KR102226980B1 - Laser oscillator and laser processing device - Google Patents

Abstract

The reflective member 100 for an infrared laser includes a substrate 1, a SiO film 6, and a metal film 3 formed between the substrate 1 and the SiO film 6.

Description

Laser oscillator and laser processing device

The present invention relates to a reflective member for an infrared laser, a laser oscillator, a laser processing device, and a method of manufacturing a reflective member for an infrared laser that reflects infrared laser light.

BACKGROUND ART A laser processing apparatus for processing a shape of an object by irradiating laser light is used in various fields. The wavelength of the laser light used by the laser processing device is selected according to the material of the object to be processed. Infrared laser light with a wavelength of 9 µm, typified by a CO ₂ (carbon dioxide) laser, is used for drilling for forming wiring electrodes on a printed circuit board made of a resin.

In the case of performing the drilling process, for the laser processing apparatus, it is required to form a processing hole having a shape closer to a true circle. In order to form a machining hole having a shape close to a true circle, it is necessary that the laser light used for processing is isotropic circular polarization. In order to satisfy such a requirement, a laser processing apparatus employing a method of converting linearly polarized laser light into circularly polarized light is provided with a laser oscillator that oscillates linearly polarized laser light, and a polarization conversion member disposed on the optical path. There is. In order for such a laser processing apparatus to emit more isotropic circularly polarized laser light, a laser oscillator that oscillates ideal linearly polarized light with a regular vibration direction is required.

Examples of the reflective member used in the wavelength region of the infrared laser light include those disclosed in Patent Literature 1 and Patent Literature 2. The reflective member disclosed in Patent Document 1 is a Cr (chromium) layer, an Au (gold) layer or Ag (silver) layer, and an HfO ₂ (hafnium oxide) layer on a Si (silicon) substrate or a Cu (copper) substrate. Alternatively, a Bi ₂ O ₃ (bismuth oxide) layer, a ZnSe (zinc selenide) layer or a ZnS (zinc sulfide) layer, and a Ge (germanium) layer are formed. The reflective member disclosed in Patent Document 2 is an Au layer, a YF ₃ (yttrium fluoride) layer or a YbF ₃ (ytterbium fluoride) layer, a ZnSe layer or a ZnS layer, and Ge on a Si substrate or a Cu substrate. A layer, a ZnSe layer or a ZnS layer, and a YF ₃ layer or a YbF ₃ layer are formed. All of the above conventional reflective members achieve a reflectance of 99.7% or more for infrared laser light.

Japanese Patent Laid-Open No. 2003-302520 Japanese Patent Laid-Open No. 2009-086533

However, when the conventional reflective member is used inside a laser oscillator, there is a problem that the laser light oscillated from the laser oscillator does not become linearly polarized. In order to obtain linearly polarized laser light, it is necessary that there is a difference between the reflectance of the reflective member for the S wave and the reflectance for the P wave. However, in the conventional reflective member, since the difference between the reflectance for the S wave and the reflectance for the P wave is small, a laser oscillator that oscillates linearly polarized light cannot be configured.

The present invention has been made in view of the above, and an object of the present invention is to obtain a reflective member for an infrared laser capable of configuring a laser oscillator that oscillates linearly polarized infrared laser light.

In order to solve the above-described problems and achieve the object, the laser oscillator according to the present invention includes a reflective member for an infrared laser having a substrate, a SiO (silicon monoxide) film, and a metal film formed between the substrate and the SiO film.

Advantageous Effects of Invention According to the present invention, an effect of obtaining a reflective member for an infrared laser capable of realizing a laser oscillator that oscillates an infrared laser light of linearly polarized light having a regular vibration direction is obtained.

1 is a diagram schematically showing a configuration of a laser processing apparatus according to an embodiment of the present invention.
2 is a configuration diagram of the laser oscillator shown in FIG. 1.
Fig. 3 is a first configuration diagram of a reflective member usable as a return mirror shown in Fig. 2;
4 is a schematic configuration diagram of a film forming apparatus used for manufacturing the reflective member shown in FIG. 3.
5 is a diagram showing optical properties of the reflective member of Example 1. FIG.
6 is a diagram showing optical properties of a reflective member of Comparative Example 1. FIG.
7 is a diagram showing optical properties of a reflective member of Comparative Example 2. FIG.
Fig. 8 is a diagram showing reflectance of reflective members of Example 1 and Comparative Example 1 together with the number of reflections.
9 is a table showing durability test results of reflective members of Example 2, Comparative Example 3, and Comparative Example 4. FIG.
10 is a diagram showing optical properties of the reflective member of Example 2. FIG.
11 is a diagram showing the optical properties of the reflective member of Example 3. FIG.
12 is a diagram showing the optical properties of the reflective member of Example 4. FIG.
13 is a diagram showing the optical properties of the reflective member of Example 5. FIG.
14 is a diagram showing optical properties of a reflective member of Comparative Example 5. FIG.
15 is a view showing reflectance of the reflective members of Examples 2 to 5 and Comparative Example 5 together with the number of reflections.
Fig. 16 is a diagram showing durability test results of reflective members of Examples 1, 3, 4, and 5;
17 is a diagram showing the refractive indices of various materials.
Fig. 18 is a diagram showing extinction coefficients of various materials.
Fig. 19 is a second configuration diagram of a reflective member usable as a return mirror shown in Fig. 2;
Fig. 20 is a third configuration diagram of a reflective member usable as a return mirror shown in Fig. 2;
Fig. 21 is a fourth configuration diagram of a reflective member usable as a return mirror shown in Fig. 2;
22 is a diagram showing optical properties of the reflective member of Example 6. FIG.
23 is a diagram showing the optical properties of the reflective member of Example 7. FIG.
24 is a diagram showing optical properties of the reflective member of Example 8. FIG.
25 is a diagram showing the optical properties of the reflective member of Example 9. FIG.
26 is a diagram showing the optical properties of the reflective member of Example 10;
Fig. 27 is a diagram showing the optical properties of the reflective member of the eleventh embodiment.
28 is a diagram showing optical properties of a reflective member of Comparative Example 6. FIG.
29 is a diagram showing optical properties of a reflective member of Comparative Example 7. FIG.
30 is a diagram showing optical properties of a reflective member of Comparative Example 8. FIG.
Fig. 31 is a diagram showing reflectance of the reflective members of the sixth to eleventh embodiments together with the number of reflections;
Fig. 32 is a diagram showing reflectance of the reflective members of Comparative Examples 6 to 8 together with the number of reflections.
33 is a table showing durability test results of reflective members of Examples 6 to 11;
Fig. 34 is another configuration diagram of the laser oscillator shown in Fig. 1;
Fig. 35 is a diagram showing an energy gain distribution in the laser oscillator shown in Fig. 34;
Fig. 36 is a diagram for evaluating the performance of a laser oscillator to which the reflective member of the present invention is applied.

Hereinafter, a method of manufacturing an infrared laser reflecting member, a laser oscillator, a laser processing device, and an infrared laser reflecting member according to an embodiment of the present invention will be described in detail with reference to the drawings. In addition, the present invention is not limited by this embodiment.

Embodiment 1.

1 is a diagram schematically showing a configuration of a laser processing apparatus according to an embodiment of the present invention. The laser processing apparatus 10 includes a laser oscillator 11, a polarization conversion member 12, a condensing optical system 13, a processing table 14, a drive unit 15, and a control unit 16.

