JP2007201209A - Optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical module suitably usable for optical communication, especially for a two-way communication system. <P>SOLUTION: The optical module 100 is provided with a substrate 110, a light-emitting element 120 placed on the substrate 110 so as to emit light, a wave separator 140 for transmitting or reflecting light corresponding to a wavelength, a light-receiving element 130 for receiving light, a first lens element 150a arranged between the light-emitting element 120 and the wave separator 140 so as to convert the light emitted from the light-emitting element 120 to parallel light, and a second lens element 150b arranged between the wave separator 140 and the light-receiving element 130 so as to collect light emitted via the wave separator 140. A recess 160 is formed in the substrate 110. The light-receiving element 130 is arranged inside the recess 160. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical module, and more particularly to an optical module suitably used in a bidirectional communication system.

  With the development of broadband, optical fibers have been introduced to ordinary homes, and single-core bidirectional communication methods such as fiber-to-the-home (FTTH) realizing high-speed communication are being realized. In the single-core bidirectional communication method, in order to reduce the cost, a method is adopted in which two types of optical signals having different wavelengths are propagated bidirectionally using a single fiber. At this time, the two-way communication system installed on the subscriber side is required to be downsized so that the installation location can be freely selected.

  In the optical communication field, as an example of a module capable of bidirectional communication using a single fiber, there is an optical semiconductor element module described in Patent Document 1, for example. In such an optical semiconductor element module, a semiconductor laser module as a transmission unit and a photodiode as a reception unit are housed in separate packages. These packages and optical components such as a band-pass filter for separating received light and transmitted light are combined into one to form a bidirectional communication module.

  However, in the bidirectional communication module configured as described above, since the transmitter and the receiver are in separate packages, it is difficult to reduce the size of the bidirectional communication module. Therefore, there was a problem that it was expensive.

JP-A-10-206678

  To solve such problems, for example, two-way communication that reduces the size of the module and reduces manufacturing costs by mounting semiconductor lasers, photodiodes, bandpass filters, and optical elements on a single substrate. Module manufacturing methods have been proposed.

  For example, the bidirectional communication module 10 may be an optical module shown in FIG. The bidirectional communication module 10 includes a laser diode 12 (hereinafter referred to as “LD”) as a light emitting element and a photodiode (Photo Diode) as a light receiving element “PD” on a substrate 11 having a groove. 13), the wavelength demultiplexer 14, and the lens elements 15a and 15b are arranged in an integrated manner.

  The light emitted from the LD 12 is collimated by the lens element 15 a and then enters the wavelength demultiplexer 14. The light incident on the wavelength demultiplexer 14 enters an optical fiber (not shown) attached to the outside of the module 10. On the other hand, the light transmitted from the outside via the optical fiber enters the wavelength demultiplexer 14, is condensed by the lens element 15 b, and enters the PD 13.

  As described above, the optical communication module in which the LD 12 serving as the light emitting unit and the PD 13 serving as the light receiving unit are mounted inside one package is suitable for downsizing and cost reduction. However, in order to construct a more accurate transmission / reception environment, unnecessary light called so-called “stray light” that leaks light from the light-emitting unit enters the light-receiving unit through various optical paths and generates optical noise. There is still a need to eliminate the problems that cause. In particular, there is no problem in normal use, but if the data becomes complicated due to high capacity, high speed, etc., the PD 13 receives light that becomes optical noise and the data deteriorates, so that the signal can be discriminated. There is a possibility that the performance of the PD 13 deteriorates, such as being difficult to attach and increasing errors.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a new and improved optical module capable of reducing optical noise received by a light receiving element. It is to provide.

  In order to solve the above problems, according to an aspect of the present invention, there is provided an optical module including a substrate, a light emitting element placed on the substrate, a wavelength demultiplexer, a light receiving element, and a lens element. Provided. Here, the substrate has a recess, and the light receiving element is disposed in the recess.

  According to such a configuration, the recess for accommodating the light receiving element is formed in the substrate, and it is possible to prevent the light receiving element from directly receiving the light emitted from the light emitting element. Furthermore, by setting the height of the concave portion formed on the substrate to be equal to or higher than the height of the light receiving element, it is possible to reduce the amount of light emitted from the light emitting element incident from the side surface side of the light receiving element. In addition, by providing a non-transmissive film that does not transmit light having a wavelength emitted from the light emitting element on the inner side surface of the recess, the amount of light incident from the side surface direction of the light receiving element can be further reduced.

