Diffraction element and laser processing device

Abstract

This diffraction element (4) diffracts laser light in a laser processing device (1). The diffraction element comprises: an incidence surface (Gp) on which a laser light is incident; and a diffraction grating structure (40) in which a plurality of low refractive index parts (42) and a plurality of high refractive index parts (41) extending in a first direction (X) which intersects the incidence surface are alternately arranged in a second direction (Y) along the incidence surface. The low refractive index parts are formed using a low refractive index material having a refractive index which transmits the laser light. The high refractive index parts are formed using a high refractive index material having a refractive index higher than the refractive index of the low refractive index material. The high refractive index material is tantalum oxide.

Description

Diffraction element and laser processing device

[0001] The present disclosure relates to a diffraction element and a laser processing apparatus.

[0002] U.S. Patent No. 6,277,999 discloses a process for encapsulating a diffraction grating. This encapsulation process involves first filling the grooves of the diffraction grating with a sacrificial layer and then removing excess material. A cover layer is then deposited over the filled diffraction grating. The cover layer is structured to provide slits for selectively etching away the sacrificial layer. This encapsulation of the diffraction grating structure can facilitate improved optical function, or the cover layer can add mechanical stability to an otherwise fragile structure.

[0003] S. Ratzsch, et al., "Encapsulation process for diffraction gratings", Optics Express Vol. 23, Issue 14, pp. 17955-17965 (2015)

[0004] The present disclosure provides a diffraction element and a laser processing apparatus that are easy to use in a laser processing apparatus.

[0005] A diffraction element according to the present disclosure diffracts laser light in a laser processing device. The diffraction element includes an incident surface on which the laser light is incident and a diffraction grating structure in which a plurality of low-refractive index portions and a plurality of high-refractive index portions extending in a first direction intersecting the incident surface are alternately arranged in a second direction along the incident surface. The low-refractive index portions are made of a low-refractive index material having a refractive index that transmits the laser light. The high-refractive index portions are made of a high-refractive index material having a refractive index higher than that of the low-refractive index material. The high-refractive index material is tantalum oxide.

[0006] A laser processing apparatus according to the present disclosure includes a light source that emits laser light and the diffraction element according to any one of aspects 1 to 6. The diffraction element is arranged to diffract the laser light from the light source.

[0007] According to the diffraction element of the present disclosure, it is possible to provide a diffraction element that is easy to use in a laser processing device.

[0008] FIG. 1 illustrates the configuration of a laser processing apparatus according to embodiment 1 of the present disclosure. FIG. 2 explains a method for combining light beams in an optical resonator in embodiment 1. Graph showing the spectrum of the resonant wavelength in the optical resonator. FIG. 3 illustrates the structure of a diffraction element in embodiment 1. FIG. 4 explains a method for manufacturing a diffraction element in embodiment 1. Table showing the refractive indexes of different materials in the diffraction element. Graph showing the diffraction efficiency of a numerical example of a diffraction element in embodiment 1. FIG. 5 illustrates the structure of a diffraction element in embodiment 2. FIG. 6 explains a method for manufacturing a diffraction element in embodiment 2. Graph showing the diffraction efficiency of numerical example 1 of a diffraction element in embodiment 2. Graph showing the diffraction efficiency of numerical example 2 of a diffraction element in embodiment 2.

[0009] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of well-known matters or redundant explanation of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art.

[0010] The applicant provides the accompanying drawings and the following description to enable those skilled in the art to fully understand the present disclosure, and does not intend for them to limit the subject matter described in the claims.

[0011] First Embodiment In a first embodiment, an example in which a diffraction element is used in a laser processing device will be described.

[0012] 1. Regarding the Laser Processing Apparatus 1.1. Configuration The configuration of the laser processing apparatus and optical resonator according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing the configuration of the laser processing apparatus 1 according to this embodiment.

[0013] 1, the laser processing apparatus 1 includes an optical resonator 2, a transmission optical system 10, a processing head 11, and a controller 12. The laser processing apparatus 1 is an example of a laser apparatus that performs various types of laser processing by irradiating various workpieces 15 with laser light. The various types of laser processing include, for example, laser welding, laser cutting, and laser drilling.

[0014] The optical resonator 2 is an example of a laser device that generates laser light output from, for example, the laser processing device 1. In this embodiment, the optical resonator 2 is a wavelength-combining external resonator that combines multiple light beams by resonating them at their respective wavelengths. The wavelength-combining optical resonator 2 makes it easy to obtain good beam quality and narrow the beam diameter.

[0015] 1, the optical resonator 2 according to this embodiment includes an LD (laser diode) array 3 in which a plurality of laser elements 31 to 33 are arranged, an output coupler 25 that emits output light, and an optical system (4, 20) arranged between the LD array 3 and the output coupler 25. Hereinafter, the laser elements 31 to 33 may be collectively referred to as "laser element 30."

[0016] The LD array 3 in the optical resonator 2 is an example of a light source including a plurality of laser elements 30. In Fig. 1, three laser elements 31 to 33 are illustrated as included in the LD array 3. The number of laser elements 30 included in the LD array 3 is, for example, several tens to several hundreds. The output of laser light from the LD array 3 as a light source is, for example, 200 W (watts) or more.

