Optical communication module

Abstract

To reduce influence of the positional displacement of a light source in an optical communication module.SOLUTION: An optical communication module 11 of the present invention according to the present invention includes: a light source 20 for emitting a first light L1; and a light regenerator 60 having an optical waveguide 40 having a core 44 and a volume hologram 62 for collecting the first light L1 and emitting a collected second light L2. The volume hologram 62 regenerates the second light L2 by the first light L1 and the second light L2 enters the core 44.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical communication module. [Background technology]

[0002] In an optical communication system, a module (optical communication module) is used that causes light emitted from a light source to enter an optical waveguide such as an optical fiber or an arrayed waveguide grating (AWG). For example, Patent Document 1 discloses an optical waveguide with connector (optical communication module) that includes an optical waveguide and an optical connector in which a recess is formed and the optical waveguide is disposed on the bottom surface of the recess. The optical waveguide has a long core portion (core) and a reflecting surface provided in the core portion. The reflecting surface bends and connects a first optical path passing through the core portion to a second optical path different from the first optical path. The second optical path extends, for example, from an intersection point between the first optical path and the reflecting surface to the outside of a recess formed in the optical connector. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-161843 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the optical waveguide with a connector disclosed in Patent Document 1, for example, a light source is disposed outside the recess, light emitted from the light source is directed from outside the recess to a reflecting surface along the second optical path, and the light reflected by the reflecting surface is made to enter the core portion along the first optical path, and the light can be propagated in the core portion. In order to make the light emitted from the light source enter the core portion with high efficiency, the arrangement of the light source is adjusted with respect to the reflecting surface, and the light emitted from the light source is made to enter the core portion within an angle range that allows propagation in the core portion.

[0005] In other words, in conventional optical communication modules including the connectorized optical waveguide disclosed in Patent Document 1, it was difficult to reduce the size if an adjustment mechanism for adjusting the position of the light source in order to couple the light emitted from the light source to the core of the optical waveguide was provided, or if a lens for converging the light from the light source toward the core portion was provided. [Means for solving the problem]

[0006] In order to solve the above problems, one embodiment of the optical communications module of the present invention comprises a light source that emits a first light, an optical waveguide having a core, and a light regeneration unit that has a volume hologram that collects the first light and emits the collected second light, wherein the volume hologram regenerates the second light using the first light, and the second light is incident on the core. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a plan view of an optical communications module according to a first embodiment. [Diagram 2] 2 is a schematic diagram of an optical system used for exposure production of a volume hologram of the optical communication module of FIG. 1. [Diagram 3] 2 is a schematic diagram of another optical system used for exposure production of a volume hologram of the optical communication module of FIG. 1. [Figure 4] FIG. 11 is a plan view of the optical communications module according to the second embodiment. [Diagram 5] 5 is a schematic diagram of an optical system used for exposure production of a volume hologram of the optical communication module of FIG. 4. [Figure 6] FIG. 11 is a plan view of an optical communications module according to a third embodiment. [Figure 7] 7 is a schematic diagram of an optical system used for exposure production of a volume hologram of the optical communications module of FIG. 6. [Figure 8] FIG. 13 is a plan view of an optical communications module according to a fourth embodiment. [Figure 9] 9 is a schematic diagram of an optical system used for exposure production of a volume hologram of the optical communication module of FIG. 8. [Figure 10]FIG. 13 is a plan view of the optical communications module according to the fifth embodiment. [Figure 11] FIG. 13 is a plan view of the optical communications module according to the sixth embodiment. [Figure 12] FIG. 13 is a schematic diagram showing ray tracing of the optical communications module according to the sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [First embodiment] A first embodiment of the present invention will be described below with reference to FIGS. 1 is a plan view showing an optical communications module 11 according to a first embodiment. In the following drawings, the scale of the dimensions of some components may be changed in order to make each component easier to see.

[0009] 1, the optical communication module 11 includes a light source 20, an optical waveguide 40, an optical regenerator 60, a mirror 100, and a housing 120. The light source 20 is, for example, a vertical cavity surface emitting laser (VCSEL) or a chip-type semiconductor laser (Laser Diode; LD) combined with a lens or the like combined with a beam shaping lens or the like, but is not particularly limited as long as it is a light source capable of emitting light (second light) L2 to be incident on the core 44 of the optical waveguide 40. The VCSEL 26, which is the light source 20, emits light (first light) L1 from an emission surface 24.

[0010] Hereinafter, the direction parallel to the optical axis AX1 of the light L1 emitted from the VCSEL 26 is referred to as the X direction, one side of the X direction is referred to as the +X side, and the other side of the X direction is referred to as the -X side. A direction perpendicular to the X direction is referred to as the Z direction, one side of the Z direction is referred to as the +Z side, and the other side of the Z direction is referred to as the -Z side. A plane including the X direction and the Z direction is referred to as the XZ plane, a direction perpendicular to the XZ plane is referred to as the Y direction, one side of the Y direction is referred to as the +Y side, and the other side of the Y direction is referred to as the -Y side. A plane including the X direction and the Y direction is referred to as the XY plane, and a plane including the Y direction and the Z direction is referred to as the YZ plane. In the claims, the "first direction" corresponds to the +X side of the X direction, and the "second direction" corresponds to the +Z side of the Z direction.

[0011] The optical waveguide 40 is an optical fiber 42 having at least a core 44 and extending, for example, along the Z direction. The optical fiber 42 has a core 44 and a cladding 46 provided on the outer periphery of the core 44. The cross section of the core 44 perpendicular to the Z direction is, for example, circular or rectangular, a perfect circle or a square. The size of the core 44 in the X direction is equal to the diameter A or the size of one side. The diameter A or the size of one side of the core 44 is, for example, about 40 μm. The core 44 has a refractive index n1 and is formed of, for example, quartz doped with an impurity such as germanium (Ge). The cladding 46 has a refractive index n2 lower than the refractive index n1 and higher than air, and is formed of, for example, quartz not doped with an impurity. The structural parameters and physical property values ​​of the optical fiber 42, including the size of the core 44 and the refractive indexes n1, n2, etc., are appropriately set according to the wavelength λ of the signal light used in the optical communication module 11 and the operating conditions of the optical communication module 11.

[0012] The end face 50 on the -Z side of the optical fiber 42 is formed so as to move to the -Z side as it progresses from the +X side to the -X side when viewed along the Y direction, and is inclined with respect to the X and Z directions. In other words, the end face 50 is so-called obliquely cut with respect to the X and Z directions. The end face 50 is inclined at an angle of -θ 20In this specification, the angle symbols are given with a "+" sign to the angle rotating clockwise on the XZ plane with respect to the reference axis or direction, and with a "-" sign to the angle rotating counterclockwise on the XZ plane with respect to the reference axis or direction.

[0013] The light regenerating unit 60 is disposed between the VCSEL 26 and the optical fiber 42 on the path of the light L1 and L2 along the optical axis AX1. The light regenerating unit 60 has a transmission type volume hologram 62. As shown in FIG. 1, the light regenerating unit 60 has a plurality of volume holograms 62, and is configured, for example, of three volume holograms 62A, i.e., a first volume hologram region, volume hologram 62B, i.e., a second volume hologram region, and volume hologram 62C, i.e., a third volume hologram region. The volume holograms 62A to 62C are disposed along the Z direction. The volume hologram 62A is adjacent to the +Z side of the volume hologram 62B. The volume hologram 62C is adjacent to the -Z side of the volume hologram 62B. That is, the volume hologram 62B is disposed between the volume holograms 62A and 62C in the Z direction. The center positions of the volume holograms 62A, 62B, and 62C in the Z direction are positions P2, P1, and P3, respectively. The "first volume hologram region" in the claims corresponds to the volume hologram 62A, and the "second volume hologram region" corresponds to the volume hologram 62B. The light reproducing unit collects the first light and emits the collected second light.

[0014] In the following, the light L1 emitted from the VCSEL 26 when placed at each of the positions P1, P2, and P3 may be referred to as light (first light) L11, L12, and L13. Also, the light L2 reproduced by the light L11, L12, and L13 in the volume holograms 62B, 62A, and 62C may be referred to as light L21, L22, and L23.

[0015] 1, light (first light) L11 emitted from the VCSEL 26 arranged at position P1 is incident on the volume hologram 62B. In the following, the VCSEL 26 being arranged at position P1 means that the position in the Z direction of the optical axis AX1 of the light L11 is position P1, and the position in the X direction of the exit surface 24 of the VCSEL 26 is position P5. The volume hologram 62B reproduces light (second light) L21 incident on the core 44 of the optical fiber 42 by the light L11 incident from the VCSEL 26 arranged at position P1.

[0016] 1, light (first light) L12 emitted from the VCSEL 26 when the VCSEL 26 is disposed at position P2 on the +Z side of position P1 is incident on the volume hologram 62A. Hereinafter, when the VCSEL 26 is disposed at position P2, it means that the position in the Z direction of the optical axis AX2 of the light L12 is position P2, and the position in the X direction of the exit surface 24 of the VCSEL 26 is position P5. The volume hologram 62A reproduces light (second light) L22 incident on the core 44 of the optical fiber 42 by the light L12 incident from the light L12 emitted from the VCSEL 26 disposed at position P2.

[0017] 1, light (first light) L13 emitted from the VCSEL 26 when the VCSEL 26 is disposed at position P3 on the -Z side of position P1 is incident on the volume hologram 62C. In the following, when the VCSEL 26 is disposed at position P3, it means that the position in the Z direction of the optical axis AX3 of the light L13 is position P3, and the position in the X direction of the exit surface 24 of the VCSEL 26 is position P5. The volume hologram 62C reproduces light (second light) L23 incident on the core 44 of the optical fiber 42 by the light L13 incident from the VCSEL 26 disposed at position P3.

[0018] In the first embodiment, each of the lights L11, L12, and L13 has an emission point (not shown) of the emission surface 24 of the VCSEL 26 as a wave source and is a spherical wave diverging from the emission point. The optical axis of each of the lights L11, L12, and L13 is parallel to the X direction. Each of the lights L21, L22, and L23 is reflected by the mirror 100 on each path toward the optical fiber 42. Each of the lights L21, L22, and L23 is a plane wave.

[0019] The optical axis AX1 of the light L21 propagating from the exit surface of the volume hologram 62B to the reflecting surface 102 of the mirror 100 is parallel to the X direction. The optical axis AX1 of the light L21 propagating from the reflecting surface 102 of the mirror 100 to the end face 50 on the -Z side of the optical fiber 42 is parallel to the Z direction.

[0020] When viewed on the XZ plane, the optical axis AX2 of the light L22 propagating from the exit surface of the volume hologram 62A to the reflecting surface 102 of the mirror 100 is inclined at an angle of +θ2 with respect to the X direction. The optical axis AX2 of the light L22 propagating from the reflecting surface 102 of the mirror 100 to the end surface 50 of the optical fiber 42 is inclined at an angle of -θ4 with respect to the Z direction. Similarly, when viewed on the XZ plane, the optical axis AX3 of the light L23 propagating from the exit surface of the volume hologram 62C to the reflecting surface 102 of the mirror 100 is inclined at an angle of -θ3 with respect to the X direction. The optical axis AX3 of the light L23 propagating from the reflecting surface 102 of the mirror 100 to the end surface 50 of the optical fiber 42 is inclined at an angle of +θ5 with respect to the Z direction. In other words, when a first light is incident on the volume hologram 62A, the optical axis of the emitted second light is along the second direction, and when the first light is incident on the second volume hologram area along the second direction, the optical axis of the emitted second light is inclined in the second direction, opposite to the first direction.

