JPH10213828A - Optical parametric oscillation laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove the complicatedness of an optical system and to relax restrictions on its use environment by making the output light of a narrow-band semiconductor laser incident on an optical parametric resonator(OPO resonator) in addition to a pump wave. SOLUTION: The laser light from a pump laser 1 is inputted to the OPO resonator 10, which performs laser oscillation by utilizing the parametric effect of nonlinear crystal NOC to obtain signal light S and idler light I. In addition to the OPO resonator 10, the narrow-band semiconductor laser 11 is provided which has, for example, relaxed usable temperature variation of ±5 deg.C and is superior in stability. The narrow-band semiconductor laser 11 oscillates the same wavelength as the oscillation wavelength λ2 or λ3 of the signal light S or idler light I by the OPO resonator 10 and the laser light is made incident on the OPO resonator 10 to equalize the oscillation wavelength λ2 or λ3 in the resonator 10 to the wavelength of the narrow-band semiconductor laser 11, thereby narrowing down the oscillation wavelength of the OPO resonator 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical parametric oscillation laser device in which the laser oscillation line width is narrow and the wavelength is variable.

[0002]

2. Description of the Related Art Reducing the oscillation line width (narrowing the band) of a laser beam will improve the resolution of the device, and therefore, the field of spectroscopy using the laser beam, In the fields of interference, optical resolution measurement, and the like, the emergence of laser light having a narrow line width has been demanded. For example, in the field of spectroscopy, the energy structure of atoms and molecules can be accurately grasped by reducing the oscillation line width of a laser.

On the other hand, optical parameters using nonlinear crystals
Technology that changes the wavelength of laser light using
is there. Optical parametric oscillation (OPO: Optical Pa
rametric Oscillation), as shown in FIG.
One wavelength λ₁Of the laser beam (pump wave P) of BBO (β-B
aB_TwoO_Four: Beta barium borate) and other nonlinear crystals
When incident on the NOC, two energy conserving forms
Wavelength (λ_Two, Λ_Three) Is generated, and λ_Two<
λ_ThreeAnd the wavelength λ_TwoIs the signal light S, the wavelength λ_ThreeA
Called Idler Hikari I. This signal light S and the eye
The laser resonator is configured to amplify the drr light I.
And the wavelength λ₁From the pump wave P of_Two, Λ_Threeof
Light S and I can be generated. In this case, the wavelength
λ₁, Λ _Two, Λ_ThreeHas the following relational expression: 1 / λ₁= 1 / λ_Two+ 1 / λ_Three Λ satisfying this equation_Two, Λ_ThreeIs determined by the phase matching process
Specifically, the nonlinear crystal N with respect to the incident laser light P
It depends on the OC angle.

[0004] Among such OPO laser devices, there is a narrow band OPO laser device for reducing the line line width as shown in FIG. FIG. 8A is a simplified configuration diagram of the device, and FIG. 8B is a diagram showing the optical path and structure of the narrow-band resonator in FIG. 8A. As can be seen from this figure, the laser light of the pump laser 1 is incident on the narrow-band resonator 2 which is an OPO laser device to oscillate the laser light having a narrow line width, and the laser light is used as another OPO laser device. Amplification is performed by the amplifier resonator 3. In the narrow-band resonator 2, a grating dg is disposed at one end of the resonator, and only light having a narrow line width selected by adjusting the angle of the grating dg is amplified. is there. In this case, the band-narrowing resonator 2 and the amplifier resonator 3
Angle adjustment of both nonlinear crystal NOCs is also required.

[0005]

As shown in FIG. 8, an OPO oscillator for narrowing the band and an OPO for amplification are conventionally used as shown in FIG.
Since the oscillator and the oscillator are combined, it is necessary to perform the adjustment of the grating and the angle adjustment of the two nonlinear crystals in synchronization with each other, which complicates the control and operation of the optical system. In addition, since an OPO resonator is used for narrowing the band, it is necessary to stabilize the temperature of the unit including the pump laser 1 and the entire resonator. However, it is difficult to control the temperature with a large unit. The use environment (especially temperature) must be very strict. Specifically, the usable temperature change is limited to ± 2 ° C.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an optical parametric oscillation laser device in which the use environment is relaxed except for the complexity of an optical system.

[0007]

In order to achieve the above-mentioned object, the present invention has the following matters specifying the invention. (1) The output light of the band-narrowed semiconductor laser is incident on an optical parametric resonator other than the pump wave. (2) In the above (1), the resonator length of the optical parametric resonator is changed in accordance with the output light of the band-narrowed semiconductor laser to change the angle of the nonlinear crystal. (3) In the above (1), the narrow band semiconductor laser is characterized in that semiconductors having different material compositions having different oscillation wavelength ranges are replaced.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an example of a simplified configuration (a) and an explanation of an optical path (b). A laser beam from a pump laser (YAG laser or the like) 1 is supplied to an OPO resonator 1.
0, and the OPO resonator 10 performs laser oscillation using the parametric effect of the nonlinear crystal NOC to obtain the signal light S and the idler light I.

On the other hand, apart from the OPO resonator 10, there is provided a narrow-bandwidth semiconductor laser 11 which can be used, for example, has a gentle temperature change of ± 5 ° C. and is excellent in stability. As shown in FIG. 2, the semiconductor laser 11a
Having a resonator on one side and a grating of 11dg at one end
The wavelength of the reflected light can be changed by changing the grating angle with respect to the incident light by utilizing the phenomenon of reflecting a single wavelength of the grating 11dg in the incident direction. Further, since the semiconductor laser 11a can be miniaturized in structure, the temperature of the entire narrow band semiconductor laser 11 can be adjusted to be less affected by a change in room temperature, and the cost can be reduced easily.

