JP2015087693A - Light-emitting device and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting device capable of suppressing the reduction of a yield, even when the number of light-emitting parts is increased.SOLUTION: A light-emitting device 100 includes an active layer 106 into which a current is injected to generate light and a first clad layer and a second clad layer holding the active layer 106. The active layer 106 constitutes an optical waveguide 160 guiding the light generated in the active layer 106. The optical waveguide 160 includes a first part 170 connecting a first light-emitting part 140 and a second light-emitting part 142 which are located in the side surface 105 of the active layer 106, a second part 180 connecting the first part 170 and a third light-emitting part 144 located in the side surface 105 of the active layer 106 between the first light-emitting part 140 and the second light-emitting part 142, and a reflection part 192 reflecting the light guided through the first part 170 toward the second part 180.

Description

  The present invention relates to a light emitting device and a projector.

  A super luminescent diode (hereinafter also referred to as “SLD”) is incoherent like a normal light emitting diode and has a broad spectrum shape, but has a single optical output characteristic similar to a semiconductor laser. This is a semiconductor light emitting device capable of obtaining an output of up to about several hundreds mW with this element.

  The SLD is used as a light source for a projector, for example. In order to realize a small and high brightness projector, it is necessary to use a light source having a large light output and a small etendue. In order to reduce the etendue, an SLD having a small interval between the light emitting portions is desired.

  For example, Patent Document 1 discloses an SLD that causes light emitted from two light emitting units to travel in the same direction.

JP 2011-155103 A

  In the SLD described in Patent Document 1, two light emitting portions are provided in one optical waveguide. For example, in order to increase the number of light emitting portions in order to increase the light output, another one is required. It is necessary to provide an optical waveguide separately. Thus, when the number of optical waveguides is increased, there is a problem that the yield decreases.

  One of the objects according to some aspects of the present invention is to provide a light emitting device capable of suppressing a decrease in yield even when the number of light emitting portions is increased. Another object of some embodiments of the present invention is to provide a projector including the light-emitting device.

The light emitting device according to the present invention is
An active layer capable of generating light when current is injected;
A first cladding layer and a second cladding layer sandwiching the active layer;
Including
The active layer constitutes an optical waveguide that guides light generated in the active layer,
The optical waveguide is
A first portion connecting a first light emitting portion and a second light emitting portion located on a side surface of the active layer;
A second part connecting the first part and a third light emitting part located on a side surface of the active layer between the first light emitting part and the second light emitting part;
A reflector that reflects the light guided through the first portion toward the second portion;
Have

In such a light emitting device, three or more light emitting portions are provided in one optical waveguide. Therefore, such a light emitting device can have a higher yield than, for example, a case where the number of light waveguides is increased by increasing the number of optical waveguides. That is, in such a light emitting device,
Even if the number of light emitting portions is increased, it is possible to suppress a decrease in yield.

In the light emitting device according to the present invention,
The second portion extends linearly from the third light emitting portion to the first portion,
The reflective portion may be provided only in a region where the first portion and the second portion overlap when viewed from the extending direction of the second portion.

  In such a light emitting device, the reflecting section can efficiently reflect the light guided through the first portion to the second portion.

In the light emitting device according to the present invention,
The reflective portion is configured by an inner surface of an opening provided in the active layer,
The opening may be surrounded by the first portion when viewed from the stacking direction of the active layer and the first cladding layer.

  In such a light emitting device, a part of the light guided through the first portion also oozes out to the waveguide portion blocked in the opening, and accordingly, the area of the region where the light is guided (the active layer and the first portion). The area of the clad layer as viewed from the stacking direction is increased. As a result, such a light emitting device can give a large gain to light.

In the light emitting device according to the present invention,
The first portion and the second portion are connected to the side surface of the active layer so as to be inclined with respect to the normal to the side surface of the active layer when viewed from the stacking direction of the active layer and the first cladding layer. Also good.

  In such a light emitting device, it is possible to reduce the direct reflection of light generated in the optical waveguide between the first light emitting unit, the second light emitting unit, and the third light emitting unit. As a result, speckle noise can be reduced.

In the light emitting device according to the present invention,
An antireflection film may be provided on a side surface of the active layer.

  In such a light emitting device, it is possible to reduce the direct reflection of light generated in the optical waveguide between the first light emitting unit, the second light emitting unit, and the third light emitting unit. As a result, speckle noise can be reduced.

The projector according to the present invention is
A light emitting device according to the present invention;
A light modulation device that modulates light emitted from the light emitting device according to image information;
A projection device for projecting an image formed by the light modulation device;
including.

  Such a projector can include a light emitting device that can suppress a decrease in yield even when the number of light emitting portions is increased.

