Optical device, optical module, and image forming apparatus

Abstract

The present disclosure provides an optical device capable of stably entering light emitted from a laser diode into an optical waveguide. The optical device includes: a waveguide module including a base layer, a cover layer, and a waveguide layer formed between the base layer and the cover layer, the waveguide layer having an optical waveguide in which an incident end surface on which propagating laser light is incident is processed into a curved surface; the light-emitting module is provided with a laser diode that emits the laser light, and a carrier that supports the laser diode such that an emission surface of the laser light and the incident end surface are disposed so as to face each other and to be separated from each other, and that is joined to the base layer so as to be integrated with the waveguide module.

Description

Technical Field

[0001] The present disclosure relates to an optical device, an optical module, and an image forming apparatus. Background Art

[0002] When used, optical devices equipped with optical waveguides are connected to laser diodes serving as light sources, optical fibers that transmit communication signals, other optical devices, etc. For example, when connecting the end faces of two optical waveguides, an organic adhesive is used (see, for example, Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 5-142441 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] Some of the traveling light is reflected between dissimilar materials. Therefore, when connecting the end faces of an optical waveguide using an organic adhesive, for example, a large amount of return light is generated at the boundary surface. It is known that when using a laser diode as a light source and guiding its output light into an optical waveguide, the generation of this return light can cause instabilities such as wavelength fluctuations.

[0008] The present disclosure has been made to solve such a problem, and provides an optical device and the like that can stably allow light emitted from a laser diode to enter an optical waveguide.

[0009] Technical solutions to solve problems

[0010] According to a first aspect of the present disclosure, an optical device is provided, comprising a waveguide module and a light-emitting module. The waveguide module includes a base layer, a cover layer, and a waveguide layer. The waveguide layer is formed between the base layer and the cover layer and has an optical waveguide whose incident end face, into which propagating laser light is incident, is processed into a curved surface. The light-emitting module includes a laser diode for emitting the laser light, and a carrier. The carrier is configured to support the laser diode such that the laser light emission surface and the incident end face are arranged opposite and spaced apart from each other, and is bonded to the base layer to form an integral part of the waveguide module.

[0011] In addition, a second aspect of the present disclosure provides an image forming apparatus, which uses an optical device, wherein the optical device has:

[0012] a substrate having a first side; and

[0013] a waveguide layer stacked on the substrate, having a second side surface continuous with the first side surface, and having an incident end face on the second side surface for allowing light to enter the waveguide,

[0014] The incident end face forms a curved surface.

[0015] Effects of the Invention

[0016] The present disclosure can provide an optical device or the like that can stably allow light emitted from a laser diode to enter an optical waveguide. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram illustrating the structure of a projector using the optical device according to this embodiment.

[0018] Figure 2 These are the top view and front view of the optical device.

[0019] Figure 3 It is a XX cross-sectional view of the first embodiment.

[0020] Figure 4 It is a XX cross-sectional view of the second embodiment.

[0021] Figure 5 FIG. 4 is a partial perspective view of a waveguide module according to the third embodiment. DETAILED DESCRIPTION

[0022] The embodiments of the present disclosure are described with reference to the accompanying drawings. In the various figures, parts marked with the same reference numerals have the same or similar structures. In addition, the invention described in the claims is not limited to the following embodiments. In addition, not all structures described in the embodiments are necessary for the technical solutions to the problems.

[0023] Figure 1 This is a schematic diagram illustrating the structure of a projector 30 that uses the optical device 10 of this embodiment. The projector 30 uses a MEMS (Micro Electro Mechanical Systems) mirror to temporally redirect and reflect the projection light emitted from the optical device 10, scanning it across a screen 40 to project an image.

[0024] The optical device 10 is primarily composed of a waveguide module 100 and a light-emitting module 200. In this embodiment, the light-emitting module 200 comprises a red light-emitting module 210, a green light-emitting module 220, and a blue light-emitting module 230. As described later, these modules are joined to the end faces of the waveguide module 100 to form an integral unit. However, in the figures, they are depicted separately from the end faces of the waveguide module 100.