  Here, the light receiving element can be disposed at a position lower than the light emitting element, and with this configuration, it is possible to reliably prevent the light receiving element from receiving unnecessary light.

  In addition, an insulating film can be further provided on the inner side surface of the recess, and this insulating film can prevent the performance of the light receiving element from being deteriorated by electrical noise.

  Furthermore, a covering plate that covers the opening of the recess formed in the substrate can be provided. A non-transmissive film is provided on the surface of the cover plate in order to block light that becomes noise directly from the light emitting element to the light receiving element or reflected from other parts such as a cover that covers the module. With this configuration, the light receiving element is covered with the concave portion and the cover plate, so that light incident from all angles of the light receiving element can be more effectively blocked. In the present invention, the phrase “the light receiving element is disposed in the recess” includes the meaning of being disposed not only in the recess but also in the area where the recess is formed, based on the substrate. This includes the case where the light receiving element is provided in the recess of the substrate by being attached to the cover plate.

  In order to solve the above problems, a first groove structure formed by etching in the first direction and a second groove structure formed by etching in the second direction that forms 90 degrees with the first direction are provided. A cube-type wavelength demultiplexer disposed on the substrate and transmitting or reflecting light according to the wavelength, a light-emitting element side lens element disposed in the first groove structure, and a second element The light receiving element side lens element disposed in the groove structure of the first light emitting element and the first groove structure disposed near the end of the first groove structure to emit light and to be emitted to the outside via the light emitting element side lens element and the wavelength demultiplexer An optical module comprising: a light emitting element for receiving a light; and a light receiving element that is disposed in a recess formed in the substrate and that receives incident light from outside via a wavelength demultiplexer and a light receiving element side lens element. It can also be provided. The height of the recess formed in the substrate is equal to or higher than the height of the light receiving element, and a non-transmissive film that does not transmit light having a wavelength emitted from the light emitting element can be provided on the inner surface of the recess.

  Also in such an optical module, a recess for accommodating the light receiving element is formed on the substrate. At this time, by setting the height of the concave portion formed on the substrate to be equal to or higher than the height of the light receiving element, the amount of light emitted from the light emitting element incident from the side surface side of the light receiving element can be reduced. Further, by providing a non-transmissive film that does not transmit light having a wavelength emitted from the light emitting element on at least the inner side surface of the recess, the amount of light incident from the side surface side of the light receiving element can be further reduced. In this way, it is possible to reduce the incidence of light, which is a factor that degrades the performance of the light receiving element, on the light receiving element as optical noise.

  As described above, according to the present invention, an optical module capable of reducing optical noise can be provided. Such an optical module can be suitably used particularly in a bidirectional communication system.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
First, the optical module 100 according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. Here, FIG. 1 is a schematic perspective view showing a schematic configuration of the optical module according to the present embodiment. FIG. 2 is a plan view of the optical module according to the present embodiment.

  As shown in FIG. 1, the optical module 100 according to the present embodiment includes a substrate 110 having V grooves 112a and 112b, a laser diode (hereinafter referred to as “LD”) 120 as an example of a light emitting element, As an example of the light receiving element, a photodiode (Photo Diode; hereinafter referred to as “PD”) 130, a wavelength demultiplexer 140, and lens elements 150a and 150b are configured. Hereinafter, each component will be described in detail.

  The substrate 110 is a substrate on which each component constituting the optical module 100 is arranged, and is made of, for example, a silicon substrate. The substrate 110 is formed with two orthogonal grooves, and is divided into four regions including three stepped portions 110a, 110b, and 110c and a planar portion 110d. In FIG. 1, a wavelength demultiplexer 140 is placed on a flat portion 110d of a substrate 110, and as shown in FIG. 2, V cross-sectional shapes are V-shaped on the upper surfaces of the step portions 110a and 110b. Grooves 112a and 112b are formed. Further, the LD 120 and the lens element 150a are disposed at the stepped portion 110a, and the PD 130 and the lens element 150b are disposed at the stepped portion 110b.