The top view which shows typically the light-emitting device which concerns on this embodiment. FIG. 3 is a cross-sectional view schematically showing the light emitting device according to the embodiment. FIG. 3 is a cross-sectional view schematically showing the light emitting device according to the embodiment. The schematic diagram which looked at the active layer of the light-emitting device which concerns on this embodiment from the extending direction of the 2nd part of an optical waveguide. As a reference example, a schematic view of an active layer viewed from the extending direction of the second portion of the optical waveguide. The top view which shows typically the light-emitting device which concerns on a reference example. Sectional drawing which shows typically the manufacturing process of the light-emitting device which concerns on this embodiment. Sectional drawing which shows typically the manufacturing process of the light-emitting device which concerns on this embodiment. Sectional drawing which shows typically the manufacturing process of the light-emitting device which concerns on this embodiment. The top view which shows typically the light-emitting device which concerns on the 1st modification of this embodiment. The top view which shows typically the light-emitting device which concerns on the 2nd modification of this embodiment. 1 is a diagram schematically showing a projector according to an embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. In addition, not all of the configurations described below are essential constituent requirements of the present invention.

1. First, the light emitting device according to the present embodiment will be described with reference to the drawings. FIG. 1 is a plan view schematically showing the light emitting device 100 according to the present embodiment. 2 is a cross-sectional view taken along the line II-II of FIG. 2 schematically showing the light emitting device 100 according to the present embodiment. 3 is a cross-sectional view taken along line III-III in FIG. 3 schematically showing the light emitting device 100 according to the present embodiment.

  As shown in FIGS. 1 to 3, the light emitting device 100 includes a substrate 102, a first cladding layer 104, an active layer 106, a second cladding layer 108, a contact layer 110, an insulating layer 112, and a first layer. An electrode 120 and a second electrode 122 are included. Hereinafter, a case where the light emitting device 100 is an InGaAlP-based (red) SLD will be described.

  The substrate 102 is, for example, a first conductivity type (for example, n-type) GaAs substrate.

  The first cladding layer 104 is formed on the substrate 102. The first cladding layer 104 is, for example, an n-type InGaAlP layer. Although not shown, a buffer layer may be formed between the substrate 102 and the first cladding layer 104. The buffer layer is, for example, an n-type GaAs layer, an AlGaAs layer, an InGaP layer, or the like. The buffer layer can improve the crystal quality of the layer formed thereabove.

  The active layer 106 is formed on the first cladding layer 104. The active layer 106 has, for example, a multiple quantum well (MQW) structure in which three quantum well structures each composed of an InGaP well layer and an InGaAlP barrier layer are stacked.

  The shape of the active layer 106 viewed from the stacking direction of the active layer 106 and the first cladding layer 104 (hereinafter also referred to as “planar shape”) has, for example, a rectangular shape. The active layer 106 has a first side surface 105 and a second side surface 107 as shown in FIG. The side surfaces 105 and 107 are surfaces facing each other (parallel surfaces) and are not in contact with the cladding layers 104 and 108 in a planar shape. The side surfaces 105 and 107 may be cleavage surfaces formed by cleavage.

An anti-reflection (AR) film 150 is provided on the first side surface 105 of the active layer 106. The antireflection film 150 is, for example, a SiO ₂ layer, a Ta ₂ O ₅ layer, an Al ₂ O ₃ layer, a TiN layer, a TiO ₂ layer, a SiON layer, a SiN layer, or a multilayer film thereof. The antireflection film 150 can reduce the reflectance of light generated in the active layer 106 at the first side surface 105.

  The active layer 106 is provided with a first opening 130, a second opening 132, and a third opening 136. In the illustrated example, a plurality (specifically, three) of the second openings 132 are provided. The openings 130, 132, and 136 penetrate the contact layer 110, the second cladding layer 108, and the active layer 106. The openings 130, 132, and 136 are bottomed holes, and the bottom surfaces of the openings 130, 132, and 136 may be located between the lower surface and the upper surface of the first cladding layer 104. The openings 130, 132, and 136 may be filled with an insulating layer (not shown). Thereby, the inner surfaces of the openings 130, 132, and 136 can be protected. In the illustrated example, the planar shape of the openings 130, 132, and 136 is a triangle.

  A part of the active layer 106 constitutes an optical waveguide 160 that guides light. The active layer 106 is a layer capable of generating light by injecting current in the optical waveguide 160. The optical waveguide 160 can guide light generated in the active layer 106. The light guided through the optical waveguide 160 can receive a gain at the portion where the current of the optical waveguide 160 is injected.