[0025] The waveguide module 100 is generally in the shape of a rectangular parallelepiped. In the figure, the short side direction in the plane direction is defined as the X-axis direction, the long side direction is defined as the Y-axis direction, and the height direction perpendicular to the plane direction is defined as the Z-axis direction. Figure 1 The waveguide module 100 is set as a reference in the illustrated manner, and the same coordinate axes are described together to indicate the directions of the structures shown in the various drawings.

[0026] The waveguide module 100 includes a waveguide layer 150 parallel to the XY plane. The waveguide layer 150 is formed of an electro-optical material such as a lithium niobate film. A portion of the waveguide layer 150 is partially removed by etching, leaving a ridge that forms a convex shape in the cross section. The ridge acts as an optical waveguide for propagating laser light. In this embodiment, three optical waveguides, namely, the first optical waveguide 110, the second optical waveguide 120, and the third optical waveguide 130, are formed as part of the waveguide layer.

[0027] The first optical waveguide 110 extends in a straight line or gently curved line from a first incident end face 111 exposed on one side of the waveguide module 100 to an emission end face 112 exposed on the opposite side of the waveguide module 100. Specifically, laser light incident on the first incident end face 111 propagates through the first optical waveguide 110 and is emitted from the emission end face 112.

[0028] The second optical waveguide 120 extends in a straight line or gently curved line from the second incident end face 121 exposed on one side of the waveguide module 100, where the first incident end face 111 is provided, to a position where it merges with the middle portion of the first optical waveguide 110. Specifically, laser light incident on the second incident end face 121 propagates through the second optical waveguide 120, merges with the first optical waveguide 110 midway, and is emitted from the emission end face 112.

[0029] The third optical waveguide 130 extends in a straight line or gently curved line from the third incident end face 131 exposed on one side of the waveguide module 100 provided with the first incident end face 111 to a mid-portion of the first optical waveguide 110. Specifically, laser light incident on the third incident end face 131 propagates through the third optical waveguide 130, merges with the first optical waveguide 110 midway, and is emitted from the emission end face 112.

[0030] The three optical waveguide configuration is not limited to the above example; any configuration may be employed in which each optical waveguide has an incident end face, merges midway along the path, and has a common exit end face. Alternatively, a configuration may be employed in which the three optical waveguides branch downstream of the merged location to have two or more exit end faces.

[0031] The red light-emitting module 210 primarily comprises a red laser diode 211 and a first carrier 212 supporting the red laser diode 211. The red laser diode 211 is fixed to a predetermined position on the first carrier 212, as will be described in detail later. Red laser light emitted from the red laser diode 211 is incident on the first incident end face 111 of the first optical waveguide 110.

[0032] The green light-emitting module 220 primarily comprises a green laser diode 221 and a second carrier 222 supporting the green laser diode 221. The green laser diode 221 is fixed to a predetermined position on the second carrier 222, as will be described in detail later. Green laser light emitted from the green laser diode 221 is incident on the second incident end face 121 of the second optical waveguide 120.

[0033] The blue light-emitting module 230 primarily consists of a blue laser diode 231 and a third carrier 232 that supports the blue laser diode 231. The blue laser diode 231 is fixed to a predetermined position on the third carrier 232, as will be described in detail later. Blue laser light emitted from the blue laser diode 231 enters the third incident end face 131 of the third optical waveguide 130. The arrangement of the light-emitting modules for each color relative to the optical waveguides is not limited to the above arrangement and can be arbitrary. For example, the red light-emitting module 210 can be arranged to correspond to the third optical waveguide 130, while the blue light-emitting module 230 can be arranged to correspond to the first optical waveguide 110.

[0034] As described above, second optical waveguide 120 and third optical waveguide 130 merge into first optical waveguide 110. Therefore, when multiple laser diodes emit light simultaneously, mixed light from these laser diodes is emitted from emission end face 112. More specifically, when the red laser diode 211, green laser diode 221, and blue laser diode 231 are individually controlled in their emission intensities and caused to emit light, light of any desired color can be emitted from emission end face 112.

