Beam combiner and beam combiner system

Abstract

The objective of the present invention is to provide: a beam combiner in which the intensity of blue laser light after coupling is sufficiently strong and a temperature rise is suppressed; and a beam combiner system including the beam combiner. A beam combiner (1) according to the present invention comprises a substrate (2) and an optical multilayer film (4) formed directly on a substrate surface (Q), which is the surface of the substrate (2). The optical multilayer film (4) has alternating low refractive index layers and high refractive index layers, transmits first laser light (L1) in the blue region of p-polarized light, and reflects polarization-converted laser light (LZ) in the blue region of s-polarized light. Each high refractive index layer of the optical multilayer film 4 is an HfO2 layer made of HfO2 and contains a monoclinic crystal. The (-111) plane of the monoclinic crystal is oriented in the direction perpendicular to the substrate surface (Q).

Description

Beam combiners and beam combiner systems

[0001] This disclosure relates to a beam combiner for combining multiple blue laser beams, and a beam combiner system including the beam combiner.

[0002] In the optical system of a laser processing machine, a beam combiner for synthesizing laser light, such as the one described in Patent Document 1 (Japanese Patent Application Publication No. 2022-6981), is used. Such a beam combiner transmits p-polarized laser light and reflects s-polarized laser light, which is polarized perpendicular to p-polarization, thereby synthesizing p-polarized and s-polarized laser light.

[0003] Japanese Patent Publication No. 2022-6981

[0004] Recently, high-quality processing of metals, including copper, aluminum, and their alloys, has been required in various processing applications, including the manufacturing of automotive batteries. The absorption rate of copper and aluminum for light with wavelengths around 1000 nm is low, at about 10-20%, making high-quality and efficient laser processing at this wavelength difficult. On the other hand, the absorption rate of copper and aluminum for light in the blue region with shorter wavelengths, such as 400 nm to 500 nm, i.e., blue light, is high, at about 20-80%. Therefore, copper and aluminum can be welded with high quality and efficiency using laser light at this wavelength (blue laser light). Laser diodes (LDs) are used to generate blue laser light. In the coupling of blue laser light, relatively large energy is handled, so the temperature rise of the beam combiner itself tends to be large. If the temperature rise of the beam combiner becomes too large, the quality of the coupled blue laser light deteriorates, affecting subsequent optical elements in the optical system. In addition, a large temperature rise of the beam combiner also affects the durability of the beam combiner. Therefore, suppression of the temperature rise of the beam combiner is required. The beam combiner of the laser processing machine described in Patent Document 1 is only described as simply combining laser beams perpendicular to each other. Furthermore, Patent Document 1 does not suggest anything about the coupling of blue laser beams or the specific structure of the beam combiner.

[0005] Therefore, one of the main objects of the present disclosure is to provide a beam combiner in which the intensity of the combined blue laser light is sufficiently strong and the temperature rise is suppressed. Another main object of the present disclosure is to provide a beam combiner system including a beam combiner in which the intensity of the combined blue laser light is sufficiently strong and the temperature rise is suppressed.

[0006] This specification discloses a beam combiner. The beam combiner may include a substrate. The beam combiner may include an optical multilayer film formed directly or indirectly on the substrate surface which is the surface of the substrate. The optical multilayer film may alternately have a low refractive index layer and a high refractive index layer. The optical multilayer film may transmit p-polarized blue laser light. The optical multilayer film may reflect s-polarized blue laser light. The high refractive index layer may be an HfO ２ -made HfO ２ layer. The high refractive index layer may contain monoclinic crystals. The (-111) plane of the monoclinic crystal may be oriented in the direction perpendicular to the substrate surface.

[0007] Furthermore, this specification discloses a beam combiner. The beam combiner may include a substrate. The beam combiner may include an optical multilayer film formed directly or indirectly on the substrate surface which is the surface of the substrate. The optical multilayer film may alternately have a low refractive index layer and a high refractive index layer. The optical multilayer film may transmit p-polarized blue laser light. The optical multilayer film may reflect s-polarized blue laser light. The high refractive index layer may be an HfO ２ -made HfO ２ layer. The temperature rise characteristic of the optical multilayer film may be a characteristic that when formed on a synthetic quartz substrate and irradiated with 500 W of p-polarized blue laser light and 500 W of s-polarized blue laser light, the temperature rise is within 100 °C.

[0008] Furthermore, this specification discloses a beam combiner system. The beam combiner system may include a first beam combiner that reflects s-polarized laser light in the short wavelength side of the blue region. The beam combiner system may include a second beam combiner that reflects s-polarized laser light in the long wavelength side of the blue region. The beam combiner system may include a first light source that outputs a first laser light which is p-polarized blue laser light. The beam combiner system may include a second-1 light source that outputs a second-1 laser light which is p-polarized laser light in the short wavelength side of the blue region. The beam combiner system may include a first polarization converter which is a polarization converter that converts the second-1 laser light into s-polarization. The beam combiner system may include a second-2 light source that outputs a second-2 laser light which is p-polarized laser light in the long wavelength side of the blue region. The beam combiner system may include a second polarization converter which is a polarization converter that converts the second-2 laser light into s-polarization. The first beam combiner may combine the first laser light and the second-1 laser light converted into s-polarization by the first polarization converter, and send the combined light as the first combined light to the second beam combiner. The second beam combiner may combine the first combined light and the second-2 laser light converted into s-polarization by the second polarization converter, and output the combined light as the second combined light.

[0009] One of the main effects of the present disclosure is to provide a beam combiner in which the intensity of the combined blue laser light is sufficiently strong and the temperature rise is suppressed. Another main effect of the present disclosure is to provide a beam combiner system including a beam combiner in which the intensity of the combined blue laser light is sufficiently strong and the temperature rise is suppressed.

[0010] This is a schematic cross-sectional view of the beam combiner according to the present disclosure. This is a block diagram of the optical system according to the first embodiment of a laser processing machine including the beam combiner according to the present disclosure. This is a block diagram of the optical system according to the second embodiment of a laser processing machine including the beam combiner according to the present disclosure. This is a block diagram of the optical system according to the third embodiment of a laser processing machine including the beam combiner according to the present disclosure. This is a graph showing the spectral transmittance of p-polarized blue light incident at an incident angle of 55° to the optical multilayer film side of Study Example 1. This is a graph showing the spectral reflectance of s-polarized blue light incident at an incident angle of 55° to the optical multilayer film side of Study Example 1. This is a graph showing the relationship between the output of the output laser light and the temperature rise in Study Examples 1 and 2. This is a schematic diagram relating to X-ray diffraction. Study Examples 1 to 5, and SiO ２ - RAS and SiO ２- This graph shows the measurement results of X-ray diffraction related to PARMS. Figure 8 is an enlarged view of the portion where 2θ is in the range of 25° to 35° for Study Examples 1 to 5. This is the pole figure for Study Example 1 where 2θ ≈ 28.5. This is the pole figure for Study Example 2 where 2θ ≈ 28.5. This is the pole figure for Study Example 3 where 2θ ≈ 28.5. This is the pole figure for Study Example 4 where 2θ ≈ 28.5. This is the pole figure for Study Example 2 where 2θ ≈ 30.5. This is the pole figure for Study Example 3 where 2θ ≈ 31.5. This is the pole figure for Study Example 4 where 2θ ≈ 30.5. This is the pole figure for Study Example 4 where 2θ ≈ 31.5. These graphs correspond to the cross-sectional views of each pole figure for Study Examples 1 to 4 at the peak of 2θ ≈ 28.5. These graphs correspond to the cross-sectional views of the pole figures for Study Examples 2 and 4 at the peak of 2θ ≈ 30.5. These graphs correspond to the cross-sectional views of the pole figures for Study Examples 3 and 4 at the peak of 2θ ≈ 31.5. These graphs show the relationship between the plate thickness of the substrate and the temperature rise for p-polarization or s-polarization. These graphs show the relationship between the temperature rise for p-polarization and the temperature rise for s-polarization. These graphs show the film absorption rate for Study Examples 9 to 12 and the temperature rise for Study Examples 9 to 10 related to p-polarization. These graphs show the film absorption rate for Study Examples 9 to 12 and the temperature rise for Study Examples 9 to 10 related to s-polarization. This image shows the electric field intensity distribution generated for p-polarized blue laser light in the optical multilayer film (RAS) of Study Example 1. This image shows the electric field intensity distribution generated for s-polarized blue laser light in the optical multilayer film (RAS) of Study Example 1. This image shows the electric field intensity distribution generated for p-polarized blue laser light in the optical multilayer film (PARMS) of Study Example 2. This image shows the electric field intensity distribution generated in the optical multilayer film of Study Example 2 in response to s-polarized blue laser light. This image shows the electric field intensity distribution generated in the optical multilayer film (IAD) of Study Example 3 in response to p-polarized blue laser light. This image shows the electric field intensity distribution generated in the optical multilayer film of Study Example 3 in response to s-polarized blue laser light. This image shows the electric field intensity distribution generated in the optical multilayer film (IBS) of Study Example 5 in response to p-polarized blue laser light. This image shows the electric field intensity distribution generated in the optical multilayer film of Study Example 5 in response to s-polarized blue laser light.This graph shows the spectral transmittance of p-polarized blue light incident at an incident angle of 55° to the optical multilayer film side of Study Example 13. This graph shows the spectral reflectance of s-polarized blue light incident at an incident angle of 55° to the optical multilayer film side of Study Example 13. This graph shows the spectral transmittance of p-polarized blue light incident at an incident angle of 55° to the optical multilayer film side of Study Example 14. This graph shows the spectral reflectance of s-polarized blue light incident at an incident angle of 55° to the optical multilayer film side of Study Example 14. This image shows the electric field intensity distribution generated in the optical multilayer film of Study Example 13 for p-polarized blue laser light. This image shows the electric field intensity distribution generated in the optical multilayer film of Study Example 13 for s-polarized blue laser light. This image shows the electric field intensity distribution generated in the optical multilayer film of Study Example 14 for p-polarized blue laser light. This image shows the electric field intensity distribution generated in the optical multilayer film of Study Example 14 for s-polarized blue laser light.

[0011] Examples of embodiments relating to this disclosure will be described below with reference to the drawings as appropriate. However, the embodiments of this disclosure are not limited to these examples.

