JP3273488B2 - Highly efficient generator of stimulated parametric light - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for efficiently generating guided parametric light for converting the wavelength of laser light.

[0002]

2. Description of the Related Art Wavelength conversion by stimulated parametric emission is considered promising as a method for generating ultra-short pulse light with a wide wavelength band by combining it with a short pulse laser light source whose wavelength cannot be largely changed. In this wavelength conversion, when induced parametric light emission is performed using a single crystal, the birefringence of the crystal causes a shift in the directions of the pump light, signal light, and idler light within the crystal, and high conversion efficiency is obtained. Absent.

[0003] In order to solve this problem, two crystals are used, and they are arranged to face each other so that the displacement of the pump light, the signal light, and the idler light in the second crystal in the light beam direction. Is reversed from the above-mentioned shift in the first crystal, thereby canceling the shift of the light beam generated in the first crystal by the second crystal, thereby increasing the conversion efficiency. (PGKryukov et al., Sov.JQ
uantm Electron. 7,127 (1977)).

[0004]

By the way, in the above-mentioned conventional device for efficiently generating stimulated parametric light, the gain in stimulated parametric light emission has an exponential dependence on the intensity of pump light. Along with the propagation in the crystal, the beam diameter and pulse width of the signal light and the idler light are reduced, and the spatial and temporal interaction with the pump light is restricted, so that a very high conversion efficiency is obtained. There was a disadvantage that it could not be done. In addition, a shift in the time axis direction caused by a group velocity difference between the pump light, the signal light, and the idler light has also caused a reduction in conversion efficiency.

The present invention has been made under such a background, and it is possible to improve the low conversion efficiency of the stimulated parametric light emission in the prior art and to carry out the wavelength conversion with high efficiency. An object is to provide a high-efficiency generator.

[0006]

According to the first aspect of the present invention,
A light generating means for generating pump light, a first nonlinear crystal that performs wavelength conversion on the pump light by stimulated parametric emission, generates signal light and idler light, and outputs the signal light and idler light together with the pump light; Separating means for separating the pump light, the signal light, and the idler light from the output light of the nonlinear crystal, a beam diameter expanding means for expanding a beam diameter of the separated signal light and the idler light, and a separated pump. Light, a propagation time adjusting means for adjusting a propagation time difference between the signal light and the idler light having the expanded beam diameter, and the pump light which is simultaneously input as a result of the propagation time being adjusted by the propagation time adjusting means. The optical axes of the pump light, the signal light, and the idler light are adjusted with respect to the signal light and the idler light. And coupling means for coupling the up light and said signal light and the idler light, the performing wavelength conversion by inducing parametric emitting the output light of said coupling means 2
And an optical axis adjustment performed by the coupling means.
Are the optical axis of the pump light, the signal light and the idler.
-While making the optical axis of the light parallel, the second nonlinear coupling
The deviation of the optical axis of each light caused by wavelength conversion in the crystal
Is characterized in the Zurasuko the optical axis of each of light to a pre-compensating position. According to a second aspect of the present invention, in the high-efficiency generator for guided parametric light according to the first aspect, the pump light is a laser light. According to a third aspect of the present invention, in the high-efficiency device for generating guided parametric light according to any one of the first to second aspects, the beam diameter expanding means is an expander. According to a fourth aspect of the present invention, in the high efficiency guided parametric light generating apparatus according to any one of the first to third aspects, the propagation time adjusting means includes:
It is a delay line for delaying the propagation of each light. The invention according to claim 5 is the invention according to claims 1 to
5. The high-efficiency device for generating stimulated parametric light according to any one of 4 ), wherein the separating means or the coupling means is a dielectric mirror. According to a sixth aspect of the present invention, in the high-efficiency apparatus for generating stimulated parametric light according to any one of the first to fourth aspects, the separating means or the coupling means is a polarization beam splitter.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION

§1. Overview The high-efficiency generator for stimulated parametric light according to the present invention specifically uses two nonlinear crystals, and after the first crystal, once separates pump light from signal light and idler light to form a signal. The light and the idler light pass through the expander and the delay line, are combined with the pump light again, and then the parametric conversion is performed again with the second crystal, thereby increasing the conversion efficiency. The difference from the conventional technique is that not only two crystals are used but also a separator, an expander, a delay line, and a coupler are arranged therebetween.

§2. In order to enhance the conversion efficiency, the spatial and temporal overlap between the pump light, the signal light, and the idler light generated in the first crystal is compensated, and the pump light, the signal light, and the idler light in the second crystal are compensated. It is necessary to maximize the spatial and temporal overlap with the second crystal so that the parametric conversion in the second crystal is performed efficiently. Therefore, in the present invention, after wavelength conversion by the first crystal, the signal light and the idler light once separated from the pump light by the separator are passed through an expander to expand the beam diameter, and are combined with the pump light using a delay line. Adjust the shift on the time axis.