  The optical waveguide 160 has a first portion 170, a second portion 180, a first reflecting portion 190, a second reflecting portion 192, and a third reflecting portion 194. The first portion 170 connects the first light emitting unit 140 and the second light emitting unit 142 located on the first side surface 105 of the active layer 106. The second portion 180 connects the first portion 170 and the third light emitting portion 144 located on the first side surface 105 between the first light emitting portion 140 and the second light emitting portion 142. This will be specifically described below.

  The first portion 170 includes a first waveguide portion 172, a second waveguide portion 174, and a third waveguide portion 176.

  The first waveguide portion 172 is viewed from the stacking direction of the active layer 106 and the first cladding layer 104 (hereinafter also referred to as “in plan view”) from the first side surface 105 to the inner surface (first surface) of the first opening 130. It extends to the side 131 of the active layer 106 that defines the shape of the opening 130. That is, one end portion of the first waveguide portion 172 is connected to the first side surface 105, and the other end portion of the first waveguide portion 172 is connected to the inner surface 131. The inner surface 131 is a flat surface, for example. The first waveguide 172 has a predetermined width in a plan view, and has a strip-like and linear longitudinal shape along the extending direction of the first waveguide 172. A connection portion between the first waveguide portion 172 and the first side surface 105 is a first emission portion (first emission surface) 140 that emits light generated in the optical waveguide 160.

  The extending direction of the first waveguide 172 includes, for example, the center of the connection portion between the first waveguide 172 and the first side surface 105, the first waveguide 172, and the inner surface 131 in plan view. And the center line C1 extending through the center of the connecting portion. In the illustrated example, the extending direction of the first waveguide 172 is the extending direction of the perpendicular P of the first side surface 105. That is, the first waveguide 172 is orthogonal to the first side surface 105.

  The first waveguide portion 172 is connected to the inner surface 131 at an angle α with respect to the normal line Q of the inner surface 131 of the first opening 130 in plan view. In other words, the extending direction of the first waveguide portion 172 has an angle α with respect to the perpendicular Q. The angle α is an acute angle that is smaller than the critical angle.

The second waveguide 174 extends from the inner surface 131 of the first opening 130 to the inner surface 137 of the third opening 136 (the side surface of the active layer 106 that defines the shape of the third opening 136). That is, one end portion of the second waveguide portion 174 is connected to the inner surface 131, and the other end portion of the second waveguide portion 174 is connected to the inner surface 137. The inner surface 137 is, for example, a flat surface.

  A connection portion between the second waveguide portion 174 and the inner surface 131 overlaps with a connection portion between the first waveguide portion 172 and the inner surface 131. That is, the waveguide portions 172 and 174 overlap on the inner surface 131. The overlapping portion (overlapping surface) of the connection portion between the first waveguide portion 172 and the inner surface 131 and the connection portion between the second waveguide portion 174 and the inner surface 131 reflects the light generated in the optical waveguide 160. This is a first reflecting portion (first reflecting surface) 190. In the illustrated example, the connection portion between the first waveguide portion 172 and the inner surface 131 and the connection portion between the second waveguide portion 174 and the inner surface 131 completely overlap.

  The second waveguide portion 174 is connected to the inner surface 131 at an angle α with respect to the normal line Q of the inner surface 131 in plan view. In other words, the extending direction of the second waveguide portion 174 has an angle α with respect to the perpendicular Q. That is, the angle of the first waveguide 172 with respect to the perpendicular Q and the angle of the second waveguide 174 with respect to the perpendicular Q are the same within the range of manufacturing variations. The angle α is an acute angle (specifically 45 °) and is equal to or greater than the critical angle. Thereby, the 1st reflection part 190 can totally reflect the light which generate | occur | produces in the optical waveguide 160, for example.

  The extending direction of the second waveguide 174 is, for example, the center of the connection between the second waveguide 174 and the inner surface 131 and the connection between the second waveguide 174 and the inner surface 137 in plan view. And the center line C2 extending through the center. In the illustrated example, the extending direction of the second waveguide 174 is a direction parallel to the first side surface 105 in plan view.

  Further, “the angle of the first waveguide portion 172 with respect to the perpendicular Q and the angle of the second waveguide portion 174 with respect to the perpendicular Q are the same within the range of manufacturing variation” refers to both manufacturing variations such as etching. This means that the angle difference is within about ± 2 °, for example. This also applies to the description that “the angle with respect to the perpendicular R of the second waveguide 174 and the angle with respect to the perpendicular R of the third waveguide 176 are the same within the range of manufacturing variation” described later.

  The second waveguide portion 174 is connected to the inner surface 137 at an angle β with respect to the normal R of the inner surface 137 in plan view. In other words, the extending direction of the second waveguide portion 174 has an angle β with respect to the perpendicular R.