[0017] In the optical resonator 2, the LD array 3 is composed of, for example, a direct diode laser. The rear end face of the LD array 3, with the light beam emission side being the front, is coated with a high-reflectivity coating with, for example, a reflectance of 99.9% or more. The front end face of the LD array 3 is coated with an anti-reflection coating with, for example, a transmittance of 99.9% or more. The multiple laser elements 30 in the LD array 3 have a common spontaneous emission spectrum that corresponds to, for example, the material of the LD light-emitting layer. This spectrum corresponds to, for example, a resonance wavelength band, for example, a blue region with wavelengths of 430 nm to 460 nm.

[0018] The optical system (4, 20) in the optical resonator 2 includes, for example, a diffraction element 4 and a condenser lens 20 that condenses each light beam incident on the diffraction element 4. The optical resonator 2 of this embodiment resonates each light beam of a specific wavelength band in the optical path that travels back and forth between the LD array 3 and the output coupler 25 via this optical system.

[0019] The condenser lens 20 includes one or more lenses, such as a collimator lens. For example, the condenser lens 20 may collimate the laser light in one or more directions selected from the arrangement direction of the laser elements 31 to 33 and a direction orthogonal to the arrangement direction, and may include a beam twister unit.

[0020] The diffraction element 4 is disposed at a position, for example, a distance corresponding to the focal length from the condenser lens 20. In this embodiment, the diffraction element 4 is a dispersive element on which a transmission type diffraction grating is formed. In the optical resonator 2 of this embodiment, the diffraction grating of the diffraction element 4 satisfies the diffraction condition for emitting the light beams from the multiple laser elements 31 to 33 in the same direction and combining them (details will be described later).

[0021] As described below, the diffraction element 4 of this embodiment has a configuration that is easy to manufacture, has high light resistance, wavelength dispersion, and diffraction efficiency that can withstand high-power laser light, and is useful for implementation in the optical resonator 2 in the laser processing device 1.

[0022] The output coupler 25 is disposed in the direction in which the light beam diffracted by the diffraction element 4 is emitted. The output coupler 25 includes, for example, a mirror element having a predetermined transmittance and reflectance. Of the light beam incident on the output coupler 25 from the diffraction element 4, a transmitted component according to the transmittance is output to, for example, the transmission optical system 10 as the output of the optical resonator 2. On the other hand, a reflected component according to the reflectance is returned to the diffraction element 4 for optical resonance. The output coupler 25 may be provided with a mechanism capable of adjusting the reflectance and transmittance.

[0023] In the laser processing device 1, the transmission optical system 10 is an optical system that transmits the laser light from the optical resonator 2 to the processing head 11, and includes, for example, an optical fiber. The processing head 11 is, for example, disposed opposite to the workpiece 15, and is a device that irradiates the workpiece 15 with the laser light transmitted from the optical resonator 2.

[0024] The controller 12 is a control device that controls the overall operation of the laser processing apparatus 1. The controller 12 includes, for example, a CPU or MPU that works in cooperation with software to realize predetermined functions. The controller 12 may include an internal memory that stores various programs and data, and various interfaces that allow the user to input oscillation conditions and the like. The controller 12 may also include hardware circuits such as an ASIC or FPGA that realize various functions. The controller 12 may also be configured integrally with a drive circuit for the light source.

[0025] 1.2 Operation The operation of the laser processing device 1 configured as above will be described below.

[0026] The laser processing device 1 (FIG. 1) of this embodiment drives the LD array 3 of the optical resonator 2 based on oscillation conditions set in, for example, a controller 12, and causes the optical resonator 2 to generate laser light. The laser processing device 1 performs various types of laser processing by irradiating the laser light generated in the optical resonator 2 from the processing head 11 to a processing object 15 under the control of, for example, the controller 12.

[0027] For example, in the laser processing device 1 as described above, the condenser lens 20 of the optical resonator 2 condenses a plurality of light beams from the LD array 3 and supplies the condensed light beams to the diffraction element 4 .

[0028] The diffraction element 4 combines multiple light beams from each LD array 3 by diffracting light so that light having a wavelength λ is incident at an incident angle α and emitted at a diffraction angle β, according to a diffraction condition such as the following equation (1): sin α + sin β = mλ / d ... (1) where d is the pitch of the diffraction element 4 and m is the diffraction order. FIG. 2 is a diagram illustrating a method for combining light beams in the diffraction element 4 of the optical resonator 2. The incident angle α (= α1 to α3) and diffraction angle β in the above equation (1) are defined at the incidence and emission of light to and from a diffraction grating structure 40 in the diffraction element 4, as shown in FIG. 2, for example.

[0029] In the diffraction element 4, as shown in Fig. 2, for example, the incident angles α (= α1, α2, α3) of the light beams from the laser elements 31, 32, 33 are different from one another. In the optical resonator 2 of this embodiment, different resonance wavelengths λ = λ1, λ2, λ3 are set for the laser elements 31, 32, 33, for example, based on the above formula (1), so that the diffraction angles β of the light beams are the same. As a result, the light beams from the multiple LD arrays 3 are diffracted and then emitted in the same direction from the diffraction element 4 along the optical path as shown in Fig. 2.