[0012] [Basic Configuration of Beam Combiner] As shown in Figure 1, the beam combiner 1 according to this disclosure comprises a substrate 2 and an optical multilayer film 4. The substrate 2 has a substrate surface Q on which the optical multilayer film 4 is directly deposited, serving as the deposition surface. The beam combiner 1 transmits p-polarized blue laser light and reflects s-polarized blue laser light in the optical multilayer film 4 laminated on the substrate surface Q. The transmittance of p-polarized light in the blue region in the optical multilayer film 4 is highest when the incident angle of the blue laser light is equal to the Brewster angle of the substrate 2. For example, the Brewster angle of a substrate 2 made of synthetic quartz is 55°. The optical multilayer film 4 may also be deposited indirectly on the substrate surface Q, which is the surface of the substrate 2, via another film. In this case, the outer surface of the other film becomes the deposition surface. In addition, another type of film, such as at least one of a protective film and an anti-fouling film, may be placed outside the optical multilayer film 4. This other type of film may be a single layer or a multilayer film. The configuration of the optical multilayer film 4 may include the configuration of the other type of film. The outside of the optical multilayer film 4 can also be called the incident medium side. The incident medium is, for example, air.

[0013] The substrate 2 is translucent. The material of the substrate 2 is not particularly limited. In order to fully exhibit the performance that the beam combiner 1 can have by suppressing the deformation of the optical multilayer film 4 formed on the substrate 2, it is desirable that the material of the substrate 2 be resistant to deformation even when receiving high-energy blue laser light. Therefore, the material of the substrate 2 is preferably glass, crystal, or ceramic. In addition, in order to obtain sufficient heat dissipation, it is more desirable that the material of the substrate 2 be one with high thermal conductivity, such as sapphire crystal or sapphire ceramic. The shape of the substrate 2 is not particularly limited, and is, for example, a parallel plate or a wedge plate.

[0014] The optical multilayer film 4 contributes to the coupling of blue laser light (blue light) and is, for example, an inorganic multilayer film using a dielectric material or a semiconductor material. More specifically, the optical multilayer film 4 is a dielectric multilayer film or a semiconductor multilayer film. The optical multilayer film 4 is formed on a part or all of at least one surface of the substrate 2.

[0015] The beam combiner 1 may further have an optical film other than the optical multilayer film 4. For example, the optical multilayer film 4 may be deposited on one side of a plate-shaped substrate 2, which is the substrate surface Q, and the optical film may be deposited on the opposite side of the substrate surface Q. In this case, the optical film may be a film that increases at least one of the reflectance and transmittance of the optical multilayer film 4 on the substrate surface Q. Alternatively, the optical film may be a film that corrects the warping of the substrate surface Q. The optical film may also be formed on a substrate 2 that is not plate-shaped.

[0016] [First Embodiment of Optical System] Figure 2 is a block diagram showing an optical system OS1 relating to a first embodiment of a laser processing machine that includes a beam combiner 1. The optical system OS1 includes a beam combiner 1, a first LD light source D1, a second LD light source D2, a half-wave plate P, a lens N, and a process fiber F. The optical system OS1 is a beam combiner system including the beam combiner 1. The optical system OS1 generates output laser light LP, which is laser light capable of processing a workpiece W. Note that the beam combiner 1 may be used for purposes other than a laser processing machine. The beam combiner system may be introduced into equipment other than a laser processing machine.

[0017] The first LD light source D1 outputs a first laser beam L1. The first laser beam L1 is blue laser light. The wavelength of the first laser beam L1 is, for example, within the wavelength range of 425 nm (nanometers) to 455 nm. The polarization of the first laser beam L1 is p-polarized. The output of the first LD light source D1 is increased by wavelength synthesis. The output of the first LD light source D1 is, for example, 400 W (watts). The second LD light source D2 outputs a second laser beam L2. The second laser beam L2 is blue laser light. The wavelength of the second laser beam L2 is, for example, within the wavelength range of 425 nm (nanometers) to 455 nm. The polarization of the second laser beam L2 is p-polarized. The output of the second LD light source D2 is increased by wavelength synthesis. The output of the second LD light source D2 is, for example, 400 W. Furthermore, the wavelength of the second laser beam L2 may be the same as or different from the wavelength of the first laser beam L1. Also, the output of the second LD light source D2 may be the same as or different from the output of the first LD light source D1. Moreover, at least one of the first laser beam L1 and the second laser beam L2 may be output from a light source other than the LD light source, either in place of the LD light source or together with the LD light source. The half-wave plate P, acting as a polarization converter, is placed between the second LD light source D2 and the beam combiner 1. The half-wave plate P converts the polarization of the second laser beam L2 output from the second LD light source D2 from p-polarization to s-polarization to obtain the polarization-converted laser beam LZ. The polarization converter may be something other than the half-wave plate P.

[0018] The beam combiner 1 is positioned at a predetermined angle, 45° in this embodiment, relative to the first laser beam L1 and the second laser beam L2. The optical multilayer film 4 is positioned on the side of the second LD light source D2. The substrate 2 and the optical multilayer film 4 transmit at least p-polarized blue light. Therefore, the substrate 2 and the optical multilayer film 4 transmit the first laser beam L1. The optical multilayer film 4 also reflects s-polarized blue light. Therefore, the optical multilayer film 4 reflects the polarization-converted laser beam LZ. The beam combiner 1 is positioned such that the point where the first laser beam L1 and the optical multilayer film 4 intersect is the same as the point where the polarization-converted laser beam LZ is incident on the optical multilayer film 4. Therefore, the first laser beam L1 and the polarization-converted laser beam LZ are combined beyond the optical multilayer film 4 to form the combined laser beam LL. The combined laser beam LL is directed towards the lens N.

[0019] Lens N is positioned between the beam combiner 1 and the process fiber F. Lens N focuses the received coupled laser light LL to form focused laser light LO. The focused laser light LO enters the process fiber F.

[0020] The process fiber F is positioned between the lens N and the workpiece W. The process fiber F is a long member and has a core FC extending in the longitudinal direction and a cladding FL covering the core FC. The process fiber F receives the focused laser beam LO at the lens N side end of the core FC. The process fiber F then passes the received focused laser beam LO through the interior of the core FC along its longitudinal direction and outputs it as output laser beam LP towards the workpiece W. By directing the output laser beam LP onto the workpiece W, processing such as cutting and welding is performed. The output of the output laser beam LP is determined based on the combined laser beam LL, which is formed by combining the first laser beam L1 and the polarization-converting laser beam LZ. Therefore, the output of the output laser beam LP is significantly increased compared to the output of the output laser beam from a single LD light source. The beam combiner 1 is also called a polarized beam combiner because it combines the first laser beam L1 and the polarization-converting laser beam LZ, which have different polarizations.

[0021] As described above, the beam combiner 1 enhances the output of the output laser light LP. However, when the first laser light L1 and the polarization-converting laser light LZ are coupled, the first laser light L1 is transmitted while the polarization-converting laser light LZ is reflected, causing the temperature of the beam combiner 1 to rise. The higher the temperature of the beam combiner 1, the greater the proportion of coupled laser light LL that does not enter the core FC of the process fiber F. This increase in the proportion of coupled laser light LL that does not enter the core FC of the process fiber F is thought to be due to minute changes in the state of the beam combiner 1, including the optical path position of the coupled laser light LL. Furthermore, this change is thought to be due to minute deformation of the beam combiner 1 that occurs with the rise in temperature. An increase in the proportion of coupled laser light LL that does not enter the core FC of the process fiber F increases the possibility of damage to the cladding FL of the process fiber F. In addition, the beam quality value (BPP) is known as a parameter for evaluating beam quality. The smaller the BPP, the higher the quality of the output laser light. Therefore, an output laser beam LP with a low BPP can be said to have excellent workability for processing the workpiece W. However, an increase in the proportion of coupled laser beam LL that does not enter the core FC of the process fiber F leads to an increase in the BPP of the output laser beam LP. As an example, in order to set the BPP to 4 or less and maintain the quality of the output laser beam LP at a predetermined level or higher while setting the output of the output laser beam LP to 1000W or more, it is preferable that the temperature rise of the beam combiner 1 be 100°C or less relative to the initial temperature. For example, if the initial temperature is 25°C, it is preferable that the temperature rise be suppressed to 125°C or less. Also, when the output of the output laser beam LP is 1000W, it is typically understood that the beam combiner 1 is irradiated with 500W p-polarized blue laser beam and 500W s-polarized blue laser beam. Therefore, specifically, the temperature rise characteristics of the optical multilayer film 4 are preferably such that, when formed on a synthetic quartz substrate measuring 1 inch square (25.4 mm square) and 1 / 4 inch (6.35 mm) thick, taking into account the size of a typical optical component, and irradiated with 500 W p-polarized blue laser light and 500 W s-polarized blue laser light, the temperature rise of the synthetic quartz substrate is suppressed to 100°C or less.If the optical multilayer film 4 has such a temperature rise characteristic, even if it is formed on another substrate 2, it exhibits a preferable temperature rise suppressing effect.

[0022] [Optical Multilayer Film] The optical multilayer film 4 includes a low refractive index layer 10 and a high refractive index layer 12. In the optical multilayer film 4, the low refractive index layer 10 and the high refractive index layer 12 are preferably arranged alternately. Further, the optical multilayer film 4 may further include a medium refractive index layer. The optical multilayer film 4 is designed by changing design elements such as the number and material of the high refractive index layer 12, the low refractive index layer 10, and the medium refractive index layer, and the increase or decrease of the physical film thickness or optical film thickness related to each layer. In addition, part or all of the structure of the optical multilayer film 4 may be replaced with another optically equivalent structure, such as when the medium refractive index layer is replaced by a combination of the optically equivalent high refractive index layer 12 and the low refractive index layer 10. Further, a film having other functions such as an antifouling film and a conductive film may be combined outside or inside the optical multilayer film 4.

[0023] The low refractive index layer 10 of the optical multilayer film 4 is formed from a low refractive index material. The low refractive index material is, for example, silicon oxide (SiO ２ ), aluminum oxide (Al ２ O ３ ), calcium fluoride (CaF ２ ), magnesium fluoride (MgF ２ ), a combination of aluminum oxide and praseodymium oxide (Al ２ O ３ -Pr ２ O ３ ), a combination of aluminum oxide and lanthanum oxide (Al ２ O ３ -La ２ O ３ ?), or a combination of aluminum oxide and tantalum oxide (Al ２ O ３ -Ta ２ O ５ ), or a mixture of two or more of these. The low refractive index material is SiO ２ ?It is preferable that this is the case. Furthermore, two materials may be selected from the low refractive index materials mentioned above to form the optical multilayer film 4. Also, when a medium refractive index layer is used, the medium refractive index layer may be, for example, Pr ２ O ３ La ２ O ３ They may also be formed from materials with a medium refractive index.

