JP5314587B2 - Optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical module in which an APC circuit for making stable emission of a light-emitting element is driven with high accuracy in a simple structure. <P>SOLUTION: The optical module includes: a substrate 2 in which an optical waveguide 1 for propagating light is formed; a light-emitting element 3 which is mounted on the substrate 2 to emit light toward the optical waveguide 1; and a light-receiving element 4 for a monitor, which is mounted on the substrate 2 to receive a part of light propagated by the optical waveguide 1. At least one side face of the optical waveguide 1 is formed on a slope 2d oppositely facing the light-receiving part of the light-receiving element 4 for the monitor. In the optical waveguide 1, there is formed a light take-out part 10 in which a part of the propagating light is reflected on the slope 2d and guided to the light-receiving part of the light-receiving element 4 for the monitor. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an optical module.

  Conventionally, light provided with a substrate on which an optical waveguide for propagating light is formed, a light emitting element that emits light toward the optical waveguide, and a light receiving element for monitoring that receives part of the light emitted from the light emitting element There is a module (see Patent Document 1).

  In order to make the light emitting element emit light stably, the light emitting element is controlled by an APC (Automatic Power Control) circuit while monitoring a part of the light emitted from the light emitting element with the light receiving element for monitoring. .

  As a means for this, by mounting the light-receiving surface of the monitor light-receiving element on the clad part of the optical waveguide of the substrate, the light emitted from the light-emitting element is not propagated in the core part of the optical waveguide. A part of the leaked light is received by the monitor light receiving element.

Japanese Patent Laid-Open No. 2002-243998

  However, in Patent Document 1, since leakage light from the light emitting element is only received by the monitor light receiving element, the amount of received light is unstable and small, and an APC circuit for stably emitting light from the light emitting element is highly accurate. There was a problem that could not be driven by.

  The present invention has been made to solve the above problems, and provides an optical module capable of driving an APC circuit for stably emitting light from a light emitting element with a simple configuration and high accuracy. It is intended.

In order to solve the above-described problems, the present invention provides a substrate on which an optical waveguide for propagating light is formed, a light emitting element attached to the substrate and emitting light toward the optical waveguide, and attached to the substrate. And a light receiving element for monitoring that receives a part of the light propagated through the optical waveguide , a waveguide forming groove is formed in the substrate, and a core portion is formed in the waveguide forming groove. An optical waveguide composed of a cladding portion is provided, and at least one side surface in the width direction of the waveguide forming groove is formed on an inclined surface facing the light receiving portion of the light receiving element for monitoring, The light is characterized in that a light extraction part is formed in the waveguide to reflect a part of the propagating light on the slope of the side surface of the waveguide forming groove and guide it to the light receiving part of the light receiving element for monitoring. Provides a module.

  As in claim 2, in claim 1, the light extraction portion is a boundary surface of materials having different refractive indexes, and the boundary surface is inclined with respect to the light propagation direction of the optical waveguide. be able to.

  As in claim 3, in claim 1 or 2, the light extraction portion is a plurality of boundary surfaces formed by inserting materials having different reflectances into the optical waveguide. It can be set as the structure inclined with respect to the light propagation direction of an optical waveguide.

According to a fourth aspect of the present invention , in any one of the first to third aspects, the light extraction portion may be formed on at least one of the core portion or the cladding portion.

As in claim 5, in claim 1, wherein the light extraction unit may be configured to be Y-branched optical waveguides formed in the core portion.

As in claim 6, according to claim 1, wherein the light extraction unit includes a plurality of interfaces with different reflective material is formed by being inserted into the core unit, T branch type formed in the core portion It can be set as the structure which is an optical waveguide.

  According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the reflective metal film is formed on the inclined surface of the optical waveguide facing the light receiving portion of the monitor light receiving element. it can.

