Optical isolator and laser irradiation device

Abstract

The purpose of the present invention is to provide an optical isolator which is capable of suppressing scattering of reflected return light in a housing and which has excellent reliability. This optical isolator (1) is provided with: a first polarizer (2) provided on the light incidence side in the optical axis direction (X); a second polarizer (3) provided on the light emission side in the optical axis direction (X); a Faraday rotator (4) disposed between the first polarizer (2) and the second polarizer (3); and a housing (6) that houses the first polarizer (2), the second polarizer (3), and the Faraday rotator (4). The first polarizer (2) is configured so as to be able to reflect the reflected return light (A) transmitted from the second polarizer (3) and the Faraday rotator (4) in a direction different from the optical axis direction (X), and an absorption member (5) that absorbs at least a portion of the reflected return light (A) is provided in the optical path of the reflected return light (A) reflected in the direction different from the optical axis direction (X).

Description

TECHNICAL FIELD

[0001] The present application relates to an optical isolator and a laser irradiation apparatus using the same. BACKGROUND

[0002] An optical isolator is a magneto-optical element that propagates light in only one direction and prevents the return of reflected light. The optical isolator is used in a laser irradiation apparatus used in optical communication systems, laser processing systems, and the like.

[0003] As such an optical isolator, an optical isolator including a Faraday rotator and polarizers (polarizers) disposed on both end surfaces of an optical axis of the Faraday rotator is disclosed in Patent Literature 1. In such an optical isolator, incident light is polarized by the polarizer on the incident surface side, the polarization plane is rotated by 45° by the Faraday rotator, and the light is emitted by the polarizer on the emission surface side. In addition, in the case where return light reaches the emission surface side, the return light is polarized by the polarizer on the emission surface side, reaches the polarizer on the incident surface side by being rotated by 45° by the Faraday rotator, but since the polarization plane of the light is orthogonal to the transmission polarization direction of the polarizer on the incident surface side, the return light does not emit from the incident surface side and can be removed.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. 2003-322826 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] However, in the optical isolator like that of Patent Literature 1, the polarizers, the Faraday rotator, and the like are disposed in the housing and used. At this time, the reflected return light that reaches the polarizer on the incident surface side is reflected by the polarizer on the incident surface side, and thus the reflected reflected return light scatters in the housing to become stray light, and there is a problem that characteristics such as isolation characteristics are adversely affected.

[0009] An object of the present application is to provide an optical isolator capable of suppressing the scattering of reflected return light in the housing and excellent in reliability, and a laser irradiation apparatus using the same.

[0010] MEANS FOR SOLVING THE PROBLEMS

[0011] Each mode of the optical isolator and the laser irradiation apparatus for solving the above problems will be described.

[0012] The optical isolator of the way 1 of the present application has: a first polarizer provided on the light incident side in the optical axis direction; a second polarizer provided on the light exit side in the optical axis direction; a Faraday rotator disposed between the first polarizer and the second polarizer; and a housing that houses the first polarizer, the second polarizer, and the Faraday rotator, the first polarizer being configured to reflect the reflected return light after transmission from the second polarizer and the Faraday rotator in a direction different from the optical axis direction, and an absorption member capable of absorbing at least a part of the reflected return light is provided in the optical path of the reflected return light reflected in a direction different from the optical axis direction.

[0013] In the optical isolator of the way 2, preferably in the way 1, the absorption member is disposed between the first polarizer and the wall portion of the housing in the optical path of the reflected return light.

[0014] In the optical isolator of the way 3, it can also be configured in the way 1 or the way 2 that the absorption member has a light attenuation surface capable of attenuating the reflected return light.

[0015] In the optical isolator of the way 4, it can also be configured in the way 3 that the light attenuation surface is configured to be capable of absorbing a part of the reflected return light and reflecting the reflected return light that is not absorbed multiple times.

[0016] In the optical isolator of the way 5, preferably in the way 3 or the way 4, the absorption member has a plurality of light attenuation surfaces, and the plurality of light attenuation surfaces are configured to be capable of absorbing a part of the reflected return light and reflecting the reflected return light that is not absorbed multiple times.

[0017] In the optical isolator of the way 6, it can also be configured in any one of the ways 3 to 5 that the absorption member has a groove portion or a hole portion, the inner wall surface of the groove portion or the hole portion of the absorption member is the light attenuation surface, and the groove portion or the hole portion has a tapered shape with a width that narrows as it goes in the direction of travel of the reflected return light.

[0018] In the optical isolator of the way 7, it can also be configured in any one of the ways 3 to 6 that the absorption member has a groove portion or a hole portion, the inner wall surface of the groove portion or the hole portion of the absorption member is the light attenuation surface, and the groove portion or the hole portion has an inverted tapered shape with a width that increases as it goes in the direction of travel of the reflected return light.

[0019] In the optical isolator of the way 8, it can also be configured in any one of the ways 3 to 7 that the absorption member includes: a member body; and a surface treatment layer that covers at least a part of the member body, is capable of absorbing at least a part of the reflected return light, and has a surface that is the light attenuation surface.

[0020] In the optical isolator of Mode 9, preferably in Mode 8, the surface treatment layer contains at least one selected from amorphous aluminum oxide, chromium, nickel, and carbon.