[0024] The high refractive index layer 12 of the optical multilayer film 4 is formed from a high refractive index material. The beam combiner 1 is required to achieve optical performance such as sufficiently high transmittance of p-polarized blue light, sufficiently high reflectance of s-polarized blue light, sufficiently wide transmission wavelength range for p-polarized blue light, and sufficiently wide reflection wavelength range for s-polarized blue light. Furthermore, the beam combiner 1 must sufficiently suppress its own temperature rise and be able to adequately handle even relatively high-energy blue laser light. Therefore, the high refractive index layer 12 is made of HfO ２ HfO ２ It is preferable that the material be a layer. That is, the high refractive index material is HfO ２ It is preferable that HfO ２ From the viewpoint of obtaining good optical performance for blue light and good performance in suppressing temperature rise, it is more preferable that the layer contains monojection crystals. Also, from the same viewpoint, HfO ２It is more preferable that the (-111) plane of the monoclinic layer is oriented perpendicular to the substrate surface Q. Furthermore, it is preferable that the crystallinity of the high refractive index layer 12 is greater than 0% and 50% or less by mass ratio. That is, it is preferable that the crystallinity (%) obtained by multiplying the quotient obtained by dividing the mass of the crystallized portion of the high refractive index layer 12 by the total mass of the high refractive index layer 12 by 100 is greater than 0 and 50 or less. Furthermore, it is preferable that the size of the wavelength range in which the transmittance of p-polarized light is 95% or more in the optical multilayer film 4 is 5 nm or more. It is more preferable that the size of the wavelength range in which the transmittance of p-polarized light is 95% or more is 10 nm or more, and even more preferable that it is 15 nm or more. And it is even more preferable that the size of the wavelength range in which the transmittance of p-polarized light is 95% or more is 20 nm or more. Furthermore, it is preferable that the size of the wavelength range in which the reflectance of s-polarized light is 95% or more in the optical multilayer film 4 is 5 nm or more. Furthermore, the wavelength range in which the reflectance of s-polarized light is 95% or more is more preferably 10 nm or more, and even more preferably 15 nm or more. And the wavelength range in which the transmittance of s-polarized light is 95% or more is even more preferably 20 nm or more. If such optical performance for blue light is obtained in the optical multilayer film 4, the output of the coupled laser light LL, and consequently the output of the output laser light LP, will be sufficient in the beam combiner 1.

[0025] The low refractive index layer 10, the high refractive index layer 12, and the medium refractive index layer of the optical multilayer film 4 are formed, for example, by physical vapor deposition. Examples of physical vapor deposition methods include vacuum deposition, ion-assisted deposition, ion plating, and sputtering.

[0026] Furthermore, as shown in Figure 1, it is preferable that the optical multilayer film 4 has a first structural part 21 and a second structural part 22. The first structural part 21 is located on the side opposite to the substrate 2 relative to the second structural part 22, i.e., on the incident medium side. The first structural part 21 has one or more low refractive index layers 10 and one or more high refractive index layers 12. The first structural part 21 has a structure that reflects s-polarized light on the short wavelength side in the blue light wavelength range, i.e., the blue region. For example, the first structural part 21 reflects s-polarized light in the wavelength range of 425 nm or more and less than 440 nm. The layer in the first structural part 21 closest to the substrate 2 may be either a low refractive index layer 10 or a high refractive index layer 12. The layer in the first structural part 21 closest to the incident medium may be either a low refractive index layer 10 or a high refractive index layer 12. The second structural part 22 is located between the substrate 2 and the first structural part 21. The second structural part 22 has one or more low refractive index layers 10 and one or more high refractive index layers 12. The second structural part 22 has a structure that reflects s-polarized light on the long wavelength side in the blue region. For example, the second structural part 22 reflects s-polarized light in the wavelength range of 440 nm to 455 nm. The layer in the second structural part 22 that is closest to the substrate 2 may be either a low refractive index layer 10 or a high refractive index layer 12. The layer in the second structural part 22 that is closest to the incident medium may be either a low refractive index layer 10 or a high refractive index layer 12. The physical film thickness of the low refractive index layer 10 in the second structural part 22 is greater than the physical film thickness of the low refractive index layer 10 in the first structural part 21. The average value of the physical film thickness of the low refractive index layer 10 in the second structural part 22 is greater than the average value of the physical film thickness of the low refractive index layer 10 in the first structural part 21. The physical film thickness of the high refractive index layer 12 in the second structural part 22 is greater than the physical film thickness of the high refractive index layer 12 in the first structural part 21. The average physical thickness of the high refractive index layer 12 in the second structural part 22 is greater than the average physical thickness of the high refractive index layer 12 in the first structural part 21. In the optical multilayer film 4 in the first embodiment of the optical system OS1, the first structural part 21 related to reflection on the short wavelength side is located on the incident medium side of the second structural part 22 related to reflection on the long wavelength side. However, this arrangement may be changed so that in the optical multilayer film 4, the first structural part 21 is located on the substrate 2 side of the second structural part 22.Hereinafter, an optical multilayer film 4 in which the first structural part 21 related to reflection on the short wavelength side is arranged on the incident medium side of the second structural part 22 related to reflection on the long wavelength side will be appropriately referred to as the first type of optical multilayer film 4, and an optical multilayer film 4 in which the first structural part 21 related to reflection on the short wavelength side is arranged on the substrate 2 side of the second structural part 22 related to reflection on the long wavelength side will be appropriately referred to as the second type of optical multilayer film 4.

[0027] [Second Embodiment of Optical System] Figure 3 is a block diagram showing the optical system OS2 of a second embodiment of a laser processing machine that includes beam combiners 1A and 1B. In the second embodiment of the optical system OS2, components and parts that are the same as those in the first embodiment of the optical system OS1 are denoted by the same reference numerals, and their descriptions are omitted as appropriate. The optical system OS2 uses two beam combiners 1A and 1B. Beam combiner 1A, as the first beam combiner, has a first type of optical multilayer film 4. Beam combiner 1B, as the second beam combiner, has an optical multilayer film 4 that includes only a second structural part 24 similar to the second structural part 22. The optical system OS2 is a beam combiner system that includes beam combiners 1A and 1B. Furthermore, beam combiner 1A has an anti-reflective coating AR1. The anti-reflective coating AR1 suppresses the reflection of blue light. The anti-reflective coating AR1 is formed on the surface opposite to the substrate surface Q. Furthermore, beam combiner 1B has an anti-reflective coating AR2. The anti-reflective coating AR2 suppresses the reflection of blue light. The anti-reflective coating AR2 is formed on the surface opposite to the substrate surface Q. In addition, three or more beam combiners may be used in the optical system OS2. Furthermore, at least one of the anti-reflective coatings AR1 and AR2 may be omitted.

[0028] In the OS2 optical system, two second LD light sources, the second-first LD light source D2A and the second-second LD light source D2B, and two half-wave plates PA and PB are used. The second-first LD light source D2A outputs the second-first blue laser light L2A on the short-wavelength side of the blue region, for example, between 425 nm and less than 445 nm. The second-second LD light source D2B outputs the second-second blue laser light L2B on the long-wavelength side of the blue region, for example, between 445 nm and 460 nm. In this example, the short-wavelength side of the blue region related to the second-first blue laser light L2A and the long-wavelength side of the blue region related to the second-second blue laser light L2B are continuous. Alternatively, the second-first LD light source D2A outputs the second-first blue laser light L2A on the short-wavelength side of the blue region, for example, between 425 nm and less than 440 nm. The second-second LD light source D2B outputs a second-second blue laser beam L2B on the longer wavelength side of the blue region, for example, between 445 nm and 460 nm. In this example, the short wavelength side of the blue region related to the second-first blue laser beam L2A and the long wavelength side of the blue region related to the second-second blue laser beam L2B are discontinuous. That is, the upper limit wavelength of the short wavelength side of the blue region is different from the lower limit wavelength of the long wavelength side of the blue region, and there is a gap between them. The wavelength range between the short wavelength side of the blue region related to the second-first blue laser beam L2A and the long wavelength side of the blue region related to the second-second blue laser beam L2B may include a transition region, which is the wavelength range in which the reflectance distribution of s-polarized light in the blue region at the second structural part 24 of the optical multilayer film 4 of the beam combiner 1B transitions from a low value to a high value. In this example, the transition region is, for example, between 440 nm and 445 nm. The half-wave plate PA, acting as the first polarization converter, converts the p-polarized second-first blue laser light L2A into the s-polarized first polarization-converted laser light LZA. The half-wave plate PB, acting as the second polarization converter, converts the p-polarized second-second blue laser light L2B into the s-polarized second polarization-converted laser light LZB. In addition, three or more beam combiner second LD light sources and polarization converters may be used in the optical system OS2.

[0029] The first LD light source D1 outputs the first laser beam L1. The first laser beam L1 includes the 1-1 laser beam L1A on the short wavelength side of the blue region and the 1-2 laser beam L1B on the long wavelength side of the blue region. For the sake of explanation, the 1-1 laser beam L1A and the 1-2 laser beam L1B are described separately, but the actual output from the first LD light source D1 is a single beam of the first laser beam L1.

[0030] The beam combiner 1A transmits the first laser beam L1. When the first laser beam L1 is incident on the beam combiner 1A at an incident angle other than the Brewster angle, a small amount of reflected light may occur, but this reflected light is suppressed by the anti-reflective film AR1. Suppression of this reflected light leads to an increase in the output laser beam LP. In addition, the beam combiner 1A reflects the first polarization-converted laser beam LZA, which is on the short wavelength side of the blue region, at the first structural part 21 located on the incident medium side of the optical multilayer film 4. The beam combiner 1A sends the first combined laser beam LMA, which is a combination of the first-first laser beam L1A and the first polarization-converted laser beam LZA, and the first-second laser beam L1B to the beam combiner 1B. For the sake of explanation, the first combined laser beam LMA and the first-second laser beam L1B are shown separately, but the actual output from the beam combiner 1A is a single beam of partially combined laser beam LM. The partially coupled laser light LM corresponds to the first coupled light in this disclosure.

