Diffraction device, laser device, interference fringe formation method, and laser beam diffraction method

Abstract

A diffraction device (10) comprises: a flow path element (12) in which a flow path through which a gas flows is formed; and an excitation light source unit (20) for irradiating the gas flowing through the flow path formed in the flow path element with a plurality of excitation laser beams, wherein the flow path element (12) has a first flow path (41) which extends along a first direction and through which a first gas (V1) containing molecules that resonantly absorb the excitation laser beams flows, and a pair of second flow paths (42, 42) which are formed so as to extend along the first direction and sandwich the first flow path therebetween along a second direction intersecting the first direction and through which a second gas (V2) containing molecules that do not resonantly absorb the excitation laser beams flows, and an opening (14) which is provided to penetrate the flow path element along the second direction so as to extend from one of the second flow paths through the first flow path to the other second flow path when viewed from a third direction intersecting the first direction and the second direction.

Description

Diffraction device, laser device, interference fringe forming method, and laser light diffraction method

[0001] The present disclosure relates to a diffraction device, a laser device, an interference fringe forming method, and a laser light diffraction method.

[0002] Patent Document 1 describes a diffractive light-collecting optical element device. This diffractive light-collecting optical element device includes a gas generating means for supplying a gas containing molecules that resonantly absorb light to form a certain region, and an optical excitation means for optically exciting the gas by irradiating the region with excitation laser light having a wavelength in the absorption band of the molecules so that the excitation laser light intersects within the region, and for generating interference fringes with curvature within the region by providing one or both of a focusing optical system and a diverging optical system in at least one of the optical paths of the two excitation laser light beams that are to be intersected.

[0003] The gas generating means has a gas generating unit and a gas flow path. The gas flow path supplies the gas generated in the gas generating unit and functions to form a certain region for exciting the gas with an excitation laser. As an example, the gas flow path has a rectangular cross-sectional shape and a sufficient length, and an opening is provided in the center. The excitation laser light and the controlled laser light are incident on the inside of the gas flow path through this opening. At the opening of the gas flow path, interference fringes are formed by the interference of the excitation laser light. The controlled laser light is diffracted by a density modulation structure excited by these interference fringes. The size of the opening is approximately 6 mm long x 10 mm wide.

[0004] Japanese Patent Application Laid-Open No. 2021-105693

[0005] Incidentally, it is desirable that the gas flow used to form the interference fringes be in a laminar flow state at the opening of the gas flow passage.

[0006] On the other hand, for example, in laser fusion or laser processing, when the controlled laser light becomes more energetic, it is thought that by increasing the cross-sectional area of ​​the laser (for example, to about 3 cm x 3 cm) in accordance with the increase in energy and keeping the energy per unit area constant, it will be possible to achieve suitable diffraction due to the density modulation structure excited by the interference fringes formed in the gas flow at the opening of the gas flow path.

[0007] On the other hand, in this case, the size of the opening of the gas flow path must also be increased in accordance with the increase in the cross-sectional area of ​​the controlled laser beam, which may cause turbulence in the gas flow passing through the opening of the gas flow path, thereby impairing the stability of diffraction control.Therefore, in the above technical field, there is a demand for ensuring the stability of diffraction control even when the size of the opening is increased.

[0008] Therefore, an object of the present disclosure is to provide a diffraction device, a laser device, an interference fringe forming method, and a laser light diffraction method that can ensure stability in diffraction control.

[0009] A diffraction device according to the present disclosure includes: [1] "a flow path element having a flow path formed therein for flowing a gas; and an excitation light source unit for irradiating a plurality of excitation laser beams onto the gas flowing through the flow path formed by the flow path element, wherein the flow path element includes: a first flow path extending along a first direction and for flowing a first gas containing molecules that resonantly absorb the excitation laser beam; a pair of second flow paths extending along the first direction and formed so as to sandwich the first flow path along a second direction intersecting the first direction, for flowing a second gas containing molecules that do not resonantly absorb the excitation laser beam; and a pair of third flow paths intersecting the first direction and the second direction. and an opening portion that penetrates the flow path element along the second direction so as to extend from one of the second flow paths to the other of the second flow paths via the first flow path, the first flow path being in communication with the opening portion such that the first gas flows through the opening portion, the pair of second flow paths being in communication with the opening portion such that the second gas flows through the opening portion in the same direction as the flow of the first gas along the second direction, sandwiching the flow of the first gas therebetween, and the excitation light source portion irradiates a region within the opening portion with a plurality of the excitation laser beams so that the plurality of the excitation laser beams intersect with each other at the opening portion.

[0010] This diffraction device includes a flow path element having a flow path formed therein for flowing a gas, and an excitation light source unit for irradiating a plurality of excitation laser beams onto the gas flowing through the flow path formed by the flow path element. The flow path element includes: a first flow path extending along a first direction for flowing a first gas containing molecules that resonantly absorb the excitation laser beam; a pair of second flow paths extending along the first direction and formed to sandwich the first flow path along a second direction intersecting the first direction for flowing a second gas containing molecules that do not resonantly absorb the excitation laser beam; and an opening formed through the flow path element along the second direction so as to extend from one of the second flow paths via the first flow path to the other of the second flow paths as viewed from a third direction intersecting the first and second directions.

[0011] The first flow path is connected to the opening so that the first gas flows through the opening, and the pair of second flow paths are connected to the opening so that the second gas flows through the opening in the same direction as the first gas flow, sandwiching the first gas flow along the second direction. This creates a second gas flow that sandwiches the first gas flow at the opening of the flow path element. As a result, the flow of the first gas in the region within the opening is less likely to be disturbed by external gas. Therefore, even if the opening of the flow path element is enlarged, the first gas containing molecules that resonantly absorb the excitation laser beam can maintain a stable laminar flow state. Therefore, by irradiating the region within the opening of the flow path element through which the first gas flows in a laminar flow state with multiple excitation laser beams that intersect with each other to generate interference fringes, a density modulation structure excited by the interference fringes can be stably formed. Therefore, with this diffraction device, stability of diffraction control can be ensured even if the opening of the flow path element is enlarged.

[0012] In this diffraction device, by sandwiching the flow of the first gas between the flows of the second gas at the opening of the flow path element, the thickness of the laminar flow of the first gas can be fixed (kept constant regardless of the passage of time). This stabilizes the optical path length difference of the controlled laser beam irradiated onto the region within the opening. As a result, the controlled laser beam can be stably controlled (for example, the diffraction efficiency is stabilized). The optical path length difference is determined by the product of the refractive index modulation amount Δn excited in the first gas by the excitation laser beam and the thickness of the laminar flow of the first gas.

[0013] The diffraction device according to the present disclosure may be [2] "the diffraction device according to the above [1], wherein the first gas contains ozone, and the plurality of excitation laser beams have a central wavelength at an absorption wavelength of ozone." In this way, by including the first gas in ozone and the excitation laser beams having a central wavelength at an absorption wavelength of ozone, interference fringes can be suitably formed in the first gas flowing through a region within the opening of the flow path element. In particular, because the flow of the first gas is sandwiched between the flows of the second gas at the opening of the flow path element, the outflow of ozone contained in the first gas to the outside is suppressed.

[0014] The diffraction device according to the present disclosure is, [3] "the flow path element includes a first plate-like member, a second plate-like member, a third plate-like member, and a fourth plate-like member that are arranged in order along the second direction, one of the second flow paths is formed between the first plate-like member and the second plate-like member, the first flow path is formed between the second plate-like member and the third plate-like member, and the other of the second flow paths is formed between the third plate-like member and the fourth plate-like member, and when viewed from the third direction, the mutually opposing surfaces of the first plate-like member and the second plate-like member and the surfaces of the third plate-like member and the fourth plate-like member are The diffraction device may be the one described in [1] or [2] above, wherein the opposing surfaces are flat, the opening extends from the first plate-like member to the fourth plate-like member as viewed from the third direction, the first plate-like member is formed such that its thickness in the second direction decreases toward the opening as viewed from the third direction, and the fourth plate-like member is formed such that its thickness in the second direction decreases toward the opening as viewed from the third direction. In this case, the second gas can flow more smoothly through the opening of the flow path element. As a result, it is possible to more reliably suppress turbulence in the flow of the first gas through the opening of the flow path element.

[0015] The diffraction device according to the present disclosure may be [4] "the diffraction device according to any one of [1] to [3] above, in which the width of the opening in the first direction and the third direction is greater than the thickness of the flow path element in the second direction." Even when the opening of the flow path element is enlarged in this way, it is possible to stably form interference fringes and a density modulation structure excited by the interference fringes, as described above. Furthermore, by enlarging the opening, it is possible to accommodate controlled laser light with a large cross-sectional area.

[0016] The diffraction device according to the present disclosure may be [5] "the diffraction device according to any one of the above [1] to [4], wherein the opening is formed as a through-hole having an inner edge around the entire periphery when viewed from the second direction." In this case, the first gas and the second gas can flow more stably through the opening, compared to when the opening of the flow path element is formed as a notch in the flow path element or when the opening is formed by dividing the flow path element in the first direction.