  The second waveguide 174 is in contact with the inner surface of the second opening 132 (the side surface of the active layer 106 that defines the shape of the second opening 132) 133 and 134 while extending from the inner surface 131 to the inner surface 137. Yes. The second waveguide portion 174 has a shape in which a part of a belt-like and linear longitudinal shape extending from the inner surface 131 to the inner surface 137 is cut out by the second opening 132 in a plan view. A contact portion between the second waveguide portion 174 and the inner surfaces 133 and 134 is a second reflection portion (second reflection surface) 192 that reflects light generated in the optical waveguide 160. It can be said that the second reflecting portion 192 is composed of inner surfaces 133 and 134. The inner surfaces 133 and 134 are, for example, flat surfaces.

  As shown in FIG. 1, the second opening 132 may have an inner surface that is not in contact with the second waveguide 174. In other words, the second opening 132 may not be surrounded by the second waveguide 174 in plan view.

The inner surfaces 133 and 134 in contact with the second waveguide 174 are inclined at an angle γ with respect to the center line C2 of the second waveguide 174 in plan view. In other words, the extending direction of the second waveguide 174 has an angle γ with respect to the inner surfaces 133 and 134. The angle (90 ° −γ) is an acute angle (specifically 45 °) and is equal to or greater than the critical angle. Thereby, the 2nd reflection part 192 can totally reflect the light which generate | occur | produces in the optical waveguide 160, for example. The second reflection unit 192 can reflect the light guided through the second waveguide unit 174 toward the second portion 180. In the example shown in FIG. 1, the inner surfaces 133 and 134 are orthogonal to each other. The center line C2 of the second waveguide 174 may be in contact with the apex formed by the inner surfaces 133 and 134 as shown in FIG. 1, or may be separated from the apex.

  Although not shown, the angle formed by the inner surface 133 of the second opening 132 and the center line C2 of the second waveguide 174 and the angle formed by the inner surface 134 of the second opening 132 and the center line C2 are as follows. Different angles may be used.

  The third waveguide 176 extends from the inner surface 137 of the third opening 136 to the first side surface 105 in plan view. In other words, one end of the third waveguide 176 is connected to the inner surface 137, and the other end of the third waveguide 176 is connected to the first side surface 105. The third waveguide 176 has a predetermined width in a plan view, and has a strip-like and linear longitudinal shape along the extending direction of the third waveguide 176. A connection portion between the third waveguide portion 176 and the first side surface 105 is a second emission portion (second emission surface) 142 that emits light generated in the optical waveguide 160.

  The extending direction of the third waveguide 176 is, for example, the center of the connection portion between the third waveguide 176 and the inner surface 137 in plan view, the third waveguide 176, the first side surface 105, and the like. And the center line C3 extending through the center of the connecting portion. In the illustrated example, the extending direction of the third waveguide 176 is the extending direction of the perpendicular P of the first side surface 105. That is, the third waveguide 176 is orthogonal to the first side surface 105.

  A connection portion between the third waveguide portion 176 and the inner surface 137 overlaps with a connection portion between the second waveguide portion 174 and the inner surface 137. That is, the waveguide portions 174 and 176 overlap on the inner surface 137. An overlapping portion (overlap surface) between the connection portion between the second waveguide portion 174 and the inner surface 137 and the connection portion between the third waveguide portion 176 and the inner surface 137 reflects the light generated in the optical waveguide 160. This is a third reflecting portion (third reflecting surface) 194. In the illustrated example, the connection portion between the second waveguide portion 174 and the inner surface 137 and the connection portion between the third waveguide portion 176 and the inner surface 137 completely overlap.

  The third waveguide portion 176 is connected to the inner surface 137 at an angle β with respect to the normal R of the inner surface 137 in plan view. In other words, the extending direction of the third waveguide 176 has an angle β with respect to the perpendicular R. That is, the angle of the second waveguide 174 with respect to the perpendicular R and the angle of the third waveguide 176 with respect to the perpendicular R are the same within the range of manufacturing variations. The angle β is an acute angle (specifically 45 °) and is equal to or greater than the critical angle. Thereby, the 3rd reflection part 194 can totally reflect the light which generate | occur | produces in the optical waveguide 160, for example.

  The second portion 180 extends linearly from the first side surface 105 to the second waveguide portion 174 of the first portion 170 in plan view. That is, one end portion of the second portion 180 is connected to the first side surface 105, and the other end portion of the second portion 180 is connected to the second waveguide portion 174. The second portion 180 has a predetermined width in a plan view, and has a strip-like and linear longitudinal shape along the extending direction of the second portion 180. A connecting portion between the second portion 180 and the first side surface 105 is a third light emitting portion (third emitting surface) 144 that emits light generated in the optical waveguide 160.