[0030] Fig. 3 is a graph showing the spectrum of the resonant wavelength λ in the optical resonator 2. In the graph of Fig. 3, the horizontal axis represents wavelength, and the vertical axis represents light intensity.

[0031] 3 shows the individual resonance spectra S1 to S3 of the multiple laser elements 31 to 33 in the LD array 3, as well as a common spontaneous emission spectrum S0. Each of the resonance spectra S1, S2, and S3 indicates the distribution of the resonance wavelength λ of each of the LDs 31, 32, and 33. The spontaneous emission spectrum S0 includes a specific wavelength band, such as the blue region. The combined light beam enters the output coupler 25.

[0032] The output coupler 25 reflects a portion of the light beam combined at the diffraction element 4 and returns it to each laser element 30 by causing it to travel backward. For example, due to the backward travel of the light path illustrated in Fig. 2, the light beams having multiple wavelengths λ1, λ2, and λ3 are separated at different angles α1, α2, and α3 for the wavelengths λ1, λ2, and λ3 at the diffraction element 4, similar to the angle of incidence α from each of the laser elements 31, 32, and 33 to the diffraction element 4, and are then emitted. Each of the separated light beams further travels backward through the condenser lens 20, etc., and is returned to the laser elements 31, 32, and 33 from which they were incident.

[0033] In this way, in the optical resonator 2, return light for laser oscillation is supplied over various resonance wavelengths λ (=λ1 to λ3), and optical resonance can be generated between the rear end face of the LD array 3 and the output coupler 25. In addition, the light beam that has passed through the output coupler 25 is used as the output of the laser processing device 1, for example.

[0034] 2. Diffraction Element The diffraction element 4 in this embodiment will be described below with reference to FIGS.

[0035] 2.1 Element Structure Fig. 4 illustrates the structure of the diffraction element 4 in embodiment 1. In the diffraction element 4 of this embodiment, as shown in Fig. 4, for example, a diffraction grating structure 40 in which a plurality of recesses 41 are periodically arranged is provided on one of the two main surfaces of a transparent substrate 45.

[0036] Hereinafter, the thickness direction of the transparent substrate 45 is defined as the X direction, the arrangement direction of the recesses 41 along the main surface of the transparent substrate 45 is defined as the Y direction, and the depth direction on the main surface perpendicular to the Y direction is defined as the Z direction. Figure 4 illustrates a partial cross section of the diffraction element 4 in the Y direction. In this embodiment, the X direction is an example of a first direction, and the Y direction is an example of a second direction.

[0037] The diffraction element 4 is disposed, for example, between the LD array 3 and the output coupler 25 in the laser processing apparatus 1 (FIG. 1), with the +X side principal surface on which the diffraction grating structure 40 is provided, of the ±X side principal surfaces, facing the direction in which the laser light emitted from the LD array 3 is incident. Hereinafter, the +X side of the ±X sides of the diffraction element 4 (FIG. 4) will be referred to as the upper side, and the -X side will be referred to as the lower side. The upper surface of the diffraction grating structure 40 will be referred to as the grating plane Gp. The grating plane Gp is ​​an example of an incident plane that serves as a reference for incidence on the diffraction grating structure 40 in this embodiment.

[0038] In the diffraction element 4, the transparent substrate 45 is made of a transparent material having a refractive index that transmits light in a predetermined wavelength range, for example, in the blue region that is the same as the laser light of the LD array 3. The transparent substrate 45 in this embodiment is made of, for example, quartz (SiO ２ ), and such transparent materials are examples of low refractive index materials.

[0039] The plurality of recesses 41 in the diffraction element 4 have the same cross-sectional shape along, for example, the Z direction. A protrusion 42 extending toward the +X side is formed between each pair of adjacent recesses 41. The protrusion 42 is an example of a low refractive index portion in this embodiment.

[0040] In the diffraction grating structure 40, the plurality of recesses 41 and the plurality of protrusions 42 are alternately and periodically arranged in the Y direction. The diffraction grating structure 40 has a grating depth Vg, a grating period Wg, a duty ratio W1 / Wg, a recess width W1, and a protrusion width W2.

[0041] The grating depth Vg is the length of the recessed portion 41 in the X direction and corresponds to the height of the protruding portion 42. In this embodiment, the grating depth Vg is, for example, 350 nm to 500 nm with the grating plane Gp as the reference. The grating period Wg is the period in which a pair of one recessed portion 41 and one protruding portion 42 is arranged in the Y direction, and is the same as the pitch d in the above-mentioned formula (1). In this embodiment, the grating period Wg is, for example, 260 nm to 300 nm. The duty ratio W1 / Wg is the ratio of the recessed portion width W1 to the grating period Wg. In this embodiment, the duty ratio W1 / Wg is, for example, 45 to 55%.

[0042] The recess width W1 is the width of one recess 41 in the Y direction. The recess 41 is, for example, rectangular and has a relatively high aspect ratio W1 / Vg (for example, 3 to 6). The protrusion width W2 is the width of one protrusion 42 in the Y direction. The protrusion 42 is, for example, rectangular and has a relatively high aspect ratio W2 / Vg (for example, 3 to 6).