[0035] Figure 2 is a top view of the optical device 10 ( Figure 2 (A)) and main view ( Figure 2(B)). As shown in the front view, the waveguide module 100 includes a substrate 160 serving as a base layer, a waveguide layer 150 stacked on the substrate 160, and a buffer layer 170 serving as a cover layer covering the waveguide layer. As the substrate 160, for example, a Si substrate or a sapphire substrate can be used. The buffer layer 170 is formed of a highly transparent material having a lower refractive index than that of the waveguide layer 150, and for example, aluminum oxide (Al2O3) can be used. In this embodiment, the space removed from the waveguide layer 150 by etching or the like to form the optical waveguide is also filled with the buffer layer 170, but this space can also be formed as a protective layer, for example, made of silicon dioxide (SiO2). In addition, in this embodiment, the substrate 160 is used as the base layer and the buffer layer 170 is used as the cover layer, but at least one of these layers can be replaced by a cladding layer, or at least one of these layers can be formed together with the cladding layer. The cladding layer is formed of a material having a refractive index lower than that of the waveguide layer 150 , and yttrium oxide (Y 2 O 3 ) can be used, for example.

[0036] The first side surface 161 of the substrate 160 and the second side surface 151 of the waveguide layer 150 may be continuous, and the second side surface 151 may include an incident end facet 111 for allowing light to enter the waveguide. The incident end facet 111 may have a curved surface, and this curved surface may be continuous with at least a portion of the first side surface. Furthermore, the second side surface 151 of the waveguide layer 150 and the third side surface 171 of the buffer layer 170 may be continuous, and the curved surface of the second side surface 151 may be continuous with at least a portion of the third side surface 171.

[0037] Each light-emitting module (red light-emitting module 210, green light-emitting module 220, and blue light-emitting module 230) is bonded to substrate 160 via its respective carrier (first carrier 212, second carrier 222, and third carrier 232), thereby being integrated with waveguide module 100. Furthermore, an antireflection film and a SAC coating may be applied to the side of waveguide module 100 that is bonded to each light-emitting module, and an antireflection film may be applied to the side opposite to the side where the emission end face 112 is provided. Furthermore, an Au coating may be applied to the surface of each carrier that is bonded to substrate 160.

[0038] Figure 3 is a sectional view of the first embodiment of the present invention. In the first embodiment, each incident end face (at Figure 3 The first incident end face 111 is shown in FIG. Figure 3 The red laser diode 211 is shown in FIG. 2 and is processed into a curved surface in a manner that the side protrudes.

[0039] Figure 3Figure 2 shows a simplified cross-section of a red laser diode 211. The red laser diode 211 includes a light-emitting portion 213. Red laser light emitted from the light-emitting portion 213 is emitted from an emission surface 214 of the red laser diode 211, propagates through air (or a transmissive medium), and enters the first optical waveguide 110 from the first incident end face 111. When the red laser light enters the first incident end face 111, a portion of it is reflected by the first incident end face 111. However, because the first incident end face 111 is curved to protrude toward the red laser diode 211, the amount of return light directly returning toward the light-emitting portion 213 is significantly reduced compared to a case where the first incident end face 111 is flat. Instead, the majority of the reflected light is scattered away from the light-emitting portion 213 in the space between the emission surface 214 and the first incident end face 111.

[0040] If the first incident end face 111 were flat, and most of the reflected light became return light and reached the light-emitting section 213, this would cause fluctuations in the wavelength and intensity of the red laser light generated by the light-emitting section 213, hindering stable light emission. However, in this embodiment, the first incident end face 111 is processed into a curved surface, and the emission surface 214 of the red laser diode 211 and the first incident end face 111 of the first optical waveguide 110 are arranged to face each other and be spaced apart. As a result, most of the reflected light does not become return light, but is instead scattered toward the periphery of the emission surface 214. As a result, the light-emitting section 213 can emit stable red laser light.