The laser oscillator 11 emits linearly polarized laser light having a regular vibration direction. The polarization conversion member 12 is disposed on the optical path until the laser light emitted from the laser oscillator 11 is irradiated onto the object 17, and the linearly polarized laser light emitted from the laser oscillator 11 is sourced. Converts to polarized light. The condensing optical system 13 condenses the laser light converted into circularly polarized light by the polarization converting member 12 to the object 17 to be processed. The condensing optical system 13 includes a condensing lens and a collimator lens. The processing table 14 is a stand on which the object 17 is mounted. The drive unit 15 moves the processing table 14. The drive unit 15 has, for example, a motor, and converts electrical energy into mechanical energy. The control unit 16 controls the operation of the laser processing apparatus 10. For example, the control unit 16 may control a timing at which the laser oscillator 11 generates laser light, and a timing and direction at which the driving unit 15 moves the processing table 14. When the driving unit 15 moves the processing table 14, the position at which the laser light is irradiated to the processing object 17 changes. The laser processing apparatus 10 converts the linearly polarized laser light oscillated by the laser oscillator 11 into circularly polarized light in the polarization conversion member 12, and processes the object to be processed 17 using the circularly polarized infrared laser light. Run. When the vibration direction of the laser light oscillated by the laser oscillator 11 is a more regular ideal linearly polarized light, the laser light used by the laser processing apparatus 10 for processing becomes a more isotropic circularly polarized light. For this reason, when performing the drilling process using the laser processing apparatus 10, it is possible to form a processing hole having a shape closer to a true circle.

2 is a configuration diagram of the laser oscillator 11 shown in FIG. 1. The laser oscillator 11 oscillates infrared laser light L having a peak wavelength in the infrared region. The infrared laser light L oscillated by the laser oscillator 11 is linearly polarized. The laser oscillator 11 includes a housing 20, a laser medium 21, a pair of electrodes 22, a partial reflection mirror 23, a total reflection mirror 24, and a return mirror 25. Equipped.

The laser medium 21 is, for example, an excitation gas such as a mixed gas obtained by adding N _{2 (nitrogen) and He (helium) to CO 2 gas.} The gas ratio of the mixed gas is CO ₂ : N ₂ :He=10:30:60. The mixed gas exemplified here is an example, and the laser medium 21 may be any one capable of generating infrared laser light having a peak wavelength in the infrared region. The pair of electrodes 22 is an example of an energy supply unit that supplies excitation energy to the laser medium 21. When a voltage is applied to the pair of electrodes 22, a discharge is generated and energy is supplied to the laser medium 21. The partial reflection mirror 23 and the total reflection mirror 24 constitute a resonator. Light is amplified while light travels back and forth between the partial reflection mirror 23 and the total reflection mirror 24. When the light intensity exceeds the threshold value, the infrared laser light L is oscillated, and the infrared laser light L is emitted from the partial reflection mirror 23. The return mirror 25 is disposed on the optical path between the partial reflection mirror 23 and the total reflection mirror 24, and is a reflection member that changes the direction of the optical path. Specifically, the return mirror 25 is arranged so as to sandwich the electrode 22 between the return mirror 25 and the partial reflection mirror 23, and the light reflected by the partial reflection mirror 23 is a total reflection mirror. It reflects in the direction incident on (24). The light reflected by the total reflection mirror 24 is incident on the return mirror 25 again, and the return mirror 25 reflects the incident light in a direction incident on the partial reflection mirror 23. By repeating the optical path using the return mirror 25, the overall length can be shortened without changing the optical path length, compared to the case where the return mirror 25 is not used, and the size of the housing 20 is reduced. can do.

The principle of the laser oscillator 11 will be described. When a voltage is applied to the electrode 22, a discharge occurs and energy is supplied to the laser medium 21. _{The CO 2} molecules in the laser medium 21 are excited by the applied energy, and the excited CO ₂ molecules emit light when transitioning to the ground state. The light emitted by the laser medium 21 is repeatedly reflected between the partial reflection mirror 23 and the total reflection mirror 24, and is again incident on the laser medium 21. _{When light is incident on the excited CO 2} molecules included in the laser medium 21, induced emission of light occurs, and the excited CO ₂ molecules emit light having the same wavelength as the incident light. While light travels back and forth in the resonator composed of the partial reflection mirror 23 and the total reflection mirror 24, the light is amplified. When the light intensity exceeds the threshold value, the infrared laser light L is oscillated from the partial reflection mirror 23. A return mirror 25 is disposed on the optical path between the partial reflection mirror 23 and the total reflection mirror 24. The return mirror 25 has a large difference between the reflectance with respect to the S wave and the reflectance with respect to the P wave. Specifically, the return mirror 25 has a high reflectance for the S wave, less attenuation of the S wave even when the light is repeatedly reflected, the reflectance for the P wave is lower than the reflectance for the S wave, and reflects the light. During repetition, the P wave is greatly attenuated. For this reason, the infrared laser light L oscillated from the partial reflection mirror 23 becomes linearly polarized light.

3 is a first configuration diagram of a reflective member 100 usable as the return mirror 25 shown in FIG. 2. The reflective member 100 is a reflective member for infrared lasers having a high reflectance for infrared laser light. In the reflective member 100, since the reflectance of the P wave is lower than that of the S wave, the P wave is attenuated more than the S wave while the reflection of light is repeated. The reflective member 100 includes a substrate 1, a silicon oxide film 2, a metal film 3, a ZnS film 4, a Ge film 5, and a SiO film 6. The silicon oxide film 2, the metal film 3, the ZnS film 4, the Ge film 5, and the SiO film 6 are on the substrate 1 from the side closer to the substrate 1 in the above-described order. It is formed with. In the following description, the term "a film formed on the substrate 1" includes a film formed directly on the substrate 1 and a film formed through another film between the film and the substrate 1.

The reflective member 100 includes at least a substrate 1, a SiO film 6, and a metal film 3 formed between the substrate 1 and the SiO film 6. It is preferable that the substrate 1 is a material excellent in corrosion resistance, for example, a Si substrate or a Cu substrate. In order to prevent light diffusion, the substrate 1 is preferably mirror-finished. The metal film 3 is a reflective film that reflects infrared laser light. It is preferable that the metal film 3 realizes a high reflectance for infrared laser light in the range of 8 µm to 11 µm, which is a wavelength range mainly used in _{CO 2 lasers.} As the metal film 3, for example, an Au film or an Ag film can be used. The SiO film 6 is formed on the substrate 1, for example, as an outermost layer of the reflective member 100. When the infrared laser light is reflected by forming the SiO film 6 on the substrate 1, the difference between the reflectance for the S wave and the reflectance for the P wave increases.

17 is a diagram showing the wavelength dependence of the refractive index (n) of SiO, Ge, ZnS and SiO _2. 18 is a diagram showing the wavelength dependence of the extinction coefficient k of SiO, Ge, ZnS and SiO _2. Fig. 17 shows the refractive index (n) at a wavelength of 8 to 11 µm, and Fig. 18 shows an extinction coefficient (k) at a wavelength of 8 to 11 µm. The extinction coefficient k is in proportion to the absorption coefficient α, and is a quantity related to the absorption of light. Since SiO ₂ is similar in composition to SiO, the refractive index (n) and extinction coefficient (k) of _{SiO 2 are shown for reference.}

Usually, as a functional film to be formed on the metal film of a reflecting mirror, a transmissive material in the used wavelength range is selected in order to prevent absorption of light. As shown in Fig. 17, Ge and ZnS are transmissive materials at a wavelength of 8 to 11 µm, and are also used in the reflective members of Patent Literature 1 and Patent Literature 2.

