JPH0369926A - Device for forming collimated beam of light - Google Patents

Abstract

PURPOSE:To form good-quality collimated beams of light without freshly using optical parts for beam shaping by generating a reflecting curved surface for forming the collimated beams of lights in juxtaposition. CONSTITUTION:A laser beam 1 which is the basic wave of high output is converged onto the end face of the optical waveguide 4 formed on a second harmonic wave generating element SHG element 3 consisting of a lithium niobate crystal substrate by a condenser lens 2. This laser beam 1 generates a second harmonic wave 5 in a certain direction with respect to the optical waveguide 4 by a nonlinear optical effect when the laser beam passes the optical waveguide 4. Since this second harmonic wave 5 is the divergent light collimated only in one direction, this wave is reflected by the reflection curved surface 7 having the curvature at which the collimated beams of light are obtainable with the directional component where this divergent light is formed. The good-quality collimated beams of light 6 are obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a nonlinear optical element that performs optical wavelength conversion using nonlinear optical effects.

[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 a long and narrow region called the waveguide.

Therefore, as shown in the schematic configuration diagram shown in Figure 3, 5) IG
The laser beam 1 that has entered the waveguide 32 of the element 31 is emitted with a second harmonic beam 33 having a Cerenkov radiation angle. This second harmonic beam 33 is collimated only in one direction, and becomes diverging light in the other orthogonal direction, resulting in SH
The light is emitted from the end face 34 of the G element 31. The second harmonic beam 33 emitted in this manner is converted into collimated light that is easy to handle by beam shaping using an asymmetric lens such as the cylindrical lens 35.

[Problem to be solved by the invention]

The second harmonic beam emitted from the input end of the waveguide of the Cerenkov radiation SHG element and the second harmonic beam emitted from near the output end have a constant spread angle, but their light emission points are different. This results in a complicated beam pattern that is curved in an arcuate shape, and it is difficult to obtain a light beam with sufficiently good collimation using the methods described in the prior art. Furthermore, when considering miniaturization as an optical wavelength conversion element, the need for an optical system for beam shaping is a problem.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a device that converts a second harmonic beam into high-quality parallel light without using any new optical components for beam shaping.

[Means to solve the problem]

Therefore, the present invention comprises a waveguide-type nonlinear optical element that emits harmonics of incident light, and a concave cylindrical reflective surface that converts the output light of the waveguide-type nonlinear optical element into parallel light. A cylindrical reflection portion may be provided on the waveguide type nonlinear optical element, or an optical member having approximately the same refractive index may be used to provide I! ! The waveguide type nonlinear element is provided at the harmonic output end face of the waveguide type nonlinear element. Further, the shape of the concave cylindrical reflecting portion and the cross section perpendicular to the optical axis of the emitted light is approximately arcuate, and the concave cylindrical reflecting surface is parallel to the optical axis of the incident light. It is characterized by

[Effect]

The second harmonic generated by the Cerenkov radiation type SHG element is
A waveguide with a certain length emits divergent light that is collimated in only one direction in the direction of the Cherenkov angle. When this second harmonic is irradiated onto an element surface parallel to 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 setting the cross section of the irradiation surface orthogonal to the direction 41 as a substantially arc-shaped reflecting surface, the second harmonic reflected by this substantially arc-shaped reflecting surface is collimated by shaping the divergence direction. It can be turned into light.

〔Example〕

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

In the figure, a high-output fundamental laser beam l is focused by a condenser lens 2 onto the end face of an optical waveguide 4 formed on an SHG element 3 made of a lithium niobate crystal substrate.

When this laser beam l passes through the optical waveguide 4, it generates a second harmonic wave 5 in a direction at a certain angle with respect to the optical waveguide 4 due to a nonlinear optical effect. Since this second harmonic 5 is a diverging light that is collimated in only one direction, by reflecting the directional component of this diverging light on a reflection curved surface 7 having a curvature that allows the collimated light to be obtained, a high-quality collimated light 6 can be obtained. can be obtained. The light is then radiated from the end face 8 of the SHG element 3.

Also, instead of using a sufficiently long element in the waveguide direction as shown in FIG. 1, as shown in another embodiment of FIG.
An optical member 9 having a refractive index substantially equal to the end face of the HG element 3
A configuration may also be adopted in which a reflective curved surface IO for beam shaping is formed and joined. If this configuration is used, the reflective curved surface IO can be created with the optical member 9 separately from the SHG element 3, so the SHG
There is no need to worry about damaging the element 31. and reflective surface 1
It becomes possible to mass-produce only the optical member 9 having 0, the quality is stable, and the cost can be reduced.

Furthermore, as shown in FIG. 2, the output end face 11 from the optical member 9 and a surface perpendicular to the output direction of the collimated light 6 may be used to prevent the collimated light 6 from being refracted.

〔Effect of the invention〕

By using the SHG element itself or by arranging them in parallel to create a reflective curved surface for forming collimated light, it is possible to create high-quality collimated light without using additional optical components for beam shaping. Furthermore, since shaping is performed at the initial stage of divergence, the second harmonic beam is less likely to be eclipsed, and beam efficiency can be increased.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, FIG. 2 is a schematic configuration diagram showing another embodiment of the present invention, and FIG. 3 is a schematic diagram showing a conventional example. It is. 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 surface 9 ... Optical member Fig. 2 (a)

Claims (4)

[Claims] (1) A parallel light generating device comprising a waveguide type nonlinear optical element that emits harmonics of incident light and a concave cylindrical reflection surface that converts the output light of the waveguide type nonlinear optical element into parallel light. (2) The parallel light generating device according to claim (1), wherein the concave cylindrical reflective surface is provided on the waveguide type nonlinear optical element. (3) The parallel light generating device according to claim (1), wherein the concave cylindrical reflecting surface is formed on one surface of an optical member having a refractive index substantially equal to that of the waveguide type nonlinear optical element. (4) The shape of the concave cylindrical reflective surface and the cross section perpendicular to the optical axis of the emitted light is approximately arcuate, and
2. The parallel light generating device according to claim 1, wherein the concave cylindrical reflecting surface is parallel to the optical axis of the incident light.