  Note that the extending direction of the second portion 180 is, for example, the center of the connection portion between the second portion 180 and the first side surface 105 and the connection between the second portion 180 and the second waveguide portion 174 in plan view. And the center line C4 extending through the center of the section. In the illustrated example, the extending direction of the second portion 180 is the extending direction of the perpendicular line P of the first side surface 105. That is, the second portion 180 is orthogonal to the first side surface 105.

  The extending direction of the second portion 180 is the same direction as the extending portions of the waveguide portions 172 and 174 of the first portion 170. That is, the center line C4 of the second portion 180 and the center lines C1 and C3 of the waveguide portions 172 and 174 are parallel to each other. Thereby, the light 20 emitted from the first light emitting unit 140, the light 22 emitted from the second light emitting unit 142, and the light 24 emitted from the third light emitting unit 144 are caused to travel in the same direction. Can do.

  The number of the second portions 180 is not particularly limited, but in the illustrated example, a plurality (specifically, three) of the second portions 180 are provided. A plurality of second openings 132 (second reflecting portions 192) and third light emitting portions 144 are provided in accordance with the number of second portions 180. The plurality of second portions 180 may extend from the second waveguide 174 at equal intervals D1. The interval D2 between the first waveguide 172 and the second portion 180 (the first waveguide 172 and the closest second portion 180) may be the same value as the interval D1. Similarly, the distance D3 between the third waveguide 176 and the second portion 180 (the third portion 180 closest to the third waveguide 176) may be the same as the distance D1.

  Note that the plurality of second portions 180 may extend from the second waveguide 174 at different intervals. In the light emitting device 100, the intensity distribution (light amount distribution) of the emitted light of the light emitting device 100 can be adjusted by adjusting the intervals between the plurality of second portions 180 and the intervals D <b> 2 and D <b> 3. In the light emitting device 100, the intensity distribution (light amount distribution) of the emitted light of the light emitting device 100 can be adjusted by adjusting the widths of the waveguide portions 172, 176 and the second portion 180.

  Here, FIG. 4 is a view of the active layer 106 as seen from the extending direction of the second portion 180 (specifically, the direction of arrow A shown in FIG. 1). As shown in FIG. 4, the second reflecting portion 192 is provided only in a region 185 where the second waveguide portion 174 and the second portion 180 of the first portion 170 overlap when viewed from the extending direction of the second portion 180. ing. That is, the second reflecting portion 192 of the light emitting device 100 does not have a portion 192a that does not overlap the region 185, as in the reference example shown in FIGS. In other words, the maximum distance L1 between the second reflecting portion 192 provided on the inner surface 133 and the second reflecting portion 192 provided on the inner surface 134 in plan view as shown in FIG. The distance L2 is equal to or less than the distance L2 between the two boundary lines B of the two portions 180. In the illustrated example, the maximum distance L1 and the distance L2 are the same. That is, the second reflecting portion 192 completely overlaps the region 185 as shown in FIG.

  Note that the boundary line B of the second portion 180 is a boundary line between the second portion 180 and the insulating layer 112 (that is, a boundary line between a columnar portion 111 and the insulating layer 112 described later) in plan view. This is a line parallel to the center line C4 of the portion 180.

  As shown in FIG. 2, the second cladding layer 108 is formed on the active layer 106. The second cladding layer 108 is, for example, a second conductivity type (for example, p-type) InGaAlP layer. The cladding layers 104 and 108 are layers having a larger band gap and a lower refractive index than the active layer 106. The cladding layers 104 and 108 have a function of confining injected carriers (electrons and holes) and light (a function of suppressing light leakage) with the active layer 106 interposed therebetween.

  In the light emitting device 100, the p-type second cladding layer 108, the active layer 106 not doped with impurities, and the n-type first cladding layer 104 constitute a pin diode. In the light emitting device 100, when a forward bias voltage of a pin diode is applied between the electrodes 120 and 122 (current is injected), an optical waveguide 160 is generated in the active layer 106, and electrons and holes are regenerated in the optical waveguide 160. Bonding occurs. This recombination causes light emission. With this generated light as a starting point, stimulated emission occurs in a chain, and the intensity of the light is amplified in the optical waveguide 160 into which current is injected. The optical waveguide 160 includes an active layer 106 that guides light and clad layers 104 and 108 that confine light.