[0043] In the diffraction element 4 of this embodiment, as shown in FIG. 4, the recesses 41 in the diffraction grating structure 40 are not hollow but are filled with a highly refractive material. The highly refractive material in the recesses 41 has a refractive index higher than that of the transparent substrate 45 (see FIG. 6). In this embodiment, the highly refractive material in the recesses 41 in the diffraction element 4 is tantalum pentoxide (TaO ). ２ O ５ ) (also called "tantalum oxide"). The recess 41 is an example of a high refractive index portion in this embodiment.

[0044] The diffraction element 4 of this embodiment also includes a cover layer 43 on the upper side of the diffraction grating structure 40. The cover layer 43 is a thin layer that covers the diffraction grating structure 40 and has a thickness of, for example, 10 nm to 2000 nm in the X direction. The cover layer 43 of this embodiment is integrally formed from the same high refractive index material as the recesses 41 in the diffraction grating structure 40.

[0045] Furthermore, the diffraction element 4 of this embodiment includes an anti-reflection coating 46 on the upper side of the cover layer 43. According to the diffraction element 4 of this embodiment, the cover layer 43 is provided on the diffraction grating structure 40, which makes it easy to apply an anti-reflection (AR) coating to the +X side of the diffraction element 4. In this embodiment, the incident surface of the diffraction element 4 is not limited to the grating surface Gp of the diffraction grating structure 40, but may be any of various upper principal surfaces of the diffraction element 4. For example, the incident surface of the diffraction element 4 may be formed by the cover layer 43, the anti-reflection coating 46, etc.

[0046] The diffraction element 4 also includes an anti-reflection coating 47, for example, on the underside of the transparent substrate 45. The reflectance of the anti-reflection coatings 46, 47 is, for example, 0.5% or less in the wavelength band of the laser light. These anti-reflection coatings 46, 47 can suppress, for example, internal reflection within the diffraction element 4 or reflection of light entering or leaving the diffraction element 4.

[0047] According to the diffraction element 4 of this embodiment configured as described above, by filling the recesses 41 with the high refractive index material, it is possible to achieve both light resistance to laser light in the high-output laser processing device 1 and ease of manufacture. Furthermore, the diffraction grating structure 40 having high aspect ratios W1 / Vg and W2 / Vg, for example, can provide high optical performance such as high diffraction efficiency.

[0048] 2.1.1 Light Resistance In the diffraction element 4 of this embodiment, tantalum oxide is used as the high refractive index material of the recesses 41 from the viewpoint of providing light resistance to high-power (e.g., 300 W) laser light in the laser processing apparatus 1. This high refractive index material of the diffraction element 4 of this embodiment can achieve greater resistance to high-power lasers than, for example, TiO2.

[0049] The light resistance effect of the diffraction element 4 of this embodiment as described above was confirmed by a light resistance test in which the temperature rise of a sample was evaluated under the following irradiation conditions: the wavelength band of the light source was 430 nm to 460 nm, the irradiation time was 2 minutes, the power was 300 W, and the beam area was 0.0152 cm. ２ and the power density is 19.76 kW / cm ２Furthermore, in the diffraction element 4 of this embodiment, a low refractive index material having high light resistance can be used in the low refractive index portion as well as the high refractive index portion. For example, SiO ２ can be adopted.

[0050] 2.2. Manufacturing Method of Diffraction Element Before explaining the manufacturing method of the diffraction element 4 of this embodiment, first, the problems with conventional manufacturing techniques will be explained.

[0051] 2.2.1. Conventional Issues According to the manufacturing process of the conventional technology (Non-Patent Document 1), a diffraction grating is manufactured in a hollow structure with a narrow pitch of 200 nm to 400 nm and a high aspect ratio, which makes it possible to achieve high performance such as high dispersion ability and diffraction efficiency. However, this conventional manufacturing process is complex and time-consuming and cost-intensive. Specifically, the process of forming the hollow structure by forming a cover layer for the diffraction grating and then removing the sacrificial layer below the cover layer is quite difficult (see Figures 1(e) and 1(f) of Non-Patent Document 1).

[0052] Therefore, in this embodiment, a diffraction element 4 that can be manufactured by a simple manufacturing process and a manufacturing method thereof are provided.

[0053] 5A to 5C, a method for manufacturing the diffraction element 4 according to the present embodiment will be described. 5A, 5B, and 5C illustrate the first, second, and third steps of this manufacturing method.

[0054] In this manufacturing method, first, as shown in FIG. 5A, a plurality of recesses 41 are periodically formed on the upper side (+X side) of a transparent substrate 45, and a low refractive index material (SiO ２ ) to form the diffraction grating structure 40. This step can be performed by, for example, exposure and etching using a mask corresponding to the protrusions 42.

[0055] Next, as shown in FIG. 5B, tantalum oxide (Ta ２ O ５5B) to form a deposition layer 44 of a highly refractive material. The deposition step of FIG. 5B is performed by, for example, a vapor deposition method. The vapor deposition method may be physical vapor deposition such as vacuum deposition or sputtering, or may be various chemical vapor deposition methods.

[0056] Next, a highly refractive material (Ta ２ O ５ 5C, the upper surface of the deposition layer 44 is polished to a flat surface, and the cover layer 43 is formed.