[0031] The beam combiner 1B transmits a portion of the combined laser beam LM. When the combined laser beam LM is incident on the beam combiner 1B at an incident angle other than the Brewster angle, a small amount of reflected light may occur, but this reflected light is suppressed by the anti-reflective coating AR2. Suppression of this reflected light leads to an increase in the output laser beam LP. Furthermore, if the beam combiner 1B has a transition region in the s-polarization reflectance distribution as described above, the s-polarization in the transition region of the combined laser beam LM is reflected by the optical multilayer film 4 of the beam combiner 1B and propagates in a direction different from the direction to the lens N. Light that propagates in a direction different from the direction to the lens N not only does not contribute to an increase in the output laser beam LP, but also becomes stray light in the optical system OS2. When stray light irradiates a component in the optical system OS2, adverse effects such as a rise in the temperature of that component may occur. Furthermore, as illustrated above, if the short-wavelength side and the long-wavelength side of the blue region are discontinuous, and the wavelength range between them includes the transition region of the s-polarization reflectance distribution of the beam combiner 1B, the generation of s-polarization reflected light in the transition region of the beam combiner 1B is suppressed. If the s-polarization reflected light in the transition region is suppressed, the adverse effects caused by this reflected light are suppressed. As will be described in detail later, a small amount of light is absorbed in the optical multilayer film 4, which is the cause of heat generation. If the second-first blue laser light L2A and the second-second blue laser light L2B are not output in the transition region, the situation in which some of the light in the transition region is absorbed by the optical multilayer film 4 and causes a temperature rise, even though it does not contribute to the increase of the output laser light LP, is suppressed. In addition, the beam combiner 1B reflects the second polarization conversion laser light LZB related to the long-wavelength side of the blue region at the second structural part 24 of the optical multilayer film 4. The beam combiner 1B sends the second combined laser beam LNB, which is formed by combining the first-to-second laser beam L1B and the second polarization-converting laser beam LZB, and the first combined laser beam LMA to the lens N. For the sake of explanation, the first combined laser beam LMA and the second combined laser beam LNB are shown separately, but the actual output from the beam combiner 1B is a single combined laser beam LN. The combined laser beam LN corresponds to the second combined beam in this disclosure.The combined laser beam LN is focused by lens N into a focused laser beam LO, which then enters the process fiber F.

[0032] In such an optical system OS2, separate beam combiners 1A and 1B are used for the short-wavelength and long-wavelength sides of the blue region. In the optical multilayer film 4 of beam combiner 1A, which processes coupling on the short-wavelength side of the blue region, a first structural part 21 that reflects s-polarized light related to the short-wavelength side of the blue region is located on the incident medium side. Therefore, the blue laser light can be mainly processed by the incident medium side portion of the optical multilayer film 4, and the temperature rise of beam combiners 1A and 1B is further sufficiently suppressed. In addition, in the optical multilayer film 4 of beam combiner 1B, which processes coupling on the long-wavelength side of the blue region, only a second structural part 24 that reflects s-polarized light related to the long-wavelength side of the blue region is located. Therefore, in beam combiner 1B, s-polarized light on the long-wavelength side of the blue region is reflected, and p-polarized and s-polarized light on the short-wavelength side of the blue region, as well as p-polarized light on the long-wavelength side, can be transmitted. Therefore, the beam combiner 1B can transmit the first combined laser beam LMA on the short wavelength side of the blue region, which is coupled by the beam combiner 1A, while reflecting the second polarization-converted laser beam LZB on the long wavelength side of the blue region and coupling it with the first-to-second laser beam L1B. Thus, the output of the combined laser beam LN and, consequently, the output of the output laser beam LP can be sufficiently obtained.

[0033] [Third Embodiment of the Optical System] Figure 4 is a block diagram showing the optical system OS3 of a third embodiment of a laser processing machine that includes beam combiners 1B and 1C. In the third embodiment of the optical system OS3, components and parts that are the same as those in the second embodiment of the optical system OS2 are denoted by the same reference numerals, and their descriptions are omitted as appropriate. In the optical system OS3, beam combiner 1C is used instead of beam combiner 1A. Beam combiner 1C, as the first beam combiner, has an optical multilayer film 4 that includes only the first structural part 25, similar to the first structural part 22. Beam combiner 1B, as the second beam combiner, has an optical multilayer film 4 that includes only the second structural part 24. The optical system OS3 is a beam combiner system that includes beam combiners 1B and 1C. Beam combiner 1C also has an anti-reflective coating AR1. At least one of the anti-reflective coating AR1 of beam combiner 1C and the anti-reflective coating AR2 of beam combiner 1B may be omitted.

[0034] The beam combiner 1C transmits the first laser beam L1. The beam combiner 1C also reflects the first polarization-converted laser beam LZA, which is on the short wavelength side of the blue region, at the first structural part 25 of the optical multilayer film 4. The beam combiner 1C sends the first combined laser beam LMA, which is the combined first-first laser beam L1A and the first polarization-converted laser beam LZA, and the first-second laser beam L1B to the beam combiner 1B. For the sake of explanation, the first combined laser beam LMA and the first-second laser beam L1B are shown separately, but the actual output from the beam combiner 1C is a single stream of partially combined laser beam LM. The partially combined laser beam LM corresponds to the first combined beam in this disclosure.

[0035] The beam combiner 1B transmits a portion of the combined laser light LM. Furthermore, the beam combiner 1B reflects the second polarization-converted laser light LZB, which corresponds to the long wavelength side of the blue region, at the second structural portion 24 of the optical multilayer film 4. The beam combiner 1B sends the second combined laser light LNB, which is the combined first-to-second laser light L1B and the second polarization-converted laser light LZB, and the first combined laser light LMA to the lens N. For the sake of explanation, the first combined laser light LMA and the second combined laser light LNB are described separately, but the actual output from the beam combiner 1B is a single combined laser light LN. The combined combined laser light LN corresponds to the second combined light in this disclosure. The combined combined laser light LN becomes a focused laser light LO through the lens N and enters the process fiber F.

[0036] In such an optical system OS3, separate beam combiners 1B and 1C are used for the short-wavelength and long-wavelength sides of the blue region. Therefore, the temperature rise of beam combiners 1B and 1C is sufficiently suppressed while obtaining sufficient output from the combined laser light LN and consequently from the output laser light LP. In optical systems OS2 and OS3, two beam combiners 1A and 1B, or two beam combiners 1C and 1B were used, but as an example of a modification of the optical system, three or more beam combiners may be provided. For example, in optical system OS3, the first beam combiner 1C may be divided into a first-first beam combiner that reflects s-polarized light on the short-wavelength side and a first-second beam combiner that reflects s-polarized light on the long-wavelength side. Furthermore, the second beam combiner 1B may be divided into a second-first beam combiner that reflects s-polarized light on the shorter wavelength side of the longer wavelength side, and a second-second beam combiner that reflects s-polarized light on the longer wavelength side of the longer wavelength side. Alternatively, the division of the first beam combiner 1C and the division of the second beam combiner 1B may be combined. In this case, half-wave plates corresponding to the number of beam combiners may be provided. Also, the second LD light source for the second laser light may be divided and provided in accordance with the number of beam combiners.

[0037] Beam combiners 1, 1A, 1B, and 1C can each be manufactured by forming an optical multilayer film 4 on the substrate surface Q.

[0038] Next, various examples related to the embodiments described above in this disclosure are presented. However, these examples are not intended to limit the scope of this disclosure.

[0039] [Examples 1-5] In Example 1, a beam combiner 1 was formed by directly forming a first type optical multilayer film 4 having a first structural part 21 and a second structural part 22 on the substrate surface Q, which is one side of a plate-shaped substrate 2 (i.e., a substrate). The substrate was made of synthetic quartz. The total number of layers of the optical multilayer film 4 in Example 1 was 69. The layer closest to the substrate was designated as the first layer, and the odd-numbered layers of the optical multilayer film 4 were SiO ２ It was made into layers. Also, the even-numbered layers of the optical multilayer film 4 are HfO ２ The layers were formed. Each layer of the optical multilayer film 4 in Study Example 1 was formed by radical-assisted sputtering (RAS). Each layer was formed with the physical film thickness (nm) shown in Table 1 below. RAS is a film deposition method that spatially separates reactive sputtering into a sputtering process and a reaction process equipped with a radical oxidation source, and independently controls each process to deposit a film on a substrate. In RAS, the substrate is placed on a rotating vertical drum. RAS is a type of magnetron sputtering. The optical multilayer film 4 in Study Example 1 was of type 1. In the optical multilayer film 4 of Study Example 1, layers 1 to 33 were the second structural part 22, and layers 34 to 69 were the first structural part 21. Note that the incident angle of the blue laser light in the various tests for Study Examples 1 to 14 below was set to 55°, which is the Brewster angle of the quartz substrate. If the incident angle of the blue laser light is the Brewster angle, sufficient p-polarized light transmittance can be obtained even if an optical film is not formed on the surface opposite to the optical multilayer film 4. Therefore, in study examples 1 to 14, no optical film was formed on the surface of the substrate opposite to the optical multilayer film 4.

[0040]

[0041] Furthermore, in Study Example 2, a different manufacturing method and physical film thickness design for each layer of the optical multilayer film 4 was formed compared to Study Example 1. The total number of layers in the optical multilayer film 4 in Study Example 2 was 69. Each layer of the optical multilayer film 4 in Study Example 2 was formed by plasma-assisted reactive sputtering (PARMS). Each layer was formed with the physical film thickness (nm) shown in Table 2 below. PARMS is a film deposition method that spatially separates reactive sputtering into a sputtering process and a reaction process equipped with an RF plasma source, and independently controls each process to deposit a film on a substrate. In PARMS, the substrate is placed on a turntable. PARMS is a type of magnetron sputtering method. The optical multilayer film 4 in Study Example 2 was of type 1. In the optical multilayer film 4 of Study Example 2, layers 1 to 37 were the second structural part 22, and layers 38 to 69 were the first structural part 21.

[0042]

[0043] Furthermore, in Study Example 3, a different manufacturing method and physical film thickness design for each layer of the optical multilayer film 4 was formed compared to Study Example 1. The total number of layers in the optical multilayer film 4 in Study Example 3 was 61. Each layer of the optical multilayer film 4 in Study Example 3 was formed by ion-assisted deposition (IAD). Each layer was formed with the physical film thickness (nm) shown in Table 3. IAD is a film deposition method in which an ion beam drawn from an ion gun installed in a chamber is irradiated onto a substrate while deposition is performed. In IAD, a dense film is formed while promoting the reaction by supplying a reactive gas to the ion gun. The optical multilayer film 4 in Study Example 3 was of type 2. In the optical multilayer film 4 of Study Example 3, layers 1 to 33 were the first structural part 21, and layers 34 to 69 were the second structural part 22.