  For example, as illustrated in FIG. 1, the light 10 generated in the first waveguide unit 172 and traveling toward the first reflection unit 190 is amplified in the first waveguide unit 172 and then reflected by the first reflection unit 190. Then, the light 12 travels through the second waveguide 174 toward the third reflection unit 194 as the light 12. At this time, the light intensity is also amplified in the second waveguide 174. A part of the light 12 traveling through the second waveguide 174 is reflected by the second reflecting unit 192, travels as the light 14 toward the third light emitting unit 144 through the second portion 180, and emits the third light. The light is emitted from the portion 144 as light 24. Note that the light intensity is also amplified in the second portion 180. The light 12 that has reached the third reflecting portion 194 is reflected by the third reflecting portion 194, travels as the light 16 toward the second light emitting portion 142, and travels through the third waveguide portion 176, and the second light emitting portion 142. Is emitted as light 22. Note that the light intensity is also amplified in the third waveguide 176.

  The light that occurs in the third waveguide 176 and travels toward the third reflector 194 is reflected by the third reflector 194 and reaches the second waveguide 174. A part of the light reaching the second waveguide 174 is reflected by the second reflecting part 192, reaches the second part 180, and is emitted from the third light emitting part 144. The other part of the light reaching the second waveguide 174 is reflected by the first reflection unit 190, reaches the first waveguide 172, and is emitted from the first light emitting unit 140. The intensity of the light traveling through each of the waveguide portions 172, 174, 176 and the second portion 180 is amplified.

  The light that occurs in the second portion 180 and travels toward the second reflecting portion 192 reaches the second waveguide portion 174 and is reflected by the second reflecting portion 192. Part of the reflected light travels toward the first reflecting portion 190, is reflected by the first reflecting portion 190, reaches the first waveguide portion 172, and is emitted from the first light emitting portion 140. Further, the other part of the reflected light is directed toward the third reflecting portion 194, reflected by the third reflecting portion 194, reaches the third waveguide portion 176, and is emitted from the second light emitting portion 142. A part of the light traveling toward the first reflecting portion 190 or the third reflecting portion 194 is reflected by the second reflecting portion 192 and is reflected by the second portion 180 (a second portion 180 different from the second portion 180 where the light is generated). 2 portion 180) and is emitted from the third light emitting portion 144. The intensity of the light traveling through each of the waveguide portions 172, 174, 176 and the second portion 180 is amplified.

  Note that some of the light generated in the first waveguide 172 is directly emitted from the first light emitting unit 140. Similarly, some of the light generated in the third waveguide unit 176 is directly emitted from the second light emitting unit 142. Some of the light generated in the second portion 180 is directly emitted from the third light emitting unit 144. Similarly, the intensity of these lights is amplified in each of the waveguide portions 172 and 176 and the second portion 180.

  The contact layer 110 is formed on the second cladding layer 108 as shown in FIG. The contact layer 110 is in ohmic contact with the second electrode 122. In the illustrated example, the planar shape of the upper surface of the contact layer 110 (the contact surface with the second electrode 122) is the same as the planar shape of the optical waveguide 160. The contact layer 110 is, for example, a p-type GaAs layer.

  The contact layer 110 and a part of the second cladding layer 108 constitute a columnar portion 111. The planar shape of the columnar part 111 is the same as the planar shape of the optical waveguide 160, for example. The current path between the electrodes 120 and 122 is determined by the planar shape of the columnar section 111. Although not shown, the side surface of the columnar part 111 may be inclined.

The insulating layer 112 is formed on the second cladding layer 108 and on the side of the columnar portion 111 (around the columnar portion 111 in plan view). The insulating layer 112 is in contact with the side surface of the columnar part 111. The upper surface of the insulating layer 112 may be continuous with the upper surface of the contact layer 110 as shown in FIG. The insulating layer 112 is, for example, a SiN layer, a SiO ₂ layer, a SiON layer, Al ₂ O
₃ layers, polyimide layer. When the above material is used for the insulating layer 112, the current between the electrodes 120 and 122 flows through the columnar portion 111 sandwiched between the insulating layers 112, avoiding the insulating layer 112.

  The insulating layer 112 has a refractive index smaller than that of the active layer 106. The effective refractive index of the vertical section of the portion where the insulating layer 112 is formed is smaller than the effective refractive index of the vertical section of the portion where the insulating layer 112 is not formed, that is, the portion where the columnar portion 111 is formed. Thereby, light can be efficiently confined in the optical waveguide 160 in the planar direction. Note that although not illustrated, the insulating layer 112 is not necessarily provided. In this case, the air surrounding the columnar portion 111 performs the same function as the insulating layer 112.

  The first electrode 120 is formed on the entire surface under the substrate 102. Specifically, the first electrode 120 is formed in contact with the lower surface of a layer (the substrate 102 in the illustrated example) that is in ohmic contact with the first electrode 120. The first electrode 120 is electrically connected to the first cladding layer 104 through the substrate 102. The first electrode 120 is one electrode for driving the light emitting device 100. As the first electrode 120, for example, an electrode in which a Cr layer, an AuGe layer, a Ni layer, and an Au layer are stacked in this order from the substrate 102 side is used.