Then, using a coupler, the beam axes of the signal light and the idler light are made parallel to the beam axis of the pump light, and the beam directions of the signal light and the idler light in the second crystal. In a state shifted in the opposite direction with respect to the displacement, the light is combined with the pump light, and parametric conversion is performed again in the second crystal. By this method, it is possible to maximize the temporal and spatial overlap between the pump light, the signal light, and the idler light in the second crystal, and to greatly improve the wavelength conversion efficiency by stimulated parametric emission. Can be.

§3. Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a device for efficiently generating guided parametric light according to an embodiment of the present invention. In this figure, 1 is a laser light source for generating a pump light 2, and 3 is a first secondary nonlinear crystal (hereinafter, 1).
Reference numeral 4 denotes pump light transmitted through the first crystal 3, and reference numerals 5 and 6 denote signal light and idler light generated as a result of stimulated parametric light emission in the first crystal 3.

Reference numeral 7 denotes a separator for separating the pump light 4 from the signal light 5 and the idler light 6. As the separator 7, a dielectric mirror and a polarizing beam splitter can be used. Reference numeral 8 denotes an expander for expanding the beam diameter of the signal light 5 and the idler light 6, and the beam diameter after the expansion can be adjusted to an arbitrary value. 9a is a delay line for providing a delay with respect to the propagation of the pump light 4 and 9b is a delay line for providing a delay with respect to the propagation of the signal light 5 and the idler light 6, respectively. The delay time can be adjusted to an arbitrary value. is there.

Reference numeral 10 denotes a coupler for re-combining the pump light 4 separated by the separator 7 with the signal light 5 and the idler light 6. The coupler 10 includes a dielectric mirror,
A polarizing beam splitter or the like can be used. Also,
At the time of the coupling, the coupler 10 has the pump light 4,
The angles and positions (deviations) of the optical axes of the signal light 5 and the idler light 6 can be adjusted to arbitrary values. 11 is 2
A second-order non-linear crystal (hereinafter referred to as a second crystal) 12 is output light finally obtained.

Next, the operation of the highly efficient device for generating guided parametric light according to the above configuration will be described. First, when the laser light source 1 generates the pump light 2, the pump light 2 enters the first crystal 3. Thereby, the first crystal 3
Performs wavelength conversion by stimulated parametric emission, and generates signal light 5 and idler light 6 as a result of the wavelength conversion. The signal light 5 and the idler light 6 generated in the first crystal 3 are output together with the pump light 4 transmitted through the first crystal 3. The separator 7 is provided with the pump light 4,
When the signal light 5 and the idler light 6 are incident, the signal light 5 and the idler light 6 are separated from the pump light 4. Next, the expander 8 enlarges the beam diameter of the signal light 5 and the idler light 6 separated by the separator 7.

The propagation time of the pump light 4 separated by the separator 7 is adjusted by the delay line 9a. On the other hand, the propagation times of the signal light 5 and the idler light 6 whose beam diameters have been expanded by the expander 8 are adjusted by the delay line 9b. This adjusts the time lag between the pump light 4 and the signal light 5 and the idler light 6.

The pump light 4, the signal light 5 and the idler light 6, whose mutual deviation on the time axis has been adjusted, enter the coupler 10 at the same timing. The coupler 10 couples the pump light 4 with the signal light 5 and the idler light 6. At this time, the optical axes of the signal light 5 and the idler light 6 are parallel to the optical axis of the pump light 4. At the same time, the optical axes of the signal light 5 and the idler light 6 are shifted from the optical axis of the pump light 4. The displacement at this time is equal to the displacement of the optical axes of the signal light 5 and the idler light 6 caused by the wavelength conversion in the second crystal 11, and
The shift direction at this time is opposite to the shift direction of the optical axes of the signal light 5 and the idler light 6 caused by the wavelength conversion.

The combined pump light 4, signal light 5 and idler light 6 are input to the second crystal 11. 2
The second crystal 11 again performs wavelength conversion by stimulated parametric emission, and then emits output light 12 by the wavelength conversion.

By this series of operations, the second crystal 11
Within, the temporal and spatial overlap between the pump light 4 and the signal light 5 and the idler light 6 can be maximized, and as a result, the overall wavelength conversion efficiency can be greatly improved.