[0021] In the optical isolator of Mode 10, preferably in Mode 8 or Mode 9, the surface treatment of the surface treatment layer is an aluminum anodization treatment, a plating treatment, a vapor deposition treatment, or a coating treatment such as a spray coating, a brush coating, or the like.

[0022] In the optical isolator of Mode 11, it is also possible to configure, in Mode 1 or Mode 2, that the absorbing member is composed of glass.

[0023] In the optical isolator of Mode 12, it is also possible to configure, in Mode 1 or Mode 2, that a surface treatment layer is provided to the inner wall surface of the housing, and the absorbing member is composed of the surface treatment layer.

[0024] The laser irradiation device of Mode 13 of the present application is characterized by comprising: a light source that generates laser light; and an optical isolator of any one of Modes 1 to 12.

[0025] Effects of Invention

[0026] According to the present application, it is possible to provide an optical isolator that can suppress scattering of reflection return light in a housing and is excellent in reliability, and a laser irradiation device using the optical isolator. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a schematic perspective view of an optical isolator of Embodiment 1 of the present application.

[0028] Figure 2 (a) of is a schematic cross-sectional view of the optical isolator of Embodiment 1 of the present application along the direction of the optical axis, Figure 2 (b) of is a schematic cross-sectional view of the optical isolator of Embodiment 1 of the present application along a direction orthogonal to the direction of the optical axis. Figure 2 (a) of is a schematic view of the cross-section shown in (a) of

[0029] Figure 3 is a schematic cross-sectional view of the optical isolator of Embodiment 1 of the present application along a direction orthogonal to the direction of the optical axis.

[0030] Figure 4 (a) of is a perspective view of an absorbing member in the optical isolator of Embodiment 1 of the present application, Figure 4 (b) of is a schematic cross-sectional view of the absorbing member of (a) of Figure 4 (a) of is a schematic cross-sectional view of the absorbing member of (a) of

[0031] Figure 5 (a) of is a perspective view of an absorbing member in the optical isolator of Embodiment 1 of the present application, Figure 5 (b) of is a schematic cross-sectional view of the absorbing member of (a) ofFigure 5 (a) is a schematic cross-sectional view of an absorbing component.

[0032] Figure 6 (a) is an enlarged perspective view showing an absorbing component in an optical isolator according to a second modified example. Figure 6 (b) is Figure 6 (a) is a schematic cross-sectional view of an absorbing component.

[0033] Figure 7 (a) is an enlarged perspective view showing an absorbing component in an optical isolator according to a third modified example. Figure 7 (b) is Figure 7 (a) is a schematic cross-sectional view of an absorbing component.

[0034] Figure 8 This is a schematic diagram of a cross section of an optical isolator according to a fourth modified example, taken along the optical axis.

[0035] Figure 9 (a) is a schematic diagram of a cross section of an optical isolator according to a second embodiment of the present invention along the optical axis direction. Figure 9 (b) is an enlarged representation Figure 9 (a) Schematic perspective view of the absorbing component in the optical isolator.

[0036] Figure 10 This is a schematic diagram of a cross section of an optical isolator according to a third embodiment of the present invention, taken along the optical axis.

[0037] Figure 11 (a) is a schematic cross-sectional view of an optical isolator according to a fourth embodiment of the present invention, taken along the optical axis. Figure 11 (b) is Figure 11 A schematic diagram of the cross section shown in (a).

[0038] Figure 12 This is a schematic diagram of a cross section along the optical axis direction of a laser irradiation device according to one embodiment of the present invention. DETAILED DESCRIPTION

[0039] Hereinafter, preferred embodiments will be described. However, the following embodiments are merely illustrative, and the present invention is not limited to the following embodiments. In addition, in each of the drawings, components having substantially the same function are sometimes referred to with the same reference numerals.

[0040] [Optical isolator]

[0041] (First embodiment)

[0042] Figure 1 It is a schematic perspective view showing an optical isolator according to the first embodiment of the present invention. Figure 2(a) is a schematic cross-sectional view of the optical isolator according to the first embodiment of the present invention, taken along the optical axis. Figure 2 (b) is Figure 2 A schematic diagram of the cross section shown in (a). Figure 3 : is a schematic cross-sectional view of the optical isolator according to the first embodiment of the present invention, taken along a direction perpendicular to the optical axis. Figure 2 In (a), for the sake of convenience, only the position of the absorbing member 5 is shown, and its shape is omitted. The shape of the absorbing member 5 is Figure 2 (b), described later Figure 4 Detailed representation is shown in (a) and (b).

[0043] like Figure 2 As shown in (a) and (b) of FIG. 1 , an optical isolator 1 includes a first polarizer 2, a second polarizer 3, a Faraday rotator 4, an absorbing member 5, and a housing 6. The first polarizer 2 is disposed on the light incident side in the optical axis direction X. The second polarizer 3 is disposed on the light exiting side in the optical axis direction X. The Faraday rotator 4 is disposed between the first polarizer 2 and the second polarizer 3.

[0044] Faraday rotator 4 includes a magnet 7 and a Faraday element 8. Magnet 7 has a rectangular cylindrical shape. Magnet 7 also has a through-hole 7a through which light passes. The direction in which light passes through through-hole 7a of magnet 7 is defined as the optical axis direction X. Faraday element 8 is made of a paramagnetic material that transmits light.