  The V-grooves 112a and 112b are formed by etching the substrate 110, and are precisely manufactured in a configuration having a (111) plane group of silicon on the slope. The V groove 112a is formed on the LD 120 side, and the V groove 112b is formed on the PD 130 side. The extending direction of the V groove 112a and the extending direction of the V groove 112b are formed to form 90 degrees.

  The LD 120 is a light emitting element that emits light, and has, for example, a substantially rectangular parallelepiped shape with a thickness of about 150 μm. The LD 120 is disposed in the vicinity of the end of the V-shaped groove 112a, emits light, and is emitted to the outside through the light emitting element side lens element 150a and the wavelength demultiplexer 140.

  The PD 130 is a light receiving element that makes light incident from the end face. For example, an end face incident type light receiving element having a substantially rectangular parallelepiped shape with a thickness of about 150 μm can be used. The PD 130 is disposed in the vicinity of the end of the V groove 112b, and receives incident light from the outside via the wavelength demultiplexer 140 and the light receiving element side lens element 150b. A metal film (not shown) is provided on the upper surface of the PD 130, and light emitted from the LD 120 incident from above can be blocked. The metal film may be any material that does not transmit infrared light, and is made of, for example, gold, aluminum, platinum, nickel, copper, silver, or the like. In the optical module 100 according to the present embodiment, the PD 130 is provided in the recess 160 formed in the stepped portion 110b. Details of this configuration will be described later.

  The wavelength demultiplexer 140 is a demultiplexer that transmits light or reflects 90 degrees according to the wavelength, and for example, a cube-type dielectric filter can be used. Employing a cube-type dielectric filter has the advantage of easy alignment. Further, since the alignment is easy, it is not necessary to make the light reflecting surface larger than necessary, and as a result, the size can be reduced. The wavelength demultiplexer 140 is placed on the planar portion 110d of the substrate 110, and the wavelength demultiplexer 140 transmits light emitted from the LD 120 (for example, light having a wavelength of 1.3 μm) and is incident from the outside. The reflected light (for example, light having a wavelength of 1.49 μm) is reflected by 90 degrees and enters the PD 130.

  The lens elements 150a and 150b are lenses that condense light or convert light into parallel light. For example, silicon microlenses can be used. The lens elements 150a and 150b each have a lens portion on which one of the diffractive optical elements is formed. By using a diffractive optical element in the lens portion, the lens elements 150a and 150b can easily bend light in an arbitrary direction by changing the mask pattern. Further, the edge portion of the lens element is formed in, for example, a substantially arc shape as a shape suitable for the V grooves 112a and 112b.

  The lens element 150a is provided on the LD 120 side. The lens portion of the lens element 150 a has a function as a collimating lens that converts light emitted from the LD 120 into parallel light and enters the wavelength demultiplexer 140. On the other hand, the lens element 150b is provided on the PD 130 side. The lens portion of the lens element 150 b has a function as a condensing lens that condenses the light demultiplexed by the wavelength demultiplexer 140 and enters the PD 130.

  The outline of the configuration of the optical module 100 according to the present embodiment has been described above. The optical module 100 according to the present embodiment is characterized in that a recess 160 is provided in the step 110b of the substrate 110 and the PD 130 is provided in the recess 160 in order to reduce the amount of light received by the PD 130 as optical noise. And

  As shown in FIGS. 1 to 3, the PD 130 of the optical module 100 according to the present embodiment is disposed inside a recess 160 formed in the substrate 110. In this configuration, the position in the height direction (Z-axis direction) of the mounting surface of the PD 130 is set lower than that of the mounting surface of the LD 120, and the PD 130 is difficult to receive unnecessary light emitted from the LD 120. . The recess 160 is recessed in the negative Z-axis direction, and the opening in the positive Z-axis direction is formed in a square shape as shown in FIG. 2, for example.

  Hereinafter, the structure of the recess 160 in which the PD 130 is disposed will be described in detail with reference to FIG. FIG. 3 is a cross-sectional view of the stepped portion 110b of the substrate 110 according to the present embodiment in FIG. 2 cut along a cutting line AA.