  A second contact layer (not shown) is provided between the first cladding layer 104 and the substrate 102, and the second contact layer is placed on the opposite side of the substrate 102 by dry etching or the like from the opposite side of the substrate 102. It is also possible to expose the first electrode 120 on the second contact layer. Thereby, a single-sided electrode structure can be obtained. This form is particularly effective when the substrate 102 is insulative.

  The second electrode 122 is formed on the contact layer 110. Furthermore, the second electrode 122 may also be formed on the insulating layer 112 as shown in FIG. The second electrode 122 is electrically connected to the second cladding layer 108 via the contact layer 110. The second electrode 122 is the other electrode for driving the light emitting device 100. For example, the active layer 106 (optical waveguide 160) positioned between the electrodes 120 and 122 can generate light by injecting current and amplify the intensity of the light. As the second electrode 122, for example, an electrode in which a Cr layer, an AuZn layer, and an Au layer are stacked in this order from the contact layer 110 side is used.

  In the example illustrated in FIG. 1, the optical waveguide 160 is a portion that does not overlap the second electrode 122 in a plan view, such as the first light emitting unit 140, the second light emitting unit 142, and the third light emitting unit 144. Have. The area of the portion is small, and the portion can also function as an optical waveguide. Although not shown, all of the optical waveguide 160 may overlap the second electrode 122 in plan view.

  In the above description, the first portion 170 has a planar shape (a U-shaped planar shape) to which the linearly extending waveguide portions 172, 174, and 176 are connected. Although not shown, the first portion 170 may have a U-shaped planar shape having a curvature. Thus, the planar shape of the first portion 170 is not particularly limited as long as the first light emitting portion 140 and the second light emitting portion 142 can be connected.

  In the above description, the AlGaInP-based light emitting device 100 has been described. However, the light emitting device according to the present invention can use any material system capable of forming an optical waveguide. As the semiconductor material, for example, semiconductor materials such as AlGaN, GaN, InGaN, GaAs, AlGaAs, InGaAs, InGaAsP, InP, GaP, AlGaP, and ZnCdSe can be used.

  In the above, the light-emitting device 100 is provided with a difference in refractive index between a region where the insulating layer 112 is formed and a region where the insulating layer 112 is not formed, that is, a region where the columnar portion 111 is formed. This is described as a so-called refractive index waveguide type that confines light. Although not shown, the light-emitting device according to the present invention does not provide a difference in refractive index by forming the columnar portion 111, and the so-called gain guide in which the optical waveguide 160 generated by injecting current becomes the waveguide region as it is. It may be corrugated.

  The light emitting device 100 can be applied to a light source such as a projector, a display, a lighting device, and a measuring device.

  For example, the light emitting device 100 has the following characteristics.

  In the light emitting device 100, the first part 170 connects the first light emitting part 140 and the second light emitting part 142 located on the first side surface 105, and the second part 180 is connected to the first part 170 and the first part 170. The third light emitting portion 144 located on the first side surface 105 between the light emitting portion 140 and the second light emitting portion 142 is connected, and the second reflecting portion 192 is light guided through the first portion 170. Is reflected toward the second portion 180. As described above, in the light emitting device 100, three or more light emitting portions are provided in one optical waveguide 160. Therefore, the light emitting device 100 can have a higher yield than, for example, a case where the number of light guides is increased by increasing the number of optical waveguides. That is, in the light emitting device 100, even if the number of light emitting portions is increased, it is possible to suppress a decrease in yield. For example, when the number of light waveguides is increased by increasing the number of optical waveguides, if a manufacturing defect occurs and a part of the waveguide is missing, the ability of light amplification (light emission amount) decreases. Yield may decrease. On the other hand, in the light emitting device 100, since the light emitting portion is branched from one waveguide, even if there is a defect in a part of the waveguide, the defect can be compensated by another waveguide part. Therefore, the ability of optical amplification is not greatly reduced.

  In the light emitting device 100, the second reflecting portion 192 is provided only in a region 185 where the first portion 170 and the second portion 180 overlap when viewed from the extending direction of the second portion 180. Therefore, the second reflection unit 192 can efficiently reflect the light guided through the second waveguide unit 174 of the first portion 170 to the second portion 180. For example, as in the reference examples shown in FIGS. 5 and 6, when the second reflecting portion 192 has a portion 192a located outside the region 185, the second waveguide portion 174 is guided and reflected at the portion 192a. The absorbed light does not reach the second portion 180 and is absorbed. Therefore, light cannot be reflected efficiently.