[0017] The diffraction device according to the present disclosure may be [6] "the diffraction device according to any one of the above [1] to [5], wherein the second gas contains at least oxygen or nitrogen." In this way, a gas containing oxygen or nitrogen can be used as the second gas that flows on both sides of the flow of the first gas.

[0018] The diffraction device according to the present disclosure may be [7] "the diffraction device according to any one of [1] to [6] above, wherein the thickness of each of the pair of second flow paths in the second direction is thinner than the thickness of each of the first flow paths in the second direction." By thinning the second flow paths in this way, the thickness of the flow of the second gas in the region within the opening can be reduced. This reduces the influence of unintended optical effects (e.g., nonlinear optical effects) that occur when the controlled laser passes through the second gas in the region within the opening.

[0019] The diffraction device according to the present disclosure may be [8] "the diffraction device according to any one of [1] to [6] above, wherein the thickness of each of the pair of second flow paths in the second direction is greater than the thickness of each of the first flow paths in the second direction." In this way, by increasing the thickness of the second flow paths, the thickness of the flow of the second gas in the region within the opening can be increased. This more reliably prevents the flow of the first gas in the region within the opening from being disturbed by external gas.

[0020] The diffraction device according to the present disclosure may be the diffraction device according to any one of [1] to [8] above, including: [9] a gas supply unit that supplies the first gas from a first end of the first flow path to the first flow path and supplies the second gas to each of the pair of second flow paths from a second end of each of the pair of second flow paths corresponding to the first end of the first flow path; a gas suction unit that sucks the first gas from a third end of the first flow path opposite the first end and sucks the second gas from a fourth end of the pair of second flow paths opposite the second end; and a control unit that controls the gas supply unit and the gas suction unit. In this case, by adjusting the supply and suction amounts of the first gas and the second gas, it is possible to stably form interference fringes and a density modulation structure excited by the interference fringes in the region within the opening.

[0021] The diffraction device according to the present disclosure may be

[10] "the diffraction device described in [9] above, wherein the control unit controls the gas supply unit and the gas suction unit so that the flow velocity of the second gas on the fourth end side of the openings of the pair of second flow paths is equal to or greater than the flow velocity of the second gas on the second end side of the openings of the pair of second flow paths." In this way, by making the flow velocity of the second gas on the fourth end side of the openings of the second flow paths (the discharge side of the second gas) equal to or greater than the flow velocity of the second gas on the second end side of the openings of the second flow paths (the supply side of the second gas), it is possible to more reliably suppress the flow of the first gas in the region within the openings from being disturbed by external gas.

[0022] The diffraction device according to the present disclosure may be

[11] "the diffraction device according to the above [9] or

[10] , wherein the control unit controls the gas supply unit and the gas suction unit so that the flow velocity of the second gas at the openings of the pair of second flow paths is equal to or greater than the flow velocity of the first gas at the openings of the first flow path." In this case, it is possible to more reliably prevent the flow of the first gas in the region within the openings from being disturbed by external gas.

[0023] The diffraction device according to the present disclosure may be

[12] "the diffraction device according to any one of [1] to

[11] above, in which the width of the opening in the first direction is greater than 1 cm." In this way, even when the opening is made larger than 1 cm, the first gas can be made to flow in a stable laminar state in the region within the opening.

[0024] The diffraction device according to the present disclosure may be

[13] "the diffraction device according to any one of [1] to

[12] above, wherein the opening is formed in a rectangular shape when viewed from the second direction." By making the opening rectangular in this way, the first gas and the second gas flow more smoothly at the inner edge of the opening (the portion of the opening communicating with the first flow path and the second flow path), compared to when the opening is circular, for example. Therefore, the flows of the first gas and the second gas are less likely to be disturbed in the region within the opening.

[0025] The diffraction device according to the present disclosure may be

[14] "the diffraction device described in

[13] above, in which, when viewed from the second direction, a pair of opposing inner edges of the opening are perpendicular to the extension direction of the first flow path." In this way, by making the pair of opposing inner edges of the opening perpendicular to the extension direction of the first flow path (i.e., the flow direction of the first gas), the first gas and the second gas flow more smoothly at the inner edges of the opening (the communication portion of the opening with the first flow path and the second flow path), compared to when the inner edges are oblique to the extension direction of the first flow path, and the flows of the first gas and the second gas are less likely to be disturbed in the region within the opening.

[0026] The diffraction device according to the present disclosure may be

[15] "the diffraction device according to any one of [1] to

[14] above, in which the distance from one end of the flow path element in the first direction to the opening and the distance from the other end of the flow path element in the first direction to the opening are each equal to or greater than the width of the opening in the first direction." In this way, by ensuring a long distance from a gas supply portion (one of the one end and the other end) of the flow path element to the opening and a long distance from a gas discharge portion (the other of the one end and the other end) of the flow path element to the opening, it is possible to stabilize the flows of the first gas and the second gas at the opening.

[0027] The diffraction device according to the present disclosure may be

[16] "the diffraction device according to any one of [1] to

[15] above, wherein, between the supply portions for the first gas and the second gas in the flow path element and the opening, a protrusion extending along the third direction and protruding toward the inside of the flow path is formed in each of the first flow path and the pair of second flow paths." In this way, by limiting the widths of the first flow path and the second flow path with the protrusion, it is possible to regulate the flows of the first gas and the second gas in the region within the opening.

[0028] The diffraction device according to the present disclosure may be

[17] "the diffraction device according to the above

[16] , in which a pair of the protrusions is formed in each of the first flow path and the pair of second flow paths so as to face each other in the second direction." In this case, the flows of the first gas and the second gas in the region within the opening can be more regulated.

[0029] The laser device according to the present disclosure may be

[18] "a laser device comprising the diffraction device according to any one of [1] to

[17] above and a controlled laser light source unit that outputs controlled laser light, wherein the controlled laser light source unit irradiates the controlled laser light onto the region within the opening of the flow path element." In this case, the diffraction device can ensure stability of diffraction control even when the opening of the flow path element is large, and therefore it is possible to suitably diffract a controlled laser light having a large cross-sectional area.

[0030] The interference fringe forming method according to the present disclosure is

[19] a flow path element including a first flow path extending along a first direction and a pair of second flow paths formed to sandwich the first flow path along a second direction extending along the first direction and intersecting the first direction, the flow path element comprising: a first step of circulating a first gas through the first flow path and circulating a second gas through the pair of second flow paths; and a second step of irradiating the first gas and the second gas with a plurality of excitation laser beams, the first gas including molecules that resonantly absorb the excitation laser beam, and the second gas including molecules that do not resonantly absorb the excitation laser beam, the flow path element being configured to irradiate one of the second flow paths with a plurality of excitation laser beams when viewed from a third direction intersecting the first direction and the second direction. the first flow path and the pair of second flow paths are in communication with the openings; in the first step, the first gas is caused to flow through the first flow path so that the first gas flows through the openings, and the second gas is caused to flow through the pair of second flow paths so that the second gas flows through the openings in the same direction as the flow of the first gas, sandwiching the flow of the first gas along the second direction; and in the second step, a region within the opening is irradiated with a plurality of the excitation laser beams so that the plurality of the excitation laser beams intersect with each other at the openings.

[0031] This interference fringe formation method uses a flow path element having: a first flow path extending along a first direction and circulating a first gas containing molecules that resonantly absorb the excitation laser light; a pair of second flow paths extending along the first direction and formed to sandwich the first flow path along a second direction intersecting the first direction and circulating a second gas containing molecules that do not resonantly absorb the excitation laser light; and an opening extending through the flow path element along the second direction so as to extend from one second flow path via the first flow path to the other second flow path when viewed from a third direction intersecting the first and second directions.

[0032] That is, in the first step, the first gas is circulated through the first flow path so that it flows through the opening, and the second gas is circulated through the second flow path so that the second gas flows through the opening in the same direction as the first gas flow while sandwiching the first gas flow along the second direction. As a result, a second gas flow is formed at the opening of the flow path element so as to sandwich the first gas flow. As a result, the flow of the first gas in the region within the opening is less likely to be disturbed by external gas. Therefore, even if the opening of the flow path element is enlarged, the first gas containing molecules that resonantly absorb the excitation laser beam can maintain a stable laminar flow state. Therefore, by irradiating the region within the opening of the flow path element through which the first gas flows in a laminar flow state with multiple excitation laser beams that intersect with each other to generate interference fringes, a density modulation structure excited by the interference fringes can be stably formed. Therefore, according to this interference fringe formation method, stability of diffraction control can be ensured even if the opening of the flow path element is enlarged.