[0041] Here, the shortest distance d1 between the emission surface 214 of the red laser diode 211 and the first incident end face 111 of the first optical waveguide 110 is preferably greater than the thickness d2 of the first optical waveguide 110. If such a space is provided, it can be expected that most of the reflected light will be scattered in the peripheral direction of the emission surface 214. In other words, when such a shortest distance is set, it is sufficient to process the curved surface of the first incident end face 111 in such a manner that most of the reflected light is scattered in the peripheral direction. Specifically, the curved surface of the first incident end face 111 can be designed as follows: to design it in such a manner that more than 10% of the reflected light is scattered in the peripheral direction, and more preferably to design it in such a manner that more than 50% of the reflected light is scattered in the peripheral direction. The curved surface of the first incident end face 111 can be, for example, a spherical surface or a cylindrical surface. In the case of a cylindrical surface, it can be Figure 3 The cylindrical surface may be a cylindrical surface with a central axis parallel to the X axis as shown, or a cylindrical surface may be a cylindrical surface with a central axis parallel to the Z axis. In the case of a cylindrical surface with a central axis parallel to the Z axis, it is preferable to form a cylindrical surface on each incident end face.

[0042] The structures of the second incident end face 121 and the green light-emitting module 220 corresponding thereto, as well as the third incident end face 131 and the blue light-emitting module 230 corresponding thereto, are identical to the structures of the first incident end face 111 and the red light-emitting module 210 corresponding thereto. Therefore, both can suppress return light and ensure stable emission of each laser beam. In particular, as described in this embodiment, in applications where laser beams of different colors are mixed in an optical waveguide and emitted as a desired color, if any of the laser beams is unstable, the color tone will vary. Therefore, the stability of each laser beam is particularly important.

[0043] Figure 4 is a XX cross-sectional view of the second embodiment of the present invention. In the second embodiment, each incident end face (at Figure 4 The first incident end face 111 is shown in FIG. Figure 4 The figure shows that the side opposite to the red laser diode 211) is excavated and processed into a curved surface.

[0044] Even when the first incident end face 111 is processed into a curved surface in this manner and the emission surface 214 of the red laser diode 211 and the first incident end face 111 of the first optical waveguide 110 are arranged to face each other and be spaced apart, most of the reflected light can be scattered toward the periphery of the emission surface 214. Therefore, the light emitting unit 213 can emit red laser light stably.

[0045] When processing into such a curved surface, the shortest distance d1 between the emission surface 214 of the red laser diode 211 and the first incident end face 111 of the first optical waveguide 110 is preferably greater than the thickness d2 of the first optical waveguide 110. Providing such a space allows for the majority of the reflected light to be scattered in the peripheral direction of the emission surface 214. In other words, when setting such a minimum distance, the curved surface of the first incident end face 111 can be processed so that most of the reflected light is scattered in the peripheral direction. Specifically, the curved surface of the first incident end face 111 can be designed so that at least 50% of the reflected light is scattered in the peripheral direction. The curved surface of the first incident end face 111 can be, for example, a spherical surface or a cylindrical surface. The structure of the second incident end face 121 and the green light-emitting module 220 corresponding to the second incident end face 121, as well as the structure of the third incident end face 131 and the blue light-emitting module 230 corresponding to the third incident end face 131 are the same as the structure of the first incident end face 111 and the red light-emitting module 210 corresponding to the first incident end face 111.

[0046] Figure 5This is a partial perspective view of a waveguide module 100 according to a third embodiment of this embodiment. The third embodiment shares the same characteristics as the second embodiment in that each incident end facet (first incident end facet 111, second incident end facet 121, and third incident end facet 131) is processed into a curved surface by being excavated toward the side opposite to the corresponding laser diode. However, the third embodiment is unique in that the three incident end faces are processed into identical curved surfaces.