[0044]

[0045] Furthermore, in Study Example 4, a different manufacturing method and physical film thickness design for each layer of the optical multilayer film 4 was formed compared to Study Example 1. Each layer of the optical multilayer film 4 in Study Example 4 was formed by electron beam deposition (EB). EB is a method of depositing a film on a substrate by evaporating a film material with an electron beam in a chamber in which an electron gun is installed. In EB, reactive film deposition is performed by supplying a reactive gas into the chamber. The physical film thickness design for each layer of the optical multilayer film 4 in Study Example 4 was similar to that of Study Example 1, but involved a mirror in the near-infrared region that also reflects p-polarized light. The optical multilayer film 4 in Study Example 4 consists of a total of 29 layers.

[0046] Furthermore, in Study Example 5, a different manufacturing method and physical film thickness design for each layer of the optical multilayer film 4 was formed compared to Study Example 1. The total number of layers in the optical multilayer film 4 in Study Example 5 was 67. Each layer of the optical multilayer film 4 in Study Example 5 was formed by ion beam sputtering (IBS). Each layer was formed with the physical film thickness (nm) shown in Table 4 below. IBS is a method of depositing a film on a substrate by sputtering a target material with an ion beam drawn from an ion gun installed in a chamber. In IBS, reactive film deposition is performed by supplying a reactive gas into the chamber. The optical multilayer film 4 in Study Example 5 was of type 2. In the optical multilayer film 4 of Study Example 5, layers 1 to 35 were the first structural part 21, and layers 36 to 67 were the second structural part 22.

[0047]

[0048] Furthermore, Table 5 summarizes the manufacturing methods for each layer of the optical multilayer film 4 in Study Examples 1 to 5. The reason why the physical film thickness of each layer of the optical multilayer film 4 was not designed to be exactly the same in Study Examples 1 to 3 and 5 is to test various elements as efficiently as possible, given that the formation of these optical multilayer films 4 is time-consuming and costly. Although the details of the design of the optical multilayer film 4 in Study Examples 1 to 3 and 5 differ, the designs themselves are extremely similar to each other.

[0049]

[0050] [Investigation of p-polarized spectral transmittance and s-polarized spectral reflectance in Study Example 1] For Study Example 1, the spectral transmittance of p-polarized blue light and the spectral reflectance of s-polarized blue light were measured. In these measurements, the blue light was set to be incident on the optical multilayer film 4 side of Study Example 1 at an incident angle of 55°, which is the Brewster angle in Study Example 1.

[0051] Figure 5 is a graph showing the spectral transmittance of p-polarized blue light in Study Example 1, obtained by such measurements. Figure 6 is a graph showing the spectral reflectance of s-polarized blue light in Study Example 1, obtained by such measurements. According to these graphs, in the beam combiner 1 of Study Example 1, the wavelength range in which the transmittance of p-polarized light is 98% or more is between 428 nm and 460 nm, and the size of this wavelength range is 32 nm. Therefore, in the beam combiner 1 of Study Example 1, the wavelength range in which the reflectance of s-polarized light is 98% or more is sufficiently wide. Consequently, the beam combiner 1 of Study Example 1 can output coupled laser light LL, and consequently output laser light LP, of sufficient intensity.

[0052] [Investigation of Temperature Rise in Study Examples 1 and 2] Furthermore, for Study Examples 1 and 2, the relationship between the output of the output laser beam LP and the temperature rise of the beam combiner 1 in Study Examples 1 and 2 was actually tested when they were incorporated into a laser processing machine having the optical system OS1. In this test, the irradiation time of the output laser beam LP was set to 30 seconds for each output.

[0053] Figure 7 is a graph showing the relationship between the output (W) of the output laser beam LP and the temperature rise (°C) of Study Examples 1 and 2, obtained from such tests. The solid line in Figure 7 corresponds to Study Example 1, and the dotted line corresponds to Study Example 2. In this test, based on a typical interpretation, it is considered that in Study Examples 1 and 2, the beam was irradiated with a first laser beam L1 of p polarization with an intensity of approximately half that of the output laser beam LP, and a polarization-converted laser beam LZ of s polarization with an intensity of approximately half that of the output laser beam LP. However, since losses in the process fiber F increase with increasing temperature rise, it is considered that when the temperature rise is high, the beam combiner 1 was irradiated with an intensity significantly exceeding that of the output laser beam LP. In Study Example 1, even with an output of 1420W of the output laser beam LP, the temperature rise was suppressed to about 62°C. Therefore, the beam combiner 1 in Study Example 1 demonstrates the realization of coupling of 1kW or more while keeping the temperature rise below 100°C. This coupling translates to a power density of 50 W / mm² in terms of output / spot area in beam combiner 1. ２ This corresponds to the degree. In Study Example 2, when the output of the output laser light LP was 790W or less, the temperature rise was suppressed to less than 100°C, but when the output of the output laser light LP was 900W, the temperature rise was 108°C, exceeding 100°C. Furthermore, when the output exceeded 900kW, the loss in the process fiber F was too large, and it was not possible to incident the blue laser light onto the process fiber F. Therefore, it was found that differences in the manufacturing method and physical film thickness design of the optical multilayer film 4 result in differences in temperature rise suppression characteristics.

[0054] [Microstructure Analysis of Optical Multilayer Film 4 by X-ray Diffraction in Study Examples 1-5] Furthermore, in order to observe the microstructure of the optical multilayer film 4 in Study Example 1, X-ray diffraction measurements using the θ-2θ method, as shown in Figure 8, were performed on Study Example 1, and the results of the measurements were analyzed. In this measurement, the angle θ of the incident X-ray X1 with respect to the measurement target M was defined as θ, and the intensity of the diffracted X-ray X2 was measured while the angle 2θ between a hypothetical straight line A containing the incident X-ray X1 and the diffracted X-ray X2 gradually changed within a predetermined range. For such measurements, a Rigaku Corporation SmartLab (In-Plane) X-ray diffractometer was used. The measurement light source was an X-ray tube. The target of the measurement light source was Cu. The driving voltage of the measurement light source was 40 kV (kilovolts), and the driving current of the measurement light source was 30 mA (milliamperes). Furthermore, the optical system for such measurements was a parallel beam optical system, as shown in Figure 8. In addition, the width of the incident slit in such measurements was 1 mm. The longitudinal limiting slit was 10 mm. The width of the light-receiving slit was 1 mm. Furthermore, the scan axis in such measurements was 2θ / ω. The scan range was from 10° to 90° at 2θ. The scan step was 0.02°. The scan speed was 2° / min. Furthermore, in the analysis of the measurement results, HfO ２ It was assumed that the material could include cubic, tetragonal, monoclinic, and orthorhombic crystals. Furthermore, in the analysis of the measurement results, the total mass ratio of crystalline and amorphous materials was calculated. In the calculation of crystallinity in the analysis of the measurement results, the peaks in the intensity distribution of diffracted X-rays X2 where 2θ is within the range of 10° to 40° were considered, and peaks outside this range were excluded. Furthermore, for study examples 2 to 5, the X-ray diffraction measurements and analyses for study example 1 described above were performed in the same manner. In addition, the SiO constituting each of the low refractive index layers 10 was also considered. ２ To investigate the influence of the layer on the measurement and analysis of X-ray diffraction, SiO ２ X-ray diffraction tests were performed on the single-layer films produced in the same manner as in Examples 1-5. ２ The following two types of test subjects were used to form a single layer film of the following material: Firstly, the substrate was coated with SiO using RAS. ２ A single layer film has been formed (SiO２ -RAS). Secondly, SiO is applied to the substrate using PARMS. ２ A single layer film has been formed (SiO ２ -PARMS)

[0055] Figure 9 shows the study examples 1 to 5, and SiO ２ - RAS and SiO ２ - This graph shows the measurement results of X-ray diffraction related to PARMS. The horizontal axis of the graph in Figure 9 is 2θ (°). The vertical axis of the graph in Figure 9 is the intensity (a.u.) of the diffracted X-ray X2. Figure 10 is an enlarged view of the portion in Figure 9 where 2θ is in the range of 25° to 35° for study examples 1 to 5. In general, SiO ２ It is known that monolayer films are amorphous. And, as shown in Figure 9, SiO ２ - RAS and SiO ２ - In both PARMS, there was no significant peak in the intensity distribution of diffracted X-rays X2 in X-ray diffraction, and SiO ２ It was confirmed that the monolayer film lacked crystallinity. Therefore, the peaks in the intensity distribution of diffracted X-rays X2 in Figures 9 and 10 indicate that the high refractive index layer 12 is HfO ２ This can be attributed to the crystalline structure of the layers.

[0056] If the test material contains monoclinic crystals, a peak in the intensity distribution of diffracted X-rays X2 occurs at an angle where 2θ ≈ 28.5° due to X-ray reflection from its (-111) plane. Furthermore, if the test material contains monoclinic crystals, a peak in the intensity distribution of diffracted X-rays X2 occurs at an angle where 2θ ≈ 31.5° due to X-ray reflection from its (111) plane. Note that the peak angle of the intensity distribution of diffracted X-rays X2 is... ２ A slight deviation may occur due to various factors, including the shift in lattice constants caused by internal stresses within the layers. When the test subject includes at least one of cubic, tetragonal, or orthorhombic crystals, a peak in the intensity distribution of diffracted X-rays X2 occurs at an angle where 2θ ≈ 30.5°. In this case, the distinction between cubic, tetragonal, and orthorhombic crystals cannot be made. Hereafter, this can be referred to as the cubic crystal system.

[0057] Example 1 does not have a cubic crystal system peak, nor does it have a peak of 2θ≈31.5° caused by X-ray reflection at the (111) plane of the monoclinic crystal, but only has a peak of 2θ≈28.5° caused by X-ray reflection at the (-111) plane of the monoclinic crystal. Example 2 does not have a peak of 2θ≈31.5° caused by X-ray reflection at the (111) plane of the monoclinic crystal, but has a peak of 2θ≈28.5° caused by X-ray reflection at the (-111) plane of the monoclinic crystal, and a cubic crystal system peak. Example 3 does not have a cubic crystal system peak, but has a peak of 2θ≈28.5° caused by X-ray reflection at the (-111) plane of the monoclinic crystal, and a peak of 2θ≈31.5° caused by X-ray reflection at the (111) plane of the monoclinic crystal. Study Example 4 has a peak at 2θ ≈ 28.5° due to X-ray reflection at the (-111) plane of the monoclinic crystal, a peak at 2θ ≈ 30.5° in the cubic crystal system, and a peak at 2θ ≈ 31.5° due to X-ray reflection at the (111) plane of the monoclinic crystal. Study Example 5 does not have any of these peaks.