[0045] The magnet 7 has a first end face 7b, a second end face 7c, and a side face 7d. The first end face 7b and the second end face 7c are opposite to each other in the optical axis direction X. The first end face 7b is one end face of the magnet 7 in the optical axis direction X. The second end face 7c is the other end face of the magnet 7 in the optical axis direction X. The side face 7d connects the first end face 7b and the second end face 7c. In addition, the through hole 7a opens in both the first end face 7b and the second end face 7c.

[0046] like Figure 3 As shown, the cross-sectional shape of the through-hole 7a of the magnet 7 along the direction perpendicular to the optical axis direction X is a square. Furthermore, the cross-sectional shape of the through-hole 7a is not limited to a generally rectangular shape including the square shape described above, but may also be a generally circular shape including a circle. Furthermore, the shape of the magnet 7 is not limited to a square tube, and may also be a cylindrical shape, for example.

[0047] A pipe member 9 is provided in the through-hole 7a of the magnet 7. In the present embodiment, the pipe member 9 is a metal pipe. The pipe member 9 has a cylindrical shape. In addition, the pipe member 9 has a through-hole 9a through which light passes. In addition, the cross-sectional shape of the through-hole 9a of the pipe member 9 in a direction orthogonal to the optical axis direction X is circular. In the present embodiment, SUS304 is used as the material of the pipe member 9. However, the shape and material of the pipe member 9 are not particularly limited.

[0048] The Faraday element 8 is disposed in the through-hole 9a of the pipe member 9. In addition, the pipe member 9 can not necessarily be provided. In this case, it is sufficient that the Faraday element 8 is provided in the through-hole 7a of the magnet 7.

[0049] Returning to Figure 2 of (a) and (b), the first polarizer 2 is provided on the first end surface 7b side of the magnet 7. The second polarizer 3 is provided on the second end surface 7c side of the magnet 7. The first polarizer 2 and the second polarizer 3 are provided in a manner sandwiching the Faraday element 8 in the optical axis direction X and in a manner facing each other.

[0050] In the optical isolator 1, light is incident from the first polarizer 2 side, passes through the Faraday element 8, and is emitted from the second polarizer 3 side. Each of the first polarizer 2 and the second polarizer 3 has a pass axis. Light that has passed through the first polarizer 2 becomes linearly polarized light corresponding to the pass axis. The Faraday element 8 rotates the polarization plane of the linearly polarized light. The angle by which the Faraday element 8 rotates the polarization plane is a rotation angle. The angle of the pass axis of the second polarizer 3 with respect to the pass axis of the first polarizer 2 is equal to the rotation angle.

[0051] In the present embodiment, each of the first polarizer 2 and the second polarizer 3 is a polarization beam splitter (PBS). Therefore, P-polarized light or S-polarized light is incident on the Faraday element 8 through the first polarizer 2. The second polarizer 3 is configured in a manner that one of the P-polarized light and the S-polarized light that is incident on the Faraday element 8 passes in the optical axis direction X. However, the first polarizer 2 and the second polarizer 3 are not limited to PBSs. As the PBS, for example, a polarization beam splitter in which two prisms are joined via a polarization separation film can be used. As the material of the prisms, for example, glass can be used.

[0052] In addition, as the Faraday element 8, a paramagnetic substance can be used. As the paramagnetic substance, a glass material is preferably used. The Faraday element 8 composed of a glass material has less variation in the Verdet constant and less reduction in the extinction ratio due to defects and the like as in a single crystal material, and has less influence of stress from an adhesive, so that a stable Verdet constant and a high extinction ratio can be maintained. Furthermore, the Faraday element 8 can use a paramagnetic substance other than a glass material.

[0053] The glass material used in the Faraday element 8 preferably contains at least one rare earth element selected from Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Tm. It is particularly preferred that it contains Tb. Tb exists in trivalent and tetravalent states in the glass material, but in this specification, these values ​​are all expressed as TbO.

[0054] In this embodiment, the first polarizer 2, the second polarizer 3, and the Faraday rotator 4 are provided in a housing 6. As a material of the housing 6, an aluminum alloy can be used, for example. However, the material of the housing 6 is not particularly limited.

[0055] In this embodiment, the light incident on the optical isolator 1 passes through the first polarizer 2, becomes linearly polarized light, and is incident on the Faraday element 8. The incident light is rotated 45° by the Faraday element 8 and passes through the second polarizer 3. A portion of the light that has passed through the second polarizer 3 becomes reflected return light A, and the polarization plane passes through the second polarizer 3 at an angle of 45°. The reflected return light A that has passed through the second polarizer 3 is further rotated 45° by the Faraday element 8. As a result, the polarization plane of the reflected return light A becomes an orthogonal polarization plane that is 90° relative to the transmission axis of the first polarizer 2. Therefore, the reflected return light A cannot pass through the first polarizer 2 and is intercepted. In addition, at the first polarizer 2, the reflected return light A is reflected and travels in a direction different from the optical axis direction X (in this embodiment, a direction orthogonal to the optical axis direction X). In this way, the first polarizer 2 can intercept the reflected return light A of the laser.