On the other hand, the SiO film 6 is a material that has been conventionally used centering on the visible light region, but its use has not been examined in the range of 8 to 11 µm in the wavelength range of the infrared laser mainly used in _{CO 2 lasers.} SiO is a transmissive material that does not absorb light in the visible region. On the other hand, as shown in Fig. 18, since the extinction coefficient k of SiO at a wavelength of 8 to 11 µm is large and absorbs light, it has not been considered for use as a conventional functional film.

The inventor of the present application pays attention to the fact that the reflective member 100 absorbs some light (=P wave), and for a film having absorption, optical constants (refractive index (n), extinction coefficient (k)) and optical properties The relationship of the Fresnel coefficient to determine the was verified. As a result, by forming the SiO film 6 rather than the transmissive material on the substrate 1, the difference between the reflectance to the S wave and the reflectance to the P wave increases when infrared laser light is reflected. Discovered what makes the character come true.

SiO ₂ , like SiO, is a transparent material in the visible region. Since the constituent elements are the same, these materials may be identified, but as shown in Figs. 17 and 18, at a wavelength of 8 to 11 μm, these are different optical constants (refractive index (n), extinction coefficient (k)) It is a material that has. That is, when formed as an optical film, they are different substances that exhibit different functions.

A ZnS film 4 may be formed between the metal film 3 and the SiO film 6, and a Ge film 5 may be formed between the ZnS film 4 and the SiO film 6. By forming the ZnS film 4 and the Ge film 5, the reflectance of the reflective member 100 to infrared laser light can be further improved.

The reflective member 100 may have a silicon oxide film 2 between the substrate 1 and the metal film 3. The silicon oxide film 2 is a SiO film, a SiO ₂ (silicon dioxide) film, or a Si ₂ O ₃ (silicon oxide) film. When the substrate 1 is a Si substrate and the metal film 3 is an Au film, if an Au film is directly formed on the Si substrate, the adhesion between the Si substrate and the Au film is insufficient, and film peeling is likely to occur. Thus, by forming the silicon oxide film 2 between the Si substrate and the Au film, the adhesion between the Si substrate and the Au film can be enhanced. Before the metal film 3 is formed, a silicon oxide film 2 as an oxide film can be generated on the surface of the Si substrate by irradiating oxide ions onto the surface of the Si substrate using a gas containing _{O 2 as a main component.} . Since the silicon oxide film 2 formed in this way is formed integrally with the Si substrate, the adhesion to the Si substrate is very strong. The process of generating the silicon oxide film 2 is performed in a vacuum in the film forming apparatus. Following the step of generating the silicon oxide film 2, the step of forming the Au film may be performed in a vacuum. Thereby, the dangling bond on the surface of the silicon oxide film 2 and the bond of the Au film are bonded to each other, and the adhesion between the silicon oxide film 2 and the Au film is also strengthened.

It is preferable that the reflective member 100 is formed by a film forming apparatus having a vacuum chamber. As a typical film forming apparatus, a vapor deposition apparatus, a sputtering apparatus, a CVD (Chemical Vapor Deposition) apparatus, etc. are mentioned.

4 is a schematic configuration diagram of a film forming apparatus used for manufacturing the reflective member 100 shown in FIG. 3. The film forming apparatus shown in FIG. 4 is a vacuum vapor deposition apparatus. Hereinafter, a method of manufacturing the reflective member 100 using a vacuum evaporation apparatus will be described.

The vacuum vapor deposition apparatus includes a vacuum container 30 and a vacuum pump 31. The vacuum pump 31 vacuum sucks the inside of the vacuum container 30. In the vacuum container 30, a vapor deposition material 32, a cooling table 33 for installing the vapor deposition material 32, an electron gun 34 for supplying energy to the vapor deposition material 32, and a film forming process A shielding plate 35 for controlling the voltage, a dome 36 for fixing the substrate 1, and an ion source 37 for irradiating ions are provided.

A plurality of evaporation materials 32 and substrate 1 stored in the crucible are prepared, the evaporation material 32 is installed on the cooling table 33 in the vacuum container 30, and the substrate 1 is placed in a dome. ) It is installed on (36). At this time, the substrate 1 is provided with the film-forming surface facing the direction of the evaporation material 32. The cooling table 33 can be provided with a plurality of crucibles. By rotating the cooling table 33, the evaporation material 32 used for evaporation can be replaced. After the vapor deposition material 32 and the substrate 1 are provided, the inside of the vacuum container 30 is evacuated by the vacuum pump 31 to lower the pressure in the vacuum container 30. After the pressure in the vacuum container 30 ^{reaches a pressure of 10 -3} Pa to 10 ^-6 Pa, the surface of the substrate 1 is irradiated with an _{O 2 ion beam from the ion source 37.} An oxide film is formed on the surface of the substrate 1 by irradiation of the _{O 2 ion beam.}

When an oxide film is formed on the surface of the substrate 1, a step of forming the metal film 3 in a vacuum is then performed. First, with the shielding plate 35 closed, an electron beam is irradiated from the electron gun 34 to the metal, which is the vapor deposition material 32, to melt the metal and evaporate it. When the shielding plate 35 is closed, the space in which the evaporated metal exists and the space in which the substrate 1 is installed are blocked. After the metal is melted and evaporated, the shielding plate 35 is opened and film formation is started in a state where the evaporation amount is stable. When the evaporated metal contacts the substrate 1 provided on the dome 36, the evaporated metal adheres to the substrate 1 and is deposited. Thereby, the metal film 3 can be formed on the substrate 1. When the designed film thickness is reached, the shielding plate 35 is closed and film formation is terminated.

When the cooling table 33 is rotated, the evaporation material 32 to which an electron beam is irradiated from the electron gun 34 can be replaced. In order to carry out the process of forming the ZnS film 4 following the process of forming the metal film 3, the evaporation material 32 is replaced with ZnS. When the process of forming the ZnS film 4 is finished, the process of forming the Ge film 5 is then performed. When the formation process of the Ge film 5 is finished, the formation process of the SiO film 6 is then performed. Thereby, the SiO film 6 is formed on the metal film 3. In each film formation step, the same procedure as that of the metal film 3 formation step is repeated. When the step of forming the SiO film 6 is completed, the substrate 1 is taken out from the vacuum container 30.

Next, examples of the reflective member 100 according to the embodiment of the present invention will be described. Hereinafter, the optical characteristics of the reflective member 100 according to the embodiment of the present invention will be examined by giving a plurality of examples and comparative examples.

First, using Example 1, Comparative Example 1 and Comparative Example 2 shown below, the effect of the SiO film 6 of the reflective member 100 and the ZnS film 4 and the Ge film 5 have. Verify the effect that comes.

[Example 1]

The material and film thickness of each layer of the reflective member 100 of Example 1 are as follows. Each layer is referred to as a first layer, a second layer, a third layer, a fourth layer, and a fifth layer in order from the side close to the substrate.

5th layer SiO 110nm

4th layer Ge 540nm

3rd layer ZnS 1090nm

Second layer Au 200nm

First layer SiO 10 nm

Substrate Si 10mm

In Example 1, the substrate 1 is a mirror-finished circular Si substrate having a diameter of 40 mm, the metal film 3 is an Au film, and the silicon oxide film 2 is a SiO film.

[Comparative Example 1]

The material and film thickness of each layer of the reflective member of Comparative Example 1 are as follows.

First layer Au 200nm

Substrate Si 10mm

Also in Comparative Example 1, the substrate is a mirror-finished circular Si substrate having a diameter of 40 mm, and an Au layer, which is a metal film, is directly formed thereon, and does not include a silicon oxide film, a ZnS film, a Ge film, and a SiO film. .