According to the present invention, a waveguide forming groove is formed on a substrate, an optical waveguide composed of a core portion and a cladding portion is disposed in the waveguide forming groove, and at least in the width direction of the waveguide forming groove. The side surface on one side is formed on a slope facing the light receiving portion of the light receiving element for monitoring, and a part of the propagating light is reflected on the slope of the side surface of the groove for forming the waveguide on the optical waveguide. A light extraction portion that leads to the light receiving portion of the light receiving element is formed. Accordingly, since a part of the light propagated through the optical waveguide is reliably guided to the light receiving portion of the monitor light receiving element, the amount of light received by the monitor light receiving element is increased, so that the light emitting element can emit light stably. The APC circuit can be driven with high accuracy. In addition, since the slope is formed on the side surface of the waveguide forming groove and the light extraction portion is formed in the optical waveguide, the configuration is simple.

  According to claim 2, as the light extraction part, for example, by making the end face of the core part of the waveguide inclined, the inclined end face becomes a boundary surface with air which is a material having a different refractive index. At this boundary surface, a part of the propagating light can be accurately reflected toward the slope of the waveguide. In addition to forming a boundary surface on the end surface of the core portion, it is also possible to form a boundary surface of a material having a different refractive index inside at least one of the core portion and the cladding portion. Furthermore, if there is only one boundary surface, reflection is performed only once on the boundary surface, so that the influence of multiple reflection can be reduced.

  According to the third aspect, as the light extraction portion, for example, an inclined notch (slit) is formed in at least one of the core portion or the clad portion of the optical waveguide, so that each notch facing the inclined notch is provided. Since the surface becomes each boundary surface with air that is a material having a different refractive index, a part of the propagating light can be accurately reflected toward the inclined surface of the optical waveguide at each boundary surface. In addition, since the reflection area is increased by a plurality of boundary surfaces, the amount of reflected light can be increased, and the amount of reflected light can be adjusted by increasing or decreasing the number of reflecting surfaces. Further, for example, if a notch (slit) is formed in the clad portion, it is possible to prevent light propagation through the core portion from becoming unstable.

  According to the fourth aspect, since the light extraction portion can be formed in at least one of the core portion and the cladding portion, the configuration becomes simple.

  According to the fifth aspect, by providing the Y-branch type optical waveguide in the core part, a part of the light propagating in the core part can be branched and propagated in the Y-branch type optical waveguide. The ratio of the amount of light can be set with high accuracy.

  According to the sixth aspect of the present invention, since a plurality of boundary surfaces and a T-branch type optical waveguide are provided in the core portion, the light reflected on the boundary surface can be branched and propagated by the T-branch type optical waveguide. Propagation loss can be reduced. In addition, since the reflection area is increased by a plurality of boundary surfaces, the amount of reflected light can be increased, and the amount of reflected light can be adjusted by increasing or decreasing the number of reflecting surfaces.

  According to the seventh aspect, since the reflectance on the slope is improved, the amount of light received by the monitor light receiving element is increased.

It is an optical module of a 1st embodiment of the present invention, (a) is a top view and (b) is a front view. It is an optical module of 2nd Embodiment of this invention, (a) is a top view, (b) is a front view. It is an optical module of 3rd Embodiment of this invention, (a) is a top view, (b) is a front view. It is an optical module of 4th Embodiment of this invention, (a) is a top view, (b) is a front view. It is an optical module of 5th Embodiment of this invention, (a) is a top view, (b) is a front view. It is an optical module of 6th Embodiment of this invention, (a) is a top view, (b) is a front view. It is an optical module of a 1st embodiment of the present invention, (a) is a perspective view and (b) is an exploded perspective view. BRIEF DESCRIPTION OF THE DRAWINGS It is an optical module of 1st Embodiment of this invention, (a) is side sectional drawing, (b) is a principal part perspective view of a core part. (A) The principal part perspective view of the core part of 2nd Embodiment, (b) is the principal part perspective view of the core part of 5th Embodiment, (c) is the principal part perspective view of the core part of 6th Embodiment. It is.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. 1A and 1B show an optical module according to the first embodiment, in which FIG. 1A is a plan view and FIG. 1B is a front view. 7A and 7B show the optical module of the first embodiment, where FIG. 7A is a perspective view and FIG. 7B is an exploded perspective view. 8A and 8B show the optical module according to the first embodiment. FIG. 8A is a side sectional view, and FIG.