[0056] like Figure 2 As shown in (b) of FIG. 1 , in the optical isolator 1, an absorbing member 5 is provided on the optical path of the reflected return light A reflected by the first polarizer 2. The absorbing member 5 is a member capable of absorbing at least a portion of the reflected return light A reflected by the first polarizer 2. In this embodiment, the absorbing member 5 is disposed between the first polarizer 2 and the wall of the housing 6.

[0057] Since the optical isolator 1 of the present embodiment includes the above-mentioned structure, scattering of the reflected return light A in the housing 6 can be suppressed, and thus the optical isolator 1 has excellent reliability.

[0058] Conventional optical isolators use components such as polarizers and Faraday rotators within a housing. However, light reflected from the polarizer on the incident side is reflected by the polarizer on the incident side. This reflected light is scattered within the housing, sometimes adversely affecting isolation characteristics and preventing sufficient reliability of the optical isolator.

[0059] In contrast, in the optical isolator 1 of this embodiment, an absorbing member 5 capable of absorbing at least a portion of the reflected return light A is provided on the optical path of the reflected return light A reflected by the first polarizer 2. Consequently, the optical isolator 1 can suppress scattering of the reflected return light A, and is unlikely to adversely affect isolation characteristics and other properties. Consequently, the optical isolator 1 has excellent reliability.

[0060] Figure 4 (a) is an enlarged perspective view showing an absorbing member in the optical isolator according to the first embodiment of the present invention. Figure 4 (b) is Figure 4 (a) is a schematic cross-sectional view of an absorbing component.

[0061] like Figure 4 As shown in (a), the absorbing member 5 of this embodiment has a structure in which a substantially V-shaped groove 11 is provided in a substantially quadrangular prism-shaped block. Figure 4 In (a), in order to illustrate the shape of the absorbing member 5, the absorbing member 5 is shown in reverse, but in fact, Figure 2 As shown in FIG. 5 ( b ), the groove portion 11 of the absorbing member 5 is arranged to face the first polarizer 2 .

[0062] In addition, if Figure 4 As shown in (b), the groove 11 of the absorbing member 5 has a tapered shape whose width narrows toward the direction of travel of the reflected return light A. Furthermore, the inner wall surfaces 5a and 5b constituting the groove 11 serve as light attenuating surfaces that absorb a portion of the reflected return light A and reflect the remaining portion.

[0063] In this embodiment, the absorbing member 5 includes a member body and a surface treatment layer. The surface treatment layer is a layer that absorbs at least a portion of the reflected return light A. In this embodiment, by covering the member body with the surface treatment layer, the inner wall surfaces 5a and 5b serving as light attenuating surfaces are formed.

[0064] As in the present embodiment, the surface treatment layer is preferably provided at least on the inner wall surfaces 5a and 5b so as to cover the component body. Furthermore, as long as the surface treatment layer can absorb at least a portion of the reflected return light A, it may cover a portion of or the entire inner wall surfaces 5a and 5b. Furthermore, the surface treatment layer may also cover the surface of the component body other than the inner wall surfaces 5a and 5b. Thus, the surface treatment layer may cover the entire surface of the component body.

[0065] As the component body, for example, an aluminum block or SUS304 can be used. Furthermore, the surface treatment layer can contain, for example, amorphous aluminum oxide, chromium, nickel, or carbon. The surface treatment of the surface treatment layer is not particularly limited, but is preferably an aluminum anodizing treatment, plating treatment, vapor deposition treatment, or a coating treatment such as spraying or brushing.

[0066] Specifically, the surface treatment layer can be appropriately selected in accordance with the wavelength of the laser used. For example, in the case where a black surface treatment layer based on aluminum anodizing treatment is used, the absorption rate of the reflected return light A can be increased in the visible wavelength region. In addition, the reflectance of the visible wavelength region (400 nm to 650 nm) based on aluminum anodizing treatment is about 3% to 10%. In addition, the black surface treatment layer obtained by aluminum anodizing treatment generally has a high reflectance in the infrared wavelength region having a longer wavelength, and thus it is difficult to appropriately use in the infrared wavelength region, but for example, by performing a treatment such as matting, the reflectance in the infrared wavelength region can be reduced and used. For example, in the case where a general glossy aluminum anodizing treatment is adopted, the reflectance at a wavelength of 1030 nm is about 60%, but by performing a treatment such as matting, the reflectance can be reduced to a range of 5% to 50%.

[0067] In addition, in the case where a black surface treatment is performed by chromium plating, electroless nickel plating, or the like, the absorption rate of the reflected return light A can be increased in the infrared wavelength region in addition to the visible wavelength region. In this case, the reflectance of the visible wavelength region (400 nm to 650 nm) based on chromium plating treatment is about 3% to 10%, and the reflectance of the infrared wavelength region (800 nm to 1400 nm) is about 3% to 10%. In addition, the reflectance of the visible wavelength region (400 nm to 650 nm) based on electroless nickel plating treatment is about 2% to 10%, and the reflectance of the infrared wavelength region (800 nm to 1400 nm) is about 4% to 15%.

[0068] The thickness of the surface treatment layer can be, for example, 1 μm or more and 100 μm or less.

