JPH11212127A - Optical system using β-barium metaborate as nonlinear optical crystal - Google Patents

Abstract

(57) [PROBLEMS] To prevent the output of an optical system using BBO as a nonlinear optical crystal from generating a second harmonic or a sum frequency by continuous oscillation or pulse oscillation to be reduced. To provide an improved optical system. SOLUTION: A BBO using a nonlinear optical crystal 5 is described.
BBO is set to 70 ° C. or higher for the optical system using An appropriate temperature equal to or higher than room temperature is detected, and BBO is set to that temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical system using β-barium metaborate (hereinafter abbreviated as BBO as appropriate) as a nonlinear optical crystal. In particular, the present invention relates to an optical system for generating a second harmonic or a sum frequency by continuous oscillation or pulse oscillation using BBO.

[0002]

2. Description of the Related Art This type of optical system using a conventional nonlinear optical crystal, for example, a continuous oscillation external resonator type second harmonic generation (see M. Oka and S. Kub).
ota, Jpn. J. Appl. Phys. Vol. 3
1 (1992) pp. 513 and M.P. Okae
t. al. , In Digest of Confer
Once on Laser and Electro
n-Optics (OSA. Washington)
D. C. 1992)), when BBO is used as the nonlinear optical crystal, there is a case where the output is reduced. For example, using BBO as a nonlinear optical crystal and 532 nm green light as a fundamental wave,
When the 266 nm ultraviolet light is generated, the coupling of the fundamental wave of the external resonator to the higher-order transverse mode occurs depending on the resonator parameters or the crystal, and the coupling efficiency of the fundamental wave to the external resonator is reduced or becomes inefficient. Stabilization may result in reduced UV light output.

[0003] Further, depending on the use conditions of the crystal, a decrease in the output of the ultraviolet light, which is the second harmonic, may be observed even without generation of a higher-order transverse mode of the fundamental wave of the external resonator.

The above phenomenon has been a serious problem when a stable continuous oscillation ultraviolet light output is obtained by installing a BBO in an external resonator. This is a problem in any optical system that uses BBO and generates second harmonics or sum frequencies by continuous oscillation or pulse oscillation.

The prior art will be described below with reference to the drawings. For example, a continuous wave fundamental wave having a wavelength of 532 nm is applied to a nonlinear optical crystal such as B
In the case of wavelength conversion to ultraviolet light having a wavelength of 266 nm using BO (this is described in M. Oka and S., supra).
Kubota, M .; Oka et. al. 2), and the structure of the external resonator portion is as shown in FIG.

[0006] In FIG.
A high-reflection mirror having an ultra-high reflectance at 2 nm, for example, a reflectance of 99.95% or more.
An input (incident) mirror having a high reflectivity at m, such as 99%, reference numeral 5 has a mirror-polished end face and a low reflectivity at a wavelength of 532 nm, such as 0.1%.
This is a nonlinear optical crystal BBO of a wavelength conversion element provided with a low reflection film having the following reflectance. Although not shown, the high-reflection mirror 3 is a VCM that is a positioning device (M.Oka, supra).
and S.M. Kubota, M .; Oka et. a
l. Etc.) and is controlled by, for example, a servo drive system. As described above, reference numerals 1 to
The element denoted by 5 constitutes an external resonator unit.

A fundamental wave (in this case, a wavelength of 532 nm) schematically shown by an arrow 6 in FIG. 2 is incident on this external resonator, the output is amplified between mirrors, and the fundamental wave enhanced by the amplification is converted into a nonlinear wave. In the optical crystal 5 (BBO), it is converted into a second harmonic (here, a wavelength of 266 nm). This second harmonic is schematically shown in FIG.

For example, in an optical system having a resonator as described above, when BBO is used as a nonlinear optical crystal, the output of the second harmonic or the like may be reduced.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned background, and has a BB as a nonlinear optical crystal.
It is an object of the present invention to provide an optical system that uses O and that does not reduce the output of an optical system that generates a second harmonic or a sum frequency by continuous oscillation or pulse oscillation.

[0010]

As a result of intensive studies, the present invention has conducted various studies on the reduction of the output of an optical system using BBO as a nonlinear optical crystal. We found that the conditions were relevant. The present invention has been made based on this finding, and an optical system using the BBO according to the present invention solves the above-mentioned problems by adopting the following configuration.

That is, the present invention relates to an optical system for generating second harmonics by continuous oscillation using β-barium metaborate as a nonlinear optical crystal, wherein the temperature of the β-barium metaborate crystal is 70 ° C. or higher. It is characterized by doing.

