Reflection mirror for high-output laser

Abstract

To provide a reflection mirror for high-output laser that can reduce heat absorption of a retention mechanism in contact with a mirror.SOLUTION: A reflection mirror 10 for high-output laser has: a wedge substrate 1; a first coating film 2 which is formed on the surface of the wedge substrate 1 that light impinges on, and reflects laser light having an arbitrary wavelength and has specific reflection factor incidence angle characteristics; and a second coating film 3 which is formed on the surface of the wedge substrate 1 on the opposite side from the side that light impinges on, and reflects the laser light having the arbitrary wavelength.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to reflective mirrors for high power lasers. [Background technology]

[0002] A conventional tip-tilt mirror generally comprises a mirror and a tip-tilt mount. A total reflection film is applied to the incident surface of the mirror. Usually, the back surface of the mirror is a roughened or polished surface, and this back surface is bonded to the tip-tilt mount. Therefore, light transmitted from the back surface enters the bonding surface between the back surface and the tip-tilt mount, and most of the light is converted to heat. Patent Document 1 discloses an infrared shielding film having a dielectric multilayer film structure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6112112 Summary of the Invention [Problem to be solved by the invention]

[0004] The transmittance of the total reflection film of a conventional tip-tilt mirror is about 1000 ppm, and the absorption of the total reflection film is less than 10 ppm, so the transmittance of the total reflection film is about two orders of magnitude larger than the absorption of the total reflection film. Therefore, if all the light that passes through the total reflection film is absorbed by the adhesive surface, there is a concern that a large thermal distortion will occur on the reflective surface, degrading the beam quality of the laser light. In addition, it is difficult to hollow out the center of the tip-tilt mount, and it is difficult to use the conventional method of reducing thermal distortion, which extracts the light that enters the mirror from the back side.

[0005] The present disclosure has been made in view of the above, and has an object to provide a reflective mirror for a high-power laser that can reduce heat absorption in a holding mechanism in contact with the mirror. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the reflection mirror for high-power laser according to the present disclosure has a wedge substrate, a first coating film formed on the light-incident surface of the wedge substrate, reflecting laser light of any wavelength and having specific reflectance incident angle characteristics, and a second coating film formed on the surface of the wedge substrate opposite to the light-incident surface, reflecting laser light of any wavelength. Effect of the Invention

[0007] The reflection mirror for high-power laser according to the present disclosure has an effect of reducing heat absorption in the holding mechanism in contact with the mirror. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram showing a schematic external view of a reflection mirror for a high-power laser according to an embodiment; [Diagram 2] FIG. 1 is a diagram showing an example of reflectance vs. incident angle characteristics of a first coating film of a reflection mirror for a high-power laser according to an embodiment; [Diagram 3] FIG. 1 is a diagram for explaining the wedge angle and the travel angle of a light beam of a reflection mirror for a high-power laser according to an embodiment; [Figure 4] FIG. 1 is a diagram for explaining an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a reflection mirror for a high-power laser according to an embodiment will be described in detail with reference to the drawings.

[0010] Embodiment FIG. 1 is a diagram showing a schematic view of the appearance of a high-power laser reflection mirror 10 according to an embodiment. The high-power laser reflection mirror 10 is a wedge mirror. The high-power laser reflection mirror 10 has a wedge substrate 1 and a first coating film 2 formed on the light-incident surface of the wedge substrate 1. The first coating film 2 reflects laser light of an arbitrary wavelength and has a specific reflectance incident angle characteristic. The high-power laser reflection mirror 10 further has a second coating film 3 formed on the surface opposite to the light-incident surface of the wedge substrate 1. The second coating film 3 reflects laser light of an arbitrary wavelength. The wedge substrate 1 reflects unwanted light in an arbitrary direction.

[0011] The second coating film 3 has a high reflectance and totally reflects the incident light. The first coating film 2 has a relatively high reflectance at the main incident angle of the laser light, but has a relatively low reflectance at the incident angle of the laser light that has passed through the first coating film 2 and been reflected by the second coating film 3. The first coating film 2 has a transmittance close to 100% at the former incident angle and a transmittance close to 0% at the latter incident angle.