[0069] In the present embodiment, a part of the reflected return light A reflected by the first polarizer 2 is absorbed by the inner wall surface 5a of the absorption member 5, and the reflected return light A that is not absorbed is reflected by the inner wall surface 5a. A part of the reflected return light A reflected by the inner wall surface 5a is absorbed by the inner wall surface 5b of the absorption member 5, and the reflected return light A that is not absorbed is reflected by the inner wall surface 5b. In addition, in the present embodiment, the inner wall surface 5a and the inner wall surface 5b are formed in the absorption member 5. Figure 4 In (b) of FIG. 8, an example of the path of the reflected return light A reflected by the inner wall surfaces 5a and 5b is indicated by a dashed line.

[0070] Thus, in the present embodiment, since a part of the reflected return light A can be absorbed by the inner wall surfaces 5a and 5b, the reflected return light A can be attenuated. Therefore, in the optical isolator 1, by providing the absorption member 5, the scattering of the reflected return light A in the housing 6 can be suppressed, and the reliability of the optical isolator 1 can be improved.

[0071] Furthermore, in this embodiment, the absorbing member 5 is arranged so that the reflected return light A is reflected twice by the inner wall surfaces 5a and 5b. However, the absorbing member 5 may be arranged so that the reflected return light A is repeatedly absorbed and reflected three or more times by the inner wall surfaces 5a and 5b. From the perspective of more reliably attenuating the reflected return light A, it is preferable to arrange the absorbing member 5 so that the reflected return light A is repeatedly absorbed and reflected by the inner wall surfaces 5a and 5b. However, in the present invention, it is sufficient that the reflected return light A is absorbed and reflected at least once by the inner wall surfaces 5a and 5b.

[0072] First variant:

[0073] Figure 5 (a) is an enlarged perspective view showing an absorbing member in the optical isolator according to the first modification. Figure 5 (b) is Figure 5 (a) is a schematic cross-sectional view of an absorbing component.

[0074] like Figure 5 As shown in (a) and (b), in the absorption member 5A of the first modified example, the groove portion 11A is formed by hollowing out a substantially quadrangular prism-shaped block into a conical shape. Figure 2 In (b), the absorbing member 5 is arranged at the position where the absorbing member 5 is arranged, and the groove portion 11A of the absorbing member 5A is arranged to face the first polarizer 2 .

[0075] like Figure 5 As shown in (b), the groove 11A in the absorbing member 5A of the first modified example also has a tapered shape, with its width narrowing toward the direction of travel of the reflected return light A. Furthermore, the inner wall surface 5Aa constituting the groove 11A serves as a light attenuating surface that absorbs a portion of the reflected return light A and reflects the unabsorbed reflected return light. Other aspects are the same as those of the first embodiment.

[0076] In the first variant, a portion of the reflected return light A reflected by the first polarizer 2 is absorbed by the inner wall surface 5Aa of the absorbing component 5A, and the reflected return light A that is not absorbed is reflected by the inner wall surface 5Aa. A portion of the reflected return light A reflected by the inner wall surface 5Aa is absorbed by other portions of the inner wall surface 5Aa of the absorbing component 5A, and the reflected return light A that is not absorbed is reflected by the above-mentioned other portions of the inner wall surface 5Aa. In this way, in the first variant, the inner wall surface 5Aa can also be used to absorb a portion of the reflected return light A, so the reflected return light A can be attenuated. In addition, since the inner wall surface 5Aa is conical, the reflected light is diffused and can be absorbed by a larger area of ​​the inner wall surface 5Aa. Therefore, by providing the absorbing component 5A, the scattering of the reflected return light A in the shell 6 can be suppressed, and the reliability of the optical isolator 1 can be improved. In addition, in Figure 5In (b), an example of the path of the reflected return light A reflected on the inner wall surface 5Aa is also shown by a dotted line, but in reality, it is also reflected in all directions and absorbed.

[0077] Second variant;

[0078] Figure 6 (a) is an enlarged perspective view showing an absorbing component in an optical isolator according to a second modified example. Figure 6 (b) is Figure 6 (a) is a schematic cross-sectional view of an absorbing component.

[0079] like Figure 6 As shown in (a), in the absorption component 5B of the second modified example, a hole portion is formed by hollowing out a roughly quadrangular prism-shaped block into a square prism-shaped irregular shape. In addition, a part of the square prism-shaped hole portion reaches the main surface of the block, thereby forming a groove portion 11B. In addition, the absorption component 5B is also Figure 2 In (b), the absorbing member 5 is arranged at the position where the absorbing member 5 is provided, and the groove portion 11B of the absorbing member 5B faces the first polarizer 2 .

[0080] like Figure 6 As shown in (b), the groove 11B in the absorbing member 5B of the second modified embodiment includes a tapered portion whose width narrows toward the direction of travel of the reflected return light A, and an inversely tapered portion whose width widens toward the direction of travel of the reflected return light A. Furthermore, the inner wall surfaces 5Ba to 5Bd forming the groove 11B serve as light-attenuating surfaces that absorb a portion of the reflected return light A and reflect the unabsorbed portion. Other aspects are the same as those of the first embodiment.