[Comparative Example 2]

The material and film thickness of each layer of the reflective member of Comparative Example 2 are as follows. Comparative Example 2 is a configuration in which the SiO film 6 as the outermost layer is omitted from the configuration of Example 1.

4th layer Ge 540nm

3rd layer ZnS 1090nm

Second layer Au 200nm

First layer SiO 10 nm

Substrate Si 10mm

5 is a diagram showing the optical properties of the reflective member 100 of the first embodiment. 6 is a diagram showing the optical properties of the reflective member of Comparative Example 1. FIG. 7 is a diagram showing the optical properties of the reflective member of Comparative Example 2. FIG. 5 to 7 are wavelengths of light incident on the reflective member, and the unit is µm. The vertical axis of FIGS. 5 to 7 represents reflectance of the reflective member for each wavelength, and the unit is %. The reflectance is shown for each of the S wave and P wave.

Referring to FIGS. 5 to 7, in the illustrated wavelength range of 8 μm to 11 μm, the reflective member 100 of Example 1 has a difference between the reflectance of the S wave and the reflectance of the P wave. It can be seen that it is larger than Example 1 and Comparative Example 2. Since the reflective member of Comparative Example 2 has a configuration in which the SiO film 6 of the outermost layer is omitted from the reflective member 100 of Example 1, the difference between the reflectance to the S wave and the reflectance to the P wave is the SiO film ( You can see that 6) makes it. In addition, comparing FIGS. 6 and 7, it can be seen that Comparative Example 2 has higher reflectance over the entire wavelength range than Comparative Example 1. Since the reflective member of Comparative Example 2 is a structure obtained by adding a SiO film, which is the silicon oxide film 2 on the substrate 1, to the reflective member of Comparative Example 1, the ZnS film 4, and the Ge film 5, SiO It can be seen that the reflectance is improved by forming the film, the ZnS film 4 and the Ge film 5.

8 is a diagram showing reflectance of reflective members of Example 1 and Comparative Example 1 together with the number of reflections. This table shows the reflectance for light having a wavelength of 9.3 µm at each number of reflections.

When the reflective member 100 is used in the laser oscillator 11, light is repeatedly reflected. In this case, the influence of the reflectance on the characteristics of the laser light from which the difference is emitted becomes large. For example, the reflectance of the reflective member 100 of Example 1 to the S wave is 99.7%, the reflectance of the reflective member of Comparative Example 1 to the S wave is 99.1%, and the difference in reflectance is 0.6% for one reflection. . However, if the reflection is repeated 50 times, the reflectance of the reflective member 100 of Example 1 to the S wave is 86.1%, and the reflectance of the reflective member of Comparative Example 1 to the S wave is 63.6%. The car becomes 22.5%. The reflectance of the reflective member 100 in Example 1 with respect to the P wave is 90.4% in one reflection, and the reflectance of the reflective member in Comparative Example 1 with respect to the P wave is 98.3%. In this case, when the reflection is repeated 50 times, the reflectance of the reflective member 100 of Example 1 with respect to the P wave becomes 0.6%, and the reflectance of the reflective member of the comparative example 1 with respect to the P wave becomes 42.4%. As can be seen from FIG. 8, in Comparative Example 1, since the difference between the reflectance to the S wave and the reflectance to the P wave is small, when used in the laser oscillator 11, the P wave component is included in the oscillated laser light. It does not become linearly polarized by mixing. On the other hand, in the first embodiment, since the difference between the reflectance for the S wave and the reflectance for the P wave is large, the P wave is attenuated each time the reflection is repeated. For this reason, when used as the return mirror 25 in the laser oscillator 11, it becomes possible to oscillate linearly polarized laser light.

Referring again to FIG. 7, the reflectance of the reflective member of Comparative Example 2 is 99.7% for the S wave and 99.4% for the P wave. In Comparative Example 2, a high reflectance was achieved as in Example 1, but since the difference in reflectance between the S wave and the P wave was small, when mounted on the laser oscillator 11, linearly polarized laser light could not be output.

Next, using Example 2, Comparative Example 3, and Comparative Example 4 shown below, the effect of the silicon oxide film 2 of the reflective member 100 is verified.

[Example 2]

The material and film thickness of each layer of the reflective member 100 of Example 2 are as follows. The substrate 1 is a mirror-finished, circular Si substrate of 40 mm in diameter, the metal film 3 is an Au film, and the silicon oxide film 2 is a SiO film.

5th layer SiO 150nm

4th layer Ge 590nm

3rd layer ZnS 1120nm

Second layer Au 200nm

First layer SiO 10 nm

Substrate Si 10mm

[Comparative Example 3]

The material and film thickness of each layer of the reflective member of Comparative Example 3 are as follows. Comparative Example 3 is a configuration in which the SiO film, which is the silicon oxide film 2, is omitted from the configuration of Example 2.

4th layer SiO 150nm

3rd layer Ge 590nm

2nd layer ZnS 1120nm

First layer Au 200nm

Substrate Si 10mm

[Comparative Example 4]

The material and film thickness of each layer of the reflective member of Comparative Example 4 are as follows. In Comparative Example 4, the SiO film, which is the silicon oxide film 2 of Example 2, is replaced with a Cr film. Cr is generally used as a material that enhances the adhesion between the substrate and the Au film.

5th layer SiO 150nm

4th layer Ge 590nm

3rd layer ZnS 1120nm

Second layer Au 200nm

1st layer Cr 10nm

Substrate Si 10mm

9 is a table showing durability test results of reflective members of Example 2, Comparative Example 3, and Comparative Example 4. FIG. In this table, the results of the tape peeling test, the results of the high temperature test, and the suitability for a laser oscillator are shown. In Fig. 9, a circle indicates that the test result satisfies the standard, and an X indicates that the standard is not satisfied. Specifically, the tape peeling test is performed by a method according to MIL (MILitary Specifications and Standard)-C-48497A. In the tape peeling test, a tape of the type designated by the above standard is used. After attaching the tape to the film surface of the reflective member, the tape is pulled out at once in a direction perpendicular to the film surface. After that, the peeling state of the film is checked using the naked eye and a microscope. The circle mark in the tape peeling test result indicates that no peeling has occurred, and the X mark indicates that peeling has occurred. In the high-temperature test, the test result is judged based on the characteristics of the reflective member after the reflective member is placed in a high temperature environment of 200°C for 48 hours. In the high-temperature test, after being placed in a high-temperature environment for 48 hours, the reflectance and the state of the film (the presence or absence of at least one of peeling and cracking, etc.) are measured. Circle marks in the results of the high-temperature test indicate that the reflectance is greater than or equal to the threshold value, and X marks indicate that the reflectance is less than the threshold value, and that a decrease in optical properties has occurred. The suitability for a laser oscillator indicates whether or not the target reflective member has suitability for use inside a laser oscillator. The circle mark of suitability for laser oscillators indicates that the suitability is provided, and the X mark indicates that the suitability is not provided. In the example of Fig. 9, when peeling does not occur as a result of the tape peeling test, and the optical characteristic satisfies the standard as a result of the high temperature test, it is determined that conformity is provided.