[0057] Thereafter, AR coating is applied to both surfaces of the diffraction element 4 on the ±X sides, to form anti-reflection coatings 46 and 47, for example, as shown in Fig. 4. In this way, the diffraction element 4 of this embodiment can be manufactured.

[0058] According to the above manufacturing method, the diffraction element 4 of this embodiment can be manufactured by filling the recesses 41 of the diffraction grating structure 40 with a high refractive index material ( FIG. 5B ) and then not removing the high refractive index material filled in the recesses 41. Moreover, there is no need to particularly structure the cover layer 43 of the diffraction element 4 with slits as in the prior art.

[0059] As described above, the diffraction element 4 of this embodiment can simplify the manufacturing process compared to the conventional technology. Furthermore, since it is not necessary to provide slits in the cover layer 43 as in the conventional technology, the mechanical stability of the diffraction element 4 can be improved. Furthermore, filling the recesses 41 in the diffraction element 4 can improve the stability of the diffraction grating structure 40 itself.

[0060] 5B and 5C, the diffraction element 4 of this embodiment can form the cover layer 43 using a deposition layer 44 obtained in the step of depositing a highly refractive material. In this respect, the diffraction element 4 of this embodiment can be manufactured using a simple manufacturing process.

[0061] 2.3. Numerical Examples Numerical examples in which the optical performance of the diffraction element 4 in this embodiment was verified by numerical simulation will be described with reference to FIGS. 6 and 7. FIG.

[0062] In this numerical example, the diffraction element 4 has dimensions of 5 mm in thickness in the X direction, 65 mm in length in the Y direction, and 15 mm in depth in the Z direction. In this example, the diffraction grating structure 40 has a grating period Wg=280 nm, a grating depth Vg=450 nm, and a duty ratio W1 / Wg=50%.

[0063] In this numerical example, a numerical simulation was performed for the case where the laser beam incident on the diffraction element 4 in the laser processing apparatus 1 has a wavelength range of 430 nm to 460 nm. ２ O ５ and SiO as a low refractive index material ２ The refractive indexes of the respective wavelengths are shown in FIG.

[0064] In this numerical example, a numerical calculation was performed on the diffraction efficiency for each wavelength when the incident angle of the above-mentioned light from the cover layer 43 to the grating surface Gp (see FIG. 4) of the diffraction element 4 was 21°. In this case, the incident angle of the light incident on the diffraction element 4 from the air outside the diffraction element 4 was 47.88°. Furthermore, rigorous coupled-wave analysis (RCWA) was used for this numerical calculation.

[0065] In the diffraction grating structure 40 of the laser processing apparatus 1, from the viewpoint of aligning the diffraction angles for different wavelengths, the incident angle α varies for each wavelength (see formula (1) and FIG. 2). For example, for wavelengths of 430 nm to 460 nm, the incident angle α on the grating plane Gp is ​​19.4° to 22.6°. However, since the change in diffraction efficiency at this time is small, the incident angle is set to a fixed value in this example.

[0066] The calculation results of such a numerical example of this embodiment are shown in Fig. 7. In Fig. 7, the horizontal axis indicates wavelength in micrometers, and the vertical axis indicates normalized diffraction efficiency in arbitrary units between 1 and 0.

[0067] 7 illustrates the diffraction efficiency T1 of the first-order transmitted light, the diffraction efficiency Ta of the entire transmitted light, and the diffraction efficiency Ra of the entire reflected light. With the diffraction element 4 of this example, it was verified that high optical performance could be obtained, for example, as shown in FIG. 7, in which the diffraction efficiency T1 of the first-order transmitted light is greater than 92.6%.

[0068] 3. Summary As described above, the diffraction element 4 in this embodiment diffracts laser light in the laser processing apparatus 1. The diffraction element 4 includes an incident surface (e.g., grating surface Gp) on which the laser light is incident, and a diffraction grating structure 40. In the diffraction grating structure 40, a plurality of convex portions 42 and a plurality of concave portions 41 extending in the X direction, which is an example of a first direction intersecting the incident surface, are alternately arranged in the Y direction, which is an example of a second direction along the incident surface. The convex portions 42 are an example of a low refractive index portion and are made of a low refractive index material having a refractive index that transmits the laser light. The concave portions 41 are an example of a high refractive index portion and are made of a high refractive index material having a refractive index higher than that of the low refractive index material. The high refractive index material is tantalum oxide.

[0069] According to the above-described diffraction element 4, by using tantalum oxide, which has high light resistance, as the high refractive index material filled into the recesses 41 and the high refractive index portions, it is possible to make it easy to use in a laser processing device.

[0070] In this embodiment, the diffraction element 4 further includes a cover layer 43. The cover layer 43 is made of a high refractive index material and covers the diffraction grating structure 40 on the incident surface. In the diffraction element 4 of this embodiment, the recesses 41 are made of a high refractive index material, which makes it possible to, for example, in the manufacturing process, eliminate the need to remove the deposition layer 44 in the recesses 41 after forming the cover layer 43, making it easier to manufacture the diffraction element 4. Furthermore, in the diffraction element 4 of this embodiment, the high refractive index portion can be formed integrally with the recesses 41, for example, which makes it easier to manufacture the diffraction element 4.

