optical crystal. An ultraviolet laser light generator comprising: a temperature controller capable of controlling the temperature rise to a slightly higher temperature within a range of 0.1 ° C to 5.0 ° C.