[0033] The laser beam diffraction method according to the present disclosure may be

[20] "a laser beam diffraction method comprising the first step and the second step included in the interference fringe formation step described in

[19] above, and a third step of diffracting the controlled laser beam by irradiating the region in the opening with the controlled laser beam while the first step and the second step are being performed." This laser beam diffraction method includes the above-described interference fringe formation method. Therefore, even if the opening of the flow path element becomes large, the above-described interference fringe formation method can ensure stability of diffraction control, and therefore, it becomes possible to suitably diffract a controlled laser beam having a large cross-sectional area.

[0034] According to the present disclosure, it is possible to provide a diffraction device, a laser device, an interference fringe forming method, and a laser light diffraction method that can ensure stability of diffraction control.

[0035] Fig. 1 is a schematic diagram showing the configuration of a laser device according to this embodiment. Fig. 2 is a side view of the flow path element shown in Fig. 1. Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2. Fig. 4 is a diagram showing the results of a simulation of the flows of a first gas and a second gas in the flow path element according to this embodiment. Fig. 5 is a diagram showing the results of a simulation of the flows of a first gas and a second gas in a flow path element according to a comparative example.

[0036] Hereinafter, a diffraction device, a laser device, an interference fringe forming method, and a laser diffraction method according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant description may be omitted. Note that each drawing may show an orthogonal coordinate system including a first axis defining a first direction D1, a second axis defining a second direction D2 intersecting the first direction D1, and a third axis defining a third direction D3 intersecting the first direction D1 and the second direction D2.

[0037] Fig. 1 is a schematic diagram showing the configuration of a laser device according to this embodiment. The laser device 100 shown in Fig. 1 includes a diffraction device 10 that forms a certain area for diffracting a controlled laser beam Lin, and a controlled laser light source unit 40 that irradiates the certain area with the controlled laser beam Lin.

[0038] The diffraction device 10 includes a gas supply unit 11, a flow path element 12, a gas suction unit 13, a control unit 15, and an excitation light source unit 20 for irradiating the fixed region with a plurality of excitation laser beams (two excitation laser beams L1 and L2 in this case). The gas supply unit 11 is, for example, a pump, and supplies gases (first gas V1 and second gas V2 described below) that resonantly absorb the excitation laser beams L1 and L2. The gas containing molecules that resonantly absorb the excitation laser beams L1 and L2 is, for example, a gas containing ozone. The ozone concentration in the gas is, for example, 0.01 mJ / cm 3 . ２ ) can be set to a value (for example, about 1% to 3%) sufficient for absorption by a gas layer having a thickness of 3 mm to 10 mm.

[0039] When the gas supply unit 11 supplies a gas containing ozone, an example of a method for generating the gas containing ozone is to supply oxygen O ２ A raw material gas containing ozone O ３ More specifically, the method may be a method for generating a gas containing oxygen (O) from a source gas source such as an oxygen cylinder or an air tank, using a pair of metal electrodes arranged in a parallel plate shape and a pair of dielectrics placed between the metal electrodes. ２ A source gas containing ozone (such as high-concentration oxygen or dehumidified air) is fed into the spatial gap between the pair of dielectrics by a diaphragm pump, and a high-frequency, high-voltage power supply applies a high-frequency voltage to the pair of metal electrodes. The high-frequency power supply may be, for example, a 13 MHz, 100 W power supply. The method for generating the ozone-containing gas is not limited to the above-described embodiment, and may also be an electrolysis method or an ultraviolet lamp method. Alternatively, the ozone-containing gas may be generated as a high-concentration ozone gas by, for example, vaporizing liquid ozone.

[0040] The flow path element 12 forms a flow path through which the gas supplied from the gas supply unit 11 flows. An opening 14 for exposing a part of the flow path to the outside is formed in the flow path element 12. The gas suction unit 13 is, for example, a pump, and sucks in the gas that has flowed through the flow path of the flow path element 12.

[0041] The control unit 15 controls the gas supply unit 11 and the gas suction unit 13 to control the flow rate of the gas in the flow path of the flow path element 12. The control unit 15 is configured as a computer device including a processor, a memory, a storage, a communication device, etc. In the control unit 15, the processor executes software (programs) loaded into the memory, etc., and controls reading and writing of data in the memory and storage, as well as communication by the communication device, thereby performing various processes for controlling the gas supply unit 11 and the gas suction unit 13.

[0042] The excitation light source unit 20 irradiates the gas flowing through the flow path formed by the flow path element 12 with multiple (here, two) excitation laser beams L1 and L2. More specifically, the excitation light source unit 20 includes an excitation light source 21 and an interference optical system 30. The interference optical system 30 includes a beam splitter 22 and reflecting mirrors 23A to 23F. The excitation light source 21 outputs excitation laser beam L for exciting the gas flowing through the flow path of the flow path element 12. When the gas containing molecules that resonantly absorb the excitation laser beam L is a gas containing ozone, the excitation laser beam L can have a center wavelength that is particularly strong in the absorption wavelength of ozone (for example, a wavelength of 230 nm to 280 nm).

[0043] The beam splitter 22 receives the excitation laser light L output from the excitation light source 21, and splits the excitation laser light L into multiple (here, two) excitation laser lights L1 and L2, and emits them.

[0044] The reflecting mirrors 23C, 23D, 23E, and 23F are arranged in this order on the optical path of the excitation laser light L1 emitted from the beam splitter 22. The reflecting mirrors 23C, 23D, 23E, and 23F sequentially reflect the excitation laser light L1, thereby causing the excitation laser light L1 to be incident on the region (the above-mentioned certain region) within the opening 14 of the flow path element 12.

[0045] The reflecting mirrors 23A, 23B, and 23F are sequentially arranged on the optical path of the excitation laser light L2 emitted from the beam splitter 22. The reflecting mirrors 23A, 23B, and 23F sequentially reflect the excitation laser light L2, causing the excitation laser light L2 to be incident on a region within the opening 14 of the flow path element 12. The reflecting mirrors 23A to 23F guide the excitation laser light L1 and L2 so that the excitation laser light L1 and the excitation laser light L2 intersect in the region within the opening 14, and irradiate the region within the opening 14 with the excitation laser light L1 and L2.

[0046] As a result, a spatially periodic intensity distribution (interference fringes) is obtained in the region within the opening 14 (the layer of the first gas V1 described below) due to interference between the excitation laser beams L1 and L2. The fringe spacing of these interference fringes is, for example, several μm, but can be variable. The reflecting mirrors 23A to 23F can be arranged so that the optical path lengths of the excitation laser beams L1 and L2 from the beam splitter 22 to the opening 14 are approximately the same. The excitation laser beams L1 and L2 can be made incident on the region within the opening 14 so that they have the same intensity. To increase the visibility of the interference fringes, the intensity of the excitation laser beams L1 and L2 can be made the same as that of the excitation laser beams L1 and L2, but interference fringes can be formed even if the intensities are not the same.

[0047] The controlled laser light source unit 40 outputs a controlled laser light Lin. The controlled laser light Lin output from the controlled laser light source unit 40 is irradiated onto an area within the opening 14 in which interference fringes are formed. This causes diffraction of the controlled laser light Lin, generating diffracted laser light Lo. The laser light Lo may be irradiated onto a processing object 50, for example, to be used for laser processing of the processing object 50.

[0048] In this case, the laser device 100 may include a shield 60 that is disposed downstream of the flow path element 12 in the optical path of the laser beam Lo and has an opening through which the laser beam Lo passes, or another shield 60 that is disposed between the flow path element 12 and the interference optical system 30 and has openings through which the controlled laser beam Lin and the excitation laser beams L1, L2 pass. When the shield 60 is provided, it is possible to prevent debris 51 generated during laser processing of the processing object 50 from entering the interference optical system 30, etc.

[0049] In addition, in the laser device 100, it is possible to perform scanning of the laser light Lo by, for example, adjusting the reflecting mirrors (e.g., reflecting mirrors 23D, 23E, etc.) of the interference optical system 30 to change the emission angles of the excitation laser lights L1 and L2.

[0050] Next, the flow path element 12 will be described in detail. FIG. 2 is a side view of the flow path element shown in FIG. 1, and FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. As shown in FIGS. 2 and 3, the flow path element 12 includes a first flow path 41 and a pair of second flow paths 42. The first flow path 41 extends along a first direction D1. The first flow path 41 allows a first gas V1 containing molecules that resonantly absorb the excitation laser beams L1 and L2 to flow through it. The second flow path 42 extends along the first direction D1. The pair of second flow paths 42 are formed to sandwich the first flow path 41 along a second direction D2 that intersects the first direction D1. The second flow path 42 allows a second gas V2 containing molecules that do not resonantly absorb the excitation laser beams L1 and L2 to flow through it.

[0051] As described above, the first gas V1 contains, for example, ozone. In this case, the first gas V1 may be composed of oxygen in addition to ozone. The second gas V2 contains, for example, oxygen or nitrogen as molecules that do not resonantly absorb the excitation laser beams L1 and L2. The second gas V2 is, for example, air (atmosphere) or nitrogen gas. For example, the second gas V2 may not contain molecules that resonantly absorb the excitation laser beams L1 and L2, or may contain such molecules at a concentration lower than the concentration of molecules that resonantly absorb the excitation laser beams L1 and L2 in the first gas V1.