[0047] Specifically, as shown in the figure, a portion of the end face of the substrate 160 and the end face of the buffer layer 170 are processed into cylindrical curved surfaces that are continuous with the curved surfaces of each incident end face. In other words, for example, the curved surfaces of each incident end face are realized by simultaneously performing grinding across each layer. If this processing method is adopted, the curved surface can be formed easily and in a short time. In addition, if the three incident end faces are the same curved surface, it can be expected that the influence of the return light in each laser diode will also be to the same extent, so the balance of the color mixing will not be seriously disrupted. In addition, Figure 5 The example shown in FIG. 1 shows a concave curved surface, but it can also be processed into a convex curved surface.

[0048] In the embodiment described above, an optical device 10 is described that mixes RGB primary laser light within an optical waveguide and emits light of a desired color. However, the application example of the optical device is not limited to this so-called RGB coupler. In optical devices for other purposes, a single light-emitting module can be used, and in this case, the optical waveguide only needs to be formed by a single path. Similarly, even when multiple light-emitting modules are connected, the number is not limited to three and can also be two or four or more. In this case, multiple incident end faces corresponding to the number of light-emitting modules are formed together with the optical waveguide. These can also merge into a single waveguide or have independent emission end faces.

[0049] Description of Reference Numerals

[0050] 10: Optical device, 20: MEMS mirror, 30: Projector, 40: Screen, 100: Waveguide module, 110: First optical waveguide, 111: First incident end facet, 112: Emission end facet, 120: Second optical waveguide, 121: Second incident end facet, 130: Third optical waveguide, 131: Third incident end facet, 150: Waveguide layer, 160: Substrate, 170: Buffer layer, 200: Light-emitting module, 210: Red light-emitting module, 211: Red laser diode, 212: First carrier, 213: Light-emitting portion, 214: Emission surface, 220: Green light-emitting module, 221: Green laser diode, 222: Second carrier, 230: Blue light-emitting module, 231: Blue laser diode, 232: Third carrier.

Claims

1. An optical device, wherein: Equipped with waveguide module and light emitting module, The waveguide module comprises: basal layer; Covering layer; and a waveguide layer formed between the base layer and the cover layer and having an optical waveguide whose incident end face, into which the propagating laser beam is incident, is processed into a curved surface; The light emitting module comprises: a laser diode that emits the laser light; and The carrier is configured to support the laser diode so that the laser light emitting surface and the incident end surface are opposed to each other and spaced apart from each other, and is bonded to the base layer to be integrated with the waveguide module.

2. The optical device according to claim 1, wherein At least a portion of each end surface of the base layer and the cover layer forms a curved surface continuous with the curved surface of the incident end surface.

3. The optical device according to claim 1, wherein The shortest distance between the emission surface and the incident end surface is greater than or equal to the thickness of the optical waveguide. The optical device according to claim 1 , wherein: The waveguide layer has a plurality of incident end faces, and the optical waveguides that are continuous with the plurality of incident end faces merge inside the waveguide module and are connected to the emission end face. The light emitting module includes a plurality of laser diodes corresponding to the plurality of incident end faces. The optical device according to claim 1 , wherein: The waveguide layer has three incident end faces, and the optical waveguides that are continuous with the three incident end faces merge inside the waveguide module and are connected to the emission end face. The light emitting module includes three laser diodes emitting red light, green light, and blue light, respectively corresponding to the three incident end faces. The optical device according to claim 5 , wherein: The three incident end faces are processed into mutually identical curved surfaces.

7. A waveguide module, wherein: have: a substrate having a first side; and a waveguide layer stacked on the substrate, having a second side surface continuous with the first side surface, and an incident end face on the second side surface for allowing light to enter the waveguide, The incident end face forms a curved surface.

8. The waveguide module according to claim 7, wherein: The curved surface constitutes a curved surface continuous with at least a portion of the first side surface.

9. The waveguide module according to claim 7, wherein: A buffer layer is provided, the buffer layer being stacked on the waveguide layer, the buffer layer being composed of a material having a lower refractive index than that of the waveguide, and the buffer layer having a third side surface continuous with the second side surface, The curved surface constitutes a curved surface continuous with at least a portion of the third side surface.

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