[0021] Each of the volume holograms 62A to 62C is made of, for example, a photopolymer. The width of each of the volume holograms 62A to 62C, i.e., the size in the Z direction perpendicular to the optical axis, is set according to the distance d in the Z direction between the position P1 and each of the positions P2 and P3. The thickness of each of the volume holograms 62A to 62C, i.e., the size in the X direction, is, for example, about 10 μm. The material of the volume hologram 62 is not particularly limited as long as it is capable of forming a volume hologram, as will be described later.

[0022] In the optical communication module 11 shown in FIG. 1, the mirror 100 reflects the light L2 regenerated from the light regenerating unit 60 toward the core 44 of the optical waveguide 40, and causes the light L2 to enter the core 44. The mirror 100 has a reflecting surface 102 that reflects the light L2. The reflecting surface 102 is disposed, for example, on the XZ plane so as to form an angle of approximately 45° with respect to the X direction and the Z direction. The mirror 100 may be attached to the optical fiber 42 with an adhesive (not shown) or the like so that the reflecting surface 102 abuts against the end face 50. Examples of the adhesive (not shown) include known ultraviolet curing resins. In this embodiment, the mirror 100 is attached to the optical fiber 42 with an adhesive (not shown) or the like, but this is not limiting. Instead of the mirror 100, the interface of the core material may be finished to a mirror surface to reflect the light L2 by utilizing the refractive index difference.

[0023] Light L11 emitted from the VCSEL 26 arranged at position P1 is incident on the volume hologram 62B. Light L21 reproduced by the volume hologram 62B travels parallel to the X direction and toward the +X side of the volume hologram 62B, and is incident on the reflecting surface 102. The light L21 is specularly reflected by the reflecting surface 102, and travels parallel to the Z direction through the core 44 from the end surface 50 of the optical fiber 42 toward the +Z side.

[0024] When the light L2 reproduced by the volume hologram 62 travels toward the +X side from the plate surface (front surface) on the +X side of the volume hologram 62B, it passes through a support plate 124 (described later) and the cladding 46 and core 44 at the end on the -Z side of the optical fiber 42, and reaches the reflecting surface 102. Since the volume hologram 62, the support plate 124, the cladding 46, and the core 44 have different refractive indices, the light L2 reproduced by the volume hologram 62 is refracted at each of the boundary surface between the volume hologram 62 and the support plate 124, the boundary surface between the support plate 124 and the cladding 46, and the boundary surface between the cladding 46 and the core 44. In each embodiment and the following description, it is assumed that the refractive index difference between the volume hologram 62 and the support plate 124, the refractive index difference between the support plate 124 and the cladding 46, and the refractive index difference between the cladding 46 and the core 44 are all very small, and the light L2 is irradiated onto the reflecting surface 102 of the mirror 100 while basically maintaining the angle it forms with respect to the X direction when reproduced from the volume hologram 62. However, if the refractive index differences described above are large enough to not be negligible, it is necessary to estimate the irradiation direction and incident angle of the light L2 on the reflecting surface 102, taking into consideration the refraction of the light L2 that occurs according to Snell's law at the boundary surface where the refractive index difference occurs.

[0025] Light L12 emitted from the VCSEL 26 arranged at position P2 is incident on the volume hologram 62A. Light L22 reproduced by the volume hologram 62A makes an angle of +θ2 with respect to the X direction, travels toward the +X side of the volume hologram 62B, and is incident on the reflecting surface 102. The light L22 is specularly reflected by the reflecting surface 102, makes an angle of -θ4 with respect to the Z direction when viewed from the Y direction, and travels from the end surface 50 of the optical fiber 42 through the core 44 toward the +Z side. The angle -θ4 is determined based on the law of reflection by the angle -θ that the reflecting surface 102 of the mirror 100 makes with respect to the Z direction. 20 and the incident angle -θ of the light L22 reproduced by the volume hologram 62A on the reflecting surface 102. 22 and the reflection angle +θ of the light L22 from the reflecting surface 102. 22 and the angle +θ2 are expressed as in the following formulas (1) and (2). Note that all angles in this specification are in degrees.

[0026]

number

[0027] Light L23 reproduced by the volume hologram 62C from the light L13 emitted from the VCSEL 26 arranged at position P3 makes an angle of -θ3 with respect to the X direction, travels toward the +X side of the volume hologram 62C, and is incident on the reflecting surface 102. The light L23 is specularly reflected by the reflecting surface 102, makes an angle of +θ5 with respect to the Z direction, travels toward the +Z side from the mirror 100, and is incident on the core 44 from the end face 50 of the optical fiber 42. Based on the law of reflection, the angle +θ5 is equal to the angle -θ that the reflecting surface 102 of the mirror 100 makes with respect to the Z direction. 20 and the incident angle -θ of the light L23 reproduced by the volume hologram 62A on the reflecting surface 102. 23 and the reflection angle +θ of the light L23 from the reflecting surface 102. 23 and the angle -θ3 is expressed as the following equations (3) and (4).

[0028]

number

[0029] 1, the light beams L21, L22, and L23 reflected by the reflecting surface 102 of the mirror 100 toward the +Z side are incident on the core 44. When the light beams incident on the core 44 travel along the boundary surface between the core 44 and the cladding 46, the light beams form an angle θ with respect to the X direction in the core 44. c、 In other words, the critical angle is expressed by the following equation (5).

[0030]

number

[0031] When viewed on the XZ plane, the angles 0 (zero), -θ4, and +θ5 that the light beams L21, L22, and L23 reflected by the mirror 100 make with respect to the Z axis are respectively -(90[deg.]-|±θ c |), +(90[deg.]-|±θ cThat is, the following conditions of the formulas (6) and (7) are satisfied.

[0032]

number

[0033] By satisfying the conditions of equations (6) and (7), at least a portion of the light L21, L22, and L23 enters the core 44 from the end face 50 of the optical fiber 42, and propagates toward the +Z side while repeatedly being totally reflected at the boundary between the core 44 and the cladding 46.

[0034] Of the light L2 reflected by the mirror 100, it is preferable that at least 50% of the light amount of the light L2 propagates in the +Z direction within the core 44. The amount of the light L2 propagating in the +Z direction within the core 44 is preferably 75% or more of the amount of the light L1, and more preferably 90% or more, but is appropriately set to meet the requirements of the optical transmission system to which the optical communication module 11 is connected. The reflecting surface 102 of the mirror 100 is angled at angles +θ2, -θ3, -θ4, +θ5 and angles θ c In addition, the above equations (1) to (7) are satisfied to obtain the angle -θ 20 The positions and fixation are determined by determining:

[0035] That is, the reflecting surface 102 specularly reflects any of the lights L21, L22, and L23 reproduced from the volume holograms 62B, 62A, and 62C in accordance with the law of reflection, and reflects the light axis at an angle of 90[deg.]-|±θ c The light beam is arranged so that it is incident on the interface between the core 44 and the cladding 46 at an angle shallower than |.

[0036] Furthermore, the amount of light L2 reflected by mirror 100 that propagates to the +Z side while repeating total reflection at the boundary surface between core 44 and clad 46 varies depending on the width of light L2 in a direction perpendicular to optical axis AX2 and diameter A of core 44, and can be estimated based on geometric optics. For example, when assuming the amount of light L2 that propagates to the +Z side while repeating total reflection at the boundary surface between core 44 and clad 46 with high efficiency of 90% or more of light L2 reflected by mirror 100, it is preferable that the intersection points of the +X side ends of light L2 reflected by reflecting surface 102, i.e., L21, L22, and L23, and end face 50 are located on the -X side of the boundary position on the +X side between core 44 and clad 46 at end face 50. In addition, it is preferable that the intersection between the -X side end of each of the light L2 reflected by the reflecting surface 102, i.e., L21, L22, and L23, and the end face 50 is located on the +X side of the boundary position on the -X side between the core 44 and the cladding 46 at the end face 50.

[0037] The wavelengths of the light L1 incident on each of the three volume holograms 62A to 62C and the light L2 reproduced by the light L1 are the same. That is, in the optical communication module described in the embodiment of this specification, one type of wavelength λ is basically used. In addition, the multiplexing method of the optical signal propagating through the core 44 of the optical fiber 42 may be, for example, a time division multiplexing (TDM) method or a phase shift keying (PSK) method.

[0038] The light L21 traveling through the core 44 to the +Z side is input as an optical signal to an optical transmission system (not shown) to which the optical communication module 11 is connected, and is processed appropriately.

[0039] The housing 120 is formed to maintain the relative arrangement of the light source 20, the optical waveguide 40, the light regenerating section 60, and the mirror 100, and to be able to house these components. The housing 120 includes, for example, a first housing section 121 formed along the X direction on the XZ plane, and a second housing section 122 formed extending from the first housing section 121 on the +X side to the +Z side. The first housing section 121 on the +X side and the second housing section 122 on the -Z side are in communication with each other.

[0040] In the first housing 121, the light source 20, the light regenerating unit 60, and the mirror 100 are sequentially arranged in the X direction from the -X side to the +X side. The +Z side end of the second housing 122 is formed so that the -Z side end of the optical fiber 42 can be inserted along the Z direction from the +Z side to the -Z side. The optical fiber 42 inserted into the second housing 122 is aligned in the Z direction so that the light L2 reflected by the reflecting surface 102 of the mirror 100 propagates to the +Z side while being totally reflected by the core 44 with the desired efficiency as described above.

[0041] The housing 120 is formed of, for example, a resin material or a metal material such as stainless steel (SUS). The reflectance of the inner surface of the housing 120 with respect to the lights L1 and L2 is reduced. For example, the inner surface of the housing 120 may have a light-shielding property. This suppresses diffuse reflection inside the housing 120 and the incidence of external light into the housing 120.

[0042] A support plate 124 is provided inside the first housing 121. The support plate 124 is disposed in the vicinity of the peripheral wall on the -X side of the second housing 122 in the X direction. A plate surface (front surface) 124b on the +X side of the support plate 124 is formed to be substantially flush with the inner peripheral surface of the peripheral wall on the -X side of the second housing 122. The support plate 124 is inverted along the YZ plane. That is, the plate surface of the support plate 124 and the surfaces of each of the volume holograms 62A to 62C extend along the YZ plane. As described above, the volume holograms 62A to 62C are formed of a material such as a photopolymer, have viscosity, and are attached to the plate surface (front surface) 124a on the -X side of the support plate 124. On the other hand, the plate surface 124b on the +X side of the support plate 124 is in contact with the end surface 42a on the -X side of the end portion on the -Z side of the optical fiber 42 aligned in the Z direction.

[0043] The support plate 124 is transmissive to at least the lights L1 and L2, and is preferably transparent to the lights L1 and L2. The support plate 124 is made of, for example, optical glass or a resin material such as PMMA (Poly Methyl Methacrylate) that has high transparency to the lights L1 and L2.

[0044] 2 and 3 are schematic diagrams of optical systems 251 and 252 for exposing and fabricating the volume holograms 62A to 62C, respectively. The volume hologram 62B can be fabricated, for example, using the optical system 251 shown in FIG. 2. In the optical system 251, a VCSEL 72A is disposed as a light source for emitting a reference beam L201 to a hologram material 75B constituting the volume hologram 62B, and a VCSEL 72B is disposed as a light source for emitting an object beam L202. The hologram material 75B may be, for example, a photopolymer.