[0052] As described above, the flow path element 12 has the opening 14. The opening 14 penetrates the flow path element 12 along the second direction D2 so as to extend from one second flow path 42 to the other second flow path 42 via the first flow path 41, as viewed from the third direction D3 intersecting the first direction D1 and the second direction D2. Therefore, the first flow path 41 communicates with the opening 14 so that the first gas V1 flows through the opening 14. Furthermore, the second flow path 42 communicates with the opening 14 so that the second gas flows through the opening 14.

[0053] The flow path element 12 has a base end 12p in the first direction D1 and a tip end 12r opposite the base end 12p in the first direction D1. A nozzle A1 and a pair of nozzles A2 are connected to the base end 12p. The nozzle A1 is connected to a first end 41p in the first direction D1 of the first flow path 41, and introduces a first gas V1 from the gas supply unit 11 into the first flow path 41 from the first end 41p. The nozzle A2 is connected to a second end 42p of the second flow path 42 that corresponds to (is on the same side as) the first end 41p, and introduces a second gas V2 from the gas supply unit 11 into the second flow path 42 from the second end 42p.

[0054] A nozzle B1 and a pair of nozzles B2 are connected to the tip 12r of the flow path element 12. The nozzle B1 is connected to the gas suction unit 13 and a third end 41r opposite the first end 41p of the first flow path 41, and sucks the first gas V1 from the third end 41r. The nozzle B2 is connected to the gas suction unit 13 and a fourth end 42r opposite the second end 42p of the second flow path 42, and sucks the second gas V2 from the fourth end 42r.

[0055] As a result, in the first flow path 41, the first gas V1 flows in the first direction D1 from the first end 41p toward the third end 41r via the opening 14, and in the second flow path 42, the second gas V2 flows in the first direction D1 from the second end 42p toward the fourth end 42r via the opening 14. That is, the first gas V1 and the second gas V2 flow in the same direction (first direction D1) in the first flow path 41 and the second flow path 42, including the region within the opening 14.

[0056] The flow path element 12 as a whole includes a first portion 12A, a second portion 12B, and a third portion 12C. The first portion 12A has a rectangular shape with a constant width in the third direction D3 when viewed from the second direction D2. The second portion 12B includes a base end 12p and extends from the first portion 12A to one side in the first direction D1. When viewed from the second direction D2, the second portion 12B has a trapezoidal shape with a width in the third direction D3 that narrows from the first portion 12A toward the base end 12p. The third portion 12C includes a tip end 12r and extends from the first portion 12A to the other side in the first direction D1. When viewed from the second direction D2, the third portion 12C has a trapezoidal shape with a width in the third direction D3 that narrows from the first portion 12A toward the tip end 12r.

[0057] Therefore, the width F1 of the first flow path 41 in the third direction D3 gradually increases in a region corresponding to the first portion 12A of the flow path element 12, is constant in a region corresponding to the second portion 12B of the flow path element 12, and gradually decreases in a region corresponding to the third portion 12C of the flow path element 12, as it moves from the first end 41p to the third end 41r. As an example, the width F1 is approximately 10 mm at the first end 41p and the third end 41r, and is approximately 45 mm in the portion corresponding to the first portion 12A. That is, the width F1 varies in a range of 10 mm to 45 mm, as an example.

[0058] Similarly, the width F2 of the second flow path 42 in the third direction D3 gradually increases in a region corresponding to the first portion 12A of the flow path element 12, is constant in a region corresponding to the second portion 12B of the flow path element 12, and gradually decreases in a region corresponding to the third portion 12C of the flow path element 12, as it moves from the second end 42p to the fourth end 42r. As an example, the width F2 is approximately 10 mm at the second end 42p and the fourth end 42r, and is approximately 45 mm in the portion corresponding to the first portion 12A. That is, the width F2 varies in a range of 10 mm to 45 mm, as an example.

[0059] The opening 14 is provided in a region (i.e., the first portion 12A) in which the width F1 of the first flow path 41 and the width F2 of the second flow path are constant in the flow path element 12. Here, the opening 14 is formed in a rectangular shape when viewed from the second direction D2. In particular, when viewed from the second direction D2, a pair of opposing (parallel) inner edges 14e of the rectangular opening 14 intersect (are perpendicular to) the extension direction (first direction D1) of the first flow path 41 and the second flow path 42.

[0060] In this embodiment, the width Q1 of the opening 14 in the first direction D1 and the width Q3 of the opening 14 in the third direction D3 are larger than the thickness T12 of the flow path element 12 in the second direction D2. The width Q1 and the width Q3 are, for example, larger than 1 cm, and are, for example, about 3 cm. Also, for example, the thickness T12 is about 25 mm.

[0061] In this embodiment, a distance Dp from one end (base end 12p) of the flow path element 12 in the first direction D1 to the opening 14 (the inner edge 14e on the base end 12p side) and a distance Dr from the other end (tip 12r) of the flow path element 12 in the first direction D1 to the opening 14 (the inner edge 14e on the tip 12r side) are each equal to or greater than the width Q1 of the opening 14 in the first direction D1. The distances Dp and Dr are, for example, approximately 75 mm.

[0062] Here, the opening 14 is formed as a through-hole having an inner edge around its entire periphery. However, the opening 14 may be formed as a notch having at least a portion without an inner edge, or may be a gap formed by dividing the flow path element 12 in the first direction D1. The opening 14 is not an optical opening such as one provided with a window material through which laser light can pass, but rather a physical (mechanical) opening formed by removing a component constituting the flow path element 12. Furthermore, the first portion 12A of the flow path element 12 has flanges 12f formed on both ends in the third direction D3, extending along the first direction D1. The flow path element 12 can be supported using these flanges 12f.

[0063] Here, the flow path element 12 includes a flat plate-like first plate-like member 71, a second plate-like member 72, a third plate-like member 73, and a fourth plate-like member 74 that are arranged in order while being spaced apart from one another along the second direction D2. One of the pair of second flow paths 42 is formed between the first plate-like member 71 and the second plate-like member 72, the first flow path 41 is formed between the second plate-like member 72 and the third plate-like member 73, and the other of the pair of second flow paths 42 is formed between the third plate-like member 73 and the fourth plate-like member 74.

[0064] When viewed from the third direction D3, the opposing surfaces of the first plate-shaped member 71 and the second plate-shaped member 72 (i.e., the surfaces that form one of the second flow paths 42) and the opposing surfaces of the third plate-shaped member 73 and the fourth plate-shaped member 74 (i.e., the surfaces that form the other of the second flow paths 42) are flat surfaces. In the present embodiment, the opposing surfaces of the second plate-shaped member 72 and the third plate-shaped member 73 (i.e., the surfaces that form the first flow path 41) are also flat surfaces.

[0065] Additionally, in the second direction D2, the distance between the first plate-shaped member 71 and the second plate-shaped member 72, the distance between the second plate-shaped member 72 and the third plate-shaped member 73, and the distance between the third plate-shaped member 73 and the fourth plate-shaped member 74 are constant along the first direction. Therefore, the thickness T41 of the first flow path 41 in the second direction D2 and the thickness T42 of the second flow path 42 in the second direction D2 are constant along the first direction D1. The thickness T42 of each of the pair of second flow paths 42 in the second direction D2 is thinner than the thickness T41 of the first flow path 41 in the second direction D2. For example, the thickness T41 is approximately 5 mm, and the thickness T42 is approximately 3 mm.

[0066] The opening 14 is formed from the first plate-shaped member 71 to the fourth plate-shaped member 74 when viewed from the third direction D3. The first plate-shaped member 71 is formed such that the thickness T1 of the first plate-shaped member 71 in the second direction D2 when viewed from the third direction D3 becomes thinner toward the opening 14. More specifically, the first plate-shaped member 71 has a pair of end portions 75 that face each other and face the opening 14, and the thickness T1 of the end portions 75 gradually decreases toward the opening 14.

[0067] As described above, the surface (inner surface) of the first plate-shaped member 71 that forms the second flow path 42 is flat, and therefore the surface (outer surface) of the first plate-shaped member 71 opposite the second flow path 42 is made into an inclined surface (curved surface), thereby gradually reducing the thickness T1. Therefore, the thickness T42 of the second flow path 42 in the second direction D2 is constant even at the end portion 75. Note that the thickness T1 is constant in portions of the first plate-shaped member 71 other than the end portion 75.

[0068] Furthermore, when viewed from the third direction D3, the fourth plate-shaped member 74 is formed so that a thickness T4 of the fourth plate-shaped member 74 in the second direction D2 becomes thinner toward the opening 14. More specifically, the fourth plate-shaped member 74 has a pair of end portions 76 that face the opening 14 and are opposed to each other, and at the end portions 76, the thickness T4 gradually decreases toward the opening 14.