  The side of the recess 160 facing the lens element 150b is opened to receive light incident through the lens element 150b by the PD 130. The inner surface of the recess 160 is formed to have an inclination (for example, 54.7 °). At this time, the height H of the recess 160 is formed to be equal to or higher than the height h of the PD 130 (that is, H ≧ h). As described above, by disposing the PD 130 so as not to protrude from the concave portion 160, the amount of unnecessary light emitted from the LD 120 directly incident on the PD 130 can be reduced.

An insulating film 164 that does not conduct electricity is provided on the inner surface of the recess 160 in order to prevent electrical noise. For example, when an electrical signal is propagated to the LD 120 at a high speed, the electrical signal may leak from the junction with the LD 120, and this leaked electrical signal may become electrical noise and have an undesirable effect on the PD 130 side. There is. An insulating film 164 is provided to prevent such electrical noise. The insulating film 164 may be, for example, _SiO 2, SiN, SiON, the TiO ₂ and the like.

  Further, a non-transmissive film 162 is provided on the surface of the insulating film 164 so as not to transmit light having a wavelength emitted from the LD 120 that becomes optical noise. The non-transmissive film 162 can be formed from, for example, a resin or metal, and specifically can be formed by vapor deposition of gold, NiCr, or the like, but can be formed with high accuracy and reflectivity of light. Since gold is high, gold can be preferably used.

  The PD 130 is placed inside the recess 160 formed in this way. At this time, the PD 130 is fixed to the substrate 110 with, for example, solder. The current output from the PD 130 can be extracted from an electrode (not shown) of the PD 130 by, for example, a wire, but is appropriately adjusted according to use. In the optical module 100 according to the present embodiment, the PD 130 can be placed on the placement surface regardless of the position of the electrode of the PD 130. For example, among the electrodes of the PD 130, when the positive electrode is on the upper surface side of the PD 130 and the negative electrode is on the bottom surface side of the PD 130 (the surface side in contact with the mounting surface of the substrate 110), a wire is connected to the positive electrode. By connecting a wire to the electrode drawn from the mounting surface, it is possible to draw the current to the outside. Therefore, it is not necessary to consider the position of the electrode of the PD 130 when mounting the PD 130, so that the degree of freedom in designing the configuration of the optical module 100 is high.

  The optical module 100 according to the first embodiment has been described above. The optical module 100 is provided with a recess 160 for disposing the PD 130 in order to make the installation surface of the PD 130 lower than the installation surface of the LD 120. At this time, the height of the concave portion 160 is preferably formed to be equal to or higher than the height of the PD 130, and a non-transmissive film 162 that does not transmit light having a wavelength emitted from the LD 120 is provided on the inner surface of the concave portion 160. . With this configuration, the PD 130 can be disposed at a position where it is difficult to receive the light emitted from the LD 120, and the light is incident from the lateral direction or the like by the non-transmissive film 162 provided on the inner surface of the recess 160. Unnecessary light can be blocked. Therefore, by providing the insulating film 164, electrical noise can be blocked.

(Second Embodiment)
Next, an optical module 200 according to the second embodiment of the present invention will be described with reference to FIGS. 4 and 5. Here, FIG. 4 is a plan view of the optical module 200 according to the present embodiment. FIG. 5 is a cross-sectional view of the stepped portion 110b of the substrate 110 of FIG. 4 according to the present embodiment taken along a cutting line AA. The configuration of the optical module 200 according to the present embodiment is the same as that of the optical module 100 according to the first embodiment, except that the lid portion 220 is provided in the concave portion 160 formed in the stepped portion 110b of the substrate 110. The same. For this reason, below, description is abbreviate | omitted about the part of the same structure as the optical module 100 concerning 1st Embodiment.

  In the optical module 200 according to the present embodiment, in order to reduce the amount of light emitted from the LD 120 that is received by the PD 130, a lid 220 is provided as a cover plate that covers the recess 160 above the PD 130. . The lid 220 is made of, for example, silicon or glass, and a non-transmissive film (not shown) that does not transmit unnecessary light is provided on at least one of the upper surface 220a and the lower surface 220b of the lid 220. It is done. The lid 220 can be fixed to the substrate 110 by using, for example, resin, solder or the like. This non-transmissive film can be formed by vapor deposition from, for example, gold, NiCr, or the like, similarly to the non-transmissive film 162 provided on the inner surface of the recess 160 formed in the optical module 100 according to the first embodiment. .