The reflective member 100 of Example 2 did not peel off as a result of the tape peeling test, and the optical properties satisfied the standard as a result of the high temperature test, so it was judged that it had suitability as a reflective member for a laser oscillator. Has been. The reflective member of Comparative Example 3 does not satisfy the standards in both the tape peeling test and the high temperature test, and it is determined that it does not have suitability as a reflective member for a laser oscillator. The reflective member of Comparative Example 3 is provided with an Au film directly on a Si substrate. If the reflective member of Comparative Example 3 is placed in a high-temperature environment, it can be considered that the cause is that Si diffuses from the substrate into the Au film and the reflectance is lowered. In the reflective member of Comparative Example 4, the standard of the tape peeling test was satisfied, but the standard of the high-temperature test was not satisfied, and it was determined that the suitability for a laser oscillator was not provided. In the reflective member of Comparative Example 4, a Cr film was formed between the Si substrate and the Au film. The Cr film improves adhesion to the substrate, and the reflective member of Comparative Example 4 satisfies the criteria of the tape peeling test. However, the reflective member of Comparative Example 4 does not satisfy the standard of the high temperature test. This can be considered that Si and Cr are diffused into the Au film in a high-temperature environment, and the reflectance of the reflective member is lowering. From the test results shown in Fig. 9, the SiO film provided between the Si substrate and the Au film strengthens the adhesion between the Si substrate and the Au film, similar to the Cr film, and prevents Si from diffusing into the Au film even under a high temperature environment, and reflectance It can be seen that it suppresses the deterioration of. By forming the SiO film between the Si substrate and the Au film, the reflective member 100 can suppress deterioration in performance over time, and has durability that can withstand the internal use of the laser oscillator 11. We have.

Next, using Example 2 above and Examples 3, 4, 5, and 5 shown below, the material of the silicon oxide film 2 of the reflective member 100 and the film of each layer Review the thickness.

The material and film thickness of each layer of the reflective member 100 of Example 2 are as described above. 10 is a diagram showing the optical properties of the reflective member 100 of the second embodiment. At a wavelength of 9.3 mu m, the reflectance of the reflective member 100 of Example 2 with respect to the S wave is 99.5%, and the reflectance with respect to the P wave is 87.2%.

[Example 3]

The material and film thickness of each layer of the reflective member 100 of Example 3 are as follows. The substrate 1 is a mirror-finished 40 mm flat Si substrate, the metal film 3 is an Au film, and the silicon oxide film 2 is a SiO ₂ film. 11 is a diagram showing the optical properties of the reflective member 100 of the third embodiment. At a wavelength of 9.3 µm, the reflectance of the reflective member 100 of Example 3 with respect to the S wave is 99.7%, and the reflectance with respect to the P wave is 95.1%.

5th layer SiO 50nm

4th layer Ge 540nm

3rd layer ZnS 920nm

Second layer Au 200nm

First layer SiO ₂ 10 nm

Substrate Si 10mm

[Example 4]

The material and film thickness of each layer of the reflective member 100 of Example 4 are as follows. The substrate 1 is a mirror-finished 40 mm flat Si substrate, the metal film 3 is an Au film, and the silicon oxide film 2 is a SiO ₂ film. 12 is a diagram showing the optical properties of the reflective member 100 of the fourth embodiment. At a wavelength of 9.3 mu m, the reflectance of the reflective member 100 of Example 4 with respect to the S wave is 99.7%, and the reflectance with respect to the P wave is 86.5%.

5th layer SiO 160nm

4th layer Ge 600nm

3rd layer ZnS 810nm

Second layer Au 200nm

First layer SiO ₂ 10 nm

Substrate Si 10mm

[Example 5]

The material and film thickness of each layer of the reflective member 100 of Example 5 are as follows. The substrate 1 is a mirror-finished 40 mm flat Si substrate, the metal film 3 is an Au film, and the silicon oxide film 2 is a Si ₂ O ₃ film. 13 is a diagram showing the optical properties of the reflective member 100 of the fifth embodiment. At a wavelength of 9.3 mu m, the reflectance of the reflective member 100 of Example 5 with respect to the S wave is 99.6%, and the reflectance with respect to the P wave is 85.1%.

5th layer SiO 180nm

4th layer Ge 550nm

3rd layer ZnS 1110nm

Second layer Au 100nm

First layer Si ₂ O ₃ 15 nm

Substrate Si 10mm

[Comparative Example 5]

The material and film thickness of each layer of the reflective member of Comparative Example 5 are as follows. The substrate is a mirror-finished 40 mm flat Si substrate, the metal film is an Au film, and a Si ₂ O ₃ film is formed between the Si substrate and the Au film. In the reflection member of Comparative Example 5, the thickness of the SiO film of the outermost layer is 340 nm, which is thicker than that of Examples 1 to 5 of the present invention. 14 is a diagram showing the optical properties of the reflective member of Comparative Example 5. FIG. At a wavelength of 9.3 µm, the reflectance of the reflective member of Comparative Example 5 with respect to the S wave was 96.8%, and the reflectance with respect to the P wave was 72.6%.

5th layer SiO 340 nm

4th layer Ge 550nm

3rd layer ZnS 1110nm

Second layer Au 100nm

First layer Si₂O₃ 15nm

Substrate Si 10mm

10 to 13, in the reflective members 100 of the second to fifth embodiments of the present invention, in the infrared wavelength region, the difference between the reflectance of the S wave and the reflectance of the P wave is the first embodiment. It can be seen that it is as large as the same.

15 is a diagram showing reflectance of reflective members of Examples 2 to 5 and Comparative Example 5 together with the number of reflections. Referring to FIG. 15, it can be seen that the difference between the reflectance for the S wave and the reflectance for the P wave increases each time reflection is repeated in the reflective member 100 of the second to fifth embodiments. For this reason, it is possible to attenuate the P wave, and at the same time, it is possible to maintain a high reflectance even if the reflection is repeated for the S wave. For this reason, when the reflective member 100 of the second to fifth embodiments is used as the return mirror 25 in the laser oscillator 11, it is possible to oscillate linearly polarized infrared laser light.

Referring to FIG. 15, in the reflective member of Comparative Example 5, the difference between the reflectance of the S wave and the reflectance of the P wave is large, and the P wave can be attenuated by repeating the reflection. However, the reflective member of Comparative Example 5 is not sufficient because the reflectance of the S wave is used as the return mirror 25 of the laser oscillator 11, and the S wave is also attenuated every time the reflection is repeated, and a laser of sufficient intensity Can't oscillate light.

16 is a diagram showing durability test results of reflective members of Examples 1, 3, 4, and 5; The test contents shown in FIG. 16 are the same as those in FIG. 9. Referring to FIG. 16, it can be seen that all of the reflective members 100 of Examples 1, 3, 4, and 5 have durability that can withstand use within the laser oscillator 11. have.

A silicon oxide film 2, Examples 1 and 2, silicon monoxide, and (SiO) film, Example 3 and Example 4, a film of silicon dioxide (SiO _2), Example 5, nitrous silicon (Si ₂ O ₃ ) It is a film. Referring to FIG. 16, it can be seen that it is possible to construct a reflective member 100 having durability that can withstand use in the laser oscillator 11 even when any silicon oxide film 2 is used.

In addition to the above experimental results, as a result of an experiment in which the film thickness of each layer of the reflective member 100 is changed, when the film thickness of each layer of the reflective member 100 is in the following range, "metal film, Ge film" Since the tensile stress of the "ZnS film, SiO film" is canceled by the compressive stress of the "ZnS film, SiO film", the durability against high temperature test is improved, and the durability that the reflective member 100 can withstand use in the laser oscillator 11 is improved. It was confirmed to be equipped. Therefore, it is preferable that the film thickness of each layer of the reflective member 100 falls within the following range.

First layer silicon oxide film (2) 1 nm or more and 50 nm or less

Second layer metal film (3) 20 nm or more and 400 nm or less

Third layer ZnS film (4) 700 nm or more and 1400 nm or less

Fourth layer Ge film (5) 450 nm or more and 650 nm or less

5th layer SiO film (6) 20 nm or more and 250 nm or less

Further, in order to obtain a reflective member that can withstand a harsher high-temperature test (72 hours) and has a long product life, it is more preferable that the film thickness of each layer of the reflective member 100 is in the following range.