[0081] In the second variant, part of the reflected return light A reflected by the first polarizer 2 is absorbed by the inner wall surface 5Bb of the absorbing component 5B, and the reflected return light A that is not absorbed is reflected by the inner wall surface 5Bb. Part of the reflected return light A reflected on the inner wall surface 5Bb is absorbed by the inner wall surface 5Ba of the absorbing component 5B, and the reflected return light A that is not absorbed is reflected on the inner wall surface 5Ba. In this embodiment, since the groove portion 11b into which the reflected return light A enters is small, it is repeatedly reflected and absorbed on the inner wall surfaces 5Ba to 5Bd, so that the reflected return light A can be further attenuated. Therefore, by providing the absorbing component 5B, the scattering of the reflected return light A in the housing 6 can be further suppressed, and the reliability of the optical isolator 1 can be improved. In addition, in Figure 6 In (b), an example of the path of the reflected return light A reflected by the inner wall surfaces 5Ba to 5Bd is also shown by the dotted line, but in reality, it is also reflected in all directions and absorbed.

[0082] Modification 3:

[0083] Figure 7(a) is an enlarged perspective view showing an absorbing component in an optical isolator according to a third modified example. Figure 7 (b) is Figure 7 (a) is a schematic cross-sectional view of an absorbing component.

[0084] like Figure 7 As shown in (a), in the absorbing member 5C of the third modified example, a substantially quadrangular prism block is hollowed out into a conical shape, and a hole 11C is formed in such a way that the apex of the cone reaches the main surface of the absorbing member 5C. Figure 2 In (b), the absorbing member 5 is also disposed at the position where the absorbing member 5 is provided, and is disposed so that the hole 11C (the apex side of the cone) of the absorbing member 5C faces the first polarizer 2 .

[0085] like Figure 7 As shown in (b), the hole 11C in the absorbing member 5C of the third modified example has an inverted tapered shape that widens toward the direction of travel of the reflected return light A. Furthermore, the inner wall surface 5Ca constituting the hole 11C serves as a light-attenuating surface that absorbs a portion of the reflected return light A and reflects the unabsorbed reflected return light. Other aspects are the same as those of the first embodiment.

[0086] In the third variant, the reflected return light A reflected by the first polarizer 2 passes through the hole portion 11C, is reflected on the wall portion of the shell 6, and reaches the inner wall surface 5Ca of the absorbing component 5C. The reflected return light A that reaches the inner wall surface 5Ca of the absorbing component 5C is absorbed by the inner wall surface 5Ca of the absorbing component 5C, and the reflected return light A that is not absorbed is reflected by the inner wall surface 5Ca. A portion of the reflected return light A reflected on the inner wall surface 5Ca is absorbed by other portions of the inner wall surface 5Ca of the absorbing component 5C, and the reflected return light A that is not absorbed is reflected on the above-mentioned other portions of the inner wall surface 5Ca. In this way, in this embodiment, since a portion of the reflected return light A is absorbed by the inner wall surface 5Ca, the reflected return light A can be attenuated. Therefore, by providing the absorbing component 5C, the scattering of the reflected return light A in the shell 6 can be suppressed, and the reliability of the optical isolator 1 can be improved. In addition, as Figure 7 As shown in (b) of FIG. 1 , in this embodiment, it is preferable to bend the wall portion of the housing 6 that reflects the reflected return light A. Figure 7 As shown by the dotted line in (b), the reflected return light A can be incident on the inner wall surface 5Ca from all directions and absorbed and reflected.

[0087] 4th variant;

[0088] Figure 8 This is a schematic diagram of a cross section of an optical isolator according to a fourth modified example, taken along the optical axis.

[0089] like Figure 8As shown, in the fourth modification of the optical isolator 1, a portion of the wall of the housing 6 is hollowed out, and an absorbing member 5D is arranged so as to fit into the hollowed-out portion. The absorbing member 5D can have the same structure as the absorbing member 5 of the first embodiment. Other aspects are also the same as those of the first embodiment.

[0090] In the fourth modified example as well, an absorbing member 5D capable of absorbing at least a portion of the reflected return light A is provided on the optical path of the reflected return light A reflected by the first polarizer 2. Therefore, scattering of the reflected return light A within the housing 6 can be suppressed, and the reliability of the optical isolator 1 can be improved.

[0091] (Second embodiment)

[0092] Figure 9 (a) is a schematic diagram of a cross section of an optical isolator according to a second embodiment of the present invention, taken along the optical axis. Figure 9 (b) is a schematic perspective view showing an enlarged view of the absorbing member of the optical isolator according to the second embodiment of the present invention.

[0093] like Figure 9 As shown in (a) and (b) of FIG. 2 , in the optical isolator 21, a substantially cylindrical absorbing member 25 is disposed in the optical path of the reflected return light A reflected by the first polarizer 2. In this embodiment, the principal surface 25a of the cylindrical absorbing member 25 faces the first polarizer 2. The absorbing member 25 is made of glass.

[0094] As the glass, for example, glass having a composition containing iron, copper, etc. can be used.

[0095] The absorbing member 25 may be made of a material other than glass. The absorbing member 25 can be appropriately selected according to the wavelength of the laser light used.

[0096] The absorbing member 25 may be made of, for example, ceramics, a porous body, or the like.

[0097] Other aspects are the same as those of the first embodiment.

[0098] In the second embodiment as well, an absorbing member 25 capable of absorbing at least a portion of the reflected return light A is provided in the optical path of the reflected return light A reflected by the first polarizer 2. Therefore, scattering of the reflected return light A within the housing 6 can be suppressed, and the optical isolator 21 can be configured to be less likely to have an adverse effect on the isolation characteristics and other properties. Consequently, the optical isolator 21 has excellent reliability.