[0069] As described above, the surface (inner surface) of the fourth plate-shaped member 74 that forms the second flow path 42 is flat, and therefore the surface (outer surface) of the fourth plate-shaped member 74 opposite the second flow path 42 is made an inclined surface (curved surface), thereby gradually reducing the thickness T4. Therefore, the thickness T42 of the second flow path 42 in the second direction D2 is constant even at the end portion 76. Note that the thickness T4 is constant in the portions of the fourth plate-shaped member 74 other than the end portion 76.

[0070] Here, between the supply portion of the flow path element 12 for the first gas V1 and the second gas V2 (i.e., the base end 12p to which the nozzles A1 and A2 are connected) and the opening 14, the first flow path 41 is formed with protruding portions 45 extending along the third direction D3 and protruding toward the inside of the first flow path 41 (the flow path interior) (along the second direction D2). A pair of protruding portions 45 are formed facing each other along the second direction D2. The pair of protruding portions 45 are spaced apart from each other along the second direction D2 and limit the cross-sectional area of ​​the first flow path 41 in a plane intersecting the first direction D1. In this embodiment, the protruding portions 45 are formed in a semi-cylindrical shape extending throughout the entire first flow path 41 in the third direction D3. As an example, the protruding portions 45 protrude approximately 2 mm from the first flow path 41. As a result, the thickness T41 of the first flow path 41 is narrowed to approximately 1 mm by the pair of protruding portions 45.

[0071] Furthermore, between the supply portions of the flow path element 12 for the first gas V1 and the second gas V2 (i.e., the base end 12p to which the nozzles A1, A2 are connected and which receive the supply of the first gas V1 and the second gas V2) and the opening 14, each of the pair of second flow paths 42 has a protrusion 46 extending along the third direction D3 and protruding toward the inside of the second flow path 42 (along the second direction D2). A pair of protrusions 46 is formed for each of the pair of second flow paths 42 so as to face each other along the second direction D2. The pair of opposing protrusions 46 are spaced apart from each other along the second direction D2 and limit the cross-sectional area of ​​the second flow path 42 in a plane intersecting the first direction D1. In this embodiment, the protrusion 46 is formed in a semi-cylindrical shape extending throughout the entire second flow path 42 in the third direction D3. As an example, the protrusion 46 protrudes approximately 1 mm from the second flow path 42. As a result, the thickness T42 of each of the pair of second flow paths 42 is narrowed to about 1 mm by the pair of protrusions 46.

[0072] As described above, in the present embodiment, the amount by which the protruding portion 45 protrudes relative to the first flow path 41 is greater than the amount by which the protruding portion 46 protrudes relative to the second flow path 42. This makes the thickness T41 of the portion of the first flow path 41 that faces the protruding portion 45 and the thickness T42 of the portion of the second flow path 42 that faces the protruding portion 46 approximately the same. Meanwhile, no protruding portion is provided in each of the first flow path 41 and the second flow path 42 between the opening 14 of the flow path element 12 and the discharge portion of the first gas V1 and the second gas V2 (i.e., the tip 12r to which the nozzles B1, B2 are connected and which discharge the first gas V1 and the second gas V).

[0073] In the flow path element 12 configured as described above, the gas supply unit 11 supplies the first gas V1 from the first end 41p of the first flow path 41 to the first flow path 41 via the nozzle A1, and supplies the second gas V2 from the second end 42p of the pair of second flow paths 42 to each of the pair of second flow paths 42 via the nozzle A2. In addition, in the flow path element 12, the gas suction unit 13 suctions the first gas V1 from the third end 41r opposite to the first end 41p of the first flow path 41 via the nozzle B1, and suctions the second gas V2 from the fourth end 42r opposite to the second end 42p of the pair of second flow paths 42 via the nozzle B2.

[0074] As described above, the control unit 15 controls the gas supply unit 11 and the gas suction unit 13 to adjust the supply and suction amounts of the first gas V1 in the first flow path 41 and the supply and suction amounts of the second gas V2 in the second flow path 42, thereby controlling the flow rates of the first gas V1 and the second gas V2. An example of the control by the control unit 15 is as follows.

[0075] That is, the control unit 15 can perform a first process of controlling the gas supply unit 11 and the gas suction unit 13 so that the flow velocity of the second gas V2 on the fourth end 42r side of the openings 14 of the pair of second flow paths 42 is equal to or greater than the flow velocity of the second gas V2 on the second end 42p side of the openings 14 of the pair of second flow paths 42. Alternatively, the control unit 15 may perform a first process of controlling the gas supply unit 11 and the gas suction unit 13 so that the flow velocity of the second gas V2 on the fourth end 42r side of the openings 14 of the pair of second flow paths 42 is greater than the flow velocity of the second gas V2 on the second end 42p side of the openings 14 of the pair of second flow paths 42.

[0076] Furthermore, the control unit 15 can perform a second process of controlling the gas supply unit 11 and the gas suction unit 13 so that the flow velocity of the second gas V2 at the openings 14 of the pair of second flow paths 42 is equal to or greater than the flow velocity of the first gas V1 at the openings 14 of the first flow path 41. Alternatively, the control unit 15 may perform a second process of controlling the gas supply unit 11 and the gas suction unit 13 so that the flow velocity of the second gas V2 at the openings 14 of the pair of second flow paths 42 is greater than the flow velocity of the first gas V1 at the openings 14 of the first flow path 41. The control unit 15 may perform the first process and the second process in an overlapping manner, or may perform only one of them.

[0077] Next, a laser beam diffraction method according to the present embodiment will be described. The laser beam diffraction method according to the present embodiment can be implemented, for example, in the laser device 100 according to the present embodiment. The laser beam diffraction method according to the present embodiment also includes an interference fringe forming method according to the present embodiment. Steps S101 and S102, which will be described later, of the laser beam diffraction method correspond to the interference fringe forming method.

[0078] 1 to 3, the control unit 15 first controls the gas supply unit 11 and the gas suction unit 13 to cause the first gas V1 to flow through the first flow path 41 and the second gas V2 to flow through the pair of second flow paths 42 in the flow path element 12 (step S101: first step). In step S101, the first gas V1 is caused to flow through the first flow path 41 so that the first gas V1 flows through the opening 14, and the second gas V2 is caused to flow through the pair of second flow paths 42 so that the second gas V2 flows through the opening 14 in the same direction as the flow of the first gas V1 (first direction D1) while sandwiching the flow of the first gas V1 along the second direction D2. Note that the flow directions of the first gas V1 and the second gas V2 are not limited to being completely aligned with (completely aligned with) the first direction D1. The first gas V1 and the second gas V2 may flow generally along the first direction D1.

[0079] 1 , a control unit (control unit 15 or another control unit) of the laser device 100 controls the excitation light source 21 to output excitation laser light L from the excitation light source 21, thereby irradiating the first gas V1 and the second gas V2 with a plurality of (here, two) excitation laser lights L1, L2 (step S102). In step S102, the excitation laser lights L1, L2 are irradiated onto a region within the opening 14 so that the excitation laser lights L1, L2 intersect with each other at the opening 14.

[0080] In the laser light diffraction method according to this embodiment, the order in which steps S101 and S102 are started is not limited, but steps S101 and S102 are performed with at least a partial overlap. That is, in a state in which the first gas V1 is flowing through the opening 14 of the flow path element 12, the excitation laser beams L1 and L2 are irradiated onto a region within the opening 14. As a result, interference between the excitation laser beams L1 and L2 occurs in a layer of the first gas V1 containing molecules that resonantly absorb the excitation laser beams L1 and L2, thereby forming interference fringes.

[0081] 1 , in a state where step S101 and the second step S102 are being performed, i.e., in a state where interference fringes are formed in the layer of the first gas V1 in the region inside the opening 14, the control unit of the laser device 100 controls the controlled laser light source unit 40 to output the controlled laser light Lin from the controlled laser light source unit 40, thereby irradiating the region inside the opening 14 with the controlled laser light (step S103: third step). As a result, the controlled laser light Lin is diffracted to obtain the laser light Lo.

[0082] 4 is a diagram showing simulation results of the flows of the first gas V1 and the second gas V2 in the flow path element according to the present embodiment. In FIG. 4, multiple results showing changes in the flows of the first gas V1 and the second gas V2 are shown in order of elapsed time, from left to right in the drawing. Referring to FIG. 4, it can be seen that with the flow path element 12 according to the present embodiment, the flow of the second gas V2 is formed so as to sandwich the flow of the first gas V1 at the opening 14. As a result, the first gas V1 flows smoothly in the region within the opening 14 even over time, and a laminar flow of the first gas V1 is maintained in the region within the opening 14.

[0083] FIG. 5 is a diagram showing simulation results of the flows of the first gas and the second gas in a flow path element according to a comparative example. In this comparative example, the flow of the second gas V2 is not formed so as to sandwich the flow of the first gas V1. Therefore, in FIG. 5, from left to right in the drawing, multiple results showing only changes in the flow of the first gas V1 are illustrated in order of elapsed time. Referring to FIG. 5, it can be seen that in the flow path element according to the comparative example, turbulence occurs in the flow of the first gas V1 over time, and the laminar flow of the first gas V1 is not maintained in the region within the opening 14.