First layer silicon oxide film (2) 1 nm or more and 50 nm or less

Second layer metal film (3) 20 nm or more and 300 nm or less

Third layer ZnS film (4) 800 nm or more and 1200 nm or less

Fourth layer Ge film (5) 500 nm or more and 600 nm or less

5th layer SiO film (6) 20 nm or more and 200 nm or less

The configurations shown in the above embodiments represent an example of the content of the present invention, and may be combined with other known techniques, and some of the configurations may be omitted or changed without departing from the gist of the present invention. Do.

For example, in the above-described embodiment, a configuration in which the ZnS film 4 and the Ge film 5 are omitted, and a configuration diagram in which the ZnS film 4 and the Ge film 5 are replaced with films of different materials, It is within the scope of the technical idea of the present invention. When replacing the ZnS film 4 and the Ge film 5 with films made of different materials, it is preferable to use a material that increases the reflectance of infrared laser light. Alternatively, in the above-described embodiment, instead of the silicon oxide film 2, a film that increases the adhesion between the metal film 3 and the substrate 1 may be used.

Embodiment 2.

In Embodiment 2, an example in which Cu (copper) is used as the substrate of the reflective member is shown. 19 is a second configuration diagram of a reflective member 200 usable as the return mirror 25 shown in FIG. 2. The reflective member 200 shown in FIG. 19 includes a substrate 1, a metal film 3, and a SiO film 6. The metal film 3 and the SiO film 6 are formed in the above-described order from the side closer to the substrate 1.

FIG. 20 is a third configuration diagram of a reflective member 300 usable as the return mirror 25 shown in FIG. 2. The reflective member 300 shown in FIG. 20 includes a substrate 1, a metal film 3, a ZnS film 4, a Ge film 5, and a SiO film 6. The metal film 3, the ZnS film 4, the Ge film 5, and the SiO film 6 are formed in the above-described order from the side closer to the substrate 1.

21 is a fourth configuration diagram of a reflective member 400 usable as the return mirror 25 shown in FIG. 2. The reflective member 400 shown in FIG. 21 includes a substrate 1, a Cr (chromium) film 7, a metal film 3, and a SiO film 6. The Cr film 7, the metal film 3, and the SiO film 6 are formed in the above-described order from the side closer to the substrate 1.

The reflective member 200, the reflective member 300, and the reflective member 400, like the reflective member 100, are reflective members for infrared lasers having a high reflectance for infrared laser light. In addition, the reflective member 200, the reflective member 300, and the reflective member 400, like the reflective member 100, have a lower reflectance for the P wave than the reflectance for the S wave. The wave is attenuated larger than the S wave.

Next, examples of the reflective member 200, the reflective member 300, and the reflective member 400 according to Embodiment 2 of the present invention will be described. Example 6 shown below is an example of the reflective member 200, Examples 7 to 10 are examples of the reflective member 300, and Example 11 is an example of the reflective member 400.

[Example 6]

The material and film thickness of each layer of the reflective member 200 of Example 6 are as follows. The substrate 1 is a Cu substrate of each flat plate with a diameter of 40 mm that has been mirror-finished, and the metal film 3 is an Au film.

Second layer SiO 150 nm

First layer Au 200nm

Substrate Cu 10mm

22 is a diagram showing the optical properties of the reflective member 200 of the sixth embodiment. At a wavelength of 9.3 μm, the reflectance of the reflective member 200 of Example 6 with respect to the S wave is 98.8%, and the reflectance with respect to the P wave is 86.1%.

[Example 7]

The material and film thickness of each layer of the reflective member 300 of Example 7 are as follows. The substrate 1 is a Cu substrate of each flat plate with a diameter of 40 mm that has been mirror-finished, and the metal film 3 is an Au film.

4th layer SiO 90nm

3rd layer Ge 570nm

2nd layer ZnS 930nm

1st layer Au 300nm

Substrate Cu 10mm

23 is a diagram showing the optical properties of the reflective member 300 of the seventh embodiment. At a wavelength of 9.3 μm, the reflectance of the reflective member 300 of Example 7 with respect to the S wave is 99.7%, and the reflectance with respect to the P wave is 92.0%. In addition, the phase difference between the P wave and the S wave in the reflective member 300 of Example 7 is -0.9°.

[Example 8]

The material and film thickness of each layer of the reflective member 300 of Example 8 are as follows. The substrate 1 is a circular Cu substrate having a diameter of 40 mm that has been mirror-finished, and the metal film 3 is an Au film.

4th layer SiO 60nm

3rd layer Ge 540nm

2nd layer ZnS 1060nm

First layer Au 100 nm

Substrate Cu 10mm

24 is a diagram showing the optical properties of the reflective member 300 of the eighth embodiment. At a wavelength of 9.3 mu m, the reflectance of the reflective member 300 of Example 8 with respect to the S wave is 99.7%, and the reflectance with respect to the P wave is 94.4%. In addition, the phase difference between the P wave and the S wave in the reflective member 300 of Example 8 is 0.1°.

[Example 9]

The material and film thickness of each layer of the reflective member 300 of Example 9 are as follows. The substrate 1 is a circular Cu substrate having a diameter of 40 mm that has been mirror-finished, and the metal film 3 is an Au film.

4th layer SiO 170nm

3rd layer Ge 530nm

2nd layer ZnS 840nm

First layer Au 100 nm

Substrate Cu 10mm

25 is a diagram showing the optical properties of the reflective member 300 according to the ninth embodiment. At a wavelength of 9.3 μm, the reflectance of the reflective member 300 of Example 9 with respect to the S wave is 99.7%, and the reflectance with respect to the P wave is 85.4%. In addition, the phase difference between the P wave and the S wave in the reflective member 300 of Example 9 is -1.0°.

[Example 10]

The material and film thickness of each layer of the reflective member 300 of Example 10 are as follows. The substrate 1 is a circular Cu substrate having a diameter of 40 mm that has been mirror-finished, and the metal film 3 is an Au film.

4th layer SiO 230nm

3rd layer Ge 530nm

2nd layer ZnS 710nm

First layer Au 100 nm

Substrate Cu 10mm

26 is a diagram showing the optical properties of the reflective member 300 of the tenth embodiment. At a wavelength of 9.3 mu m, the reflectance of the reflective member 300 of Example 10 with respect to the S wave is 99.1%, and the reflectance with respect to the P wave is 80.6%. In addition, the phase difference between the P wave and the S wave in the reflective member 300 of Example 10 is -1.3°.

[Example 11]

The material and film thickness of each layer of the reflective member 400 of Example 11 are as follows. The substrate 1 is a Cu substrate of each flat plate with a diameter of 40 mm that has been mirror-finished, and the metal film 3 is an Au film.

3rd layer SiO 150nm

Second layer Au 200nm

1st layer Cr 10nm

Substrate Cu 10mm

27 is a diagram showing the optical properties of the reflective member 400 of the eleventh embodiment. At a wavelength of 9.3 µm, the reflectance of the reflective member 400 of Example 11 with respect to the S wave is 98.8%, and the reflectance with respect to the P wave is 86.1%.

[Comparative Example 6]

The material and film thickness of each layer of the reflective member of Comparative Example 6 are as follows. The substrate is a circular Cu substrate with a diameter of 40 mm mirror-finished, and the metal film is an Au film. The reflective member of Comparative Example 6 has a configuration in which the outermost layer is not a SiO film but a SiO _{2 film.}

Second layer SiO ₂ 150 nm

First layer Au 100 nm

Substrate Cu 10mm

28 is a diagram showing the optical properties of the reflective member of Comparative Example 6. FIG. At a wavelength of 9.3 μm, the reflectance of the reflective member of Comparative Example 6 with respect to the S wave was 97.7%, and the reflectance with respect to the P wave was 92.9%.