[0058] As described above, the temperature rise in Study Example 1 was suppressed compared to the temperature rise in Study Example 2. Furthermore, according to the X-ray diffraction results of Study Example 1, HfO ２ The layer does not have a cubic crystal structure, but rather a monoclinic crystal structure. Furthermore, according to the X-ray diffraction results of Study Example 2, HfO ２ The layers can be said to have a cubic crystal structure and a monoclinic crystal structure. Therefore, the temperature rise suppression in beam combiner 1 is HfO ２ This can be attributed to the fact that the layer has a monoclinic crystal structure rather than a cubic crystal structure. Here, "lacking a crystal structure" means that the crystal structure is not detectable to such an extent that it does not appear as a peak in the intensity distribution of diffracted X-rays. In practice, this may include cases where the crystal structure is present in trace amounts that do not affect the appearance of the peak.

[0059] [Investigation of the orientation of the monoclinic (-111) plane in Study Examples 1 to 4] Furthermore, in particular, HfO in Study Example 1 ２To observe the orientation of the monoclinic (-111) plane in the layer, pole figures of the peak at 2θ ≈ 28.5° in the intensity distribution of diffracted X-rays X2 were created for Study Examples 1 to 4. The pole figures show the intensity distribution of diffracted X-rays X2 on a hypothetical hemisphere H containing pole K in Figure 8. These pole figures were created to analyze the mechanism behind the presence of a peak related to the monoclinic (-111) plane in Study Example 1, while a peak related to the monoclinic (111) plane does not appear.

[0060] Figure 11 is the pole figure for Study Example 1. Figure 12 is the pole figure for Study Example 2. Figure 13 is the pole figure for Study Example 3. Figure 14 is the pole figure for Study Example 4. In the color diagrams of each pole figure, the type of color indicates the intensity of the diffracted X-rays X2, and the colors are assigned in order of increasing intensity: red, yellow, green, light blue, or blue. There are intermediate colors that change gradually between each color. The maximum intensity in each pole figure is approximately 1000. The minimum intensity in each pole figure is approximately 0. Also, in Figures 11 to 18, the upper pole figure is a perspective view with pole K positioned in the upper center of the pole figure. The lower pole figure is a top view with pole K positioned in the center of the pole figure. In the pole figures of Study Examples 1 to 3, the intensity distribution of the diffracted X-rays X2 was uniform in all in-plane rotation directions φ. Furthermore, since the pole diagrams of Study Examples 1 to 3 show a ring-shaped strong strength region near pole K, the HfO of Study Examples 1 to 3 ２ It was found that the crystals in the layer have orientation in the direction of χ = 0°. The direction of χ = 0° is the direction from the incident point O, where the incident X-ray X1 strikes the measurement target M, to the pole point K. On the other hand, since no asymmetry in the intensity distribution is observed in the pole figure of Study Example 4, it can be concluded that HfO by EB ２ It was found that the layers do not exhibit orientation even when rotated in the χ direction.

[0061] Figure 15 is the pole figure for 2θ ≈ 30.5° in Study Example 2. Figure 16 is the pole figure for 2θ ≈ 31.5° in Study Example 3. Figure 17 is the pole figure for 2θ ≈ 30.5° in Study Example 4. Figure 18 is the pole figure for 2θ ≈ 31.5° in Study Example 4. Figure 15 shows the HfO related to PARMS in Study Example 2. ２The cubic crystal system of the layer was found to be oriented in the direction of χ = 0° and tilted with respect to the direction of χ = 10°. Figure 16 shows the HfO related to IAD in Study Example 3. ２ It was found that the (111) plane of the monoclinic layer has orientation in the direction of χ = 0° and is tilted with respect to the χ = 0° direction. As shown in Figure 17, the HfO related to EB in Study Example 4 ２ It was found that the cubic crystal system of the layer does not have orientation. Figure 18 shows the HfO related to EB in Study Example 4. ２ It was found that the (111) plane of the monoclinic layer does not have orientation.

[0062] Figure 19 is a graph corresponding to the cross-sectional views of the pole figures for each of the study examples 1 to 4 at the peak of 2θ ≈ 28.5 related to the (-111) plane of the monoclinic crystal. Figure 20 is a graph corresponding to the cross-sectional views of the pole figures for each of the study examples 2 and 4 at the peak of 2θ ≈ 30.5 related to the cubic crystal system. Figure 21 is a graph corresponding to the cross-sectional views of the pole figures for each of the study examples 3 and 4 at the peak of 2θ ≈ 31.5 related to the (111) plane of the monoclinic crystal. The cross-sections of these pole figures are virtual planes extending in the up, down, left, and right directions in Figure 8, and include the incident point O and the pole point K.

[0063] According to Figure 19, the HfO related to the RAS in Study Example 1 ２ The (-111) plane of the monoclinic layer can be said to be oriented in the direction perpendicular to the substrate surface Q. HfO in Study Example 1 has such orientation. ２ If the layer is monoclinic, the peak at 2θ ≈ 31.5 corresponding to the monoclinic (111) plane will not appear. Also, according to Figure 19, the HfO related to PARMS in Study Example 2 ２ The (-111) plane of the monoclinic layer can be said to be oriented in a direction inclined at 12° with respect to the perpendicular to the substrate surface Q. Furthermore, according to Figure 19, the HfO related to IAD in Study Example 3 ２ The (-111) plane of the monoclinic layer can be said to be oriented in the direction perpendicular to the substrate surface Q. In addition, according to Figure 19, the HfO related to EB in Study Example 4 ２ It can be said that there is no orientation of the layers.

[0064] According to Figure 20, the cubic crystal system related to PARMS in Study Example 2 is oriented in a direction inclined at 12° with respect to the perpendicular to the substrate surface Q. In addition, according to Figure 20, the HfO related to EB in Study Example 4 ２ There is no orientation of the layers. Also, according to Figure 21, HfO in Study Example 4 ２ No orientation of the (111) planes of the monoclinic layers is observed.

[0065] As mentioned above, it has been found that Study Example 1 exhibits relatively superior temperature rise suppression. Furthermore, from the X-ray diffraction analysis results, the HfO of the optical multilayer film 4 in Study Example 1 was found to be ２ It was found that the layer has monoclinic crystals with its (-111) plane oriented perpendicular to the substrate surface Q. Therefore, the optical multilayer film 4 is HfO with the (-111) plane of the single crystal oriented perpendicular to the substrate surface Q. ２ By including a layer, the temperature rise can be suppressed.

[0066] [Investigation of the dependence of temperature rise on plate thickness and polarization related to Study Examples 1 and 2] A temperature rise evaluation test was conducted on a test subject that had the same optical multilayer film 4 as Study Example 1 and either Study Examples 1 or 2, but with a different plate thickness. The temperature rise evaluation test was conducted as follows: The test subject was directly irradiated with p-polarized (p-pol) blue laser light, and the temperature rise was measured. The power density of this blue laser light was 10 kW / cm². ２(kilowatts per square centimeter). Similarly, the temperature rise was measured for s-polarized light, except that the polarization of the blue laser light was changed to s-polarized (s-pol) using a half-wave plate. The temperature rise was measured using thermography. The substrate thickness variations were 1 mm and 3 mm, compared to 6.35 mm in Study Examples 1 and 2. The following combinations of optical multilayer film 4 type and substrate thickness were prepared for the test subjects. First, as Study Example 1 itself, a combination of optical multilayer film 4 related to RAS and a substrate with a thickness of 6.35 mm was prepared. Also, as Study Example 6, a combination of optical multilayer film 4 related to RAS and a substrate with a thickness of 1 mm was prepared. Also, as Study Example 7, a combination of optical multilayer film 4 related to PARMS and a substrate with a thickness of 3 mm was prepared. Also, as Study Example 8, a combination of optical multilayer film 4 related to PARMS and a substrate with a thickness of 1 mm was prepared.

[0067] Figure 22 is a graph showing the relationship between substrate thickness and temperature rise for p-polarized or s-polarized beams, obtained from this temperature rise evaluation test. According to Figure 22, whether the test subject is for RAS or PARMS, the temperature rise of the beam combiner 1 is suppressed by increasing the substrate thickness. This is presumed to be due to the difference in the heat capacity of the substrate. Therefore, if the substrate is thicker, the heat capacity of the substrate is correspondingly larger. In other words, the temperature rise of the beam combiner 1 depends on the substrate thickness, and a thicker substrate will have a relatively smaller temperature rise when subjected to a unit amount of heat than a thinner substrate. Therefore, if a thicker substrate is used, the temperature rise of the beam combiner 1 will be further suppressed.

[0068] Furthermore, as shown in Figure 22, the temperature rise caused by p-polarized blue laser light is generally greater than that caused by s-polarized blue laser light, regardless of whether the test subject is RAS or PARMS. Figure 22 also shows that the temperature rise is more suppressed for RAS test subjects compared to PARMS test subjects. Figure 23 is a graph showing the relationship between the temperature rise with p-polarized light and the temperature rise with s-polarized light, obtained from this temperature rise evaluation test. Figure 23 shows that, regardless of the thickness of the substrate, the ratio of the temperature rise with p-polarized light to the temperature rise with s-polarized light remains constant for both RAS and PARMS. Therefore, it was found that the polarization dependence of the temperature rise is determined by the optical multilayer film 4.

[0069] [Investigation of film absorption rate for study examples 9-12] In order to investigate in detail the polarization dependence of the temperature rise in the optical multilayer film 4, the film absorption rate of 455 nm blue laser light for p-polarization and s-polarization was measured for study examples 9-12 shown below. The average output of the blue laser light was approximately 0.6 W. The diameter of the blue laser beam was 56 μm (micrometers). The incident angle of the blue laser light, i.e., the angle between the blue laser light and the optical multilayer film 4, was 55°. This measurement was performed using the Photothermal Common Path Interferometry (PCI) method. Furthermore, the temperature rise for p-polarization and s-polarization was also measured for study examples 9 and 10. The substrates for study examples 9-12 were circular substrates made of synthetic quartz, with a diameter of 30 mm and a thickness of 1 mm. In study example 9, the optical multilayer film 4 of study example 1 (RAS) was formed on one side of the substrate. In Study Example 10, the optical multilayer film 4 of Study Example 2 (PARMS) was formed on one side of the substrate. In Study Example 11, the optical multilayer film 4 of Study Example 3 (IAD) was formed on one side of the substrate. In Study Example 12, the optical multilayer film 4 of Study Example 5 (IBS) was formed on one side of the substrate.