[0099] (Third embodiment)

[0100] Figure 10 This is a schematic diagram of a cross section of an optical isolator according to a third embodiment of the present invention, taken along the optical axis.

[0101] As shown in FIG. 1, in the optical isolator 31, a surface treatment layer is formed on the inner wall surface 36a of the housing 36. In the present embodiment, the surface treatment layer is the absorption member 35. Figure 10

[0102] The surface treatment layer of the absorption member 35 can contain, for example, amorphous aluminum oxide, chromium, nickel, carbon, or the like. In addition, the surface treatment of the surface treatment layer is not particularly limited, and is preferably an aluminum anodization treatment, a plating treatment, a vapor deposition treatment, or a coating treatment such as spraying or brushing.

[0103] Specifically, the surface treatment layer can be appropriately selected in accordance with the wavelength of the laser used. For example, in the case where a black surface treatment layer based on an aluminum anodization treatment is used, the absorption of the reflected return light A can be increased in the visible wavelength region. In addition, the reflectance in the visible wavelength region (400 nm to 650 nm) based on the aluminum anodization treatment is about 3% to 10%. In addition, the black surface treatment layer obtained by the aluminum anodization treatment generally has a high reflectance in the infrared wavelength region having a longer wavelength, and thus is difficult to be appropriately used in the infrared wavelength region, but can be used by reducing the reflectance in the infrared wavelength region by performing a mat treatment or the like. For example, in the case where a general glossy aluminum anodization treatment is performed, the reflectance at a wavelength of 1030 nm is about 60%, but by performing a mat treatment or the like, the reflectance can be reduced to a range of 5% to 50%.

[0104] In addition, in the case where a black surface treatment is performed by chrome plating, electroless nickel plating, or the like, the absorption of the reflected return light A can be increased in the infrared wavelength region in addition to the visible wavelength region. Specifically, the reflectance in the visible wavelength region (400 nm to 650 nm) based on the chrome plating treatment is about 3% to 10%, and the reflectance in the infrared wavelength region (800 nm to 1400 nm) is about 3% to 10%. In addition, the reflectance in the visible wavelength region (400 nm to 650 nm) based on the electroless nickel plating treatment is about 2% to 10%, and the reflectance in the infrared wavelength region (800 nm to 1400 nm) is about 4% to 15%.

[0105] The thickness of the surface treatment layer of the absorption member 35 can be, for example, 1 μm or more and 100 μm or less.

[0106] The other aspects are the same as those of the first embodiment.

[0107] ​In the third embodiment as well, an absorbing member 35 capable of absorbing at least a part of the reflected return light A is provided on the optical path of the reflected return light A reflected by the first polarizer 2. Therefore, scattering of the reflected return light A within the housing 36 can be suppressed, and the optical isolator 31 can be configured so as not to easily adversely affect the isolation characteristics and the like. Therefore, the optical isolator 31 is excellent in reliability.

[0108] (4th Embodiment)

[0109] Figure 11 (a) of FIG. 4 is a schematic cross-sectional view of an optical isolator according to the fourth embodiment of the present application along the optical axis direction. In addition, Figure 11 (b) of FIG. 4 is a schematic view of the cross-section shown in Figure 11 (a) of FIG. 4.

[0110] As shown in Figure 11 (a) of FIG. 4 and Figure 11 (b) of FIG. 4, in the optical isolator 41, a through-hole 45 is provided in a part of the wall portion of the housing 46. The through-hole 45 is provided so as to pass at least a part of the reflected return light A reflected by the first polarizer 2. Therefore, the through-hole 45 is provided on the optical path of the reflected return light A.

[0111] The shape of the through-hole 45 is not particularly limited as long as at least a part of the reflected return light A can pass therethrough, and can be formed in a substantially circular shape, a substantially rectangular shape, or a long hole, for example.

[0112] The size of the through-hole 45 is not particularly limited, and can be 1 mm or more and 8 mm or less, for example. The through-hole 45 can be plugged with a transparent member through which the reflected return light A can be transmitted, or an antireflection film can be formed on the transparent member to make it easier for the reflected return light A to be transmitted.

[0113] The other aspects are the same as in the first embodiment.

[0114] In the fourth embodiment, the through-hole 45 is provided in the optical path of the reflected return light A reflected by the first polarizer 2 in such a manner that at least a part of the reflected return light A can pass therethrough. Therefore, scattering of the reflected return light A within the housing 46 can be suppressed, and the optical isolator 41 can be configured so as not to easily adversely affect the isolation characteristics and the like. Therefore, the optical isolator 41 is excellent in reliability.

[0115] [Laser Irradiation Apparatus]

[0116] Figure 12 is a schematic view of a cross-section of a laser irradiation apparatus according to an embodiment of the present application along the optical axis direction.

[0117] As shown in Figure 12As shown, the laser irradiation device 51 includes the optical isolator 1 and a light source 52. As the absorbing member 5 of the optical isolator 1, as described above, it is possible to appropriately select according to the wavelength of the laser light AO emitted from the light source 52.