[0071] In the diffraction element 4 of this embodiment, an anti-reflection coating 46 that suppresses reflection of laser light on the incident surface is provided on the cover layer 43. According to the diffraction element 4 of this embodiment, the anti-reflection coating 46 can be formed on the cover layer 43, which makes it easier to manufacture the diffraction element 4.

[0072] In the diffraction element 4 of this embodiment, in the diffraction grating structure 40, the length of the high refractive index portion in the Y direction, i.e., the grating depth Vg, may be 350 nm to 500 nm. The period of the pair of high refractive index portion and low refractive index portion in the X direction, i.e., the grating period Wg, may be 260 nm to 300 nm. The ratio of the width of the high refractive index portion to the grating period Wg, i.e., the duty ratio W1 / Wg, may be 45 to 55%. This allows the diffraction element 4 of this embodiment to achieve high diffraction efficiency for laser light in the blue region, for example.

[0073] In this embodiment, the diffraction element 4 includes a transparent substrate 45. The transparent substrate 45 is an example of a substrate that is integral with the low refractive index portion of the diffraction grating structure 40 and transmits laser light. The diffraction element 4 of this embodiment can be used as a transmission type diffraction grating and is easy to use in, for example, the laser processing apparatus 1.

[0074] In this embodiment, the laser processing apparatus 1 includes an LD array 3 and a diffraction element 4. The LD array 3 is an example of a light source that emits laser light. The diffraction element 4 is arranged to diffract the laser light from the LD array 3. According to the laser processing apparatus 1 of this embodiment, the high light resistance of the diffraction element 4 makes it possible to use high-power laser light.

[0075] In the laser processing apparatus 1 of this embodiment, the laser light includes a plurality of light beams having different wavelengths (see FIG. 3). The diffraction element 4 is arranged to combine the plurality of light beams by diffraction according to wavelength (see FIG. 2). In such a laser processing apparatus 1, the diffraction element 4 of this embodiment makes it easy to achieve high output by wavelength-combined laser output.

[0076] In the laser processing apparatus 1 of this embodiment, the output of the laser light from the light source such as the LD array 3 is 200 W or more. In such a laser processing apparatus 1, the diffraction element 4 of this embodiment is easy to use because it has high light resistance.

[0077] In the laser processing apparatus 1 of this embodiment, the wavelength of the laser light from the light source is in the blue region of 430 nm to 460 nm. In such a laser processing apparatus 1, the diffraction element 4 of this embodiment is easy to use because it has high light resistance.

[0078] 8 to 11, a second embodiment will be described. In the first embodiment, a diffraction element 4 in which a cover layer 43 is made of a high refractive index material has been described. In the second embodiment, a diffraction element 4A in which a cover layer 43A is made of a low refractive index material will be described.

[0079] Hereinafter, the description of the configuration and operation similar to those of the laser processing device 1 and the diffraction element 4 according to the first embodiment will be omitted as appropriate, and only the diffraction element 4A according to this embodiment will be described.

[0080] Fig. 8 illustrates the structure of a diffraction element 4A according to embodiment 2, similarly to Fig. 4. The diffraction element 4A according to this embodiment has a configuration similar to that of the diffraction element 4 according to embodiment 1, but includes a cover layer 43A made of a low refractive index material instead of the cover layer 43 made of a high refractive index material, as illustrated in Fig. 8.

[0081] In the diffraction element 4 of the first embodiment, the cover layer 43 is integrally formed with the high refractive index material filling the recesses 41 (FIG. 4). In the diffraction element 4A of this embodiment, the cover layer 43A is formed separately from the recesses 41. In this embodiment, the cover layer 43A is formed of the same low refractive index material as the transparent substrate 45, for example, SiO ２ It consists of:

[0082] The diffraction element 4A of this embodiment has, for example, a grating depth Vg of 400 nm to 600 nm, a grating period Wg of 280 nm to 350 nm, and a duty ratio W1 / Wg of 45% to 55%. The diffraction element 4A of this embodiment has high light resistance similar to that of the diffraction element 4 of the first embodiment, and can also improve optical performance such as wavelength dispersion and diffraction efficiency.

[0083] 9A and 9B are diagrams illustrating a method for manufacturing the diffraction element 4A in embodiment 2. In the method for manufacturing the diffraction element 4A in this embodiment, for example, the first and second steps (FIGS. 5A and 5B) in embodiment 1 are performed, and then the third and fourth steps shown in FIGS. 9A and 9B are sequentially performed instead of the third step (FIG. 5C).

[0084] Specifically, after the deposition process of FIG. 5B, a high refractive index material (Ta ２ O ５ 9A, in this embodiment, when polishing the deposition layer 44, the deposition layer 44 is polished down to the lattice plane Gp, for example, as shown in FIG. 9A.

[0085] Next, as shown in FIG. 9B, SiO ２ 9B is performed by evaporation, for example, in the same manner as in the deposition process of FIG.

[0086] Thereafter, AR coating is performed in the same manner as in the first embodiment, and the diffraction element 4A of this embodiment can be manufactured as shown in FIG.

[0087] Numerical examples of the diffraction element 4A in this embodiment will be described below.