[Comparative Example 7]

The material and film thickness of each layer of the reflective member of Comparative Example 7 are as follows. The substrate is a circular Cu substrate with a diameter of 40 mm mirror-finished, and the metal film is an Au film. The reflective member of Comparative Example 7 has a configuration in which the outermost layer is not a SiO film, but a ZnS film.

2nd layer ZnS 150nm

First layer Au 100 nm

Substrate Cu 10mm

29 is a diagram showing the optical properties of the reflective member of Comparative Example 7. FIG. At a wavelength of 9.3 µm, the reflectance of the reflective member of Comparative Example 7 with respect to the S wave was 99.1%, and the reflectance with respect to the P wave was 98.2%.

[Comparative Example 8]

The material and the film thickness of each layer of the reflective member of Comparative Example 8 are the configurations cited in Patent Document 1. The substrate is a mirror-finished circular Cu substrate having a diameter of 40 mm, and the metal film of the second layer is an Au film. The reflective member of Comparative Example 7 has a configuration in which the outermost layer is not a SiO film but a Ge film.

7th layer Ge 670nm

6th layer ZnS 1170nm

5th layer Ge 670nm

4th layer ZnS 1170nm

3rd layer HfO ₂ 100nm

2nd layer Au 300nm

1st layer Cr 100nm

Substrate Cu 4mm

30 is a diagram showing the optical properties of the reflective member of Comparative Example 8. FIG. At a wavelength of 9.3 μm, the reflectance of the reflective member of Comparative Example 8 with respect to the S wave was 99.9%, and the reflectance with respect to the P wave was 99.7%.

31 and 32 are diagrams showing reflectances of the reflective members of Examples 6 to 11 and the reflective members of Comparative Examples 6 to 8 together with the number of reflections, respectively. In the reflective members 200, 300, and 400 of the sixth to eleventh embodiments, the difference between the reflectance for the S wave and the reflectance for the P wave increases each time the reflection is repeated. For this reason, it is possible to attenuate the P wave, and at the same time, it is possible to maintain a high reflectance even if the reflection is repeated for the S wave. When the reflection is repeated 50 times, the reflectance of the S wave is 50% or more, and the ratio of the reflectance of the S wave and P wave is 10 or more. When the reflective members 200, 300, and 400 of Examples 6 to 11 are used as the return mirror 25 in the laser oscillator 11, it is possible to oscillate linearly polarized infrared laser light.

On the other hand, in the reflective member of Comparative Example 6, the reflectance for the S wave decreases every time the reflection is repeated, and when the reflection is repeated 50 times, the reflectance of the S wave does not reach 40% as a reference. For this reason, the reflective member of Comparative Example 6 is not sufficient because the reflectance of the S wave is used as the return mirror 25 of the laser oscillator 11, and the S wave is also attenuated every time the reflection is repeated, and sufficient intensity. Cannot oscillate the laser light.

In addition, in the reflective member of Comparative Example 7, when the reflection is repeated 50 times, the reflectance to the S wave exceeds 40%. However, the ratio of the reflectance of the S wave and the P wave is almost 1:1, and a difference in reflectance is not obtained. For this reason, when the reflective member of Comparative Example 7 is mounted on a laser oscillator, since the P wave component is mixed with the oscillated laser light, linearly polarized laser light cannot be output. Also for the reflective member of Comparative Example 8, for the same reason, linearly polarized laser light cannot be output.

33 is a table showing durability test results of reflective members of Examples 6 to 11. In this table, the results of the tape peeling test, the results of the high temperature test, and the suitability for a laser oscillator are shown. In the reflective members 200, 300, and 400 of Examples 6 to 11, as a result of the tape peeling test, no peeling occurred, and as a result of the high-temperature test, the optical properties satisfied the standard. It is determined that it has suitability as a reflective member. In the case of the Cu substrate, the diffusion of the substrate elements into the Au film as in the Si substrate was not observed. In order to enhance adhesion, a film such as oxide or sulfide may be formed between the Cu substrate and the metal film.

The reflective member 300 of Examples 7 to 10 includes a substrate, a metal film, a ZnS film, a Ge film, and a SiO film, and a metal film, a ZnS film, a Ge film, and a SiO film are formed on the substrate. From the nearer side, they are formed in the above-described order. In such a reflective member 300, by setting the film thickness of each layer in the following range, a difference in reflectance is created between the S wave and the P wave while obtaining a high reflectance for the S wave, and further, S The phase difference between the wave and the P wave can be controlled within ±1°. Such a reflective member contributes to high output and stabilization of oscillation of the laser oscillator.

First layer metal film 50 nm or more and 300 nm or less

2nd layer ZnS film 820 nm or more and 1080 nm or less

Third layer Ge film 520 nm or more and 590 nm or less

4th layer SiO film 40 nm or more and 180 nm or less

As described above, by applying the reflective member of the present invention, a linearly polarized laser oscillator having an industrially usable output can be realized.

Embodiment 3.

In Embodiment 3, an example of a laser oscillator using at least one of the reflective member 100, the reflective member 200, the reflective member 300, and the reflective member 400 of the present invention is shown.

34 is another configuration diagram of the laser oscillator 11 shown in FIG. 1. The laser oscillator 11 includes a partial reflection mirror 41, an orthogonal mirror 42 for reflecting the laser light reflected by the partial reflection mirror 41 along the optical axis of the laser light, and a pair of discharge electrodes ( 43, 44), and provided with a laser gas functioning as a laser medium. The partial reflection mirror 41 functions as an output mirror that takes out a part of the oscillated laser light to the outside as the laser light 45. The orthogonal mirror 42 has two reflective surfaces that are orthogonal, and a line where both reflective surfaces intersect is referred to as a "curve" in this specification. The gas flow direction of the laser gas, the discharge direction of the pair of discharge electrodes 43 and 44, and the direction of the optical axis between the partial reflection mirror 41 and the orthogonal mirror 42 are orthogonal to each other. The direction of the laser gas flow is referred to as the x direction, the discharge directions of the discharge electrodes 43 and 44 are referred to as the y direction, and the optical axis between the partial reflection mirror 41 and the orthogonal mirror 42 is referred to as the z direction.

The discharge electrodes 43 and 44 are provided on the rear surfaces opposite to the facing surfaces of the dielectric plates 46 and 47, respectively, and are connected to the high-frequency power supply 49 via a power supply line 48. When an alternating voltage is applied between the discharge electrodes 43 and 44, a uniform glow discharge is formed. A laser gas is supplied between the discharge electrodes 43 and 44 in the direction indicated by the arrow 50, and when molecules or atoms in the laser gas are excited at the laser phase level by glow discharge, the amplifying action of light is exhibited. For example, when a mixed gas containing _{CO 2} molecules is used as the laser gas, laser amplification with a wavelength of 9.3 μm is possible due to the transition between vibration levels of the _{CO 2 molecules.}

FIG. 35 is a diagram showing an energy gain distribution in the laser oscillator 11 shown in FIG. 34. The gain distribution along the y direction of the discharge direction is generally constant. On the other hand, the gain distribution along the x direction in the gas flow direction varies greatly depending on the position. This is because, when the laser gas passes through the glow discharge 51, the laser phase level is sequentially accumulated with an increase in the passing time. The gain is low on the gas upstream side of the glow discharge 51, the highest on the gas downstream side, and becomes a mountain-shaped distribution shape that gradually decreases outside the glow discharge 51.