  As shown in FIG. 7A, the optical module includes a mount substrate 2 on which an optical waveguide 1 for propagating light is formed on a surface (upper surface) 2a. The light emitting device 3 is mounted (mounted) on the surface 2 a of the mount substrate 2, converts an electric signal into an optical signal, and emits the light downward toward the optical waveguide 1. Further, a monitor light receiving element 4 that is attached (mounted) to the surface 2a of the mount substrate 2 and receives a part of the light propagating through the optical waveguide 1 by a downward light receiving surface and converts the optical signal into an electric signal. I have.

  The mount substrate 2 is a light-emitting side mount substrate. A light-receiving side mount substrate (not shown) is provided separately from the light-receiving side mount substrate. The light-receiving side mount substrate converts an optical signal into an electrical signal. A light receiving element (not shown) is attached. The optical waveguide of the light emitting side mount substrate and the light receiving side mount substrate is connected by an external waveguide substrate (not shown), and the optical signal of the light emitting element of the light emitting side mount substrate is the light receiving side mount. Light is received by the light receiving element of the substrate.

  The mount substrate 2 has a rectangular shape extending in the front-rear direction A and has a thickness of about 200 μm to 2 mm. The mount substrate 2 needs to be rigid in order to avoid the influence of heat during mounting and the influence of stress due to the use environment. Further, in the case of optical transmission, since light transmission efficiency from the light emitting element to the light receiving element is required, it is necessary to mount each element with high accuracy and to suppress position fluctuation during use as much as possible. For this reason, a silicon substrate is employed as the mount substrate 2 in this embodiment.

  The mount substrate 2 is preferably made of a material having a linear expansion coefficient close to that of the light emitting element (optical element) 3, and is made of a compound semiconductor such as GaAs of the same system as the VCSEL material described later, other than silicon. May be. Alternatively, a resin substrate may be used depending on the ceramic substrate and the use environment.

  In the present embodiment, a surface emitting laser (VCSEL (Vertical Cavity Surface Emitting Laser)) that is a semiconductor laser is employed as the light emitting element 3. The light emitting element 3 may be an LED or the like.

  An IC substrate (not shown) on which an IC circuit for transmitting an electrical signal to the light emitting element 3 is formed is also mounted on the surface 2 a of the mount substrate 2.

  As shown in FIG. 7B, a waveguide forming groove 2c extending from a position directly below the light emitting element 3 to the front end 2b of the mount substrate 2 is formed on the surface 2a of the mount substrate 2. .

  In the waveguide forming groove 2c, a mirror portion 5 for reflecting the main optical path a [see FIG. 1A] in the forward direction is formed at a position directly below the light emitting element 3. The inclination angle of the mirror unit 5 is, for example, 45 ° with respect to the light propagation direction.

  Further, both side surfaces in the width direction B of the waveguide forming groove 2c are formed on inclined surfaces 2d for reflecting the reflected light b (see FIG. 1B) upward. The inclination angle of the inclined surface 2d is, for example, 45 ° with respect to the light propagation direction. The inclined surface 2d may be only the side surface on one side (left side in FIG. 1) to which the monitor light receiving element 4 is attached.

  Further, fan-shaped slopes 2e for reflecting the leaked light c (see FIG. 3B) of the light emitting element 3 in the forward direction are formed between both sides of the mirror part 5 and the rear parts of both slopes 2d. Yes.

  In the waveguide forming groove 2c, there is disposed an optical waveguide 1 composed of a core portion 7 having a substantially square cross section having a high refractive index through which light propagates and a cladding portion 8 having a lower refractive index. ing. The outer surface of the clad portion 8 has the same shape as the inner surface of the waveguide forming groove 2c.

  The clad portion 8 extends along the waveguide forming groove 2c to the front end portion 2b of the mount substrate 2, but the end surface of the core portion 7 is a waveguide as shown in FIG. It is formed on an inclined surface 7a facing the inclined surface 2d on one side (left side in FIG. 1) of the forming groove 2c. The inclination angle of the inclined surface 7a is, for example, 45 ° with respect to the light propagation direction.