[0118] In the laser irradiation device 51, the laser light AO emitted from the light source 52 passes through the first polarizer 2 to become linearly polarized light, and is incident on the Faraday element 8. The incident light is rotated by 45° due to the Faraday element 8, and passes through the second polarizer 3. A portion of the light that has passed through the second polarizer 3 becomes the reflection return light A, and the polarization plane passes through the second polarizer 3 at an angle of 45°. On the other hand, the reflection return light A that has passed through the second polarizer 3 is further rotated by 45° due to the Faraday element 8. Due to this, the polarization plane of the reflection return light A becomes a polarization plane that is orthogonal to the transmission axis of the first polarizer 2 at 90°. Therefore, the reflection return light A cannot be transmitted from the first polarizer 2 and is intercepted. Furthermore, in the first polarizer 2, the reflection return light A is reflected and travels in a direction orthogonal to the optical axis direction X. Due to this, the first polarizer 2 is able to intercept the reflection return light A of the laser light AO.

[0119] In addition, in the laser irradiation device 51, since at least a portion of the reflection return light A that has been reflected by the first polarizer 2 is absorbed by the absorbing member 5, it is possible to attenuate the reflection return light A. Therefore, in the laser irradiation device 51, by providing this absorbing member 5, it is possible to suppress scattering of the reflection return light A within the housing 6, and it is possible to be configured so as not to easily cause adverse effects on the isolation characteristics and the like of the optical isolator 1. Therefore, the reliability of the laser irradiation device 51 is excellent.

[0120] Explanation of Reference Signs

[0121] 1, 21, 31, 41... optical isolator

[0122] 2... first polarizer

[0123] 3... second polarizer

[0124] 4... Faraday rotator

[0125] 5, 5A, 5B, 5C, 5D, 25, 35... absorbing member

[0126] 5a, 5b, 5Aa, 5Ba, 5Bb, 5Bc, 5Bd, 5Ca, 36a... inner wall surface

[0127] 6, 36, 46... housing

[0128] 7... magnet

[0129] 7a, 9a, 45... through hole

[0130] 7b... first end surface

[0131] 7c … 2nd end surface

[0132] 7d … side surface

[0133] 8 … Faraday element

[0134] 9 … tube member

[0135] 11, 11A, 11B … groove portion

[0136] 11C … hole portion

[0137] 25a … main surface

[0138] 51 … laser irradiation device

[0139] 52 … light source

[0140] A0 … laser A … reflected return light

[0141] X … optical axis direction

Claims

1. An optical isolator, characterized in that: include: a first polarizer disposed on the light incident side in the optical axis direction; a second polarizer disposed on the light-emitting side in the optical axis direction; a Faraday rotator disposed between the first polarizer and the second polarizer; and a housing that houses the first polarizer, the second polarizer, and the Faraday rotator, wherein The first polarizer is configured to reflect the reflected return light after passing through the second polarizer and the Faraday rotator in a direction different from the optical axis direction. An absorbing member capable of absorbing at least a portion of the reflected return light is provided in an optical path of the reflected return light reflected in a direction different from the optical axis direction.

2. The optical isolator according to claim 1, wherein: The absorbing member is arranged between the first polarizer and the wall of the housing in the optical path of the reflected return light.

3. The optical isolator according to claim 1 or 2, wherein: The absorption member has a light attenuating surface capable of attenuating the reflected return light.

4. The optical isolator according to claim 3, wherein: The light attenuation surface is configured to absorb a portion of the reflected return light and reflect the reflected return light that is not absorbed multiple times.

5. The optical isolator according to claim 3, wherein: The absorption component has a plurality of light attenuation surfaces. The plurality of light attenuation surfaces are arranged so as to absorb a portion of the reflected return light and reflect the reflected return light that is not absorbed multiple times.

6. The optical isolator according to claim 3, wherein: The absorbing member has a groove portion or a hole portion, The inner wall surface of the groove or hole of the absorbing component is the light attenuation surface. The groove portion or the hole portion has a tapered shape in which the width becomes narrower toward the traveling direction of the reflected return light.

7. The optical isolator according to claim 3, wherein: The absorbing member has a groove portion or a hole portion, The inner wall surface of the groove or hole of the absorbing component is the light attenuation surface. The groove portion or the hole portion has an inverted tapered shape in which the width increases toward the traveling direction of the reflected return light.

8. The optical isolator according to claim 3, wherein: The absorbent component comprises: the component body; and a surface treatment layer covering at least a portion of the component body and capable of absorbing at least a portion of the reflected return light; The surface of the surface treatment layer serves as the light attenuation surface.

9. The optical isolator according to claim 8, wherein: The surface treatment layer includes at least one selected from amorphous aluminum oxide, chromium, nickel, and carbon.

10. The optical isolator according to claim 8, wherein: The surface treatment of the surface treatment layer is aluminum anodizing treatment, plating treatment, evaporation treatment, spraying treatment or brushing treatment.

11. The optical isolator according to claim 1 or 2, wherein: The absorbing member is made of glass.

12. The optical isolator according to claim 1 or 2, wherein: A surface treatment layer is provided on the inner wall surface of the shell. The absorbent member is composed of the surface-treated layer.

13. A laser irradiation device, characterized in that: include: a light source that produces laser light; and The optical isolator according to claim 1 or 2.

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