[0088] 10 and 11 show the diffraction efficiencies of Numerical Examples 1 and 2 of the diffraction element 4A of Embodiment 2, respectively, in the same manner as in FIG. 7 of Embodiment 1. In Numerical Examples 1 and 2, the diffraction efficiency of the diffraction element 4A of Embodiment 2 was numerically simulated in the same manner as in the Numerical Example ( FIG. 7 ) of Embodiment 1. In Numerical Examples 1 and 2 of FIGS. 10 and 11 , the dimensions of the diffraction element 4A are set to the same values ​​as in the Numerical Example of Embodiment 1.

[0089] In Numerical Example 1 of this embodiment, the diffraction grating structure 40A in the diffraction element 4A is set to a grating period Wg = 340 nm, a grating depth Vg = 535 nm, and a duty ratio W1 / Wg = 50%. In this case, the angle of incidence α on the grating surface Gp of the diffraction element 4A varies from 23.6° to 27.5° in the same wavelength band as in embodiment 1, but since the change in diffraction efficiency due to this difference is minimal, it was set to α = 25.5°. In this case, the angle of incidence from the outside of the diffraction element 4A was 37.38°. According to this example, as shown in FIG. 10, the diffraction efficiency T1 of the first-order transmitted light was greater than 93.3%, confirming the improvement in the optical performance of the diffraction element 4A.

[0090] In Numerical Example 2, the diffraction grating structure 40A in the diffraction element 4A was set to a grating period Wg = 280 nm, a grating depth Vg = 438 nm, and a duty ratio W1 / Wg = 50%. The incident angle α on the grating surface Gp of the diffraction element 4A in this case varied from 29.3° to 34.3° in the same wavelength band as in the above examples, but since the change in diffraction efficiency due to this difference was minimal, it was set to α = 31.8°. In this case, the incident angle from the outside of the diffraction element 4A was 46.62°. According to this example, as shown in FIG. 11, the diffraction efficiency T1 of the first-order transmitted light was greater than 95.3%, confirming the high-performance effect of the diffraction element 4A.

[0091] In this embodiment, the cover layer 43A of the diffraction element 4A is made of a low refractive index material and covers the diffraction grating structure 40A on the incident surface. The diffraction element 4A of this embodiment can easily improve optical performance such as wavelength dispersion and diffraction efficiency, and is easy to use in, for example, the laser processing apparatus 1.

[0092] In the diffraction element 4A of this embodiment, the low refractive index material may be quartz. In the diffraction grating structure 40A, the grating depth Vg may be 400 nm to 600 nm, the grating period Wg may be 280 nm to 350 nm, and the duty ratio W1 / Wg may be 45% to 55%. As a result, the diffraction element 4A of this embodiment can also achieve high diffraction efficiency, similar to, for example, embodiment 1.

[0093] (Other Embodiments) As described above, embodiments 1 and 2 have been described as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited to these and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. It is also possible to combine the components described in each of the above embodiments to create new embodiments. Therefore, other embodiments will be described below as examples.

[0094] In the above-described first embodiment, the diffraction element 4 has been described in which the cover layer 43 is integrally formed with the recessed portion 41 serving as the high refractive index portion. In the diffraction element 4 of this embodiment, the cover layer 43 may be made of, for example, a high refractive index material, or may be formed separately from the recessed portion 41 serving as the high refractive index portion.

[0095] In the above embodiments, the diffraction element 4, 4A is described as having a cover layer 43, 43A made of a high-refractive index material or a low-refractive index material. In the diffraction element of this embodiment, the cover layer 43, 43A is not necessarily provided, and an element configuration such as that shown in FIG. 5A may be employed. For example, in the diffraction element 4 of this embodiment, instead of providing the cover layer 43, 43A as in embodiments 1 and 2, an anti-reflection coating 46 may be provided on the grating surface Gp of the diffraction grating structure 40, 40A. Alternatively, a film material or the like may be used instead of the cover layer 43, 43A.

[0096] In each of the above embodiments, quartz (SiO ２ In the diffraction element 4 of this embodiment, the low refractive index material is not limited to quartz, but may be any other transparent material having high light resistance.

[0097] Furthermore, in each of the above embodiments, an example has been described of a wavelength combining type laser processing apparatus 1. In this embodiment, the laser processing apparatus 1 is not particularly limited to a wavelength combining type, but may be, for example, a spatial combining type, or may be provided with a laser light source that is not a light source array, such as an LD array 3. In such a laser processing apparatus 1, the diffraction element 4 is easy to use, as in the above embodiments.

[0098] Furthermore, in each of the above embodiments, an example has been described in which the wavelength band of the laser light in the laser processing apparatus 1 is in the blue region. In this embodiment, the wavelength band of the laser light is not limited to the above, and may be, for example, in the red region, or may have a wavelength of, for example, 900 nm to 950 nm.

[0099] (Examples of Aspects) Various aspects of the present disclosure will be exemplified below.

[0100] A first aspect of the present disclosure is a diffraction element for diffracting laser light in a laser processing device. The diffraction element includes an incident surface on which the laser light is incident and a diffraction grating structure in which a plurality of low refractive index portions and a plurality of high refractive index portions extending in a first direction intersecting the incident surface are alternately arranged in a second direction along the incident surface. The low refractive index portions are made of a low refractive index material having a refractive index that transmits the laser light. The high refractive index portions are made of a high refractive index material having a refractive index higher than that of the low refractive index material. The high refractive index material is tantalum oxide.