[0084] As described above, the diffraction device 10 according to this embodiment includes a flow path element 12 having a flow path formed therein for flowing a gas, and an excitation light source unit 20 for irradiating the gas flowing through the flow path formed by the flow path element 12 with excitation laser beams L1, L2. The flow path element 12 includes: a first flow path 41 extending along a first direction D1 and for flowing a first gas V1 containing molecules that resonantly absorb the excitation laser beams L1, L2; a pair of second flow paths 42 extending along the first direction D1 and formed to sandwich the first flow path 41 along a second direction D2 intersecting the first direction D1; and an opening 14 penetrating the flow path element 12 along the second direction D2 so as to extend from one second flow path 42 to the other second flow path 42 via the first flow path 41, as viewed from a third direction D3 intersecting the first direction D1 and the second direction D2.

[0085] The first flow path 41 communicates with the opening 14 so that the first gas V1 flows through the opening 14, and the pair of second flow paths 42 communicate with the opening 14 so that the second gas V2 flows through the opening 14 in the same direction as the flow of the first gas V1, sandwiching the flow of the first gas V1 along the second direction D2. As a result, in the opening 14 of the flow path element 12, a flow of the second gas V2 is formed to sandwich the flow of the first gas V1. As a result, the flow of the first gas V1 in the region within the opening 14 is less likely to be disturbed by external gas.

[0086] Therefore, even if the opening 14 of the flow path element 12 becomes large, the first gas V1 containing molecules that resonantly absorb the excitation laser beams L1 and L2 can continue to maintain a stable laminar flow state. Therefore, by irradiating the region within the opening 14 of the flow path element 12 through which the first gas V1 flows in a laminar flow state with the excitation laser beams L1 and L2 so that they intersect with each other to generate interference fringes, it is possible to stably form a density modulation structure excited by the interference fringes. Therefore, with the diffraction device 10, stability of diffraction control can be ensured even if the opening 14 of the flow path element 12 becomes large.

[0087] In the diffraction device 10 according to this embodiment, the flow of the first gas V1 is sandwiched between the flows of the second gas V2 at the opening 14 of the flow path element 12, thereby fixing the thickness of the laminar flow of the first gas V1 (maintaining a constant thickness regardless of the passage of time). This stabilizes the optical path length difference of the controlled laser beam Lin irradiated onto the region within the opening 14. As a result, the controlled laser beam Lin can be stably controlled (for example, the diffraction efficiency is stabilized). The optical path length difference is determined by the product of the refractive index modulation amount Δn excited in the first gas V1 by the excitation laser beams L1 and L2 and the laminar flow thickness of the first gas V1.

[0088] Furthermore, in the diffraction device 10 according to this embodiment, the first gas V1 may contain ozone, and the excitation laser beams L1 and L2 may have central wavelengths at the absorption wavelength of ozone. In this manner, when the first gas V1 contains ozone and the excitation laser beams L1 and L2 have central wavelengths at the absorption wavelength of ozone, interference fringes can be suitably formed for the first gas V1 flowing through the region within the opening 14 of the flow path element 12. In particular, because the flow of the first gas V1 is sandwiched between the flows of the second gas V2 at the opening 14 of the flow path element 12, the outflow of ozone contained in the first gas V1 to the outside is suppressed.

[0089] Furthermore, in the diffraction device 10 according to this embodiment, the flow path element 12 includes a first plate-shaped member 71, a second plate-shaped member 72, a third plate-shaped member 73, and a fourth plate-shaped member 74 that are arranged in this order along the second direction D2. One of the pair of second flow paths 42 is formed between the first plate-shaped member 71 and the second plate-shaped member 72, the first flow path 41 is formed between the second plate-shaped member 72 and the third plate-shaped member 73, and the other of the pair of second flow paths 42 is formed between the third plate-shaped member 73 and the fourth plate-shaped member 74.

[0090] When viewed from the third direction D3, the opposing surfaces of the first plate-shaped member 71 and the second plate-shaped member 72 and the opposing surfaces of the third plate-shaped member 73 and the fourth plate-shaped member 74 are flat. The opening 14 is formed from the first plate-shaped member 71 to the fourth plate-shaped member 74 when viewed from the third direction D3. The first plate-shaped member 71 is formed such that its thickness T1 in the second direction D2 decreases toward the opening 14 when viewed from the third direction D3, and the fourth plate-shaped member 74 is formed such that its thickness T4 in the second direction D2 decreases toward the opening 14 when viewed from the third direction D3.

[0091] This allows the second gas V2 to flow more smoothly through the opening 14 of the flow path element 12. As a result, it is possible to more reliably prevent the flow of the first gas V1 from being disturbed at the opening 14 of the flow path element 12.

[0092] Furthermore, in the diffraction device 10 according to this embodiment, the width Q1 of the opening 14 in the first direction D1 and the width Q3 in the third direction D3 are larger than the thickness T12 of the flow path element 12 in the second direction D2. In this way, even when the opening 14 of the flow path element 12 is enlarged, it is possible to stably form the interference fringes and the density modulation structure excited by the interference fringes as described above. Furthermore, by enlarging the opening 14, it is possible to accommodate the controlled laser beam Lin having a large cross-sectional area.

[0093] Furthermore, in the diffraction device 10 according to this embodiment, the opening 14 is formed as a through-hole having an inner edge around the entire circumference when viewed from the second direction D2. Therefore, compared to when the opening 14 of the flow path element 12 is formed as a notch in the flow path element 12 or when it is formed by dividing the flow path element 12 in the first direction D1, it is possible to allow the first gas V1 and the second gas V2 to flow through the opening 14 more stably.

[0094] In the diffraction device 10 according to this embodiment, the second gas V2 may contain at least oxygen or nitrogen. In this manner, a gas containing oxygen or nitrogen can be used as the second gas V2 that flows on both sides of the flow of the first gas V1.

[0095] Furthermore, in the diffraction device 10 according to this embodiment, the thickness T42 of the pair of second flow paths 42 in the second direction D2 is thinner than the thickness T41 of the first flow path 41 in the second direction D2. By thinning the second flow paths 42 in this way, the thickness of the flow of the second gas V2 in the region within the opening 14 can be reduced. This makes it possible to reduce the influence of unintended optical effects (e.g., nonlinear optical effects) that occur when the controlled laser beam Lin passes through the second gas V2 in the region within the opening 14.

[0096] The diffraction device 10 according to this embodiment also includes a gas supply unit 11 that supplies a first gas V1 to the first flow path 41 from the first end 41p side of the first flow path 41 and supplies a second gas V2 to each of the pair of second flow paths 42 from a second end 42p side of each of the pair of second flow paths 42 that corresponds to the first end 41p of the first flow path 41, a gas suction unit 13 that sucks the first gas V1 from a third end 41r side opposite the first end 41p of the first flow path 41 and sucks the second gas V2 from a fourth end 42r side opposite the second end 42p of each of the pair of second flow paths 42, and a control unit 15 that controls the gas supply unit 11 and the gas suction unit 13. Therefore, by adjusting the supply and suction amounts of the first gas V1 and the second gas V2, it is possible to stably form interference fringes and a density modulation structure excited by the interference fringes in the region within the opening 14.

[0097] Furthermore, in the diffraction device 10 according to this embodiment, the control unit 15 can control the gas supply unit 11 and the gas suction unit 13 so that the flow velocity of the second gas V2 on the fourth end 42r side of the openings 14 of the pair of second flow paths 42 is equal to or greater than the flow velocity of the second gas V2 on the second end 42p side of the openings 14 of the pair of second flow paths 42. In this way, by making the flow velocity of the second gas V2 on the fourth end 42r side of the openings 14 of the second flow paths 42 (the discharge side of the second gas V2) equal to or greater than the flow velocity of the second gas V2 on the second end 42p side of the openings 14 of the second flow paths 42 (the supply side of the second gas V2), the flow of the first gas V1 in the region within the openings 14 can be more reliably prevented from being disturbed by external gas.

[0098] Furthermore, in the diffraction device 10 according to this embodiment, the control unit 15 can control the gas supply unit 11 and the gas suction unit 13 so that the flow velocity of the second gas V2 at the openings 14 of the pair of second flow paths 42 is equal to or greater than the flow velocity of the first gas V1 at the openings 14 of the first flow path 41. In this case, the flow of the first gas V1 in the region within the openings 14 can be more reliably prevented from being disturbed by external gas.

[0099] Furthermore, the diffraction device 10 according to this embodiment may be the diffraction device described in any one of [1] to

[11] above, in which the width of the opening 14 in the first direction D1 is greater than 1 cm. In this way, even when the opening is made larger than 1 cm, the first gas V1 can be kept in a stable laminar flow state in the region within the opening 14.