Further, the present invention provides a non-linear optical crystal having β
An optical system using barium metaborate to generate a sum frequency by continuous oscillation, wherein the temperature of the β-barium metaborate crystal is 70 ° C. or more.

In the above invention, it is possible to adopt a configuration in which an external resonance type second harmonic or sum frequency is generated by continuous oscillation.

Further, the present invention provides a nonlinear optical crystal comprising β
An optical system using barium metaborate to generate a sum frequency by pulse oscillation, wherein the temperature of the β-barium metaborate crystal is 70 ° C. or more.

Also, the present invention provides a nonlinear optical crystal having β
An optical system using barium metaborate to generate a sum frequency by pulse oscillation, wherein the temperature of the β-barium metaborate crystal is 70 ° C. or more.

Further, the present invention provides a non-linear optical crystal having β
An optical system that uses barium metaborate to generate second harmonics by continuous oscillation or pulse oscillation, and that the temperature of the β-barium metaborate crystal is at an appropriate temperature equal to or higher than room temperature at which a decrease in output is stably prevented. And detecting the temperature of the β-barium metaborate crystal at the temperature.

Further, the present invention provides a nonlinear optical crystal having β
-An optical system that uses barium metaborate to generate a sum frequency by continuous oscillation or pulse oscillation, and detects an appropriate temperature above room temperature at which the output of the β-barium metaborate crystal is stably prevented from decreasing. And a temperature of the β-barium metaborate crystal.

The present invention has found that, for an optical system using a BBO, the reduction in output is related to the temperature condition of the BBO of the optical system. By solving the above-mentioned problems, the above-mentioned object can be solved. In particular, it has been found that an optimum temperature condition can be found at a temperature of room temperature or higher, and a general-purpose optical system can be obtained at 70 ° C. or higher. It is a thing.

That is, according to the knowledge of the present inventors, coupling of the fundamental wave of the external resonator to a higher-order transverse mode occurs.
The coupling efficiency of the fundamental wave to the external resonator is reduced or destabilized, and as a result, the output of the ultraviolet light is reduced mainly due to the temperature condition of BBO, that is, BB at room temperature under normal conditions.
O is used, and the temperature condition of this BBO is set to 70 ° C.
The critical temperature may be different depending on the above or the BBO crystal. In such a case, the above problem can be solved by finding the optimum temperature condition.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The specific structure of the present invention will be described below with reference to the drawings, together with the description of the embodiments. However, needless to say, the present invention is not limited by the embodiments described below.

The present invention relates to an optical system for generating second harmonics by continuous oscillation using β-barium metaborate as a nonlinear optical crystal, wherein the temperature of the β-barium metaborate crystal is 70 ° C. or higher. And an optical system for generating a sum frequency by continuous oscillation using β-barium metaborate as a nonlinear optical crystal, wherein the temperature of the β-barium metaborate crystal is 70 ° C. or higher. In this case, external resonance type second harmonic generation or sum frequency generation can be performed by continuous oscillation.

According to the present invention, an optical system for generating a continuous oscillation and generating an external resonance type second harmonic generating ultraviolet light having a wavelength of 400 nm or less can be provided.

Further, the above-mentioned invention can provide an optical system for generating a continuous oscillation and an external resonance type sum frequency generating ultraviolet light having a wavelength of 400 nm or less.

Further, the present invention can be an external resonance type second harmonic generation optical system for generating light having a wavelength of 266 nm from light having a wavelength of 532 nm of continuous oscillation.

Further, the above-mentioned invention provides a continuous oscillation of 1064 nm.
From light having a wavelength of 532 nm and continuous wave light having a wavelength of 532 nm.
An external resonance type optical system for generating a sum frequency that generates light having a wavelength of 55 nm can be provided.

Further, the above-mentioned invention provides a continuous oscillation of 1064 nm.
From light having a wavelength of 266 nm and continuous wave light having a wavelength of 266 nm.
An external resonance type optical system for generating a sum frequency that generates light having a wavelength of 13 nm can be provided.

Further, the present invention relates to a method of converting continuous oscillation light having a wavelength of 532 nm and continuous oscillation light having a wavelength of
An external resonance type optical system for generating a sum frequency that generates light having a wavelength of 3 nm can be provided.

Further, the present invention relates to a continuous wave Ti: sapphire laser having a wavelength of 700 nm to 900 nm.
An external resonance type second harmonic generation optical system that generates light having a wavelength of 350 nm to 450 nm can be provided.