[0045] The VCSEL 72A emits reference light L201 having at least the same wavelength as the light L1 emitted by the VCSEL 26, and may be, for example, a light source with the same specifications as the VCSEL 26, or the VCSEL 26 before being mounted on the optical communications module 11. The reference light L201 is incident at the same angle ±θ as the light L11 with respect to the X direction from the emission point source of the VCSEL 72A. 11The reference light L201 is a spherical wave that spreads with a radiation angle distribution of . In other words, the reference light L201 has the same radiation angle distribution as the light L1. The wavefront of the reference light L201 is the same as that of the light L1. The relative arrangement of the VCSEL 72A and the hologram material 75B is the same as the relative arrangement of the VCSEL 26 and the volume hologram 62B when they are disposed at position P1. A beam splitter 154 is disposed between the VCSEL 72A and the hologram material 75B. The reference light L201 emitted from the VCSEL 72A passes through the beam splitter 154 and enters the hologram material 75B.

[0046] The VCSEL 72B emits object light L202 having at least the same wavelength as the light L1 emitted by the VCSEL 26, and may be, for example, a light source with the same specifications as the VCSEL 26, or the VCSEL 26 before being mounted on the optical communication module 11. A collimator lens 152 is disposed between the VCSEL 72B and the beam splitter 154. The object light L202 emitted from the VCSEL 72B is collimated by the collimator lens 152, enters the surface of the beam splitter 154 opposite to the surface on which the reference light L201 is incident, and is reflected. The optical axis of the object light L202 reflected by the beam splitter 154 is overlapped with the optical axis of the reference light L201 transmitted through the beam splitter 154. The reference light L201 and the object light L202, whose optical axes overlap with each other, enter the hologram material 75B. Although FIG. 2 illustrates a plate-type beam splitter 154, a cube-type beam splitter may also be used in the optical system 251.

[0047] A volume hologram 62B is formed by holographically recording interference fringes between the reference beam L201 and the object beam L202 in a region where the reference beam L201 and the object beam L202 incident on the hologram material 75B overlap each other.

[0048] The volume hologram 62A can be produced by using, for example, the optical system 252 shown in FIG. 3. In the optical system 252, VCSELs 72A and 72B and a collimator lens 152 are arranged. The VCSEL 72A emits a reference light L201 to a hologram material 75A constituting the volume hologram 62A. The VCSEL 72B emits an object light L204. When viewed on the XZ plane, the width of the object light L204, i.e., the size in the Z direction perpendicular to the optical axis, is equal to or greater than the width of the light L22 reproduced by the volume hologram 62A in the optical communication module 11 shown in FIG. 1, i.e., the size in the Z direction. In addition, the angle +θ that the optical axis of the object light L204 makes with respect to the optical axis of the reference light L201 D is equal to the angle +θ2 that the optical axis AX2 of the light L22 makes with the optical axis AX2 of the light L12 incident on the volume hologram 62A and with the X direction when viewed on the XZ plane in the optical communication module 11 shown in Fig. 1. The hologram material 75A can be, for example, a photopolymer.

[0049] The reference light L201 emitted from the VCSEL 72A is incident on the hologram material 75B. The object light L204 emitted from the VCSEL 72B is collimated by the collimator lens 152. The optical axis of the collimated object light L204 is at an angle of +θ with respect to the optical axis of the reference light L201 on the XZ plane. D Reference beam L201 and object beam L204 are incident on hologram material 75A.

[0050] A volume hologram 62A is formed by holographically recording interference fringes between the reference beam L201 and the object beam L204 in a region where the reference beam L201 and the object beam L204 incident on the hologram material 75A overlap each other.

[0051] The volume hologram 62C can be produced using an optical system (not shown) similar to the optical system 252. However, in the optical system producing the volume hologram 62C, the width of the object light L204, i.e., the size in the direction perpendicular to the optical axis, when viewed on the XZ plane is equal to or larger than the width of the light L22 reproduced by the volume hologram 62C, i.e., the size in the Z direction, when viewed on the XZ plane in the optical communication module 11 shown in FIG. 1. In addition, the angle that the optical axis of the object light L204 makes with the optical axis of the reference light L201 when viewed on the XZ plane is set to be the same as the angle -θ3 that the optical axis AX3 of the light L22 reproduced by the volume hologram 62C makes with the optical axis AX3 of the light L12 incident on the volume hologram 62A and the axis parallel to the X direction when viewed on the XZ plane in the optical communication module 11 shown in FIG. 1.

[0052] In the above-mentioned optical system capable of producing the volume hologram 62C, by irradiating the reference light L201 and the object light L204 onto the holographic material constituting the volume hologram 62C, interference fringes between the reference light L201 and the object light L204 are holographically recorded in the area of ​​the holographic material where the reference light L201 and the object light L204 overlap, thereby forming the volume hologram 62C.

[0053] The optical communication module 11 of the first embodiment described above includes the light source 20, the optical waveguide 40 having the core 44, and the optical regeneration unit 60 disposed between the light source 20 and the optical waveguide 40 on the path of the light L1 incident from the light source. The optical regeneration unit 60 has a volume hologram 62 that regenerates the light L2 incident on the core 44 by the light L1 incident from the light source 20. According to the optical communication module 11 of the first embodiment, even if the position of the light source 20 is shifted, if the emission source of the light source 20 is within the range of the position of the emission source of the reference wave at the time of hologram recording of the volume hologram 62 in the Z direction, the light L2 can be regenerated from the volume hologram 62 as object light by the light L1 from the light source 20 and can be incident on the core 44 of the optical waveguide 40. Therefore, according to the optical communication module 11 of the first embodiment, the influence of the positional shift of the light source 20 can be reduced, and the light L1 emitted from the light source 20 can be easily coupled to the core 44 of the optical waveguide 40.

[0054] Furthermore, according to the optical communications module 11, the light regenerating section 60 can be configured with a size on the order of several tens of μm to several hundreds of μm using the volume hologram 62, so that the overall module can be easily miniaturized.

[0055] In the optical communication module 11 of the first embodiment, the light regenerating section 60 has a plurality of volume holograms 62A to 62C arranged along the Z direction (predetermined direction). The optical communication module 11 of the first embodiment has, for example, three volume holograms 62A to 62C as the volume hologram 62. The first light L1 emitted from the light source 20 is incident on at least one of the volume holograms 62A to 62C. Regardless of whether the light source 20 is disposed at a position P1 corresponding to the volume hologram 62B, a position P2 corresponding to the volume hologram 62A, or a position P3 corresponding to the volume hologram 62C, the light source 20 can regenerate any of the corresponding lights L21, L22, and L23 from any of the lights L11, L12, and L13 emitted from the light source 20 and make the corresponding lights incident on the core 44 of the optical waveguide 40. When a predetermined position of the first housing part 121 of the housing 120 of the light source 20 is set to position P2, even if the position mounted on the first housing part 121 is shifted to position P1 or position P3, light L2 can be regenerated from light L1 emitted from the light source 20 and can be coupled with high efficiency to the core 44 of the optical waveguide 40.

[0056] In order to effectively suppress the influence of misalignment of the light source 20, for example, the distance d between the positions P1 and P2 and the distance d between the positions P1 and P3 may be set to approximately an integer multiple of the mounting accuracy of the light source 20 on the first housing unit 121. In accordance with such settings, the distance d between the centers of the volume holograms 62A and 62B in the Z direction and the distance d between the centers of the volume holograms 62B and 62C in the Z direction may be approximately an integer multiple of the mounting accuracy of the light source 20 on the first housing unit 121.

[0057] The optical communication module 11 of the first embodiment further includes a mirror 100 that reflects the light L2 reproduced from the light regenerating section 60 to the core 44 of the optical waveguide 40 and propagates through the core 44. According to the optical communication module 11 of the first embodiment, the light L2 reproduced from the volume hologram 62 can be reflected so as to be folded back in a desired direction according to the law of reflection, so that the degree of freedom in design can be expanded for the relative arrangement of the optical waveguide 40 with respect to the light source 20, the diameter A, shape and number of the cores 44, the direction of the axis of the core 44 of the optical waveguide 40 directed toward the paths of the light L1 and the light L2, the shape of the housing 120, and the like. The size of the mirror 100 can be kept on the order of several tens of μm to several hundreds of μm, similar to the light source 20 and the optical waveguide 40, so that the overall size of the module can be suppressed.

[0058] In the optical communication module 11 of the first embodiment, the light L2 is a plane wave. In this case, the beam width of the light L2 is substantially constant along the path of the light L2, so that, for example, the arrangement of the mirror 100 and the end face 50 on the incident side of the optical waveguide 40 can be easily adjusted during mounting, and the distance between the exit face of the volume hologram 62 of the light regenerating unit 60 and the end face 50 of the optical waveguide 40 can be easily adjusted.

[0059] [Second embodiment] Next, a second embodiment of the present invention will be described with reference to FIGS. 4 is a plan view showing the optical communications module 12 of the second embodiment. The optical communications module of the second embodiment has the same configuration as the optical communications module 11 of the first embodiment, except that the light regenerating section 60 has volume holograms 62D to 62F, which will be described below, instead of volume holograms 62A to 62C as the volume hologram 62. In the following, in the optical communications modules of the second and subsequent embodiments, configurations common to the optical communications modules of the higher-level embodiments are given the same reference numerals as the common configurations, and descriptions thereof will be omitted. Mainly, only the contents of the optical communications modules of the second and subsequent embodiments that are different from the optical communications modules of the higher-level embodiments will be described.

[0060] FIG. 4 is a plan view showing an optical communication module 12 of the second embodiment. As shown in FIG. 4, the optical communication module 12 includes a light source 20, an optical waveguide 40, a light regenerating section 60, a mirror 100, a housing 120, and a support plate 124. The volume hologram 62 of the light regenerating section 60 is composed of, for example, three volume holograms 62D, 62E, and 62F. The volume holograms 62D to 62F are arranged along the Z direction. The volume hologram 62D is adjacent to the +Z side of the volume hologram 62E. The volume hologram 62F is adjacent to the -Z side of the volume hologram 62E. That is, the volume hologram 62E is arranged between the volume holograms 62D and 62F in the Z direction.

[0061] Each of the lights L11, L12, and L13 in the second embodiment is a spherical wave whose wave source is the emission point of the VCSEL 26 arranged at each of the positions P2, P1, and P3, similarly to the lights L11, L12, and L13 in the first embodiment, and converges toward the emission point. However, each of the lights L21, L22, and L23 in the second embodiment is a part of one spherical wave whose wave source is a point R1 on the reflecting surface 102 of the mirror 100, and converges toward a point R1 at a position P1 in the Z direction from the recording surface of the volume hologram 62E, and is diffused from the point R1 to a predetermined area of ​​the boundary surface between the core 44 and the cladding 46 of the optical fiber 42 after being reflected by the reflecting surface 102 of the mirror 100. The point R1 is set within the range of the core 44 in the X direction. Note that the point R1 may have a certain size, and may be at least smaller than the size of the lights L11, L12, and L13 in the Z direction.

