JP2751119B2 - Parallel light creation device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonlinear optical element that performs light wavelength conversion using a nonlinear optical effect.

[Conventional technology]

A second harmonic beam generated by a Cerenkov radiation type second harmonic generation (hereinafter, referred to as SHG) element using an optical waveguide has a light emitting point in an elongated region called a waveguide.

Therefore, as shown in the schematic configuration diagram of FIG. 3, the laser beam 1 incident on the waveguide 32 of the SHG element 31 is emitted with the second harmonic beam 33 having a Cherenkov radiation angle. This second harmonic beam 33 is collimated in only one direction,
In the other orthogonal direction, the divergent light is emitted from the end face 34 of the SHG element 31. The second harmonic beam 33 emitted in this manner has been converted into collimated light that is easy to handle by performing beam shaping using an asymmetric lens such as a cylindrical lens 35.

[Problems to be solved by the invention]

The second harmonic beam emitted from the entrance end of the waveguide of the Cherenkov radiation type SHG element and the second harmonic beam emitted from the vicinity of the exit end have a constant divergence angle but different emission points. A complicated beam pattern curved in an arc shape is obtained, and it is difficult to obtain a light beam having sufficiently good collimation by the method described in the related art. Further, when considering miniaturization as an optical wavelength conversion element, it is problematic to require an optical system for beam shaping.

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus for converting a second harmonic beam into high-quality parallel light without newly using a beam shaping optical component.

[Means for solving the problem]

Therefore, in the present invention, the waveguide-type nonlinear optical element that emits a harmonic of the incident light, and a concave cylindrical reflection surface that converts the output light of the waveguide-type nonlinear optical element into parallel light, wherein the concave A cylindrical reflection portion is provided on the waveguide type nonlinear optical element, or provided on a harmonic emission end face of the waveguide type nonlinear optical element formed of an optical member having substantially the same refractive index. Further, the concave cylindrical reflecting portion and the cross section orthogonal to the optical axis of the outgoing light have a substantially arc shape, and the concave cylindrical reflecting surface is parallel to the optical axis of the incident light. It is characterized by.

[Action]

The second harmonic of the Cherenkov radiation type SHG element is
Light is emitted from a waveguide having a certain length as divergent light collimated in only one direction in the direction of the Cherenkov angle. When this second harmonic is applied to the element surface in parallel with the element surface on which the waveguide is formed, the second harmonic on the irradiated surface is at the same distance from the light emitting point. Therefore, by forming the cross section of the irradiation surface perpendicular to the direction of the diverging light as a substantially arc-shaped reflecting surface, the second harmonic reflected by the substantially arc-shaped reflecting surface is shaped in the diverging direction to form the collimated light. Can be

〔Example〕

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

In the figure, a laser beam 1 serving as a high-output fundamental wave is converged by a condenser lens 2 on an end face of an optical waveguide 4 formed on a SHG element 3 made of a lithium niobate crystal substrate.
When the laser light 1 passes through the optical waveguide 4, a second harmonic 5 is generated in a direction at a certain angle with respect to the optical waveguide 4 by a nonlinear optical effect. Since the second harmonic 5 is divergent light that is collimated in only one direction, the directional component that becomes the divergent light is reflected by a reflection curved surface 7 having a curvature at which the collimated light is obtained, so that a high-quality collimated light 6 is obtained. Can be obtained. And the end face 8 of the SHG element 3
Will be radiated from

Also, instead of using a sufficiently long element in the waveguide direction as shown in FIG. 1, as shown in another embodiment of FIG.
Optical member 9 having a refractive index substantially equal to the end face of SHG element 3
A reflection curved surface 10 for shaping the beam may be formed and joined. If this configuration is used, the reflection curved surface 10 can be formed by the optical member 9 separately from the SHG element 3, so that there is no fear of damaging the SHG element 31. Then, it becomes possible to mass-produce only the optical member 9 having the reflection curved surface 10, so that the quality can be stabilized and the cost can be reduced.

Further, as shown in FIG. 2 (b), the collimated light 6 may be prevented from being refracted by comprising an exit end face 11 from the optical member 9 and a surface orthogonal to the exit direction of the collimated light 6.

〔The invention's effect〕

By forming a reflective curved surface for forming a collimated light in parallel with the SHG element itself, high-quality collimated light can be created without newly using an optical component for beam shaping. In addition, since shaping is performed at an early stage of divergence, the second harmonic beam is less eccentric and the beam efficiency can be increased.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention, FIGS. 2 (a) and 2 (b) are schematic configuration diagrams showing another embodiment of the present invention,
FIG. 3 is a schematic configuration diagram showing a conventional example. 1 laser light 2 condensing lens 3,31 SHG element 4,32 optical waveguide 5,33 second harmonic beam 6 collimated light 7,10 reflection curved surface 8,11 , 34 …… End face 9 …… Optical member

Claims (4)

(57) [Claims] 1. A parallel light generating apparatus comprising: a waveguide type nonlinear optical element for emitting harmonics of incident light; and a concave cylindrical reflection surface for converting light emitted from the waveguide type nonlinear optical element into parallel light. 2. The parallel light generating apparatus according to claim 1, wherein said concave cylindrical reflection surface is provided in said waveguide type nonlinear optical element. 3. The parallel light generating apparatus according to claim 1, wherein said concave cylindrical reflection surface is formed on one surface of an optical member having a refractive index substantially equal to that of said waveguide type nonlinear optical element. 4. The concave cylindrical reflection surface and a cross section orthogonal to the optical axis of the outgoing light are formed in a substantially arc shape, and the concave cylindrical reflection surface is parallel to the optical axis of the incident light. Claim (1) characterized in that:
The collimated light producing device as described in the above.