Further, the present invention provides a non-linear optical crystal having β-
Using barium metaborate, the second harmonic generation by pulse oscillation, or, the optical system to generate a sum frequency,
The temperature of the β-barium metaborate crystal is set to 70 ° C. or more.

According to the present invention, an optical system for generating a second harmonic by pulse oscillation for generating ultraviolet light having a wavelength of 400 nm or less can be provided.

Further, the present invention can be an optical system for generating a sum frequency by pulse oscillation for generating ultraviolet light having a wavelength of 400 nm or less.

The present invention also provides a pulse oscillation of 532 nm.
An optical system for generating a sum frequency that generates light having a wavelength of 266 nm from light having a wavelength of.

Also, the present invention provides a pulse oscillation of 1064n
An optical system that generates a sum frequency that generates light having a wavelength of 355 nm from light having a wavelength of m and light having a wavelength of 532 nm of pulse oscillation can be provided.

Further, the present invention provides a pulse oscillation of 1064n
An optical system that generates a sum frequency that generates light having a wavelength of 213 nm from light having a wavelength of m and light having a wavelength of 266 nm of pulse oscillation.

The present invention also provides a pulse oscillation of 532 nm.
From the light of the wavelength of 355 nm of the pulse oscillation
An optical system that generates a sum frequency that generates light having a wavelength of 213 nm can be used.

Further, the present invention provides a β-
An optical system using barium metaborate to generate a second harmonic or generate a sum frequency, and for the temperature of the β-barium metaborate crystal, an appropriate temperature equal to or higher than room temperature at which output reduction is stably prevented. Is detected, and a β-barium metaborate crystal is used as the temperature.

According to the present invention, the second harmonic can be generated by continuous oscillation or the second harmonic can be generated by pulse oscillation.

Further, the present invention can be configured to generate a sum frequency by continuous oscillation or to generate a sum frequency by pulse oscillation.

Hereinafter, specific embodiments of the present invention will be described. Embodiment 1 Referring to FIG. In this embodiment, the nonlinear optical crystal 5 of the wavelength conversion optical system described with reference to FIG.
The temperature of BBO used as the temperature was 70 ° C.

For comparison, data on the case where BBO is actually used at room temperature (25 ° C.) for the prior art shown in FIG. 2 are shown. FIG. 4 and FIG.
5 shows a temporal change of an ultraviolet light output when a 2 nm second harmonic is generated. The horizontal axis indicates time, and the vertical axis indicates ultraviolet light output.

FIG. 4 shows an example of a decrease in the ultraviolet light output, and as shown in the figure, the original value is not restored. FIG. 5 shows an example of the instability of the ultraviolet light output, in which the ultraviolet light output fluctuates for 1 to 2 hours.

On the other hand, the non-linear optical crystal 5 BB
When O was heated to 70 ° C. to generate the same second harmonic of ultraviolet light, the ultraviolet light output was stabilized.

Actually, by applying the present invention, the BBO is reduced to 70
FIG. 3 shows a temporal change of the ultraviolet light output when the second harmonics of the ultraviolet light are generated by heating to the temperature of ° C. The horizontal axis indicates time, and the vertical axis indicates ultraviolet light output.

From FIG. 3, when BBO is set to 70 ° C. or more,
It can be seen that the ultraviolet light output is also stable.

In this example, when various BBO samples were examined, the above-mentioned output deterioration was observed at 25 to 60 ° C., but the UV light output became stable at 70 ° C. or higher for all samples. . From this, at 70 ° C. or higher, for various BBO samples,
It was found that the effect of the present invention was exhibited.

Second Embodiment In the first embodiment, good results were obtained by heating BBO to 70 ° C. or higher, but in this example, BBO used was
At a temperature equal to or higher than room temperature, the output was reduced or unstable, and based on this, an appropriate temperature equal to or higher than room temperature at which output reduction was stably prevented was detected. BBO was set at that temperature and performed with good results.

Embodiments 3 to 10 In Embodiment 1 described above, a second harmonic having a fundamental wave of 532 nm was generated and an ultraviolet light output was obtained.
With the same optical system as in the first embodiment in which O was set to 70 ° C., the following output was obtained, and the same effect as in the first embodiment was obtained.

Embodiment 3 An output was obtained by external resonance type second harmonic generation in which light having a wavelength of 266 nm was generated from light having a wavelength of 532 nm of continuous oscillation.

Fourth Embodiment A continuous oscillation light having a wavelength of 1064 nm and a continuous oscillation 53
An output was obtained by external resonance type sum frequency generation in which light having a wavelength of 355 nm was generated from light having a wavelength of 2 nm.