[0070] Figure 24 is a graph showing the film absorptivity of study examples 9-12 related to p-polarization and the temperature rise of study examples 9-10. Figure 25 is a graph showing the film absorptivity of study examples 9-12 related to s-polarization and the temperature rise of study examples 9-10. Film absorptivity is expressed in parts per million (ppm). Also, to make Figure 24 easier to read, the film absorptivity of p-polarization in study example 11 (IAD) is shown as 1 / 10 of the actual value in Figure 24. That is, the film absorptivity of p-polarization in study example 11 is actually 4773 ppm, but in Figure 24 it is shown as 477.3 ppm for the sake of clarity of the other film absorptivity values. To draw attention to this point in Figure 24, an asterisk "*" is written next to "IAD" in Figure 24. According to Figures 24 and 25, it was found that there is a correlation between the temperature rise of the beam combiner 1 and the film absorptivity of the optical multilayer film 4. Furthermore, as shown in Figures 24 and 25, it was found that s-polarized light had a higher film absorptiality but a lower temperature rise compared to p-polarized light. This phenomenon is thought to be related to the layered structure of the optical multilayer film 4. Moreover, as shown in Figures 24 and 25, it was found that the film absorptiality of Study Example 9 (RAS) was lower than that of Study Example 10 (PARMS) for both p-polarized and s-polarized light, and that the difference in film absorptiality for s-polarized light was greater than the difference in film absorptiality for p-polarized light between Study Examples 9 and 10. In addition, it was found that the film absorptiality of Study Example 10 (PARMS) was equivalent to that of Study Example 12 (IBS) for p-polarized light, while the film absorptiality of Study Example 10 was high and the film absorptiality of Study Example 12 was extremely low for s-polarized light. This phenomenon is thought to be related to the layered structure of the optical multilayer film 4.

[0071] [Investigation of the electric field intensity distribution of optical multilayer films 4 in Study Examples 1-3 and 5] To further investigate the polarization dependence of the temperature rise in optical multilayer films 4, the electric field intensity distribution generated by the reception of p-polarized and s-polarized blue laser light was calculated for the optical multilayer films 4 in Study Examples 1-3 and 5 using computer simulations. The conditions for the blue laser light were set to a wavelength of 400 nm to 480 nm and an incident angle of 55°. The intensity of the incident light was set to 1. The first axis (horizontal axis) in the electric field intensity distribution was defined as the distance (nm) from the interface between the incident medium and the optical multilayer film 4. The second axis (vertical axis) in the electric field intensity distribution was defined as the wavelength (nm) of the blue light. It was considered that in regions where the electric field intensity in the optical multilayer film 4 is strong, the amount of film absorption increases, and this contributes greatly to the temperature rise. Figure 26 is an image showing the electric field intensity distribution generated for p-polarized blue laser light in the optical multilayer film 4 (RAS) of Study Example 1. Figure 27 shows the electric field intensity distribution generated in the optical multilayer film 4 of Study Example 1 for s-polarized blue laser light. Figure 28 shows the electric field intensity distribution generated in the optical multilayer film 4 of Study Example 2 (PARMS) for p-polarized blue laser light. Figure 29 shows the electric field intensity distribution generated in the optical multilayer film 4 of Study Example 2 for s-polarized blue laser light. Figure 30 shows the electric field intensity distribution generated in the optical multilayer film 4 of Study Example 3 (IAD) for p-polarized blue laser light. Figure 31 shows the electric field intensity distribution generated in the optical multilayer film 4 of Study Example 3 for s-polarized blue laser light. Figure 32 shows the electric field intensity distribution generated in the optical multilayer film 4 of Study Example 5 (IBS) for p-polarized blue laser light. Figure 33 shows the electric field intensity distribution generated in the optical multilayer film 4 of Study Example 5 for s-polarized blue laser light. In each color image, the type of color indicates the electric field strength, with the colors assigned in order of increasing strength being red, yellow, green, light blue, blue, or white. Intermediate colors exist between each color, with gradual changes in intensity. Electric field strengths greater than 4 in each image are assigned white. The minimum intensity in each image is approximately 0.

[0072] According to Figures 26, 28, 30, and 32, the wavelength dependence of the electric field intensity distribution generated by p-polarization is small in each of the optical multilayer films 4 in Study Examples 1-3 and 5. This is thought to be due to the transmission of p-polarization through the optical multilayer film 4. In particular, in the wavelength range of 420 nm to 480 nm, the electric field intensity distributions caused by the reception of p-polarization in each of the optical multilayer films 4 in Study Examples 1-3 and 5 are similar to each other. Furthermore, according to Figures 27, 29, 31, and 33, the wavelength dependence of the electric field intensity distribution generated by s-polarization is large in each of the optical multilayer films 4 in Study Examples 1-3 and 5. This is thought to be due to the reflection of s-polarization by the optical multilayer film 4. The electric field intensity distributions caused by the reception of s-polarization in each of the optical multilayer films 4 in Study Examples 1-3 and 5 are different to each other. Such differences in electric field intensity distributions are thought to be based on the differences in the layered structure of each of the optical multilayer films 4 in Study Examples 1-3 and 5. As described above, it was found that the optical multilayer film 4 is highly dependent on s-polarization. In particular, when the optical multilayer film 4 is of type 1, it is highly dependent on the longer wavelength side of s-polarized blue laser light. Therefore, study examples 1 and 2, in which the optical multilayer film 4 is of type 1, exhibit high temperature rise suppression characteristics on the shorter wavelength side of s-polarized blue laser light. On the other hand, when the optical multilayer film 4 is of type 2, it is highly dependent on the shorter wavelength side of s-polarized blue laser light. Therefore, study examples 3 and 5, in which the optical multilayer film 4 is of type 2, exhibit high temperature rise suppression characteristics on the longer wavelength side of s-polarized blue laser light.

[0073] [Effects of Study Examples 1-3, 5-12] Study Examples 1, 6, and 9 comprise a substrate and an optical multilayer film 4 directly formed on the substrate surface Q, which is the surface of the substrate. The optical multilayer film 4 alternately has a low refractive index layer 10 and a high refractive index layer 12. The optical multilayer film 4 transmits the first laser light L1 in the blue region of p polarization and reflects the polarization-converted laser light LZ in the blue region of s polarization. The high refractive index layer 10 is made of HfO ２ HfO ２The layer contains monoclinic crystals. The (-111) plane of the monoclinic crystals is oriented perpendicular to the substrate surface Q. Thus, a beam combiner 1 is provided in which the temperature rise is suppressed. If the temperature rise of the beam combiner 1 is suppressed, damage to the cladding FL of the process fiber F is suppressed. Thus, deterioration of the beam quality value BPP of the output laser light LP is suppressed.

[0074] Furthermore, in Study Example 1, as shown in Figure 5, the transmittance distribution of p-polarized light in the blue region of the optical multilayer film 4 has a wavelength range of 32 nm, where the transmittance of p-polarized light is 95% or more, and this range is 15 nm or more. Moreover, in Study Example 1, as shown in Figure 6, the reflectance distribution of s-polarized light in the blue region of the optical multilayer film 4 has a wavelength range of 70 nm, where the reflectance of p-polarized light is 95% or more, and this range is 15 nm or more, and this range is at least 410 nm to 480 nm. The transmittance distribution of p-polarized light and the reflectance distribution of s-polarized light in Study Examples 6 and 9 also have similar wavelength ranges to Study Example 1 because the structure of the optical multilayer film 4 in Study Examples 6 and 9 is the same as that of Study Example 1. Therefore, the beam combiner 1 can combine the polarization-converted laser light LZ based on the first laser light L1 and the second laser light L2, which have a wide wavelength range, even with light sources such as the first LD light source D1 and the second LD light source D2, while minimizing the loss of these outputs.

[0075] Furthermore, in the examples 1, 6, and 9, HfO ２ The layer is formed by radical-assisted sputtering. Therefore, a beam combiner 1 is provided in which the intensity of the coupled laser light LL and thus the output laser light LP resulting from the coupling of the first laser light L1 and the polarization-converting laser light LZ in the blue region is sufficiently strong, and the temperature rise is suppressed. ２The layer may be identified by a manufacturing method called radical-assisted sputtering, and even if this is the case, such identification is considered permissible due to so-called impossible and impractical circumstances. That is, as mentioned above, even if time, cost, expensive and rare measuring equipment, and various simulations are used, different HfO ２ There are circumstances that prevent the complete and perfect determination of differences in the microstructure of the layers. Therefore, the complete and perfect identification of the microstructure is impossible and impractical with the current state of technology. Furthermore, considering that the invention relates to a thin film, which cannot be directly observed visually, and that appropriate protection should be provided through multifaceted expression of the invention, HfO ２ Even if the layer is identified by a manufacturing method called radical-assisted sputtering, such identification should be permitted.

[0076] Furthermore, in study examples 1-2 and 5-12, the optical multilayer film 4 has a first structural part 21 and a second structural part 22. The first structural part 21 reflects the polarization-converted laser light LZ of s-polarization related to the short wavelength side of the blue region. The second structural part 22 reflects the polarization-converted laser light LZ of s-polarization related to the long wavelength side of the blue region. Moreover, in study examples 1-2 and 6-10, as the first type of optical multilayer film 4, the first structural part 21 is positioned on the incident medium side of the second structural part 22. Also, in study examples 3, 5, 11, and 12, as the second type of optical multilayer film 4, the first structural part 21 is positioned on the substrate side of the second structural part 22. Thus, the wavelength ranges related to reflection are shared in the optical multilayer film 4, and the temperature rise of the beam combiner 1 is suppressed.

[0077] Furthermore, Example 1 comprises a substrate and an optical multilayer film 4 directly formed on the substrate surface Q, which is the surface of the substrate. The optical multilayer film 4 alternates between a low refractive index layer 10 and a high refractive index layer 12. The optical multilayer film 4 transmits a first p-polarized laser beam L1 in the blue region and reflects a second s-polarized laser beam L2 in the blue region. The high refractive index layer 12 is made of HfO ２ HfO ２It is a layer. The temperature rise characteristics of the optical multilayer film 4 are such that when formed on a 1-inch square (25.4 mm square) 1 / 4-inch (6.35 mm) thick synthetic quartz substrate and irradiated with 500 W p-polarized blue laser light and 500 W s-polarized blue laser light, the temperature rise remains below 100°C. The temperature rise characteristics in Study Examples 6 and 9 are the same as those in Study Example 1 because the structure of the optical multilayer film 4 in Study Examples 6 and 9 is the same as that of Study Example 1. Therefore, in the beam combiner 1 of Study Examples 1, 6, and 9, the deterioration of the beam quality value BPP of the output laser light LP is suppressed, and damage to the cladding FL of the process fiber F is suppressed.