[0101] In a second aspect, the diffraction element according to the first aspect further comprises a cover layer made of a low refractive index material or a high refractive index material, which covers the diffraction grating structure on the incident surface.

[0102] In a third aspect, in the diffraction element according to the second aspect, the cover layer is provided with an anti-reflection coating that suppresses reflection of laser light on the incident surface.

[0103] In a fourth aspect, in the diffraction element according to any one of the first to third aspects, the cover layer is made of a high refractive index material. In the diffraction grating structure, the length of the high refractive index portion in the first direction is 350 nm to 500 nm, the period of the pair of the high refractive index portion and the low refractive index portion in the second direction is 260 nm to 300 nm, and the ratio of the width of the high refractive index portion to the period is 45 to 55%.

[0104] In a fifth aspect, in the diffraction element according to any one of the first to third aspects, the cover layer is made of a low refractive index material, such as quartz. In the diffraction grating structure, the length of the high refractive index portion in the first direction is 400 nm to 600 nm, the period of the pair of high refractive index portion and low refractive index portion in the second direction is 280 nm to 350 nm, and the ratio of the width of the high refractive index portion to the period is 45 to 55%.

[0105] In a sixth aspect, the diffraction element according to any one of the first to fifth aspects includes a substrate that is integral with the low refractive index portion in the diffraction grating structure and transmits laser light.

[0106] A seventh aspect is a laser processing apparatus comprising a light source that emits laser light and a diffraction element according to any one of the first to sixth aspects, wherein the diffraction element is arranged to diffract the laser light from the light source.

[0107] In an eighth aspect, in the laser processing apparatus according to the seventh aspect, the laser light includes a plurality of light beams having different wavelengths, and the diffraction element is arranged to combine the plurality of light beams by diffraction according to wavelength.

[0108] In a ninth aspect, in the laser processing apparatus according to the seventh or eighth aspect, the output of the laser light from the light source is 200 W or more.

[0109] In a tenth aspect, in the laser processing apparatus according to any one of the seventh to ninth aspects, the wavelength of the laser light from the light source is 430 nm to 460 nm.

[0110] As described above, the embodiments have been described as examples of the technology in the present disclosure, and for that purpose, the accompanying drawings and detailed description have been provided.

[0111] Therefore, the components shown in the accompanying drawings and detailed description may include not only essential components for solving the problem, but also components that are not essential for solving the problem in order to illustrate the above technology. Therefore, the fact that these non-essential components are shown in the accompanying drawings or detailed description should not be interpreted as immediately indicating that these non-essential components are essential.

[0112] Furthermore, since the above-described embodiments are intended to illustrate the technology of the present disclosure, various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents.

[0113] The present disclosure is applicable to a diffraction element used in, for example, a laser processing device.

Claims

1. A diffraction element that diffracts laser light in a laser processing device, comprising: an incident surface on which the laser light is incident; and a diffraction grating structure in which a plurality of low refractive index portions and a plurality of high refractive index portions extending in a first direction intersecting the incident surface are alternately arranged in a second direction along the incident surface, wherein the low refractive index portions are made of a low refractive index material having a refractive index that transmits the laser light, and the high refractive index portions are made of a high refractive index material having a refractive index higher than the refractive index of the low refractive index material, and the high refractive index material is tantalum oxide.

2. The diffraction element according to claim 1, further comprising a cover layer made of the low refractive index material or the high refractive index material and covering the diffraction grating structure on the incident surface.

3. The diffraction element according to claim 2, wherein the cover layer is provided with an anti-reflection coating for suppressing reflection of the laser light at the incident surface.

4. A diffraction element according to claim 2 or 3, wherein the cover layer is made of the high refractive index material, and in the diffraction grating structure, the length of the high refractive index portion in the first direction is 350 nm to 500 nm, the period of the pair of the high refractive index portion and the low refractive index portion in the second direction is 260 nm to 300 nm, and the ratio of the width of the high refractive index portion to the period is 45 to 55%.

5. A diffraction element according to claim 2 or 3, wherein the cover layer is made of the low refractive index material, the low refractive index material is quartz, and in the diffraction grating structure, the length of the high refractive index portion in the first direction is 400 nm to 600 nm, the period of the pair of the high refractive index portion and the low refractive index portion in the second direction is 280 nm to 350 nm, and the ratio of the width of the high refractive index portion to the period is 45 to 55%.

6. The diffraction element according to any one of claims 1 to 3, further comprising a substrate that is integral with the low refractive index portion in the diffraction grating structure and transmits the laser light.

7. A laser processing device comprising: a light source that emits the laser light; and a diffraction element according to any one of claims 1 to 3, wherein the diffraction element is arranged so as to diffract the laser light from the light source.

8. The laser processing device according to claim 7, wherein the laser light includes a plurality of light beams having mutually different wavelengths, and the diffraction element is arranged so as to combine the plurality of light beams by diffraction according to wavelength.

9. The laser processing device according to claim 7, wherein the output of the laser light from the light source is 200 W or more.

10. The laser processing device according to claim 7, wherein the wavelength of the laser light from the light source is 430 nm to 460 nm.

Images