Embodiment 5 Continuous oscillation light having a wavelength of 1064 nm and continuous oscillation of 26
Output was obtained by external resonance type sum frequency generation in which light having a wavelength of 213 nm was generated from light having a wavelength of 6 nm.

Embodiment 5 Continuous oscillation light having a wavelength of 532 nm and continuous oscillation light having a wavelength of 355 nm are used.
An output was obtained by external resonance type sum frequency generation in which light having a wavelength of 213 nm was generated from light having a wavelength of nm.

Embodiment 6 Continuous-wave Ti: sapphire laser light having a wavelength of 700 nm to 900 nm is converted to a wavelength of 350 nm to 450 nm.
The output was obtained by external resonance type second harmonic generation that generates light of the following type.

Embodiment 7 An output was obtained by a sum frequency generating optical system for generating light having a wavelength of 266 nm from light having a wavelength of 532 nm of pulse oscillation.

Eighth Embodiment Pulsed light having a wavelength of 1064 nm and pulsed light 5
An output was obtained by sum frequency generation in which light having a wavelength of 355 nm was generated from light having a wavelength of 32 nm.

Embodiment 9 Pulsed light having a wavelength of 1064 nm and pulsed light 2
The output was obtained by a sum frequency generation optical system that generates light having a wavelength of 213 nm from light having a wavelength of 66 nm.

Embodiment 10 Pulsed light having a wavelength of 532 nm and pulsed light having a wavelength of 35
The output was obtained by a sum frequency generation optical system that generates light of wavelength 213 nm from light of wavelength 5 nm.

[0057]

As described above, according to the present invention,
An optical system using BBO as a nonlinear optical crystal,
With respect to an optical system that generates a second harmonic or a sum frequency by continuous oscillation or pulse oscillation, it is possible to provide an optical system whose output is not reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a general continuous oscillation external resonator type second harmonic generation.

FIG. 3 is a diagram illustrating the operation of the first embodiment of the present invention.

FIG. 4 is a diagram illustrating an operation of a comparative example.

FIG. 5 is a diagram showing an operation of a comparative example.

[Explanation of symbols]

1-3: High reflectivity mirror, 4: Input (incident) mirror, 5: BB used as nonlinear optical crystal
O.

Claims (25)