[0100] Furthermore, in the diffraction device 10 according to this embodiment, the opening 14 is formed in a rectangular shape when viewed from the second direction D2. By forming the opening 14 in a rectangular shape, the first gas V1 and the second gas V2 flow more smoothly at the inner edge of the opening 14 (the portion of the opening 14 that communicates with the first flow path 41 and the second flow path 42), compared to, for example, a case in which the opening 14 is circular. Therefore, the flows of the first gas V1 and the second gas V2 are less likely to be disturbed in the region within the opening 14.

[0101] Furthermore, in the diffraction device 10 according to the present embodiment, when viewed from the second direction D2, a pair of opposing inner edges 14e of the opening 14 are perpendicular to the extension direction (first direction D1) of the first flow path 41. In this way, by making the pair of opposing inner edges 14e of the opening 14 perpendicular to the extension direction of the first flow path (i.e., the flow direction of the first gas), the first gas V1 and the second gas V2 flow smoothly along the inner edge 14e of the opening 14 (the portion of the opening 14 communicating with the first flow path 41 and the second flow path 42), compared to when the inner edge 14e is oblique to the extension direction of the first flow path 41. Therefore, the flows of the first gas V1 and the second gas V2 are less likely to be disturbed in the region within the opening 14.

[0102] Furthermore, in the diffraction device 10 according to this embodiment, the distance Dp from the base end 12p, which is one end of the flow path element 12 in the first direction D1, to the opening 14, and the distance Dr from the tip 12r, which is the other end of the flow path element 12 in the first direction D1, to the opening 14 are each equal to or greater than the width Q1 of the opening 14 in the first direction D1. In this way, by ensuring a long distance Dp from the gas supply portion (base end 12p) of the flow path element 12 to the opening 14 and a long distance Dr from the gas discharge portion (tip 12r) of the flow path element 12 to the opening 14, it is possible to stabilize the flows of the first gas V1 and the second gas V2 at the opening 14.

[0103] Furthermore, in the diffraction device 10 according to this embodiment, between the base end 12p in the flow direction (first direction D1) of the first gas V1 and the second gas V2 in the flow path element 12 and the opening 14, the first flow path 41 is formed with a protrusion 45 that extends along the third direction D3 and protrudes toward the inside of the first flow path 41, and each of the pair of second flow paths 42 is formed with a protrusion 46 that extends along the third direction D3 and protrudes toward the inside of the second flow path 42 along the second direction D2. In this way, by limiting the widths of the first flow path 41 and the second flow path 42 with the protrusions 45, 46, the flows of the first gas V1 and the second gas V2 in the region within the opening 14 can be regulated.

[0104] Furthermore, in the diffraction device according to this embodiment, a pair of protrusions 45 are formed in the first flow path 41 so as to face each other along the second direction D2, and a pair of protrusions 46 are formed in each of the pair of second flow paths 42 so as to face each other in the second direction D2. This makes it possible to further regulate the flows of the first gas V1 and the second gas V2 in the region within the opening 14. In this embodiment, between the base end 12p and the opening 14, the first flow path 41 is formed with the protrusion 45, and each of the pair of second flow paths 42 is formed with the protrusion 46. However, between the opening 14 and the tip 12r, no protrusion is formed in the first flow path 41, and no protrusion 46 is formed in each of the pair of second flow paths 42. With this configuration, the flow of the first gas V1 and the second gas V2 can be adjusted by the protrusions 45, 46 on the base end 12p side of the opening 14, while no protrusions are provided on the tip end 12r side of the opening 14, allowing the gas to flow smoothly (preventing gas turbulence), and maintaining the gas flow at the opening 14 in a laminar state.

[0105] Furthermore, the laser device 100 according to this embodiment includes the diffraction device 10 described above and a controlled laser light source unit 40 that outputs the controlled laser beam Lin. The controlled laser light source unit 40 irradiates the controlled laser beam Lin onto an area within the opening 14 of the flow path element 12. According to this laser device 100, the diffraction device 10 described above can ensure stability of diffraction control even when the opening 14 of the flow path element 12 is large, and therefore it is possible to suitably diffract the controlled laser beam Lin having a large cross-sectional area.

[0106] Furthermore, in the interference fringe formation method according to this embodiment, in step S101, the first gas V1 is caused to flow through the first flow path 41 so that the first gas V1 flows through the opening 14, and the second gas V2 is caused to flow through the second flow path 42 so that the second gas V2 flows through the opening 14 in the same direction as the flow of the first gas V1 while sandwiching the flow of the first gas V1 along the second direction D2. As a result, at the opening 14 of the flow path element 12, a flow of the second gas V2 is formed so as to sandwich the flow of the first gas V1.

[0107] As a result, the flow of the first gas V1 in the region within the opening 14 is less likely to be disturbed by external gas. Therefore, even if the opening 14 of the flow path element 12 is enlarged, the first gas V1, which contains molecules that resonantly absorb the excitation laser beams L1 and L2, can continue to maintain a stable laminar flow state. Therefore, by irradiating the region within the opening 14 of the flow path element 12, through which the first gas V1 flows in a laminar flow state, with the excitation laser beams L1 and L2 so that they intersect with each other to generate interference fringes, a density modulation structure excited by the interference fringes can be stably formed. Therefore, according to this interference fringe formation method, stability of diffraction control can be ensured even if the opening 14 of the flow path element 12 is enlarged.

[0108] Furthermore, in addition to the above steps S101 and S102, the laser beam diffraction method according to this embodiment includes step S103, in which, while steps S101 and S102 are being performed, the controlled laser beam Lin is irradiated onto an area within the opening 14, thereby diffracting the controlled laser beam Lin. This laser beam diffraction method includes the above-mentioned interference fringe formation method. Therefore, even if the opening 14 of the flow path element 12 becomes large, the above-mentioned interference fringe formation method can ensure stability in diffraction control, making it possible to suitably diffract the controlled laser beam Lin having a large cross-sectional area.

[0109] The above embodiment has described one aspect of the present disclosure. Therefore, the present disclosure is not limited to the above embodiment and may be modified as desired.

[0110] For example, in the above embodiment, the thickness T42 of each of the pair of second flow paths 42 in the second direction D2 is thinner than the thickness T41 of each of the first flow paths 41 in the second direction D2. However, the thickness T42 of each of the pair of second flow paths 42 in the second direction D2 (or one of them) may be thicker than the thickness T41 of each of the first flow paths 41 in the second direction D2. As an example, the thickness T41 may be approximately 3 mm, and the thickness T42 may be approximately 5 mm. In this way, by increasing the thickness of the second flow path 42, the thickness of the flow of the second gas V2 in the region within the opening 14 can be increased. This more reliably prevents the flow of the first gas V1 in the region within the opening 14 from being disturbed by an external gas. Note that, when the thickness T41 of the first flow path 41 is reduced, the concentration of molecules that resonantly absorb the excitation laser beams L1 and L2 contained in the first gas V1 can be increased, or the intensity of the excitation laser beams L1 and L2 can be increased.

[0111] In the above embodiment, the width Q1 of the opening 14 in the first direction D1 and the width Q3 of the opening 14 in the third direction D3 are set to be larger than the thickness T12 of the flow path element 12 in the second direction D2. However, at least one of the width Q1 and the width Q3 may be equal to or smaller than the thickness T12.

[0112] In the above embodiment, the distance Dp from the base end 12p of the flow path element 12 to the opening 14 and the distance Dr from the tip 12r of the flow path element 12 to the opening 14 are each equal to or greater than the width Q1 of the opening 14 in the first direction D1. However, at least one of the distances Dp and Dr may be less than the width Q1.

[0113] Furthermore, in the above embodiment, the protrusions 45, 46 are provided on the first flow path 41 and the second flow path 42. However, the protrusions 45, 46 do not have to be provided on at least one of the first flow path 41 and the second flow path 42. Alternatively, even when the protrusions 45, 46 are provided on the first flow path 41 and the second flow path 42, they are not limited to being provided in pairs facing each other, and a single protrusion 45, 46 may be provided, or three or more protrusions 45, 46 may be provided. The positions at which the protrusions 45, 46 are provided may also be changed.

[0114] Furthermore, when viewed from the third direction D3, the first plate-shaped member 71 does not have to be formed so that the thickness of the first plate-shaped member 71 in the second direction D2 becomes thinner as it approaches the opening 14, and when viewed from the third direction D3, the fourth plate-shaped member 74 does not have to be formed so that the thickness of the fourth plate-shaped member 74 in the second direction D2 becomes thinner as it approaches the opening 14.

[0115] In addition, the control unit 15 does not need to perform the first process of controlling the gas supply unit 11 and the gas suction unit 13 so that the flow velocity of the second gas V2 on the fourth end 42r side of the openings 14 of the pair of second flow paths 42 is less than the flow velocity of the second gas V2 on the second end 42p side of the openings 14 of the pair of second flow paths 42.