  The inclined surface 7 a of the core portion 7 constitutes the light extraction portion 10. Here, the light extraction portion 10 is a boundary surface between the core portion 7 and the air, which are materials having different refractive indexes, and the inclined surface 7a that is the boundary surface is inclined at 45 ° with respect to the light propagation direction of the optical waveguide. Will be.

  The monitor light receiving element 4 is attached to the surface 2 a of the mount substrate 2 at a position where the light receiving surface faces the inclined surface 2 d of the waveguide forming groove 2 c facing the light extraction portion 10.

  Therefore, the light emitted from the light emitting element 3 is reflected forward by the mirror unit 5 and propagates forward by the core unit 7 of the optical waveguide 1.

  At this time, a part of the light propagating in the core portion 7 is reflected to the side of the inclined surface 7 a of the waveguide forming groove 2 c on the inclined surface 7 a of the core portion 7 before the front end portion 2 b of the mount substrate 2. Then, the light is reflected upward again by the inclined surface 2d, and is guided to the light receiving portion of the monitoring light receiving element 4.

  In the optical module of the first embodiment, an inclined surface 2 d facing the light receiving portion of the monitor light receiving element 4 is formed on the side surface of the waveguide forming groove 2 c of the optical waveguide 1. Further, a part of the propagating light is reflected on the core portion 7 of the optical waveguide 1 by the inclined surface 2 a that reflects the inclined surface 2 d of the waveguide forming groove 2 c of the optical waveguide 1 and guides it to the light receiving portion of the monitor light receiving element 4. A certain light extraction portion 10 is formed.

  Accordingly, a part of the light propagated by the core portion 7 of the optical waveguide 1 is reflected by the inclined surfaces 7 a and 2 d and reliably guided to the light receiving portion of the monitoring light receiving element 4.

  As a result, the amount of light received by the monitor light receiving element 4 is increased, so that an APC circuit for stably emitting light from the light emitting element 3 can be driven with high accuracy. In addition, since the inclined surface 2d is formed on the side surface of the waveguide forming groove 2c of the optical waveguide 1 and the light extraction portion 10 that is the inclined surface 7a is formed on the core portion 7 of the optical waveguide 1, the configuration is simple. .

  Further, the light extraction portion 10 is a boundary surface between the core portion 7, which is a material having a different refractive index, and air, and this boundary surface is inclined with respect to the light propagation direction of the optical waveguide 1. Specifically, as the light extraction portion 10, for example, the end surface of the core portion 7 of the optical waveguide 1 is inclined. As a result, the inclined slope 7a becomes a boundary surface with air, which is a material having a different refractive index. Therefore, a part of the light propagating on the inclined surface 7a, which is the boundary surface, is used for forming a waveguide of the optical waveguide 1. It can be reflected accurately toward the slope 2d of the groove 2c.

  In addition to forming a boundary surface on the end surface of the core portion 7, it is also possible to form a boundary surface made of a material having a different refractive index in at least one of the core portion 7 and the cladding portion 8, as will be described later. is there.

  Further, since the boundary surface is inclined with respect to the propagation direction of the light propagating through the core portion 7 like the slope 7a of the core portion 7, the multiple reflected light propagating through the core portion 7 is clad on the boundary surface. It can be made to radiate | emit to the part 8, and the intensity | strength of multiple reflected light can be reduced. Thereby, it is possible to reduce the deterioration of noise characteristics due to the multiple reflected light received by the monitor light receiving element 4.

  Further, in the first embodiment (the same applies to each of the following embodiments), the reflection surface uses the inclined surface 2d of the waveguide forming groove 2c of the optical waveguide 1, for example, the inclined surface 2d of the silicon mount substrate 2. In addition, if a reflective metal film is formed on the inclined surface 2d, the reflectance at the inclined surface 2d is improved, so that the amount of light received by the monitoring light receiving element 4 is increased.

  2A and 2B show an optical module according to the second embodiment. FIG. 2A is a plan view and FIG. 2B is a front view. FIG. 9A is a perspective view of the main part of the core part. The difference from the first embodiment is that the light extraction portion 10 is a plurality of boundary surfaces formed by inserting materials having different reflectances into the core portion 7 of the optical waveguide 1.