[Claims] 1. An optical system for generating a second harmonic by continuous oscillation using β-barium metaborate as a nonlinear optical crystal, wherein the temperature of the β-barium metaborate crystal is 70 °.
An optical system using β-barium metaborate, wherein the temperature is set to not less than ° C. 2. The optical system using barium meta-borate according to claim 1, wherein an external resonance type second harmonic is generated by continuous oscillation. 3. An optical system for generating a sum frequency by continuous oscillation using β-barium metaborate as a nonlinear optical crystal, wherein the temperature of the β-barium metaborate crystal is 70 ° C. or higher. , An optical system using β-barium metaborate. 4. The β-cell according to claim 1, wherein a sum frequency of an external resonance type is generated by continuous oscillation.
Optical system using barium metaborate. 5. An optical system for generating a continuous oscillation and an external resonance type second harmonic generating an ultraviolet light having a wavelength of 400 nm or less using β-barium metaborate as a nonlinear optical crystal, wherein β-metaboric acid is used. The optical system according to claim 1, wherein the temperature of the barium crystal is 70 ° C or higher. 6. An optical system that uses a barium meta-borate as a non-linear optical crystal and generates a continuous oscillation and an external resonance type sum frequency generating an ultraviolet light having a wavelength of 400 nm or less, wherein the β-barium meta-borate crystal is used. The optical system using β-barium metaborate according to claim 3, wherein the temperature is 70 ° C or higher. 7. An external resonance type second harmonic generation optical system using β-barium metaborate as a nonlinear optical crystal and generating light having a wavelength of 266 nm from light having a continuous oscillation of 532 nm. The optical system according to claim 1, wherein the temperature of the β-barium metaborate crystal is 70 ° C or higher. 8. An external resonance type sum using continuous-wave 1064 nm wavelength light and continuous-wave 532 nm wavelength light to generate 355 nm wavelength light using β-barium metaborate as a nonlinear optical crystal. An optical system for generating a frequency, wherein the temperature of the β-barium metaborate crystal is 70 ° C.
The optical system according to claim 3, wherein the optical system uses barium metaborate. 9. An external resonance type sum using continuous-wave light having a wavelength of 1064 nm and light having a wavelength of 213 nm from continuous-wave light having a wavelength of 266 nm using β-barium metaborate as a nonlinear optical crystal. An optical system for generating a frequency, wherein the temperature of the β-barium metaborate crystal is 70 ° C.
The optical system according to claim 3, wherein the optical system uses barium metaborate. 10. A sum of an external resonance type using β-barium metaborate as a nonlinear optical crystal and generating continuous oscillation light having a wavelength of 532 nm and continuous oscillation light having a wavelength of 213 nm from light having a wavelength of 213 nm. An optical system for generating a frequency, wherein the temperature of the β-barium metaborate crystal is 70 ° C.
The optical system according to claim 3, wherein the optical system uses barium metaborate. 11. A continuous-wave Ti: sapphire laser using β-barium metaborate as a nonlinear optical crystal, which has a wavelength of 700 to 900 nm and a wavelength of 350 nm.
2. The optical system according to claim 1, wherein the optical system is an external resonance type second harmonic generation optical system that generates light of from 450 nm to 450 nm, wherein the temperature of the β-barium metaborate crystal is 70 ° C. or higher. An optical system using β-barium metaborate. 12. An optical system for generating second harmonics by pulse oscillation using β-barium metaborate as a nonlinear optical crystal, wherein the temperature of the β-barium metaborate crystal is 70 ° C. or higher. An optical system using the β-barium metaborate according to claim 1. 13. An optical system for generating a sum frequency by pulse oscillation using β-barium metaborate as a nonlinear optical crystal, wherein the β-barium metaborate crystal has a temperature of 70%.
An optical system using β-barium metaborate, wherein the temperature is set to not less than ° C. 14. An optical system for generating second harmonics by pulse oscillation for generating ultraviolet light having a wavelength of 400 nm or less using β-barium metaborate as a nonlinear optical crystal, wherein the temperature of the β-barium metaborate crystal is Is 70 ° C. or higher, the optical system using β-barium metaborate according to claim 12. 15. An optical system that uses β-barium metaborate as a nonlinear optical crystal to generate a sum frequency by pulse oscillation for generating ultraviolet light having a wavelength of 400 nm or less,
The optical system according to claim 13, wherein the temperature of the β-barium metaborate crystal is 70 ° C or higher. 16. A sum frequency generating optical system for generating light having a wavelength of 266 nm from light having a wavelength of 532 nm of pulse oscillation using β-barium metaborate as a nonlinear optical crystal, wherein β-barium metaborate is used. Set the crystal temperature to 7
The optical system according to claim 13, wherein the temperature is 0 ° C. or higher. 17. A method using β-barium metaborate as a non-linear optical crystal, from light having a wavelength of 1064 nm for pulse oscillation and light having a wavelength of 532 nm for pulse oscillation,
An optical system for generating a sum frequency that generates light having a wavelength of m, wherein the temperature of the β-barium metaborate crystal is 70 ° C. or more, wherein the β-barium metaborate according to claim 13 is used. Optical system used. 18. A light source having a pulse oscillation wavelength of 1064 nm and a pulse oscillation wavelength of 266 nm using β-barium metaborate as a non-linear optical crystal, the light having a wavelength of 213 nm.
An optical system for generating a sum frequency that generates light having a wavelength of m, wherein the temperature of the β-barium metaborate crystal is 70 ° C. or more, wherein the β-barium metaborate according to claim 13 is used. Optical system used. 19. Using light of β-barium metaborate as a nonlinear optical crystal, light having a wavelength of 532 nm for pulse oscillation and light having a wavelength of 355 nm for pulse oscillation have a wavelength of 213 nm.
A sum frequency generation optical system that generates light having a wavelength of
The optical system according to claim 13, wherein the temperature of the β-barium metaborate crystal is 70 ° C or higher. 20. An optical system for generating second harmonics using β-barium metaborate as a nonlinear optical crystal, wherein the temperature of the β-barium metaborate crystal is stably prevented from lowering the output. An optical system using β-barium metaborate, wherein the appropriate temperature is detected and β-barium metaborate crystal is used as the temperature. 21. The optical system using barium β-metaborate according to claim 20, wherein the second harmonic is generated by continuous oscillation. 22. The optical system according to claim 20, wherein the second harmonic is generated by pulse oscillation. 23. An optical system for generating a sum frequency using β-barium metaborate as a nonlinear optical crystal,
As for the temperature of the β-barium metaborate crystal, an appropriate temperature equal to or higher than room temperature at which the output reduction is stably prevented is detected.
An optical system using β-barium metaborate, wherein the barium metaborate crystal is kept at the temperature. 24. The optical system using barium β-metaborate according to claim 20, wherein the sum frequency is generated by continuous oscillation. 25. The optical system according to claim 20, wherein the sum frequency is generated by pulse oscillation.