[0116] Furthermore, the control unit 15 does not need to perform the second process of controlling the gas supply unit 11 and the gas suction unit 13 so that the flow rate of the second gas V2 at the openings 14 of the pair of second flow paths 42 is less than the flow rate of the first gas V1 at the openings 14 of the first flow path 41.

[0117] Here, the width Q1 of the opening 14 in the first direction D1 and the width Q3 of the opening 14 in the third direction D3 may each be about 1 cm. In this case, the thickness T41 of the first flow path 41 in the second direction D2 may be about 1 mm, and the thickness T42 of the second flow path 42 in the second direction D2 may be about 1.6 mm.

[0118] Furthermore, the width Q1 of the opening 14 in the first direction D1 and the width Q3 of the opening 14 in the third direction D3 may each be approximately 300 μm. In this case, the thickness T41 of the first flow path 41 in the second direction D2 may be approximately 300 μm, and the thickness T42 of the second flow path 42 in the second direction D2 may be approximately 500 μm.

[0119] As shown in these modified examples, the flow path element 12 with a three-layer flow path structure including a first flow path 41 and a pair of second flow paths 42 is effective even when a relatively small opening 14 having widths Q1 and Q3 of 1 cm or less is configured. The reasons for this are as follows. In the flow path element 12, by reducing the thickness T41 of the first flow path 41, the thickness of the first gas V1 containing molecules that resonantly absorb the excitation laser beams L1 and L2 in the second direction D2 can be reduced (i.e., a thin gas element can be created). By reducing the thickness of the first gas V1, it is possible to reduce undesired nonlinear optical effects when a high-intensity controlled laser beam Lin is incident on the first gas V1. Furthermore, although there is a concern that reducing the thickness of the first gas V1 may reduce the stability of the gas flow, the flow path element 12 can stabilize the flow (concentration and thickness) of the first gas V1.

[0120] 10...diffraction device, 11...gas supply section, 12...flow path element, 12p...base end, 12r...tip, 13...gas suction section, 14...opening, 15...control section, 14e...inner edge, 20...excitation light source section, 40...controlled laser light source section, 41...first flow path, 42...second flow path, 45, 46...protrusion, 71...first plate-shaped member, 72...second plate-shaped member, 73...third plate-shaped member, 74...fourth plate-shaped member, 100...laser device, L1, L2...excitation laser light, Lin...controlled laser light, V1...first gas, V2...second gas.

Claims

1. A flow path element having a flow path formed therein for circulating a gas; and an excitation light source unit for irradiating a plurality of excitation laser beams onto the gas flowing through the flow path formed by the flow path element, wherein the flow path element has: a first flow path extending along a first direction and for circulating a first gas containing molecules that resonantly absorb the excitation laser beam; a pair of second flow paths extending along the first direction and formed to sandwich the first flow path along a second direction intersecting the first direction, for circulating a second gas containing molecules that do not resonantly absorb the excitation laser beam; and an opening formed through the flow path element along the second direction so as to extend from one of the second flow paths to the other of the second flow paths via the first flow path, as viewed from a third direction intersecting the first and second directions; wherein the first flow path is in communication with the opening so that the first gas flows through the opening, the pair of second flow paths communicate with the opening such that the second gas flows through the opening in the same direction as the flow of the first gas, sandwiching the flow of the first gas along the second direction; and the excitation light source unit irradiates a region within the opening with a plurality of the excitation laser beams so that the plurality of excitation laser beams intersect with each other at the opening.

2. The diffraction device according to claim 1, wherein the first gas contains ozone, and the plurality of excitation laser beams have central wavelengths at an absorption wavelength of ozone.

3. The flow path element includes a first plate-shaped member, a second plate-shaped member, a third plate-shaped member, and a fourth plate-shaped member arranged in order along the second direction, one of the second flow paths is formed between the first plate-shaped member and the second plate-shaped member, the first flow path is formed between the second plate-shaped member and the third plate-shaped member, and the other of the second flow paths is formed between the third plate-shaped member and the fourth plate-shaped member, when viewed from the third direction, the opposing surfaces of the first plate-shaped member and the second plate-shaped member and the opposing surfaces of the third plate-shaped member and the fourth plate-shaped member are flat, when viewed from the third direction, the opening is formed from the first plate-shaped member to the fourth plate-shaped member, and the first plate-shaped member is formed so that the thickness of the first plate-shaped member in the second direction becomes thinner toward the opening when viewed from the third direction, The diffraction device according to claim 1 , wherein the fourth plate-shaped member is formed such that, when viewed from the third direction, the thickness of the fourth plate-shaped member in the second direction decreases toward the opening.

4. A diffraction device according to any one of claims 1 to 3, wherein the width of the opening in the first direction and the third direction is greater than the thickness of the flow path element in the second direction.

5. A diffraction device according to any one of claims 1 to 4, wherein the opening is formed as a through hole having an inner edge around the entire periphery when viewed from the second direction.

6. A diffraction device according to any one of claims 1 to 5, wherein the second gas contains at least oxygen or nitrogen.

7. A diffraction device according to any one of claims 1 to 6, wherein the thickness of each of the pair of second flow paths in the second direction is thinner than the thickness of each of the first flow paths in the second direction.

8. A diffraction device according to any one of claims 1 to 6, wherein the thickness of each of the pair of second flow paths in the second direction is greater than the thickness of each of the first flow paths in the second direction.

9. A diffraction device according to any one of claims 1 to 8, comprising: a gas supply unit that supplies the first gas to the first flow path from a first end side of the first flow path and supplies the second gas to each of the pair of second flow paths from a second end side of the pair of second flow paths corresponding to the first end of the first flow path; a gas suction unit that sucks the first gas from a third end side of the first flow path opposite the first end, and sucks the second gas from a fourth end side of the pair of second flow paths opposite the second end; and a control unit that controls the gas supply unit and the gas suction unit.

10. The diffraction device according to claim 9, wherein the control unit controls the gas supply unit and the gas suction unit so that the flow velocity of the second gas on the fourth end side of the openings of the pair of second flow paths is equal to or greater than the flow velocity of the second gas on the second end side of the openings of the pair of second flow paths.

11. A diffraction device according to claim 9 or 10, wherein the control unit controls the gas supply unit and the gas suction unit so that the flow velocity of the second gas at the openings of the pair of second flow paths is equal to or greater than the flow velocity of the first gas at the openings of the first flow path.

12. A diffraction device according to any one of claims 1 to 11, wherein the width of the opening in the first direction is greater than 1 cm.

13. The diffraction device according to any one of claims 1 to 12, wherein the opening is formed in a rectangular shape when viewed from the second direction.

14. A diffraction device according to claim 13, wherein, when viewed from the second direction, a pair of opposing inner edges of the opening are perpendicular to the extending direction of the first flow path.

15. A diffraction device according to any one of claims 1 to 14, wherein the distance from one end of the flow path element in the first direction to the opening, and the distance from the other end of the flow path element in the first direction to the opening, are each equal to or greater than the width of the opening in the first direction.

16. A diffraction device according to any one of claims 1 to 15, wherein a protrusion extending along the third direction and protruding toward the inside of the flow path is formed in each of the first flow path and the pair of second flow paths between the supply portions for the first gas and the second gas in the flow path element and the opening.

17. The diffraction device according to claim 16, wherein a pair of the protrusions are formed in each of the first flow path and the pair of second flow paths so as to face each other in the second direction.

18. A laser device comprising: a diffraction device according to any one of claims 1 to 17; and a controlled laser light source unit that outputs controlled laser light, wherein the controlled laser light source unit irradiates the controlled laser light onto the region within the opening of the flow path element.

19. A flow path element including a first flow path extending along a first direction and a pair of second flow paths formed to sandwich the first flow path along a second direction extending along the first direction and intersecting the first direction, comprising: a first step of circulating a first gas through the first flow path and circulating a second gas through the pair of second flow paths; and a second step of irradiating the first gas and the second gas with a plurality of excitation laser beams, wherein the first gas includes molecules that resonantly absorb the excitation laser beam, and the second gas includes molecules that do not resonantly absorb the excitation laser beam, the flow path element includes an opening that penetrates the flow path element along the second direction so as to extend from one of the second flow paths via the first flow path to the other of the second flow paths, as viewed from a third direction intersecting the first direction and the second direction, and the first flow path and the pair of second flow paths are in communication with the opening, a first step of circulating the first gas through the first flow path so that the first gas flows through the opening, and a second step of circulating the second gas through the pair of second flow paths so that the second gas flows through the opening in the same direction as the flow of the first gas while sandwiching the flow of the first gas along the second direction; and a second step of irradiating a region within the opening with a plurality of the excitation laser beams so that the plurality of excitation laser beams intersect with each other at the opening.

20. A laser light diffraction method comprising the first and second steps of the interference fringe forming method described in claim 19, and a third step of diffracting the controlled laser light by irradiating the controlled laser light onto the region within the opening while the first and second steps are being carried out.

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