Here, like the optical module 100 according to the first embodiment, an insulating film 164 that does not conduct electricity is provided on the inner surface of the recess 160 to prevent electrical noise. As the insulating film 164, for example, SiO ₂ can be used. In addition, a non-transmissive film 162 is provided on the surface of the insulating film 164 so as not to transmit light having a wavelength emitted from the LD 120 that causes optical noise. The non-permeable film 162 can be formed from, for example, resin or metal, and specifically can be formed by vapor deposition of gold, NiCr, or the like.

  As in the optical module 200 according to the second embodiment described above, by providing the lid portion 220 in the concave portion 160 in which the PD 130 is disposed, the PD 130 excludes the side on which light is incident through the lens element 150b. The periphery of the substrate 110 is surrounded by the substrate 110 provided with the non-permeable membrane 162 and the lid 220. Thereby, compared with the optical module 100 according to the first embodiment, it is possible to prevent the PD 130 from receiving unnecessary light incident not only from the lateral direction but also from above the PD 130, so that optical noise is reduced. The performance of the PD 130 can be prevented from being deteriorated. Further, as with the optical module 100 according to the first embodiment, by providing the insulating film 164, electrical noise can be blocked.

(Modification)
As a modification of the optical module 200 according to the second embodiment, as shown in FIGS. 6 and 7, a configuration of an optical module in which the arrangement position of the light receiving elements is changed can be considered. Here, FIG. 6 is a cross-sectional view of the stepped portion 110b of the substrate 110 shown in FIG. 4 taken along the cutting line AA. 7 is a cross-sectional view of the stepped portion 110b of the substrate 110 shown in FIG. 4 cut along a cutting line BB. Note that a description of the same components as those of the optical module 200 according to the second embodiment will be omitted.

  As shown in FIGS. 6 and 7, in the modified example of the optical module 200, the lid portion 240 is provided in the concave portion 160 formed in the stepped portion 110 b of the substrate 110, as in the optical module 200 according to the second embodiment. It has been. At this time, the PD 230 can be provided on the surface of the lid portion 240 on the concave portion 160 side (that is, the lower surface 240b).

  Depending on the angle at which the maximum light receiving sensitivity of the PD 230 is exhibited, for example, as shown in FIG. 7, a reflection film (not shown) is provided on the inner surface 160 c of the concave portion 160 with the light incident through the lens element 150 b. The PD 230 can be arranged so that the reflected light is received by the PD 230. Since the incident light is received by the PD 230 in this way, for example, the projecting portion 242 is formed on the lower surface 240b side of the lid portion 240, and the projecting portion 242 can be provided with the PD 230. Since the PD 230 receives reflected light, the protrusion 242 may be formed in a substantially triangular prism shape having a substantially triangular cross-sectional shape in the YZ plane, for example. And PD230 can receive incident light by providing PD230 in the inclined surface of the projection part 242 so that the inner surface 160c of the recessed part 160 may be opposed. By adopting such a structure, the electrode of the PD 230 can be pulled out simply by arranging the electrode on the lid 240. For this reason, simplification of the manufacturing process can be expected.

  The above configuration is an example, and the condensing point can be changed by changing the shape of the lens element 150b at an angle at which the maximum light receiving sensitivity of the PD 230 is exhibited. The angle of the inclined surface is not limited. Further, the shape of the protrusion 242 is not limited to a substantially triangular prism shape, and can be appropriately changed depending on the configuration of the optical module, the shape of the PD 230, and the like.

  Further, the PD 230 can be arranged so as to directly receive the light incident through the lens 150b depending on the angle at which the maximum light receiving sensitivity of the PD 230 is obtained. For example, it can be realized by arranging the light receiving portion of the PD 230 toward the lens element 150b side so that light is condensed on the light receiving portion of the PD 230 by the lens element 150b. In the case of such a configuration, since there is no reflection by a reflection film (not shown) provided on one inner side surface 160c of the recess 160, an increase in incident efficiency to the PD 230 can be expected due to no reflection loss.