[0062] The light L21 reproduced from the volume hologram 62E travels parallel to the X direction and toward the +X side of the volume hologram 62E, and is focused at a point R1 on the reflecting surface 102 of the mirror 100. The optical axis AX1 of the light L21 reproduced from the volume hologram 62E is approximately parallel to the X direction and forms approximately 45 degrees with respect to the perpendicular line of the reflecting surface 102. The light L21 focused at the point R1 is specularly reflected by the reflecting surface 102, and diffuses from the point R1 with the same radiation angle distribution as when it was incident, and travels through the core 44 parallel to the Z direction and toward the +Z side.

[0063] The light L22 reproduced from the volume hologram 62D travels parallel to the X direction and toward the +X side of the volume hologram 62E, and is focused at a point R1 on the reflecting surface 102 of the mirror 100. The optical axis AX2 of the light L22 reproduced from the volume hologram 62E forms an angle of +θ2 with respect to the X direction and an angle of -θ with respect to the perpendicular line of the reflecting surface 102. 22 The light L22 focused at point R1 is specularly reflected by the reflecting surface 102, diffuses from point R1 with the same radiation angle distribution as at the time of incidence, and travels toward the +Z side through the core 44. The optical axis AX2 of the light L22 specularly reflected by the reflecting surface 102 forms an angle -θ4 with the Z direction and an angle of 90 [deg.]-|-θ4| with the X direction.

[0064] The light L23 reproduced from the volume hologram 62F travels parallel to the X direction and toward the +X side of the volume hologram 62E, and is focused at a point R1 on the reflecting surface 102 of the mirror 100. The optical axis AX3 of the light L23 reproduced from the volume hologram 62E makes an angle of -θ3 with respect to the X direction and an angle of -θ 23 The light L23 focused at point R1 is specularly reflected by the reflecting surface 102, diffuses from point R1 with the same radiation angle distribution as at the time of incidence, and travels toward the +Z side through the core 44. The optical axis AX3 of the light L23 specularly reflected by the reflecting surface 102 forms an angle of +θ5 with the Z direction and an angle of 90 [deg.]-|+θ5| with the X direction.

[0065] As in the optical communications module 11 of the first embodiment, in the optical communications module 12 of the second embodiment, the angle -θ 20 is appropriately set to satisfy the above-mentioned formulas (1) to (7). In other words, the reflecting surface 102 of the mirror 100 is rotated at angles +θ2, -θ3, -θ4, +θ5 and angles θ c In addition, the above equations (1) to (7) are satisfied to obtain the angle -θ 20 The positions and fixation are determined by determining:

[0066] However, in the optical communication module 12, since each of the light beams L21, L22, and L23 reflected by the reflecting surface 102 of the mirror 100 is a spherical wave diverging from the point R1, the amount of light L2 reflected by the mirror 100 that propagates to the +Z side while repeating total reflection at the boundary surface with the cladding 46 within the core 44 also changes depending on the radiation angle distribution of each of the light beams L21, L22, and L23 with respect to the point R1. For example, in the light beam L21 reflected by the reflecting surface 102, when the outermost light beam LB1 in the circumferential direction from the optical axis AX1 with respect to the point R1 is irradiated from within the core 44 to the boundary surface with the cladding 46, the angle ±90[deg.]-|-θ4| with respect to the X direction is the angle |±θ c When the angle ±90[deg.]-|-θ4| is greater than the angle |±θ c |, the light L21 reflected by the reflecting surface 102 is reflected by an angle |±θ c The light L21 incident at an angle smaller than | is refracted at the interface between the core 44 and the cladding 46 and leaks out into the cladding 46. In other words, the angle ±90 [deg.]-|-θ4| is smaller than the angle |±θ c |, the light L21 reflected by the reflecting surface 102 is reflected by an angle |±θ c Light L21 incident at an angle equal to or greater than | is totally reflected at the boundary surface between the core 44 and the cladding 46, and propagates to the +Z side.

[0067] Similarly, the light beams L22 and L23 reflected by the reflecting surface 102 are reflected by an angle |±θ c Light L22 and L23 incident at angles equal to or greater than | propagates toward the +Z side while repeatedly being totally reflected at the boundary surface between the core 44 and the cladding 46.

[0068] Fig. 5 is a schematic diagram of an optical system 253 for exposing and fabricating each of the volume holograms 62D to 62F. Each of the volume holograms 62D to 62F can be fabricated, for example, using the optical system 253 shown in Fig. 5. In the optical system 253, hologram materials 75D to 75F constituting the volume holograms 62D to 62F are arranged in the Z direction in the same relative arrangement as the volume holograms 62D to 62F in the optical communication module 12, that is, the hologram materials 75D, 75E, and 75F are arranged from the +Z side to the -Z side along the Z direction.

[0069] In the optical system 253, a VCSEL 72A and a VCSEL (not shown) that emits an object beam L206 are arranged. The VCSEL 72A emits a reference beam L201 to a hologram material 75E that constitutes a volume hologram 62E. The optical axis of the object beam L206 emitted from the VCSEL (not shown) is parallel to the X direction, and overlaps with the optical axis of the reference beam L201 when viewed along the Y direction at least in the hologram material 75E. The object beam L206 is a spherical wave that travels from the -X side through the hologram materials 75D to 75F to the +X side of the hologram materials 75D to 75F and is focused at a point Q1. The relative positions of the hologram materials 75D to 75F and the point Q1 are the same as the relative positions of the volume holograms 62D to 62F and the point R1 in the optical communication module 12. The radiation angle distribution of the object light L206 is a radiation angle +θ, which represents the maximum angle formed by the lights L21, L22, and L23 converging from the volume holograms 62D, 62E, and 62F to the point R1 in the optical communication module 12 with respect to the X direction. 72 or radiation angle -θ 73 The wavefront of the object light L206 is the same as the wavefront of the lights L21, L22, and L23.

[0070] In the optical system 253, a VCSEL (not shown) that emits object light L206 in the X direction is arranged on the -X side of holographic materials 75D to 75F, and object light L206 can be generated, for example, by arranging an imaging lens (not shown) between the VCSEL 72E and the holographic materials 75D to 75F.

[0071] In addition, in the optical system 253, since the optical axis of the reference light L201 and the object light L206 for the hologram material 75E overlap with each other, a beam splitter 156 is disposed between the VCSEL 72A and the hologram material 75E in the X direction as necessary. In addition, in Fig. 5, the relative position of the VCSEL 72A and the reference light L201 along the X direction before being folded back by the beam splitter 156 are indicated by dashed lines. The VCSEL 72A is disposed on the -X side of the hologram materials 75D to 75F and on the +Z or -Z side of the diffusing object light L206, or on the +Y or -Y side (not shown), and is disposed on the +Z side in Fig. 5.

[0072] The reference light L201 emitted from the VCSEL72A has a wavelength of ±θ 11 While diffusing with a radiation angle distribution of , it travels to the -Z side, is reflected by beam splitter 154, travels to the +X side, and enters hologram material 75E. When object light L206 emitted from a VCSEL (not shown) passes through volume holograms 62D to 62F from the -X side, it passes through beam splitter 154, overlaps with reference light L201, and enters hologram material 75E. The interference fringes between the reference light L201 and object light L206 that have entered hologram material 75E are holographically recorded in hologram material 75E, forming volume hologram 62E.

[0073] Subsequently, the VCSEL 72A and the beam splitter 156 are moved, for example, by the distance d to the +Z side from the time of exposure of the hologram material 75E, so that the reference light L212 having the same radiation angle distribution as the reference light L201 can be emitted from the VCSEL 72A and made to enter the hologram material 75D. The interference fringes between the reference light L212 and the object light L206 that have entered the hologram material 75D are holographically recorded in the hologram material 75D, thereby forming a volume hologram 62D.

[0074] Next, the beam splitter 156 is moved, for example, by a distance d to the -Z side from the time of exposure of the hologram material 75E and inverted in the Z direction, and the VCSEL 72A is moved to a predetermined position on the -Z side of the beam splitter 156 that has been moved and inverted as described above, and to the -Z side of the object light L206. The predetermined position on the -Z side means a position on the optical axis of the reference light L213 from the beam splitter 156 that has been moved to the -Z side and inverted in the Z direction as described above, the same distance as the distance on the optical axis of the reference light L201 between the beam splitter 156 and the VCSEL 72A at the time of exposure of the hologram material 75E. The reference light L213 having the same radiation angle distribution as the reference light L201 can be emitted from the VCSEL 72A that has been moved to the predetermined position and can be made to enter the hologram material 75F. The interference fringes between the reference light L213 and the object light L206 that have entered the hologram material 75F are holographically recorded in the hologram material 75F, thereby forming a volume hologram 62F.

[0075] In addition, when it is possible to simultaneously prepare a plurality of light sources such as VCSELs capable of emitting reference light L201 having the same radiation angle distribution as VCSEL 26, the above-mentioned hologram materials 75E, 75D, and 75F may all be exposed simultaneously. In that case, for example, VCSEL 72A that emits reference light L212 may be disposed on the -Y side or +Y side of object light L206, and the orientation of beam splitter 156 may be adjusted to match VCSEL 72A disposed as described above.

[0076] The optical communications module 12 of the second embodiment described above includes a light source 20, an optical waveguide 40 having a core 44, and an optical regenerating section 60 disposed between the light source 20 and the optical waveguide 40 on the path of light L1 incident from the light source. As with the optical communications module 11 of the first embodiment, the optical communications module 12 of the second embodiment reduces the influence of misalignment between the positions P1, P2, and P3 of the light source 20, and can easily couple the light L1 emitted from the light source 20 to the core 44 of the optical waveguide 40 while achieving miniaturization.

[0077] Moreover, in the optical communications module 12 of the second embodiment, the light regenerating section 60 has a plurality of volume holograms 62D to 62F arranged along the Z direction. According to the optical communications module 12 of the second embodiment, similarly to the optical communications module 11 of the first embodiment, regardless of whether the light source 20 is arranged at position P1, P2, or P3, light L2 can be regenerated from light L1 emitted from the light source 20 by the volume hologram 62, coupled to the core 44 of the optical waveguide 40, and propagated to the +Z side within the core 44 while repeatedly being totally reflected at the boundary surface between the core 44 and the cladding 46.

[0078] Furthermore, since the optical communications module 12 of the second embodiment further includes the mirror 100, the light L2 reproduced from the volume hologram 62 is reflected in a desired direction in accordance with the laws of reflection, and the degree of freedom in design can be increased, for example, in the relative positioning of the optical waveguide 40 with respect to the light source 20, the diameter A, shape and number of the cores 44, and the direction of the axis of the core 44 of the optical waveguide 40 directed toward the paths of the light L1 and L2.

[0079] In the optical communication module 12 of the second embodiment, the light L2 is a spherical wave. Specifically, the light L2 reproduced from the volume hologram 62 is a spherical wave that is once focused on point R1 on the reflecting surface 102 of the mirror 100 with the point R1 as the wave source, and is a spherical wave that is reflected by the reflecting surface 102 and propagates in the core 44 while diffusing from point R1 to the +Z side with point R1 as the wave source. According to the optical communication module 12 of the second embodiment, a focusing function is imparted during exposure production of the volume hologram 62, and the light L2 reproduced by the volume hologram 62 can be generally focused toward point R1 by the focusing function. This makes it possible to reduce the beam diameter of the light L2 reproduced by the volume hologram 62 and increase the coupling efficiency of the light L2 to the core 44.

