JP2000187130A - Laser synthesizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser synthesizer which is made smaller in space and less in reflection loss. SOLUTION: The laser beams from exit ports 1 arranged laterally on the same axis are collimated by a collimating lenses to parallel light beams, which are further made into the parallel light beams in the same direction perpendicular to the same axis by prisms 3. These parallel light beams are condensed by a condenser lens 4 to an incident port 5. The prisms are used in place of mirrors, by which the synthesizer of the smaller space may be obtained as there is no thickness of the mirrors. In addition, the reflection principle of the prisms utilizes the critical angle of high-refractive index material and the air of a low refractive index. Since the reflectivity is high and the absorption of the laser beams is little, there is substantially no temperature elevation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser combiner that combines two laser beams to increase the output.

[0002]

2. Description of the Related Art A large output laser beam can be obtained by combining two laser beams generated by a low output laser generator. By repeating such a combination, a laser beam having a higher output can be obtained. Such a synthesizer is called a laser synthesizer.

FIG. 2 shows a configuration of a conventional laser synthesizer. A mirror 6 inclined at 45 ° to the left and right with respect to the central axis, a collimator lens 2 and a laser beam emission port 1 are provided on the horizontal axis orthogonal to the central axis. A condenser lens 4 and an entrance 5 are provided on the central axis. With this configuration, the laser light emitted from the emission port 1 becomes parallel light by the collimating lens 2, and the parallel light reflected by the mirror 6 is condensed by the condenser lens 4 and is incident on the entrance. Thus, the left and right incident laser beams are combined, and the output is the sum of the two inputs.

[0004]

When the laser beam is bent by 90 ° by the mirror 6 as described above, a dead space as shown by oblique lines on the central axis occurs due to the thickness of the mirror 6, and the diameter of the condenser lens 4 becomes large. Thus, the required numerical aperture NA of the optical fiber at the entrance 5 becomes large. This requires a large space. The mirror 6 is formed by attaching a dielectric multilayer film to a base material as shown in FIG. 3, and the thickness of the multilayer film matches the phase of the wavelength reflected at the boundary surface between the multilayer film surface and the base material. It is designed to be. However, when the temperature rises due to the absorption of the laser beam, the thickness of the multilayer film changes, the phase shifts, and a part of the peak and a part of the valley overlap and absorption occurs. For this reason, the reflectance becomes less than 100%. When light of random polarization strikes the mirror 6, the S-polarized component (the component in the direction perpendicular to the P-polarized light) is reflected 100%, but a part of the P-polarized component (the component in the in-plane vibration direction) is absorbed. And reflection loss occurs.

The present invention has been made to solve such a problem. That is, an object of the present invention is to provide a laser combiner having a small space and a small reflection loss.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, laser light from emission ports arranged on the same axis on the left and right is converted into parallel light by a collimating lens,
Further, the prism makes parallel light perpendicular to the same axis and in the same direction, and the parallel light is condensed on the entrance by a condenser lens.

[0007] By using a prism instead of a mirror, there is no mirror thickness, so that a combiner with a small space can be obtained. Further, the principle of reflection of the prism utilizes a critical angle between a high refractive index material and low refractive index air, and has a high reflectance and little absorption of laser light, so that there is almost no rise in temperature. Also, there is no polarization response of the reflectance.

In the invention according to claim 2, the prism is made of synthetic or fused quartz for optical parts.

A general prism is made of optical glass. A prism used in a system using a laser as a light source is often used because multi-component glass is an inexpensive and stable glass type. However, this multi-component glass contains impurities in quartz and is good when the output of the laser is small.
In the case of a laser having a large output, the laser beam may be absorbed, the temperature may rise, deformation may occur, and the laser beam may crack. For this reason, conventionally, a mirror has been used for synthesizing a laser beam having a large output. However, when experiments were conducted using prisms made of synthetic or fused silica for high-purity optical components, the absorption of laser light was large even for laser light with large output that could be deformed or cracked with multi-component glass. It was found that there was almost no increase in temperature, and no deformation or cracking occurred.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a laser synthesizer according to an embodiment of the present invention. On a horizontal axis orthogonal to the central axis, the prism 3 is arranged symmetrically with respect to the central axis and so that laser light incident along the horizontal axis is emitted in parallel with the central axis. An emission port 1 for emitting laser light from an optical fiber is provided on the left and right horizontal axes of the central axis,
Further, on the horizontal axis between the exit 1 and the prism 3, the exit 1
A collimator lens 2 for converting the laser beam from the lens into parallel light and entering the prism 3 is provided. A condensing lens 4 is provided on the central axis on the exit side of the prism 3, and an entrance port 5 is provided at a focal position of the condensing lens 5 on the central axis and connected to an optical fiber. The prism 3 is made of synthetic or fused quartz for optical parts.

With this configuration, the laser beams from the left and right exit ports 1 are collimated by the collimating lens 2 and are incident on the prism 3 to be bent at a right angle and exit as parallel beams.
The condenser lens 4 collects the parallel light from both prisms 3 on the entrance 5. The entrance 5 is connected to an optical fiber, and the combined light is sent to the irradiation target by the optical fiber.

Since the prism 3 does not have a dead space due to its thickness unlike the mirror 6 shown in FIG. 2, the prism 3 is smaller than the mirror 6, the condensing lens 4 is correspondingly smaller, and the numerical aperture of the entrance 5 is further reduced. Since the NA is also small, the device is compact. In terms of performance, the reflection principle of the prism utilizes the critical angle between the high-refractive-index material and the low-refractive-index air, has high reflectivity, hardly absorbs laser light, and is made of optical components as a material. Because of the use of synthetic or fused quartz, the rise in internal temperature is small, and thermal deformation and cracking hardly occur. Further, since both P-polarized light and S-polarized light are almost certainly reflected, there is no polarization dependence of the reflectance, and the reflectance is relatively high.

[0013]

As described above, the present invention can provide a compact device by using a prism instead of a mirror as a component for bending a laser beam at a right angle.
In addition, by forming the prism using synthetic optical parts or using fused silica, a high reflectance can be obtained without thermal deformation or cracking, no polarization dependence of reflectance.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a laser synthesizer according to an embodiment of the present invention.

FIG. 2 shows a laser synthesizer using a conventional mirror.

FIG. 3 is a diagram illustrating a decrease in mirror performance due to a rise in temperature.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outlet 2 Collimating lens 3 Prism 4 Condensing lens 5 Inlet 6 Mirror

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshio Kojima 1 Shin-Nakahara-cho, Isogo-ku, Yokohama-shi, Kanagawa Ishikawashima-Harima Heavy Industries, Ltd. Yokohama Engineering Center (72) Inventor Fumio Matsuzaka Toyosu 3, Koto-ku, Tokyo No. 1-115, Ishikawajima-Harima Heavy Industries Co., Ltd. Tojin Technical Center (72) Inventor Taketo Yagi 1 Shinnakahara-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Ishikawajima Harima Heavy Industries, Ltd. Technical Research Institute BA03 CA13 CA32 CA39

Claims (2)

[Claims] 1. A laser beam from an emission port arranged on the same axis on the left and right is converted into parallel light by a collimating lens, and further converted into parallel light perpendicular to the same axis and in the same direction by a prism. A laser synthesizer characterized in that the light is condensed on an entrance by using a laser beam. 2. The laser synthesizer according to claim 1, wherein the prism is made of synthetic or fused quartz for optical parts.