  Also in this modification, a non-transmissive film (not shown) that does not transmit light having a wavelength emitted from the LD 120 is provided on at least one of the upper surface 240a and the lower surface 240b of the lid 240. Can do. As a result, optical noise incident from above can be blocked.

  The optical module 200 according to the second embodiment and the modifications thereof have been described above. Similar to the optical module 100 according to the first embodiment, the optical module 200 is provided with a recess 160 for disposing the PD 130 (or 230). A non-transmissive film 162 that does not transmit light having a wavelength emitted from the LD 120 is provided on the inner surface of the recess 160. Then, the amount of unnecessary light that the PD 130 (or 230) receives compared with the optical module 100 according to the first embodiment by covering the upper portion of the recess 160 with the lid 220 (or 240). , Can be greatly reduced. Further, as with the optical module 100 according to the first embodiment, by providing the insulating film 164 on the inner side surface of the recess 160, electrical noise can be blocked.

  Note that the current output from the PD 130 (or 230) is drawn from the electrode (not shown) of the PD 130 (or 230) by, for example, a wire, as in the optical module 100 according to the first embodiment. Can do. For example, when the PD 130 is provided on the bottom surface of the concave portion 160, a lead electrode from the inside to the outside is provided in the concave portion 160, and the electrode of the PD 130 and the lead electrode are connected by, for example, a wire. The electrode can be pulled out. When the PD 230 is provided on the lid 240, the electrode is easily pulled out by soldering the electrode provided on the lid 240 and the electrode provided on the step 110b of the substrate 110. be able to. Here, the lid portion 240 can be fixed to the substrate 110 with solder at a portion where the electrode is drawn out. As described above, when the PD 130 (or 230) is provided, it is not necessary to consider the position of the electrode of the PD 130 (or 230). Therefore, there is an advantage that the degree of freedom in design is high with respect to the configuration of the optical module 200.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, in the above embodiment, the recess formed in the substrate has an opening formed in a substantially square shape. However, the present invention is not limited to this example, and may be, for example, other polygons or circles. Good. In the above embodiment, the inner surface of the recess has an inclination. However, the present invention is not limited to this example, and may be formed to be substantially perpendicular to the mounting surface of the light receiving element, for example. Good. However, when an insulating film or a non-permeable film is provided on the inner surface of the recess, it is recommended that the inner surface of the recess is inclined as in the above-described embodiment because these films can be easily deposited on the inner surface.

  In the above embodiment, the shape of the light receiving element is a substantially rectangular parallelepiped shape. However, the present invention is not limited to this example, and the shape of the light receiving element is determined in consideration of the configuration of the optical module, the shape of the recess, and the like. do it. For example, a light receiving element having an L-shaped curve may be used.

It is a schematic perspective view which shows schematic structure of the optical module concerning the 1st Embodiment of this invention. It is a top view of the optical module concerning a 1st embodiment. It is sectional drawing which cut | disconnected the optical module concerning 1st Embodiment in the cutting line AA. It is a top view of the optical module concerning a 2nd embodiment. It is sectional drawing which cut | disconnected the optical module concerning 2nd Embodiment in the cutting line AA. It is sectional drawing which shows the modification of the optical module concerning 2nd Embodiment, and shows the state cut | disconnected in the cutting line AA of FIG. It is sectional drawing which shows the modification of the optical module concerning 2nd Embodiment, and shows the state cut | disconnected in the cutting line BB of FIG. It is a schematic perspective view which shows schematic structure of the conventional optical module.

Explanation of symbols

100, 200 Optical module 110 Substrate 120 Light emitting element (LD)
130,230 Light receiving element (PD)
140 Wavelength demultiplexer 150a, 150b Lens element 162 Non-transmissive film 164 Insulating film 220, 240 Lid 242 Projection

Claims (4)

A substrate, a light emitting element mounted on the substrate, a wavelength demultiplexer, a light receiving element, and a lens element;
The optical module, wherein the substrate has a recess, and the light receiving element is disposed in the recess. The height of the recess formed in the substrate is equal to or higher than the height of the light receiving element,
The optical module according to claim 1, wherein a light non-transmissive film is provided on an inner surface of the concave portion.   The optical module according to claim 1, wherein an insulating film is provided on an inner surface of the recess. The optical module according to claim 1, further comprising a cover plate that covers the opening of the recess.

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