Next, the correspondence between the invention described in claim 1 and this embodiment will be described. Light generating means Laser light source 1 First nonlinear crystal First crystal 3 Separating means Separator 7 Beam diameter expanding means Expander 8 Propagation time adjusting means Delay lines 9a, 9b Coupling means ... Coupler 10 Second nonlinear crystal... Second crystal 11

Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to the embodiments, and changes in design and the like may be made without departing from the gist of the present invention. Even if there is, it is included in the present invention.

[0020]

EXAMPLE The conversion efficiency obtained by this configuration was estimated by numerical calculation. As a result, only 2.6% was obtained with one crystal, but the conversion efficiency was reduced to 9.4% by providing an expander. And 3.4% by providing a delay line and by adjusting and combining the beam axis.
The conversion efficiency was improved to 7%, and a high conversion efficiency as high as 19.7% was obtained. The effectiveness of the present embodiment became clear.

[0021]

As described above, according to the present invention,
Separation means, beam diameter expansion means between two nonlinear crystals,
By providing the propagation time adjusting means and the coupling means, an extremely excellent effect that conversion efficiency can be greatly improved in wavelength conversion by stimulated parametric emission is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an apparatus for generating stimulated parametric light with high efficiency according to an embodiment of the present invention.

[Explanation of symbols]

1 ... laser light source, 2,4 ... pump light, 3 ...
1st crystal, 5 ... signal light, 6 ... idler light, 7 ... separator, 8 ... expander, 9a,
9b delay line, 10 coupler, 11 second crystal, 12 output light

Continuation of the front page (56) References JP-A-6-186605 (JP, A) JP-A-4-257283 (JP, A) JP-A-63-165825 (JP, A) JP-A-51-99495 (JP) JP-A-2-202079 (JP, A) JP-A-4-251227 (JP, A) JP-A-63-159832 (JP, A) JP-A-6-265950 (JP, A) US Pat. No. 5,117,126 (US, A) US Pat. No. 5,047,668 (US, A) Tadashi Nishikawa, Tadashi Uesugi, 1992 (Heisei 4) Spring No. 50-150453 (JP, A) Proceedings of the 39th Lecture Meeting on Applied Physics, March 28, 1992, Third Volume, p.906, Tadashi Nishikawa, Nao Uesugi, 1993 Autumn Meeting, 54th Lecture Meeting of the Japan Society of Applied Physics Proceedings, September 27, 1993, Third Volume, p. 927, p. G. FIG. Kryukov et al. , Soviet Journal of Quantum Electronics, Vol. 7, No. 1 (1977), p. 127-128 (58) Fields surveyed (Int. Cl. ⁷ , DB name) G02F 1/37-1/39 H01S 3/108-3/109 INSPEC (DIALOG) JICST file (JOIS) WPI (DIALOG)

Claims (6)

(57) [Claims] 1. A light generating means for generating pump light, performing wavelength conversion on the pump light by stimulated parametric light emission to generate signal light and idler light,
A first nonlinear crystal that is output together with the pump light, separating means for separating the pump light, the signal light, and the idler light from the output light of the first nonlinear crystal; the separated signal light and the idler light Beam diameter enlarging means for enlarging the beam diameter of the beam; propagation time adjusting means for adjusting a propagation time difference between the separated pump light, the signal light and the idler light whose beam diameter has been enlarged; and the propagation time adjusting means. As a result of the adjustment of the propagation time, the pump light, the signal light, and the idler light, which are simultaneously input, are subjected to the optical axis adjustment of the pump light, the signal light, and the idler light, and the pump light and the idler light are adjusted. Coupling means for coupling the signal light and the idler light; and performing wavelength conversion on the output light of the coupling means by stimulated parametric emission. And a second nonlinear crystal, the coupling means the optical axis adjustment performed by the optical axis of the pumping light
Make the optical axis of the signal light and the idler light parallel
Together with the wavelength conversion by the second nonlinear crystal.
Move each of the light beams to a position where the deviation of the optical axis of each of the light beams
High efficiency generator of induced parametric optical characterized the Zurasuko the optical axis of the. 2. The highly efficient device for generating guided parametric light according to claim 1 , wherein said pump light is a laser beam. 3. The highly efficient device for generating guided parametric light according to claim 1 , wherein said beam diameter expanding means is an expander. apparatus. 4. A high-efficiency generator of the induction parametric light according to any one of claims 1 to 3, wherein the propagation time adjusting means, characterized in that said a delay line for delaying the propagation of each light A highly efficient generator of guided parametric light. 5. A high-efficiency generator of the induction parametric light according to any one of claims 1 to 4, wherein the separating means or the coupling means of the induction parametric light, which is a dielectric mirror High efficiency generator. 6. The high efficiency generator of the induction parametric light according to any one of claims 1 to 4, wherein the separating means or the coupling means of the induction parametric light, which is a polarization beam splitter High efficiency generator.