  Specifically, by inserting an inclined cut (slit) 7b in the core portion 7 as the light extraction portion 10, the respective cut surfaces facing the inclined cut become inclined surfaces 7c and 7d, Each of the inclined surfaces 7c and 7d becomes a boundary surface with air which is a material having a different refractive index.

  Therefore, part of the propagating light can be accurately reflected toward the inclined surface 2d of the waveguide forming groove 2c of the optical waveguide 1 by the inclined surfaces 7c and 7d which are the boundary surfaces.

  Further, since the reflection area is increased by the slopes 7c and 7d, which are a plurality of boundary surfaces, the amount of reflected light can be increased, and the amount of reflected light can be adjusted by increasing or decreasing the number of reflecting surfaces.

  The notches (slits) 7b of the core part 7 may be air gaps (air) or may be filled with the same material as the clad part 8 (which has a refractive index different from that of the core part 7).

  3A and 3B show an optical module according to the third embodiment. FIG. 3A is a plan view and FIG. 3B is a front view. The difference from the first embodiment is that the light extraction portion 10 is formed in the cladding portion 8.

  Specifically, an inclined surface 8 a is formed inside the cladding portion 8 as the light extraction portion 10. For example, by forming the front clad portion 8A and the rear clad portion 8B with materials having different refractive indexes from the inclined surface 8a as a boundary, the inclined surfaces 8a are bonded and integrated to form the inclined surface 8a. It becomes a boundary surface between the front clad portion 8A and the rear clad portion 8B, which are materials having different refractive indexes.

  Therefore, the leaked light c leaking from the light emitting element 3 and propagating through the cladding portion 8 can be accurately reflected toward the inclined surface 2d of the waveguide forming groove 2c of the optical waveguide 1 by the inclined surface 8a which is the boundary surface. .

  Further, if the inclined surface 8a is formed in the cladding part 8, light used for monitoring the optical power can be extracted without attenuating the optical power propagating through the core part 7.

  4A and 4B show an optical module according to the fourth embodiment. FIG. 4A is a plan view and FIG. 4B is a front view. The difference from the third embodiment is that the light extraction portion 10 is a plurality of boundary surfaces formed by inserting materials having different reflectances into the cladding portion 8 of the optical waveguide 1.

  Specifically, by inserting an inclined cut (slit) 8b in the cladding portion 8 as the light extraction portion 10, the respective cut surfaces facing the inclined cut become inclined surfaces 8c and 8d, Each of the slopes 8c and 8d becomes a boundary surface with air which is a material having a different refractive index.

  Therefore, the leakage light c leaking from the light emitting element 3 and propagating through the cladding portion 8 is accurately reflected toward the inclined surface 2d of the waveguide forming groove 2c of the optical waveguide 1 by the inclined surfaces 8c and 8d which are the boundary surfaces. Can do.

  In addition, since the reflection area is increased by the slopes 8c and 8d, which are a plurality of boundary surfaces, the amount of reflected light can be increased, and the amount of reflected light can be adjusted by increasing or decreasing the number of reflecting surfaces.

  Note that the notches (slits) 8b of the cladding part 8 may be air gaps (air), but may be filled with a material having a refractive index different from that of the cladding part 8.

  FIG. 5 shows an optical module according to the fifth embodiment, in which (a) is a plan view and (b) is a front view. FIG. 9B is a perspective view of the main part of the core part.

  The difference from the first embodiment is that the light extraction unit 10 is integrally formed with a Y-branch type optical waveguide (branch core unit) 11 in the core unit 7. The inclination angle of the Y-branch optical waveguide 11 is, for example, 45 ° with respect to the light propagation direction.

  Therefore, by providing the Y-branch optical waveguide 11 in the core part 7, a part of the light propagating in the core part 7 of the optical waveguide 1 [see arrow d in FIG. Therefore, the ratio of the amount of light received by the monitor light receiving element 4 can be set with high accuracy.