[0080] [Third embodiment] Next, a third embodiment of the present invention will be described with reference to FIGS. 6 is a plan view showing an optical communications module 13 of the third embodiment. As shown in FIG. 6, the optical communications module 13 includes a light source 20, an optical waveguide 40, a light regenerating section 60, a mirror 100, a housing 120, and a support plate 124, similar to the optical communications module 11. However, in the optical communications module 13 of the third embodiment, the light regenerating section 60 includes a transmission type volume hologram (first volume hologram) 65 and a transmission type volume hologram (second volume hologram) 67. That is, the optical communications module 13 of the third embodiment is a module that includes a volume hologram 65 instead of the volume hologram 62 of the optical communications module 11 of the first embodiment, and further includes a volume hologram 67 between the support plate 124 and the end of the optical fiber 42 on the -Z side in the X direction of the optical communications module 11 of the first embodiment.

[0081] The volume hologram 65 has a plurality of volume holograms 66, and is composed of, for example, three volume holograms 66A, 66B, and 66C. The volume holograms 66A to 66C are arranged along the Z direction. The center positions of the volume holograms 66A, 66B, and 66C in the Z direction are positions P2, P1, and P3, respectively.

[0082] The volume hologram 66B is incident on the light L11 emitted from the VCSEL 26 arranged at position P1 as shown by the solid line in FIG. 6. The volume hologram 66B reproduces the light L31 collimated by the incident light L11. The volume hologram 66A is incident on the light L12 emitted from the VCSEL 26 arranged at position P2 as shown by the dashed line in FIG. 6. The volume hologram 66A reproduces the light L32 collimated by the incident light L12. The volume hologram 66C is incident on the light L13 emitted from the VCSEL 26 arranged at position P3 as shown by the dashed line in FIG. 6. The volume hologram 66C reproduces the light L33 collimated by the incident light L13.

[0083] In the following, the lights L32, L31, and L33 reproduced from the volume holograms 66A, 66B, and 66C may be collectively referred to as light L3. The optical axis of the light L3 reproduced from the volume hologram 66 forms an angle of +θ7 with respect to the X direction and travels from the volume hologram 66 to the +X side.

[0084] Like the volume hologram 62, each of the volume holograms 65 and 67 is formed of a material such as a photopolymer, and has viscosity. The volume hologram 65 is attached to the plate surface 124a of the support plate 124. The volume hologram 67 is attached to the plate surface (front surface) 124b on the +X side of the support plate 124. In other words, the -X side surface of the volume hologram 67 is in contact with the plate surface 124b of the support plate 124. The -Z side end of the optical fiber 42 is in contact with the +X side surface of the volume hologram 67.

[0085] As shown by various lines in FIG. 6, any one of the lights L31, L32, and L33 reproduced from the volume hologram 65 is incident on the volume hologram 67. The volume hologram 67 reproduces any one of the lights L21, L22, and L23 as light L2 by any one of the incident lights L31, L32, and L33. The light L2 is a parallel light. The optical axis of the light L21 reproduced from the volume hologram 67 is approximately parallel to the X direction, as in the first embodiment. The optical axes of the lights L22 and L23 reproduced from the volume hologram 67 form angles +θ2 and -θ3 with respect to the X direction, as in the first embodiment. The angle +θ2 is different from the angle +θ7.

[0086] The light L2 reproduced from the volume hologram 67 is incident on the reflecting surface 102 of the mirror 100, is specularly reflected by the reflecting surface 102 based on the same principle as that explained for the optical communication module 11 of the first embodiment, and travels toward the +Z side within the core 44 of the optical fiber 42. The light L2 that travels at an incline with respect to the X direction and the Z direction when specularly reflected by the reflecting surface 102 travels toward the +Z side while repeating total reflection at the boundary surface between the core 44 and the cladding 46 of the optical fiber 42, if the above-mentioned formulas (6) and (7) are satisfied.

[0087] Each of the volume holograms 66A to 66C can be produced by using, for example, an optical system (not shown) similar to the optical system 252 shown in Fig. 3. However, in the optical system for producing each of the volume holograms 66A to 66C, the width of the object light L204 in the optical system 252, i.e., the size in the direction perpendicular to the optical axis, is equal to or larger than the width of the light L2 reproduced from each of the volume holograms 66A to 66C in the optical communication module 13 shown in Fig. 6, i.e., the size in the direction perpendicular to each of the optical axes AX2, AX1, and AX3. Also, in the optical system for producing each of the volume holograms 66A to 66C, the angle +θ F is set to be the same as the angle +θ7 that the optical axis AX31 of the light L3 reproduced by the volume hologram 66 in the optical communication module 13 shown in Figure 1 makes with each of the optical axes AX1, AX2, and AX3 of the light L1 incident on the volume hologram 66.

[0088] In the above-mentioned optical system capable of producing each of the volume holograms 66A to 66C, by irradiating the reference light L201 and the object light L204 onto the holographic material constituting each of the volume holograms 66A to 66C, interference fringes between the reference light L201 and the object light L204 are holographically recorded in the area of ​​the holographic material where the reference light L201 and the object light L204 overlap, thereby forming each of the volume holograms 66A to 66C.

[0089] The volume hologram 67 can be produced, for example, by using an optical system 254 shown in FIG. 7. In the optical system 254, VCSELs 72A and 72B and collimator lenses 152 and 155 are arranged. As shown in FIG. 7, the VCSEL 72A emits a reference light L221 to a hologram material 77 constituting the volume hologram 67. An example of the hologram material 77 is a photopolymer. The reference light L221 emitted from the VCSEL 72A is collimated by the collimator lens 155. As shown by a solid line in FIG. 7, the optical axis of the reference light L221 corresponding to the light L31 of the optical communication module 13 forms an angle of +θ7 with respect to the X direction. The width of the reference light L221, i.e., the size in a direction perpendicular to the optical axis, is equal to or larger than the width of the light L31 reproduced by the volume hologram 66B in the optical communication module 13, i.e., the size in a direction perpendicular to the optical axis AX31.

[0090] The VCSEL 72B emits object light L225 to the hologram material 77. The object light L225 emitted from the VCSEL 72B is collimated by the collimator lens 152. As shown by the dashed line in Fig. 7, the optical axis of the object light L225 corresponding to the light L21 of the optical communications module 13 is approximately parallel to the X direction. The width of the object light L225, i.e., the size in the direction perpendicular to the optical axis, is equal to or greater than the width of the light L21 reproduced by the volume hologram 67 in the optical communications module 13, i.e., the size in the Z direction perpendicular to the optical axis AX1 of the light L21.

[0091] The collimated reference light L221 and object light L225 are incident on the hologram material 77. Interference fringes between the reference light L221 and the object light L225 are holographically recorded in a region where the reference light L221 and the object light L225 incident on the hologram material 77 overlap with each other, thereby forming a volume hologram 67 that reproduces the light L21 of the optical communication module 13.

[0092] Next, the VCSEL 72A and the collimator lens 155 are moved, for example, by the distance d to the +Z side from the time of exposure production of the volume hologram 67 that reproduces the light L21 of the optical communication module 13, and the reference light L221 is made incident on the hologram material 77. Also, the VCSEL 72B and the collimator lens 152 are moved, for example, by the distance d to the +Z side from the time of exposure production of the volume hologram 67 that reproduces the light L21 of the optical communication module 13, and the angle +θ H1 is changed to an angle +θ2, and object light L225 is made incident on hologram material 77. A volume hologram 67 that reconstructs light L22 from optical communications module 13 is formed in a region where reference light L221 and object light L225 incident on hologram material 77 overlap each other.

[0093] Next, the VCSEL 72A and the collimator lens 155 are moved, for example, by the distance d to the -Z side from the time of exposure production of the volume hologram 67 that reproduces the light L21 of the optical communication module 13, and the reference light L221 is made incident on the hologram material 77. Also, the VCSEL 72B and the collimator lens 152 are moved, for example, by the distance d to the -Z side from the time of exposure production of the volume hologram 67 that reproduces the light L21 of the optical communication module 13, and the angle -θ H2 is changed to an angle -θ3, and object light L225 is made incident on hologram material 77. A volume hologram 67 that reconstructs light L23 from optical communications module 13 is formed in a region where reference light L221 and object light L225 incident on hologram material 77 overlap each other.

[0094] In addition, when multiple light sources, such as VCSEL72A capable of emitting reference light L221 and VCSEL72B capable of emitting object light L225, can be prepared simultaneously, the exposure of the volume hologram 67 that reproduces the light L21, L22, and L23 of the optical communication module 13 may all be performed simultaneously, as described above.

[0095] The optical communications module 13 of the third embodiment described above includes a light source 20, an optical waveguide 40 having a core 44, and an optical regenerating section 60 disposed between the light source 20 and the optical waveguide 40 on the path of light L1 incident from the light source. According to the optical communications module 13 of the third embodiment, similarly to the optical communications module 11 of the first embodiment, the influence of misalignment between the positions P1, P2, and P3 of the light source 20 can be reduced, light L1 emitted from the light source 20 can be easily coupled to the core 44 of the optical waveguide 40, and miniaturization can be achieved.

[0096] Moreover, in the optical communications module 13 of the third embodiment, the light regenerating section 60 has a plurality of volume holograms 66A to 66C arranged along the Z direction. According to the optical communications module 13 of the third embodiment, similarly to the optical communications module 11 of the first embodiment, regardless of whether the light source 20 is arranged at position P1, P2, or P3, light L2 can be regenerated from the light L1 emitted from the light source 20 by the light regenerating section 60 having volume holograms 65, 67, coupled to the core 44 of the optical waveguide 40, and propagated to the +Z side within the core 44.

[0097] Furthermore, since the optical communications module 13 of the third embodiment further includes a mirror 100, the light L2 regenerated from the light regenerating section 60 is reflected in a desired direction in accordance with the laws of reflection, and the degree of design freedom can be increased in the relative positioning of the optical waveguide 40 with respect to the light source 20, the diameter A, shape and number of the cores 44, the direction of the axis of the cores 44 of the optical waveguide 40 directed toward the paths of the light L1 and L2, etc.

[0098] In the optical communication module 13 of the third embodiment, the light L2 is a plane wave. In the optical communication module 13 of the third embodiment, the light regenerating section 60 includes volume holograms 65 and 67. The volume hologram 65 regenerates the light L3 traveling from the incident light L1 toward the volume hologram 67. The volume hologram 67 regenerates the light L2 from the incident light L3. Each of the lights L31, L32, and L33 constituting the light L3 is a plane wave. In the optical communication module 11 of the first embodiment, when the volume hologram 62 is exposed and fabricated, it is necessary to expose and interfere the reference light L201, which is a spherical wave, and the object light L202, which is a plane wave, and adjust the angle that the optical axis of the object light L202 makes with respect to the X direction. In the optical communication module 12 of the second embodiment, when the volume hologram 62 is exposed and fabricated, it is necessary to expose and interfere the reference light L201, which is a spherical wave, and the object light L202. That is, in the optical communication module 11 of the first embodiment and the optical communication module 12 of the second embodiment, high accuracy is required for adjusting the angles of incidence of the reference light L201 and the object light L202 with respect to the hologram material during exposure and for adjusting the exposure position where the reference light L201 and the object light L202 are superimposed. On the other hand, in the optical communication module 13 of the third embodiment, the angle +θ7 that the optical axis of the object light L204, which is a plane wave, makes with respect to the X direction is kept constant during exposure production of the volume hologram 65, and the angle of incidence with respect to the hologram material is easily adjusted. Also, during exposure production of the volume hologram 67, the reference light L221 and the object light L225, which are plane waves, are exposed and interfere with each other, so that the angles of incidence and the exposure positions of the reference light L221 and the object light L225 with respect to the hologram material are easily adjusted. According to the optical communication module 13 of the third embodiment, the difficulty of exposure during production of the volume hologram 67 can be reduced.