[0078] [Optical Systems Including Multiple Beam Combiners, Study Examples 13-14] Study Example 13 was designed as a specific example of a second beam combiner 1B having an optical multilayer film 4 containing only the second structural part 24 in optical systems OS2 and OS3. Study Example 14 was designed as a specific example of a first beam combiner 1C having an optical multilayer film 4 containing only the first structural part 25 in optical system OS3. Each layer of the optical multilayer film 4 in Study Examples 13 and 14 was formed in computer simulation with the physical film thickness (nm) shown in Table 6 below. Study Examples 13 and 14 were formed in the same manner as Study Example 1, except for the physical film thickness design. The total number of layers in Study Example 13 was 41. The total number of layers in Study Example 14 was 41.

[0079]

[0080] For examples 13 and 14, the spectral transmittance of p-polarized blue light and the spectral reflectance of s-polarized blue light were calculated in the simulation.

[0081] Figure 34 is a graph showing the spectral transmittance of p-polarized blue light in Study Example 13, obtained from simulation calculations. Figure 35 is a graph showing the spectral reflectance of s-polarized blue light in Study Example 13, obtained from simulation calculations. According to the graph in Figure 34, in Beam Combiner 1 of Study Example 13, the wavelength range in which the transmittance of p-polarized light is 98% or higher includes the region from 410 nm to 462 nm. Therefore, the wavelength range in which the transmittance of p-polarized light is 98% or higher is sufficiently wide, from 52 nm upwards, covering the entire blue region. Also, according to the graph in Figure 35, in Beam Combiner 1 of Study Example 13, the wavelength range in which the reflectance of s-polarized blue light is 98% or higher includes the region from 445 nm to 480 nm, covering the longer wavelength side of the blue region. On the other hand, in Beam Combiner 1 of Study Example 13, the reflectance on the shorter wavelength side of the blue region for s-polarized light is reduced to about 20%.

[0082] Figure 36 is a graph showing the spectral transmittance of p-polarized blue light in Study Example 14, obtained from simulation calculations. Figure 37 is a graph showing the spectral reflectance of s-polarized blue light in Study Example 14, obtained from simulation calculations. According to the graph in Figure 36, in Beam Combiner 1 of Study Example 14, the wavelength range in which the transmittance of p-polarized light is 98% or higher includes the region from 425 nm to 470 nm. Therefore, the wavelength range in which the transmittance of p-polarized light is 98% or higher is sufficiently wide, from 45 nm upwards, covering the entire blue region. Also, according to the graph in Figure 37, in Beam Combiner 1 of Study Example 14, the wavelength range in which the reflectance of s-polarized blue light is 98% or higher includes the region from 410 nm to 445 nm, covering the short-wavelength side of the blue region. On the other hand, in Beam Combiner 1 of Study Example 14, the reflectance on the long-wavelength side of the blue region for s-polarized light is reduced to about 20%.

[0083] Therefore, Example 13 can be used as a second beam combiner 1B in optical systems OS2 and OS3. Also, Example 14 can be used as a first beam combiner 1C in optical system OS3.

[0084] Furthermore, for the optical multilayer films 4 in study examples 13 and 14, the intensity distribution of the electric field generated by the reception of p-polarized and s-polarized blue laser light was calculated by computer simulation, similar to study examples 1 to 3 and 5.

[0085] Figure 38 shows the electric field intensity distribution generated in the optical multilayer film 4 of Study Example 13 for p-polarized blue laser light. Figure 39 shows the electric field intensity distribution generated in the optical multilayer film 4 of Study Example 13 for s-polarized blue laser light. According to Figure 38, the wavelength dependence of the electric field intensity distribution generated by p-polarization is small. This is thought to be because the p-polarized light is transmitted through the optical multilayer film 4 of Study Example 13. According to Figure 39, the wavelength dependence of the electric field intensity distribution generated by s-polarization is large. In particular, the electric field intensity is small on the longer wavelength side of the blue region, farther from the incident medium. This is thought to be because the s-polarized blue light on the longer wavelength side is reflected by the optical multilayer film 4 of Study Example 13.

[0086] Figure 40 shows the electric field intensity distribution generated in the optical multilayer film 4 of Study Example 14 for p-polarized blue laser light. Figure 41 shows the electric field intensity distribution generated in the optical multilayer film 4 of Study Example 14 for s-polarized blue laser light. According to Figure 40, the wavelength dependence of the electric field intensity distribution generated by p-polarization is small. This is thought to be because the p-polarized light is transmitted through the optical multilayer film 4 of Study Example 14. According to Figure 41, the wavelength dependence of the electric field intensity distribution generated by s-polarization is large. In particular, the electric field intensity is small on the side farther from the incident medium on the short wavelength side of the blue region. This is thought to be because the s-polarized blue light on the short wavelength side is reflected by the optical multilayer film 4 of Study Example 14.

[0087] The effects of the examples 13 and 14 are summarized below.

[0088] As shown in Figures 3 and 4, the optical systems OS2 and OS3 as beam combiner systems include: first beam combiners 1A and 1C having an optical multilayer film 4 including first structural parts 21 and 25 that reflect s-polarized laser light on the short wavelength side of the blue region; second beam combiner 1B having an optical multilayer film 4 including a second structural part 24 that reflects s-polarized laser light on the long wavelength side of the blue region; first LD light source D1 that outputs first laser light L1 which is p-polarized blue laser light; second-first LD light source D2A that outputs second-first laser light L2A which is p-polarized laser light on the short wavelength side of the blue region; half-wave plate PA which is a polarization converter that converts second-first laser light L2A to s-polarized light; second-second LD light source D2B that outputs second-second laser light which is p-polarized laser light on the long wavelength side of the blue region; and half-wave plate PB which is a polarization converter that converts second-second laser light L2B to s-polarized light. The first beam combiner 1A combines the first laser beam L1 with the first polarization-converted laser beam LZA, which has been converted from the second-first laser beam L2A to s-polarized light by the half-wave plate PA, and sends the resulting first combined laser beam LM to the second beam combiner 1B. The second beam combiner 1B combines the first combined laser beam LM with the second polarization-converted laser beam LZB, which has been converted from the second-second laser beam L2B to s-polarized light by the half-wave plate PB, and outputs the second combined laser beam LN. Thus, the optical system OS2 is provided in which the intensity of the second combined laser beam LN and thus the output laser beam LP is sufficiently strong, and the temperature rise of the beam combiners 1A and 1B is suppressed by the sharing of reflections. Furthermore, the optical system OS3 is provided such that the intensity of the second combined laser light LN and thus the output laser light LP is sufficiently strong, and the temperature rise of the beam combiners 1C and 1B is suppressed by the division of reflection. Moreover, in the optical system OS2, the optical multilayer film 4 of the first beam combiner 1A that reflects the first polarization-converted laser light LZA on the short wavelength side has a first structural part 21 related to the reflection of s-polarized light on the short wavelength side and a second structural part 22 related to the reflection of s-polarized light on the long wavelength side, and the first structural part 21 is positioned on the incident medium side of the second structural part 22.Therefore, in the optical multilayer film 4 of the first beam combiner 1A, the portion where s-polarized light reflection mainly occurs is located on the side farther from the substrate, further suppressing the temperature rise of the beam combiner 1A.

[0089] 1, 1A, 1B, 1C... Beam combiner 2... Substrate 4... Optical multilayer film OS1, OS2, OS3... Optical system (beam combiner system) (of a blue laser processing machine) Q... Substrate surface.

Claims

1. The device comprises a substrate and an optical multilayer film formed directly or indirectly on the surface of the substrate, wherein the optical multilayer film alternates between low refractive index layers and high refractive index layers, transmits p-polarized blue laser light and reflects s-polarized blue laser light, and the high refractive index layers are made of HfO ２ HfO ２ A beam combiner characterized by having a layer containing monoclinic crystals, wherein the (-111) plane of the monoclinic crystals is oriented in the direction perpendicular to the surface of the substrate.

2. The beam combiner according to claim 1, characterized in that, in the transmittance distribution of p-polarized light in the blue region of the optical multilayer film, the wavelength range of the portion where the transmittance of p-polarized light is 95% or more is 15 nm or more, and in the reflectance distribution of s-polarized light in the blue region of the optical multilayer film, the wavelength range of the portion where the reflectance of s-polarized light is 95% or more is 15 nm or more.

3. The HfO ２ The beam combiner according to claim 1, characterized in that the layer is formed by radical-assisted sputtering.

4. The beam combiner according to claim 1, wherein the optical multilayer film has a first structural part and a second structural part, the first structural part reflects s-polarized laser light on the short wavelength side of the blue region, and the second structural part reflects s-polarized laser light on the long wavelength side of the blue region.

5. The beam combiner according to claim 4, characterized in that the first structural part is arranged on the incident medium side of the second structural part.

6. The beam combiner according to claim 4, characterized in that the first structural part is arranged on the substrate side of the second structural part.

7. The beam combiner comprises: a first beam combiner according to claim 1, which reflects the s-polarized blue laser light relating to the short wavelength side of the blue region; a second beam combiner according to claim 1, which reflects the s-polarized blue laser light relating to the long wavelength side of the blue region; a first light source that outputs a first laser light which is p-polarized blue laser light; a second-first light source that outputs a second-first laser light which is p-polarized laser light relating to the short wavelength side of the blue region; a first polarization converter which converts the second-first laser light to s-polarized light; a second-second light source that outputs a second-second laser light which is p-polarized laser light relating to the long wavelength side of the blue region; and a second polarization converter which converts the second-second laser light to s-polarized light, wherein the first beam combiner combines the first laser light and the second-first laser light converted to s-polarized light by the first polarization converter and sends it to the second beam combiner as first combined light. The beam combiner system is characterized in that the second beam combiner combines the first combined light and the second-second laser light, which has been converted to s-polarization by the second polarization converter, and outputs it as the second combined light.

8. The beam combiner system according to claim 7, wherein the optical multilayer film relating to the first beam combiner has a first structural portion that reflects s-polarized laser light relating to the short wavelength side of the blue region and a second structural portion that reflects s-polarized laser light relating to the long wavelength side of the blue region, and the first structural portion is arranged on the incident medium side of the second structural portion.

Images