[0010] The narrow band semiconductor laser 11 oscillates the same wavelength as the oscillation wavelengths λ ₂ and λ ₃ of the signal light S or the idler light I by the OPO resonator 10, and the laser light is oscillated.
By incident (seed) on the PO resonator 10, FIG.
As shown in FIG. ₃ , the oscillation wavelength λ ₂ or λ ₃
Can be matched with the wavelength of the semiconductor laser 11 having a narrow band, and the oscillation wavelength of the OPO resonator 10 can be narrowed.

Since the laser beam width of the narrow band semiconductor laser 11 is very narrow (for example, 0.01 cm ^-1 or less), the wavelength of the narrow band semiconductor laser 11 is
It is necessary to control the resonator length of the OPO resonator 10 in order to tune the oscillation output of FIG.
As shown in (2), the resonator length is changed by using the piezo element PZ, thereby stabilizing the oscillation wavelength of the OPO resonator 10 and maintaining the narrow band. Specifically, as shown in FIG. 1B, the OPO resonator 10 is provided with a line width monitor 10a.
The voltage applied to the piezo element PZ provided in the end mirror is changed in accordance with the line width of
Order).

Also, tuning of the nonlinear crystal NOC is required along with the narrowing of the oscillation wavelength of the OPO resonator 10, and the length of the oscillator is actually increased so that the narrowing of the oscillation mode of the OPO resonator 10 is maintained. While being controlled by the piezo element PZ, the wavelength of the narrow-band semiconductor laser 11 and the nonlinear crystal NO
The angle of C will be tuned.

Further, in changing the wavelength, the angle of the grating 11dg of the band-narrowed semiconductor laser 11 is changed, and the obtained wavelength and the angle of the nonlinear crystal NOC are controlled in synchronization to control the band. O to maintain
The resonator length of the PO resonator 10 is controlled using the piezo element PZ.

In the narrow band semiconductor laser 11 of the present invention,
A wider range of oscillation wavelengths can be obtained. That is,
As shown in FIG. 4, the oscillation wavelength range is changed by changing the material composition of the semiconductor laser. In FIG. 4, InGaAl
P is in the range of α, AlGaAs / GaAs is in the range of β, I
nGaAs has a wavelength range of γ, and InGaAsP has a wavelength range of δ. Therefore, by replacing a semiconductor laser of a different type with this material composition, narrow band oscillation in a wide wavelength range becomes possible. As a result, a wide range of oscillation of α, β, γ, δ becomes possible due to a change in the composition of the semiconductor, and a fine adjustment wavelength can be changed by adjusting the angle of a grating or the like, and a narrow band oscillation wavelength can be obtained. .

5 and 6 show examples of the structure of the OPO resonator 10. FIG. 5 shows a linear resonator structure, and FIG.
This shows a ring-shaped resonator structure that is smaller and has better stability than that of FIG.

[0016]

As described above, first, the output light of the narrow band semiconductor laser is made incident on the optical parametric resonator in addition to the pump wave, so that the narrow band oscillation of the narrow band semiconductor laser alone is achieved. Therefore, unlike the conventional case using the OPO, the device is hardly affected by the pulse pump light, and the device can be made compact.
Since it is controlled separately from the PO resonator, precise synchronized operation as in the conventional method is not required, stable laser oscillation can be obtained, and the narrow band semiconductor laser itself has excellent stability. (Relaxed temperature conditions).

Secondly, by changing the resonator length of the optical parametric resonator and changing the angle of the nonlinear crystal in accordance with the output light of the narrow-band semiconductor laser, precise synchronization control as in the conventional method is achieved. Is not necessary, and simple adjustment is possible.

Third, in a semiconductor laser having a narrow band,
By replacing a semiconductor having a material composition with a different oscillation wavelength range, oscillation in a wide wavelength range becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration and a resonator structure according to an example of an embodiment of the present invention.

FIG. 2 is a simplified configuration diagram of a band narrowed semiconductor laser.

FIG. 3 is a principle diagram showing a relationship between a pump wave and signal light and idler light.

FIG. 4 is a graph showing a relationship between a material composition and an oscillation wavelength.

FIG. 5 is a diagram of a linear resonance structure.

FIG. 6 is a diagram of a ring-shaped resonance structure.

FIG. 7 is a diagram illustrating the principle of parametric oscillation.

FIG. 8 is a diagram showing the overall configuration and a narrowed-band resonator structure of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pump laser 10 OPO resonator 11 Narrow band semiconductor laser 11a Semiconductor laser 11dg Grating NOC Nonlinear crystal PZ Piezo element S Signal light I Idler light

Claims (3)

[Claims] 1. An optical parametric oscillation laser device in which output light of a narrow band semiconductor laser is incident on an optical parametric resonator other than a pump wave. 2. The optical parametric oscillation laser device according to claim 1, wherein the resonator length of the optical parametric resonator is changed in accordance with the output light of the band-narrowed semiconductor laser to change the angle of the nonlinear crystal. 3. The optical parametric oscillation laser device according to claim 1, wherein said narrow band semiconductor laser is configured such that semiconductors having different material compositions having different oscillation wavelength ranges are replaced.