[0099] [Fourth embodiment] Next, a third embodiment of the present invention will be described with reference to FIGS. Fig. 8 is a plan view showing an optical communications module 14 of the fourth embodiment. As shown in Fig. 8, the optical communications module 14 includes a light source 20, an optical waveguide 40, a light regenerating section 60, a mirror 100, a housing 120, and a support plate 124, similar to the optical communications module 13. However, in the optical communications module 14 of the fourth embodiment, the light regenerating section 60 includes a volume hologram (first volume hologram) 65, and a transmission type volume hologram (second volume hologram) 68 instead of the volume hologram 67 of the optical communications module 13 of the third embodiment.

[0100] As shown by various lines in FIG. 8, any one of the lights L31, L32, and L33 reproduced from the volume hologram 65 is incident on the volume hologram 68. The volume hologram 68 reproduces any one of the lights L21, L22, and L23 as light L2 by any one of the incident lights L31, L32, and L33. The optical axis of the light L21 reproduced from the volume hologram 67 is approximately parallel to the X direction, as in the first embodiment. The optical axes of the lights L22 and L23 reproduced from the volume hologram 67 form angles +θ2 and -θ3 with respect to the X direction, as in the first embodiment. The angle +θ2 is different from the angle +θ7. However, in the optical communications module 14 of the fourth embodiment, the light L2 reproduced from the volume hologram 68 is a spherical wave that converges to a point R1 on the reflecting surface 102 of the mirror 100, similar to the light L2 reproduced from the volume hologram 62 of the optical communications module 12 of the second embodiment. That is, each of the light beams L21, L22, and L23 reproduced from the volume hologram 68 is a spherical wave that converges with the point R1 as its wave source.

[0101] The light L2 reproduced from the volume hologram 68 is incident on the reflecting surface 102 of the mirror 100, is specularly reflected by the reflecting surface 102 based on the same principle as that explained for the optical communication module 12 of the second embodiment, and travels toward the +Z side within the core 44 of the optical fiber 42. The light L2 that travels at an incline with respect to the X direction and the Z direction when specularly reflected by the reflecting surface 102 travels toward the +Z side while repeating total reflection at the boundary surface between the core 44 and the cladding 46 of the optical fiber 42, if the above-mentioned formulas (6) and (7) are satisfied.

[0102] Each of the volume holograms 66A to 66C of the optical communications module 14 of the fourth embodiment can be fabricated by exposure in the same manner as each of the volume holograms 66A to 66C of the optical communications module 13 of the third embodiment.

[0103] Fig. 9 is a schematic diagram of an optical system 255 for exposing and fabricating a volume hologram 68 of the optical communications module 14 of the fourth embodiment. The volume hologram 68 can be fabricated, for example, by using the optical system 255 shown in Fig. 9. As shown in Fig. 9, the optical system 255 includes a VCSEL 72A that emits reference light L221 and a VCSEL (not shown) that emits object light L206.

[0104] The VCSEL 72A emits a reference light L221 to a hologram material 78 constituting the volume hologram 68. An example of the hologram material 78 is a photopolymer. The reference light L221 emitted from the VCSEL 72A is collimated by a collimator lens 155. As shown by a solid line in FIG. 8, the optical axis of the reference light L221 corresponding to the light L31 of the optical communication module 13 forms an angle of +θ7 with respect to the X direction. The width of the reference light L221, i.e., the size in the direction perpendicular to the optical axis, is equal to or larger than the width of the light L31 reproduced by the volume hologram 66B in the optical communication module 14, i.e., the size in the direction perpendicular to the optical axis AX31.

[0105] In the optical system 255, the optical axis of the object light L206 emitted from a VCSEL (not shown) is parallel to the X direction and overlaps with the optical axis of the reference light L221 when viewed along the Y direction at least within the hologram material 78. The object light L206 is a spherical wave that travels from the -X side through the hologram material 78 toward the +X side of the hologram material 78 and converges at a point Q1. The relative position between the hologram material 78 and the point Q1 is the same as the relative position between the volume hologram 68 and the point R1 in the optical communications module 14. The radiation angle distribution of the object light L206 is expressed by a radiation angle +θ, which represents the maximum angle formed with respect to the X direction by the lights L21, L22, and L23 that converge to the point R1 from each of the volume holograms 68 in the optical communications module 14. 72 or radiation angle -θ73 The wavefront of the object light L206 is the same as the wavefront of the lights L21, L22, and L23.

[0106] In the optical system 255, since the object light L206 is a spherical wave as described above and the beam diameter of the object light L206 expands as it moves from the +X side to the -X side, when the VCSEL 72A and the collimator lens 155 overlap within the irradiation range of the object light L206, a beam splitter (not shown) may be disposed in an appropriate position on the path of the reference light L221 with an appropriate attitude, as described for example in the optical system 253. By disposing the beam splitter in this manner, the combination of the VCSEL 72A that emits the reference light L221 and the collimator lens 155 that collimates the reference light L221 can be disposed on any one of the +Z side, -Z side, +Y side, or -Y side of the irradiation range of the object light L206.

[0107] A volume hologram 68 that reproduces the light L2 of the optical communications module 14 is formed in a region where the reference light L221 and the object light L206 incident on the hologram material 78 overlap each other. Note that, for example, in the same way as in the exposure production of the volume hologram in the third embodiment, if a plurality of light sources such as the VCSEL 72A capable of emitting the reference light L221 can be prepared at the same time, the exposure of the volume holograms 67 that reproduce the light L21, L22, and L23 of the optical communications module 14 may all be performed at the same time.

[0108] The optical communications module 14 of the fourth embodiment described above includes a light source 20, an optical waveguide 40 having a core 44, and a light regenerating section 60 disposed between the light source 20 and the optical waveguide 40 on the path of light L1 incident from the light source. As with the optical communications module 11 of the first embodiment, the optical communications module 14 of the fourth embodiment reduces the influence of misalignment between the positions P1, P2, and P3 of the light source 20, and can easily couple the light L1 emitted from the light source 20 to the core 44 of the optical waveguide 40 while achieving miniaturization.

[0109] Moreover, in the optical communications module 14 of the fourth embodiment, the light regenerating section 60 has a plurality of volume holograms 66A to 66C arranged along the Z direction. According to the optical communications module 14 of the fourth embodiment, similarly to the optical communications module 11 of the first embodiment, regardless of whether the light source 20 is arranged at position P1, P2, or P3, light L2 can be regenerated from the light L1 emitted from the light source 20 by the light regenerating section 60 having volume holograms 65, 67, coupled to the core 44 of the optical waveguide 40, and propagated to the +Z side within the core 44.

[0110] Furthermore, since the optical communications module 14 of the fourth embodiment further includes a mirror 100, the light L2 regenerated from the light regenerating section 60 is reflected in a desired direction in accordance with the laws of reflection, and the degree of freedom in design can be increased with respect to the relative positioning of the optical waveguide 40 with respect to the light source 20, the diameter A, shape and number of the cores 44, the direction of the axis of the cores 44 of the optical waveguide 40 directed toward the paths of the light L1 and L2, etc.

[0111] In the optical communication module 14 of the fourth embodiment, the light L2 is a spherical wave. In the optical communication module 14 of the fourth embodiment, the light regenerating section 60 includes two volume holograms 65 and 68. The volume hologram 65 regenerates the light L3 traveling toward the volume hologram 68 from the incident light L1. The volume hologram 68 regenerates the light L2 from the incident light L3. Each of the lights L31, L32, and L33 constituting the light L3 is a plane wave. In the optical communication module 14 of the fourth embodiment, when the volume hologram 68 is exposed and fabricated, the reference light L221, which is a plane wave, and the object light L206, which is a spherical wave, are exposed and interfered with each other, but the angle +θ7 that the optical axis of the reference light L221 makes with the X direction is kept constant, and the angle of incidence with respect to the hologram material 78 is easily adjusted. Furthermore, the object light L206 having the same wavefront and including the light L21, L22, and L23 of the optical communications module 14 can be made incident on the hologram material 78 as a simple spherical wave, which makes it easy to adjust the angle of incidence with respect to the hologram material 78. Therefore, according to the optical communications module 14 of the fourth embodiment, the difficulty of exposure during production of the volume hologram 68 can be reduced.

[0112] [Fifth embodiment] Next, a fifth embodiment of the present invention will be described with reference to FIG. Fig. 10 is a plan view showing an optical communications module 15 of the fifth embodiment. As shown in Fig. 10, the optical communications module 15 includes a light source 20, an optical waveguide 40, a light regenerating section 60, a mirror 100, a housing 120, and a support plate 124, similar to the optical communications module 13. However, in the optical communications module 15 of the fifth embodiment, the light regenerating section 60 includes a reflection type volume hologram (first volume hologram) 171 and a reflection type volume hologram (second volume hologram) 172.

[0113] The volume hologram 171 has a plurality of volume holograms 173, and is composed of, for example, three volume holograms 173A, 173B, and 173C. The volume holograms 173A to 173C are arranged along the Z direction. The center positions of the volume holograms 173A, 173B, and 173C in the Z direction are positions P2, P1, and P3, respectively.

[0114] In the optical communication module 15 of the fifth embodiment, the housing 120 extends in the YZ plane and is formed of a material that is transparent to each of the lights L1, L2, and L3. The material of the housing 120 may be the same as that of the support plate 124, such as optical glass or PMMA. The support plate 124 in the fifth embodiment is a light guide plate capable of guiding the light L3. The support plate 124 is provided on the surface 120b on the +X side of the housing 120. That is, the surface 120b of the housing and the plate surface 124a of the support plate 124 abut against each other. The VCSEL 26 disposed at any one of the positions P1, P2, and P3 is in contact with the bottom wall part on the -X side of the housing 120 and is disposed on the -Z side in the Z direction facing the inside of the housing 120. The volume hologram 171 is provided at a position in the Z direction corresponding to the positions P1, P2, and P3, and on the plate surface 124b on the +X side of the support plate 124. On the other hand, the volume hologram 172 is provided on the +Z side in the Z direction in contact with the upper wall of the housing 120 and facing the inside of the housing 120. The -Z side end of the optical fiber 42 is provided on the plate surface 124b on the +Z side of the support plate 124. In addition, the -Z side end of the optical fiber 42 faces the volume hologram 172 in the X direction, with the support plate 124 in between.

[0115] As shown by various lines in FIG. 10, the light beams L11, L12, and L13 emitted from the VCSEL 26 when the VCSEL 26 is disposed at the positions P1, P2, and P3 are incident on the volume holograms 173B, 173A, and 173C. The volume holograms 173B, 173A, and 173C reproduce the light beams L31, L32, and L33 that are collimated from the incident light beams L11, L12, and L13. As shown in FIG. 10, the light beams L31, L32, and L33 reproduced by the volume holograms 173B, 173A, and 173C are emitted from the volume holograms 173B, 173A, and 173C to the -X side and the +Z side, and guided through the support plate 124. The angles that the optical axes of the light beams L31, L32, and L33 make with respect to the X direction are the same as each other, i.e., +θ 30 It is.