[0012] Fig. 2 is a diagram showing an example of the reflectance incident angle characteristic of the first coating film 2 of the reflection mirror for high-power laser 10 according to the embodiment. Fig. 2 shows an example of the reflectance incident angle characteristic of the first coating film 2 when the former incident angle is 45° and the latter incident angle is 0°. In the example of Fig. 2, the reflectance incident angle characteristic of the first coating film 2 has a change point in the range from 20° to 30°.

[0013] The wedge angle θ of the high-power laser reflecting mirror 10, which is a wedge mirror w and the travelling angle of the light beam will be described with reference to FIG. 3. FIG. 3 shows the wedge angle θ w 3 is a diagram for explaining the angle θ of the light ray and the traveling angle of the light ray. For convenience of explanation, the first coating film 2 and the second coating film 3 are not shown in FIG. inindicates the incident angle of the laser light to the first coating film 2. in indicates the refraction angle of the incident laser light with respect to the first coating film 2. out indicates the angle of incidence of the laser light reflected by the second coating film 3 with respect to the first coating film 2. θ out indicates the refraction angle of the laser light reflected by the second coating film 3 relative to the first coating film 2.

[0014] When the refractive index of the wedge substrate 1 is n, according to Snell's law, θ in and θ' in The relationship between these is expressed by the following equation (1), and θ out and θ' out The relationship is expressed by the following equation (2).

[0015]

number

[0016]

number

[0017] From the geometric calculation, the wedge angle θ w is expressed by the following equation (3).

[0018]

number

[0019] In the above example, θ in = 45°, θ out = 0°, and when n = 1.2, θ w = 18.052° is sufficient.

[0020] When n ≒ 1, equation (3) can be approximately expressed as equation (4) below. By transforming equation (4), θ in , θ out and θ wThe relationship can be expressed by the following equation (5).

[0021]

number

[0022]

number

[0023] For the first coating film 2, the reflectance is increased and a specific reflectance incident angle characteristic is realized by using a dielectric multilayer HR (High Reflective) coating, etc. For the second coating film 3, a total reflection surface is realized by using a dielectric multilayer HR coating or a metal film mirror coating, etc. EXAMPLES

[0024] An embodiment will be described with reference to Fig. 4. Fig. 4 is a diagram for explaining the embodiment. In a high-power laser reflection mirror 10, which is a wedge mirror, a first coating film 2 is formed on the incident surface of a wedge substrate 1 for laser light, and a second coating film 3 is formed on the opposite surface. The second coating film 3 is connected to a tip-tilt mirror mount 5 by a wedge-shaped mechanical component 4, and a beam damper 6 that absorbs unnecessary reflected light is disposed in front of the first coating film 2.

[0025] Most of the incident laser light 7 is totally reflected by the first coating film 2. Laser light 8 that passes through the first coating film 2 is totally reflected by the second coating film 3, passes through the first coating film 2, and is converted to heat by the beam damper 6. Normally, the movable angle of the tip-tilt mirror mount 5 is about several degrees, and by increasing the size of the beam damper 6, it is possible for the beam damper 6 to absorb unnecessary incident light even when the tip-tilt mirror mount 5 is tilted.

[0026] Thus, in the wedge mirror, the light of the incident laser light 7 that has passed through the first coating film 2 is reflected by the second coating film 3, and passes through the first coating film 2 again to be emitted to the outside of the wedge mirror. Therefore, the wedge mirror of the embodiment can reduce heat absorption in the holding mechanism in contact with the wedge mirror.

[0027] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies. Parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0028] 1 wedge substrate, 2 first coating film, 3 second coating film, 4 wedge-shaped mechanical part, 5 tip-tilt mirror mount, 6 beam damper, 7 incident laser light, 8 laser light, 10 high-power laser reflection mirror.

Claims

1. A wedge substrate; a first coating film formed on a light-incident surface of the wedge substrate, the first coating film reflecting laser light of an arbitrary wavelength and having a specific reflectance and incident angle characteristic; a second coating film formed on a surface of the wedge substrate opposite to the surface on which the light is incident and which reflects laser light of an arbitrary wavelength; A reflection mirror for a high-power laser comprising:

2. The wedge substrate reflects unwanted light in any direction.

2. The reflection mirror for a high-power laser according to claim 1.

3. A tip-tilt mirror mount; A beam damper to absorb unwanted reflected light and 2. The reflection mirror for high-power laser according to claim 1, further comprising:

4. The beam damper is disposed in front of the first coating film.

4. The reflection mirror for a high-power laser according to claim 3.

Images