When a planar reflecting mirror other than the orthogonal mirror 42 is used, a problem arises in that a high-order transverse mode appears in the y direction. Therefore, the reference axis 52 is set in the direction of an angle of 45 degrees with respect to the y direction, which is the discharge direction, and the orthogonal mirror 42 is arranged so that the curve of the orthogonal mirror 42 is parallel to the reference axis 52. . Thereby, the laser light reflected by the orthogonal mirror 42 becomes the same as the image in which the mirror-symmetric image with respect to the reference axis 52 of the incident laser light is rotated 90 degrees around the optical axis. That is, the effects of the gain distribution 62 along the y direction and the gain distribution 63 along the x direction can be averaged. Therefore, in such a laser oscillator 11, a high-order transverse mode can be suppressed in the x-direction and y-direction, and laser light having excellent isotropic beam intensity can be stably obtained.

In the laser oscillator 11 having such a configuration, in order to obtain linearly polarized laser light, at least one of the two reflective surfaces of the orthogonal mirror 42 is a reflective member (100, 200, 300, and 400). It is at least one of them. For example, when the reflective member on which the Au film is formed as shown in Comparative Example 1 is applied to both surfaces of the orthogonal mirror 42, as described above, linearly polarized lasers are not generated. Randomly polarized laser light, which cannot be said to be isotropic, appears.

On the other hand, by applying at least one of the reflective members 100, 200, 300 and 400 to at least one of the two reflective surfaces of the orthogonal mirror 42, while the laser is amplified, orthogonal The S-wave laser light to the mold mirror 42 survives, and the P-wave laser light orthogonal thereto disappears. That is, linearly polarized laser light is realized.

In this way, in order to realize the laser oscillator 11 that has sufficient output for industrial use, has an isotropic beam intensity, and oscillates a linearly polarized laser, the reflective members 100, 200, 300 of the present invention. , 400) is indispensable.

36 shows the results of evaluating performance by applying the reflective members of Examples 2, 6, 7, Comparative Example 1, Comparative Example 6, and Comparative Example 8 to one surface of an orthogonal mirror and mounted on a laser oscillator. Show. Here, the evaluation results are indicated by the symbols ◎, ○, and × in order from the good result. By adopting the configuration of a laser oscillator in which the partial reflection mirror 41 and the orthogonal mirror 42 constitute a resonator, laser light that is isotropic with respect to the beam intensity is obtained. On the other hand, when comparing the realization of linearly polarized light, linearly polarized light is obtained in the laser oscillator to which the reflective member of the present invention is applied, but linearly polarized light is not obtained in the laser oscillator to which the conventional reflective member shown in Comparative Examples 1 and 8 is applied. Further, when the reflective member of the present invention was applied, industrially usable oscillation output could be realized, but in the laser oscillator to which the conventional reflective member shown in Comparative Example 6 was applied, sufficient oscillation output was not obtained.

When a laser oscillator is actually used, in reality, the density and distribution of gas flows inside the oscillator are not constant, so the optical axis is not necessarily straight, but slightly crooked. That is, not only the S-wave component laser resonates as a theory, but a part of the S-wave component laser turns into a P-wave component, and the P-wave component laser resonates like the S-wave component for a certain period of time. For the above reason, this P-wave component also changes to an S-wave component when reflected by an orthogonal mirror. When the P wave returns to the S wave, if there is a phase difference between the original S wave and the P wave, the energy of the P wave is not supplied and disappears. For this reason, in order to realize a laser oscillator excellent in energy utilization efficiency, it is preferable to use the following reflective members having controlled phase difference.

First layer metal film 50 nm or more and 300 nm or less

2nd layer ZnS film 820 nm or more and 1080 nm or less

Third layer Ge film 520 nm or more and 590 nm or less

4th layer SiO film 40 nm or more and 180 nm or less

The configurations shown in the above embodiments represent an example of the content of the present invention, and may be combined with other known techniques, and some of the configurations may be omitted or changed without departing from the gist of the present invention. Do. According to the present invention, it is possible to realize a laser oscillator that has sufficient output for industrial use, has an isotropic beam intensity, and oscillates a linearly polarized laser.

1: substrate 2: silicon oxide film
3: metal film 4: ZnS film
5: Ge film 6: SiO film
7: Cr film 10: laser processing device
11: laser oscillator 12: polarization conversion member
13: condensing optical system 14: processing table
15: drive unit 16: control unit
17: object to be processed 41: partial reflection mirror
42: orthogonal mirror 43, 44: discharge electrode
46, 47: dielectric plate 48: feed line
49: high frequency power
100, 200, 300, 400: reflective member

Claims (15)

In a laser oscillator that oscillates infrared laser light,
It has a reflective member for an infrared laser,
The reflective member for infrared lasers,
The substrate,
SiO film,
Characterized in that it has a metal film formed between the substrate and the SiO film
Laser oscillator. The method according to claim 1,
A ZnS film formed between the metal film and the SiO film,
Characterized in that it further comprises a Ge film formed between the ZnS film and the SiO film
Laser oscillator. The method according to claim 2,
The thickness of the metal film is 20 nm or more and 400 nm or less,
The film thickness of the ZnS film is 700 nm or more and 1200 nm or less,
The thickness of the Ge film is 450 nm or more and 650 nm or less,
The SiO film has a thickness of 20 nm or more and 250 nm or less.
Laser oscillator. The method according to claim 1,
The metal film is characterized in that the Au film
Laser oscillator. The method of claim 4,
The substrate is a Si substrate,
Characterized in that it further comprises a silicon oxide film formed between the substrate and the Au film
Laser oscillator. The method of claim 5,
The silicon oxide film has a thickness of 1 nm or more and 50 nm or less.
Laser oscillator. The method of claim 5,
The silicon oxide film is characterized in that the SiO film, SiO ₂ film or Si ₂ O _{3 film}
Laser oscillator. The method of claim 6,
The silicon oxide film is characterized in that the SiO film, SiO ₂ film or Si ₂ O _{3 film}
Laser oscillator. The method according to claim 2,
The thickness of the metal film is 20 nm or more and 300 nm or less,
The thickness of the ZnS film is 820 nm or more and 1080 nm or less,
The thickness of the Ge film is 520 nm or more and 590 nm or less,
The SiO film has a thickness of 40 nm or more and 180 nm or less.
Laser oscillator. The method according to claim 1,
Characterized in that it outputs laser light with a wavelength of 8.3㎛ or more and 9.8㎛ or less
Laser oscillator. The method according to any one of claims 1 to 10,
With a partial reflection mirror,
An orthogonal mirror having two reflective surfaces orthogonal to each other, and reflecting the laser light reflected by the partial reflecting mirror along the optical axis of the laser light,
A pair of discharge electrodes,
And a laser gas supplied between the pair of discharge electrodes and functioning as a laser medium,
The discharge direction of the pair of discharge electrodes, the gas flow direction of the laser gas, and the direction of the optical axis are orthogonal to each other,
The orthogonal mirror has a reference axis in which a curve, which is a line where the two reflective surfaces of the orthogonal mirror intersect, crosses at an angle of 45 degrees with respect to the discharge direction in a plane orthogonal to the optical axis. Are arranged to be parallel,
At least one of the two reflective surfaces of the orthogonal mirror is a reflective member for the infrared laser.
Laser oscillator. It is characterized by comprising the laser oscillator according to any one of claims 1 to 10.
Laser processing device. Comprising the laser oscillator according to claim 11
Laser processing device. delete delete

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