[0116] Parallel light beams L31, L32, and L33 are incident on the volume hologram 172. The volume hologram 172 reproduces light beams L21, L22, and L23 by the incident light beams L31, L32, and L33. Each of the light beams L21, L22, and L23 is a spherical wave that is focused with a point R1 as a wave source. The optical axis of the light beam L21 reproduced from the volume hologram 172 is approximately parallel to the X direction, as in the first embodiment. The optical axes of the light beams L22 and L23 reproduced from the volume hologram 172 form angles +θ2 and -θ3 with respect to the X direction, as in the first embodiment.

[0117] The light L2 reproduced from the volume hologram 172 is incident on the reflecting surface 102 of the mirror 100, is specularly reflected by the reflecting surface 102 based on the same principle as that explained for the optical communication module 12 of the second embodiment, and travels toward the +Z side within the core 44 of the optical fiber 42. The light L2 that travels at an incline with respect to the X direction and the Z direction when specularly reflected by the reflecting surface 102 travels toward the +Z side while repeating total reflection at the boundary surface between the core 44 and the cladding 46 of the optical fiber 42, if the above-mentioned formulas (6) and (7) are satisfied.

[0118] Each of the volume holograms 173A to 173C can be produced using, for example, an optical system (not shown) similar to the optical system 252 shown in FIG. 3. However, in the optical system producing the volume holograms 173A to 173C, the VCSEL 72B that emits the object light L204 is disposed on the +X side of the hologram material constituting each of the volume holograms 173A to 173C. The emission end of the VCSEL 72B is directed toward the hologram material, and the object light L204 travels in the opposite direction to the direction shown in FIG. 3 and enters the hologram material from the +X side. The width of the object light L204, i.e., the size in the direction perpendicular to the optical axis, is equal to or larger than the width of the light L32, L31, and L33 reproduced by each of the volume holograms 173A to 173C in the optical communication module 15 shown in FIG. 10, i.e., the size in the direction perpendicular to the optical axis. The angle that the optical axis of the object light L204 makes with respect to the optical axis of the reference light L201, i.e., the X direction, is expressed as the angle +θ that the optical axes of the lights L32, L31, and L33 reproduced by each of the volume holograms 173A to 173C in the optical communication module 15 shown in FIG.30 Make it the same as.

[0119] In the above-mentioned optical system capable of producing each of the volume holograms 173A to 173C, by irradiating reference light L201 and object light L204 onto the holographic material constituting each of the volume holograms 173A to 173C, interference fringes between the reference light L201 and the object light L204 are holographically recorded in the area of ​​the holographic material where the reference light L201 and the object light L204 overlap, thereby forming each of the volume holograms 173A to 173C.

[0120] The volume hologram 172 can be produced by using, for example, an optical system (not shown) that is a partial modification of the optical system 253 shown in Fig. 5. However, in the optical system that produces the volume hologram 172, the VCSEL 72A that emits the reference light L201 is disposed on the +X side of the hologram material that constitutes the volume hologram 172. In the optical system that produces the volume hologram 172, the width of the reference light L201 in the optical system 253, i.e., the size in a direction perpendicular to the optical axis, is equal to or larger than the width of the light L32, L31, and L33 reproduced from each of the volume holograms 173A to 173C in the optical communication module 15 shown in Fig. 10, i.e., the size in a direction perpendicular to each of the optical axes AX2, AX1, and AX3. The angle that the optical axis of the reference light L201 makes with respect to the X direction is expressed as the angle +θ that the optical axes of the lights L32, L31, and L33 reproduced by each of the volume holograms 173A to 173C in the optical communication module 15 shown in FIG. 30 Make it the same as.

[0121] In the above-mentioned optical system capable of producing the volume hologram 172, by irradiating the reference light L201 and the object light L206 onto the holographic material constituting the volume hologram 172, interference fringes between the reference light L201 and the object light L206 are holographically recorded in the area of ​​the holographic material where the reference light L201 and the object light L206 overlap, thereby forming the volume hologram 172.

[0122] The optical communications module 15 of the fifth embodiment described above includes a light source 20, an optical waveguide 40 having a core 44, and a light regenerating section 60 disposed between the light source 20 and the optical waveguide 40 on the path of light L1 incident from the light source. According to the optical communications module 15 of the fifth embodiment, like the optical communications module 11 of the first embodiment, the influence of misalignment between the positions P1, P2, and P3 of the light source 20 can be reduced, light L1 emitted from the light source 20 can be easily coupled to the core 44 of the optical waveguide 40, and miniaturization can be achieved.

[0123] Moreover, in the optical communications module 15 of the fifth embodiment, the light regenerating section 60 has a plurality of volume holograms 173A-173C arranged along the Z direction. According to the optical communications module 14 of the fourth embodiment, similarly to the optical communications module 11 of the first embodiment, regardless of whether the light source 20 is arranged at position P1, P2, or P3, light L2 can be regenerated from the light L1 emitted from the light source 20 by the light regenerating section 60 having volume holograms 65, 68, coupled to the core 44 of the optical waveguide 40, and propagated to the +Z side within the core 44.

[0124] Furthermore, since the optical communications module 15 of the fifth embodiment further includes a mirror 100, the light L2 regenerated from the light regenerating section 60 is reflected in a desired direction in accordance with the laws of reflection, and the degree of design freedom can be increased in the relative positioning of the optical waveguide 40 with respect to the light source 20, the diameter A, shape and number of the cores 44, the direction of the axis of the cores 44 of the optical waveguide 40 directed toward the paths of the light L1 and L2, etc.

[0125] The optical communications module 15 of the fifth embodiment also includes reflection-type volume holograms 171 and 172 as the light regenerating section 60. The volume hologram 171 is formed by exposing the light at different exposure points in an optical system for fabricating the volume hologram, i.e., by emitting spherical waves from different sources of the reference light L201 at the same angle +θ 30In other words, the volume holograms 173A to 173C are array holograms that reconstruct light L31, L32, and L33 from light L11, L12, and L13, respectively. Light L3 emitted from the volume hologram 171 is incident at the same angle +θ with respect to the X direction regardless of the incidence positions P1, P2, and P3 in the Z direction on the volume hologram 171. 30 The light L3 is guided through the support plate 124 as a plane wave having a shape of a square. The volume hologram 172 is not an array hologram like the volume hologram 171, but a simple single volume hologram produced by interference exposure between the reference light L201, which is a plane wave, and the object light L206, which is a spherical wave. The light L3 guided through the support plate 124 is all focused at the same point R1, regardless of the difference in the Z-direction position at which it enters the volume hologram 172. In this way, in the optical communication module 15 of the fifth embodiment, the light L1 is converted into light L3 by the volume hologram 171, the light L3 is guided to the support plate 124 as a light guide plate, the light L3 is converted into light L2 by the volume hologram 172, and the light L2 is input to the core 44 of the optical waveguide 40 via the mirror 100 and coupled thereto, so that the installation area of ​​the light source 20, the relative position with respect to the optical waveguide 40, and the like can be freely designed.

[0126] [Sixth embodiment] Next, a sixth embodiment of the present invention will be described with reference to FIGS. Fig. 11 is a plan view showing an optical communications module 16 of the sixth embodiment. As shown in Fig. 11, the optical communications module 16 includes a light source 20, an optical waveguide 40, an optical regenerating section 60, and a housing and a support plate (not shown). The optical regenerating section 60 has a transmission type volume hologram 180. The size of the volume hologram 180 in the Z direction is larger than the distance in the Z direction from position P2 to position P3, i.e., twice the distance d.

[0127] When the VCSEL 26 is disposed at each of the positions P1, P2, and P3 as shown by solid lines in FIG. 11, the light beams L11, L12, and L13 emitted from the VCSEL 26 are incident on the volume hologram 180. The volume hologram 180 reproduces one of the light beams L21, L22, and L23 by one of the light beams L11, L12, and L13 incident thereon. As described in the first embodiment and the like, each of the light beams L11, L12, and L13 is a spherical wave that diffuses from the exit surface 24 of the VCSEL 26 disposed at each of the positions P1, P2, and P3 toward the +X side with a predetermined radiation angle distribution. Each of the light beams L21, L22, and L23 is a plane wave that travels from the volume hologram 180 toward the overlapping region OV on the +X side with the positions P1, P2, and P3 of the volume hologram 180 in the Z direction being approximately the center. The angles that the optical axes of the lights L21, L22, and L23 form with respect to the X direction are +θ2, substantially 0, and −θ3. Note that the angles +θ2 and −θ3 are omitted in FIG.

[0128] In the optical communication module 16, the axis and core 44 of the optical fiber 42 extend along the X direction. The end face 50 of the optical fiber 42 is parallel to the Z direction and is at an angle of approximately 90 degrees with respect to the X direction. The end face 50 is disposed on the +X side of the volume hologram 180 and spaced apart from the volume hologram 180. The region of the core 44 of the end face 50 includes and overlaps with the overlap region OV of the light L21, L22, and L23. That is, the region of the core 44 of the end face 50 and the overlap region OV overlap with each other in the X direction. The size in the Z direction of the region of the core 44 of the end face 50 is equal to or larger than the size in the Z direction of the overlap region OV.

[0129] That is, in the optical communications module 16 of the sixth embodiment, the mirror 100 included in the optical communications module 11 of the first embodiment and the like is not disposed, and the light L2 reproduced from the volume hologram 180 is directly coupled to the core 44 of the optical fiber 42. In the optical communications module 16, as described in the first embodiment, the conditions for the light L2 reproduced from the volume hologram 180 to enter the core 44 of the optical fiber 42 and propagate to the +X side while being totally reflected at the boundary surface between the core 44 and the cladding 46 are expressed by the following formulas (8) and (9).

[0130]

number

[0131] In the X direction, the distance between the emission surface of the light source 20 and the center of the volume hologram 180 is D a In addition, the distance between the center of the volume hologram 180 and the overlapping area OV is D b The volume hologram 180 can be produced by using an optical system 256 illustrated in conjunction with the optical communication module 16 shown in Fig. 11. In the optical system 256, a VCSEL 81A is disposed as a light source that emits a reference beam L221, and a VCSEL 81B is disposed as a light source that emits an object beam L222.

[0132] The VCSEL 81A is disposed on the -X side of the hologram material 90 constituting the volume hologram 180. The VCSEL 81A is disposed on the -X side of the position of the VCSEL 26 when the hologram material 90 is disposed at the same position as the volume hologram 180 of the optical communication module 16. The center of the VCSEL 81A in the Z direction is at position P1. The reference light L221 emitted from the VCSEL 81A is a spherical wave that diffuses from the emission surface of the VCSEL 81A toward the +X side at a predetermined radiation angle. The reference light L221 is irradiated onto substantially the entire hologram material 90 in the Z direction, and enters the hologram material 90 from the surface on the -X side.

[0133] The VCSEL 81B is disposed on the +X side of the hologram material 90. The VCSEL 81B is disposed on the +X side of the overlapping region OV when the hologram material 90 is disposed at the same position as the volume hologram 180 of the optical communication module 16. The center of the VCSEL 81B in the Z direction is at position P1. The object light L222 emitted from the VCSEL 81B is a spherical wave that diffuses from the emission surface of the VCSEL 81B toward the -X side at a predetermined radiation angle. The object light L222 is irradiated onto substantially the entire hologram material 90 in the Z direction, and enters the hologram material 90 from the surface on the +X side.