  Further, even on the slope 11 a of the Y-branch optical waveguide 11, the leaked light c leaking from the light emitting element 3 and propagating through the cladding portion 8 is accurately reflected toward the slope 2 d of the waveguide forming groove 2 c of the optical waveguide 1. Therefore, the amount of reflected light can be increased.

  6A and 6B show an optical module according to the sixth embodiment. FIG. 6A is a plan view and FIG. 6B is a front view. FIG. 9C is a perspective view of the main part of the core part.

  The difference from the first embodiment is that the light extraction unit 10 includes a plurality of boundary surfaces formed by inserting materials having different reflectances into the core part 7 of the optical waveguide 1, and a T-branch in the core part 7. This is the point that the optical waveguide 12 is integrally formed.

  Specifically, by inserting an inclined cut (slit) 7b in the core portion 7 as the light extraction portion 10, the respective cut surfaces facing the inclined cut become inclined surfaces 7c and 7d, Each of the inclined surfaces 7c and 7d becomes a boundary surface with air which is a material having a different refractive index. Further, the inclination angle of the T-branch optical waveguide 12 is, for example, 90 ° with respect to the light propagation direction.

  Therefore, by providing a plurality of boundary surfaces and the T-branch type optical waveguide 12 in the core part 7, the light reflected by the inclined surfaces 7c and 7d can be branched and propagated by the T-branch type optical waveguide 12. Propagation loss can be reduced.

  Further, since the reflection area is increased by the plurality of inclined surfaces 7c and 7d, the amount of reflected light can be increased, and the amount of reflected light can be adjusted by increasing or decreasing the number of reflecting surfaces.

  The notches (slits) 7b of the core part 7 may be air gaps (air) or may be filled with the same material as the clad part 8 (which has a refractive index different from that of the core part 7).

  In each of the above embodiments, the light extraction part 10 is provided on one of the core part 7 and the clad part 8 and the configuration is simplified, but the light extraction part 10 is provided on both the core part 7 and the clad part 8. It is also possible.

DESCRIPTION OF SYMBOLS 1 Optical waveguide 2 Mount board | substrate 2a Surface 2c Waveguide formation groove | channel 2d Slope 3 Light emitting element 4 Monitor light receiving element 7 Core part 7a Slope 7b Cut 7c, 7d Slope 8 Clad part 8a Slope 8b Cut 8c, 8d Slope 10 Light extraction part 11 Y-branch waveguide 12 T-branch waveguide

Claims (7)

A substrate on which an optical waveguide for propagating light is formed, a light emitting element that is attached to the substrate and emits light toward the optical waveguide, and a part of the light that is attached to the substrate and propagates through the optical waveguide And a light receiving element for monitoring that receives light,
In the substrate, a waveguide forming groove is formed,
An optical waveguide composed of a core part and a clad part is disposed in the waveguide forming groove,
The side surface of at least one side in the width direction of the waveguide forming groove is formed on a slope facing the light receiving part of the light receiving element for monitoring,
The optical waveguide is formed with a light extraction portion that reflects a part of the propagating light on a slope of a side surface of the waveguide forming groove and guides it to a light receiving portion of the light receiving element for monitoring. Optical module.   The optical module according to claim 1, wherein the light extraction portion is a boundary surface of materials having different refractive indexes, and the boundary surface is inclined with respect to a light propagation direction of the optical waveguide.   The light extraction portion is a plurality of boundary surfaces formed by inserting materials having different reflectivities into the optical waveguide, and the boundary surfaces are inclined with respect to the light propagation direction of the optical waveguide. The optical module according to claim 1 or 2. The optical module according to claim 1, wherein the light extraction portion is formed in at least one of the core portion or the cladding portion. The optical module according to claim 1, wherein the light extraction portion is a Y-branch optical waveguide formed in a core portion. 2. The light extraction portion is a plurality of boundary surfaces formed by inserting materials having different reflectances into the core portion, and a T-branch optical waveguide formed in the core portion. The optical module as described in.   The optical module according to claim 1, wherein a reflective metal film is formed on an inclined surface facing the light receiving portion of the monitor light receiving element.

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