[0134] In the optical system 256, by irradiating the reference light L221 and the object light L222 onto the hologram material 90, interference fringes between the reference light L221 and the object light L222 are holographically recorded in the area of ​​the hologram material 90 where the reference light L221 and the object light L222 overlap, thereby forming a volume hologram 180.

[0135] 12 is a schematic diagram of a beam of light L1 incident on a volume hologram 180 of the optical communications module 16 and a beam of light L2 reproduced from the volume hologram 180. In FIG. 12, the thickness of the volume hologram 180 is ignored. As described above, the volume hologram 180 is formed by the interference of the reference light L221, which is a spherical wave, and the object light L222, and functions as a lens. In the optical communications module 16 shown in FIG. 11, the distance in the X direction from the exit surface 24 of the VCSEL 26 to the surface on the -X side of the volume hologram 180 is defined as D a The distance in the X direction from the surface on the +X side of the volume hologram 180 to the overlapping region OV is D b Then, applying the lens formula of geometric optics, the following equation (10) is obtained.

[0136]

number

[0137] In the above formula (10), f represents the focal length when the volume hologram 180 is regarded as a lens. For example, f=200 μm, D a If you set = 200 μm, D b =∞, and the light L2, which is a parallel light, is reproduced from the volume hologram 180. Under this condition, for the optical system 256, the distance in the X direction from the exit surface of the VCSEL 81A to the surface on the -X side of the volume hologram 180 is D A The distance in the X direction from the exit surface of the VCSEL 81B to the surface on the +X side of the volume hologram 180 is D B For example, D A = 400 μm, D B= 400 μm, and for volume hologram 180 formed by the interference of spherical wave reference light L221 and object light L222, a numerical simulation was used to trace the light rays when the position of the emission source of light L1 was shifted by d = 50 μm in the Z direction at position P5 on the -Z side from volume hologram 180. As a result, as shown in FIG. 12, when spherical wave light L1 is emitted from position P5, light L2 reproduced by volume hologram 180 is all parallelized as derived by equation (10). Furthermore, the numerical simulation showed that even if the position of the emission source of light L1 is shifted along the Z direction at position P5, the light L2 on the +X side from volume hologram 180 is parallelized. b = 200 μm, forming an overlap region OV. The results of the numerical simulation show that by using the lens characteristics of the volume hologram 180, it is possible to reduce the influence of misalignment during mounting of the VCSEL 26 without using an array hologram in which multiple volume holograms are arranged as in the optical communication modules of the first to fifth embodiments.

[0138] The optical communications module 16 of the sixth embodiment described above includes a light source 20, an optical waveguide 40 having a core 44, and a light regenerating unit 60 disposed between the light source 20 and the optical waveguide 40 on the path of light L1 incident from the light source. The optical communications module 16 of the sixth embodiment reduces the influence of misalignment between the positions P1, P2, and P3 of the light source 20, as in the optical communications module 11 of the first embodiment, and allows the light L1 emitted from the light source 20 to be easily coupled to the core 44 of the optical waveguide 40.

[0139] In addition, when the light regenerating section 60 includes an array hologram as in the optical communication module 11 of the first embodiment, it is necessary to perform split exposure to each hologram material during fabrication of the array hologram, followed by cutting and pasting the volume hologram, or to perform multiple exposure to one hologram material the same number of times as the number of holograms in the array hologram. In addition, high positional accuracy is required when the volume hologram, which is an array hologram, is installed in the housing. On the other hand, since the light regenerating section 60 of the optical communication module 16 of the sixth embodiment includes the above-mentioned volume hologram 180, the positional accuracy required for the arrangement of the VCSEL relative to the hologram material in the optical system during exposure fabrication is not excessively high. Therefore, it is possible to improve the ease of manufacturing the volume hologram 180 and the optical communication module 16 including it.

[0140] Moreover, the optical communication module 16 of the sixth embodiment includes a transmission type volume hologram 180 as the light regenerating unit 60. The volume hologram 180 is produced by interference exposure between the reference light L201 and the object light L202, which are spherical waves, and exhibits imaging characteristics derived from the geometric lens formula. If an area away from the volume hologram 180 by a predetermined distance in the X direction (direction perpendicular to the surface of the volume hologram) is taken as the installation area of ​​the light source 20 within a range in which the lens formula can be applied, the light L1 emitted from the light source 20 can be made to enter the volume hologram 180, and the light L2 reproduced from the volume hologram 180 can be applied to the overlapping area OV even if the emission surface of the light source 20 is placed at any position within the installation area, that is, within a range that overlaps with the area in which the volume hologram 180 is formed in the Z direction in the installation area. By arranging the end face 50 of the core 44 of the optical waveguide 40 in the overlapping region OV, the light L2 irradiated to the overlapping region OV can be easily coupled to the core 44. According to the optical communications module 16 of the sixth embodiment, the influence of the positional deviation of the light source 20 on the coupling efficiency of the light L2 to the core 44 of the optical waveguide 40 can be mitigated. Note that the radiation angle distribution of the light source 20, the distance D a , D b , D A , D B etc. can be optimized based on equations (8)-(10).

[0141] Although the preferred embodiment of the present invention has been described above in detail, the present invention is not limited to the specific embodiment, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims. Also, the components of multiple embodiments can be combined as appropriate.

[0142] For example, in a modification of the optical communications module 11 of the first embodiment, the end of the optical fiber 42 constituting the optical waveguide 40 may be moved toward the +Z side from the position shown in FIG. 1 and away from the mirror 100. The end face 50 of the optical fiber 42 may be approximately parallel to the X direction. In such a configuration, the light L21, L22, and L23 reflected by the mirror 100 toward the +Z side is reflected by the maximum light receiving angle θ of the optical fiber 42. MAX The maximum acceptance angle θ MAX is determined by the refractive index n1 of the core 44 and the refractive index n2 of the cladding 46 of the optical fiber. In this modified example, the angle -θ is set so that the light L2 irradiated from the volume hologram 62 to the mirror 100 is coupled to the core 44 after being reflected by the mirror 100, and propagates to the +Z side within the core 44 while repeating total reflection at the interface between the core 44 and the cladding 46. 20 The angles and the radiation angle distribution of the lights L1 and L2 can be set and adjusted.

[0143] In the optical communication module of each embodiment described above, three positions P1, P2, and P3 including the positional deviation when the light source 20 is mounted are exemplified, but the number of positions where the light source 20 is assumed to be disposed is not specified as long as it is two or more. In addition, the position where the light source 20 is assumed to be disposed does not have to be along the Z direction or one direction, and can be set in any desired direction. A light source such as a VCSEL during exposure production of a volume hologram may be disposed in accordance with the position where the light source 20 is assumed to be disposed.

[0144] In the optical communication module of each of the above-described embodiments, a long optical fiber core has been exemplified as the optical waveguide, but the optical waveguide need only have a core and is not limited to an optical fiber core, and may be, for example, a planar lightwave circuit in which one or more cores are formed on a substrate such as silicon and embedded in a cladding.

[0145] For example, in the above-described embodiment, the configuration according to the present invention is used as an optical communications module, but the configuration according to the present invention can also be applied to an optical transceiver or a light source module in which light emitted from a light source is made to enter an optical waveguide and emitted from the exit end of the optical waveguide.

[0146] The optical communications module according to the aspect of the present invention may have the following configuration. One embodiment of the optical communications module of the present invention comprises a light source that emits a first light, an optical waveguide having a core, and a light regeneration unit that has a volume hologram that collects the first light and emits the collected second light, wherein the volume hologram regenerates the second light using the first light, and the second light is incident on the core.

[0147] In one embodiment of the optical communications module of the present invention, the light regeneration unit may have a plurality of volume holograms arranged along a predetermined direction, and a first light emitted from the light source may be incident on at least one of the volume holograms.

[0148] The optical communications module according to one aspect of the present invention may further include a mirror that reflects the second light regenerated from the light regenerating section to the core and causes the second light to propagate within the core.

[0149] In the optical communications module according to one aspect of the present invention, the second light may be a plane wave.

[0150] In the optical communications module according to one aspect of the present invention, the second light may be a spherical wave that is converged toward the incident surface of the core.

[0151] In one embodiment of the optical communications module of the present invention, the volume hologram may include a first volume hologram and a second volume hologram, wherein the first volume hologram reconstructs a third light traveling from the first light toward the second volume hologram, and the second volume hologram reconstructs the second light from the incident third light.

[0152] In the optical communications module according to one aspect of the present invention, the third light may be a plane wave.

[0153] In one embodiment of the optical communications module of the present invention, the volume hologram includes a first volume hologram region and a second volume hologram region, the second volume hologram region is located on the first direction side of the first volume hologram region, and the volume hologram may be configured such that when a first light is incident on the first volume hologram region along a second direction perpendicular to the first direction, the optical axis of the emitted second light is parallel to the second direction, and when the first light is incident on the second volume hologram region along the second direction, the optical axis of the emitted second light is inclined with respect to the second direction, opposite to the first direction. [Explanation of symbols]

[0154] 11, 12, 13, 14, 15, 16... Optical communication module, 20... Light source, 40... Optical waveguide, 60... Light regeneration unit, 62, 62A, 62B, 62C, 62D, 62E, 62F, 65, 66, 66A, 66B, 66C, 67, 68, 171, 172, 173, 173A, 173B, 173C, 180... Volume hologram, 100... Mirror

Claims

1. A light source that emits a first light of one wavelength; an optical waveguide having a core; a light reproducing unit having a volume hologram that collects the first light and emits the collected second light; Equipped with the light regenerating unit has a plurality of the volume holograms arranged along a predetermined direction and corresponding to the one type of wavelength, The first light emitted from the light source is incident on at least one of the volume holograms, the volume hologram reproduces the second light by the first light, The second light is incident on the core. Optical communications module.

2. Further comprising a mirror that reflects the second light regenerated from the light regenerating unit to the core and propagates within the core.

2. The optical communication module according to claim 1.

3. the second light is a plane wave; 3. The optical communication module according to claim 1 or 2.

4. The second light is a spherical wave converging toward the incident surface of the core.

3. The optical communication module according to claim 1 or 2.

5. the volume hologram includes a first volume hologram and a second volume hologram; the first volume hologram reproduces a third light traveling from the first light toward the second volume hologram; The second volume hologram reconstructs the second light from the third light incident thereon.

5. The optical communication module according to claim 1.

6. the third light is a plane wave; 6. The optical communication module according to claim 5.

7. the volume hologram includes a first volume hologram region and a second volume hologram region; the second volume hologram region is located on a first direction side of the first volume hologram region, the volume hologram is configured such that, when the first light is incident on the first volume hologram region along a second direction perpendicular to the first direction, an optical axis of the emitted second light is parallel to the second direction, and, when the first light is incident on the second volume hologram region along the second direction, an optical axis of the emitted second light is inclined with respect to the second direction in a direction opposite to the first direction.

5. The optical communication module according to claim 1.

8. The optical waveguide and the mirror are arranged so that a reflective surface of the mirror abuts against an end face of the optical waveguide.

3. The optical communication module according to claim 2.

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