  In the light emitting device 100, an antireflection film 150 is provided on the first side surface 105. Thereby, the reflectance at the first side surface 105 of the light generated in the optical waveguide 160 can be lowered. Further, the antireflection film 150 can reduce the direct multiple reflection of light generated in the optical waveguide 160 between the light emitting portions 140, 142, and 144. Thereby, since a direct resonator cannot be constituted, laser oscillation of light generated in the optical waveguide 160 can be suppressed. As a result, the light emitting device 100 can emit light 20, 22, and 24 as SLD, and can reduce speckle noise.

  Although not shown, the antireflection film 150 may not be provided.

In the light emitting device 100, the angles α, β, (90 ° −γ) are set to be equal to or larger than the critical angle, and the inclination angles of the waveguide portions 172, 176 and the second portion 180 with respect to the perpendicular P of the first side surface 105 are greater than the critical angle. It is small. Thereby, the reflectance in the 1st side surface 105 can be made lower than the reflectance in the inner surfaces 131, 133, 134, and 137. As a result, a part of the first side surface 105 is made to function more reliably as the light emitting portions 140, 142, 144, and the inner surfaces 131, 133,
A part of 134 and 137 can be made to function as the reflectors 190, 192 and 194.

  In the light emitting device 100, the second opening 132 has an inner surface that is not in contact with the second waveguide 174. That is, the second opening 132 is not surrounded by the second waveguide 174 in plan view. Therefore, in the light emitting device 100, for example, the alignment accuracy between the second waveguide 174 and the second opening 132 is higher than that of the second opening 132 surrounded by the second waveguide 174 in plan view. Can be relaxed.

  In the light emitting device 100, the light generated in the optical waveguide 160 is emitted with various gains, depending on the location where the light is generated, as compared with a configuration without the second portion 180. Therefore, the light emitted from the light emitting device 100 includes light of various wavelengths. Therefore, in the light emitting device 100, speckle noise can be reduced as compared with a configuration in which the second portion 180 is not provided.

2. Method for Manufacturing Light-Emitting Device Next, a method for manufacturing a light-emitting device according to the present embodiment will be described with reference to the drawings. 7 to 9 are cross-sectional views schematically showing the manufacturing process of the light emitting device 100 according to this embodiment, and correspond to FIG.

  As shown in FIG. 7, on the substrate 102, the first cladding layer 104, the active layer 106, the second cladding layer 108, and the contact layer 110 are epitaxially grown in this order. Examples of the epitaxial growth method include a MOCVD (Metal Organic Chemical Deposition) method and an MBE (Molecular Beam Epitaxy) method.

  As shown in FIG. 8, the contact layer 110 and the second cladding layer 108 are patterned to form a columnar portion 111. The patterning is performed by, for example, photolithography and etching.

  As shown in FIG. 3, the contact layer 110, the second cladding layer 108, the active layer 106, and the first cladding layer 104 are patterned to form openings 130, 132, and 136. The patterning is performed, for example, by photolithography and etching (specifically, dry etching using chlorine). Note that the step of forming the openings 130, 132, and 136 may be performed before the step of forming the columnar portion 111.

  As shown in FIG. 9, the insulating layer 112 is formed so as to cover the side surface of the columnar part 111. Specifically, first, an insulating member (not shown) is disposed above the second cladding layer 108 (including on the contact layer 110) by a CVD (Chemical Vapor Deposition) method (more specifically, a plasma CVD method) or a coating method. )) Is formed. Next, the upper surface of the contact layer 110 is exposed, for example, by etching. Through the above steps, the insulating layer 112 can be formed.

  As shown in FIG. 2, the second electrode 122 is formed on the contact layer 110. Next, the first electrode 120 is formed on the lower surface of the substrate 102. The electrodes 120 and 122 are formed by, for example, a vacuum deposition method or a sputtering method. Note that the order of forming the electrodes 120 and 122 is not particularly limited.

As shown in FIG. 1, an antireflection film 150 is formed on the first side surface 105 of the active layer 106. The antireflection film 150 is formed by, for example, a CVD method or a sputtering method. Note that the step of forming the antireflection film 150 may be performed before the step of forming the electrodes 120 and 122.

  Through the above steps, the light emitting device 100 can be manufactured.

3. Modified example of light emitting device 3.1. First Modification Next, a light-emitting device according to a first modification of the present embodiment will be described with reference to the drawings. FIG. 10 is a plan view schematically showing a light emitting device 200 according to a first modification of the present embodiment. Hereinafter, in the light emitting device 200 according to the first modification of the present embodiment, members having the same functions as those of the constituent members of the light emitting device 100 according to the present embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. To do.

  In the light emitting device 100, as shown in FIG. 1, the second opening 132 is not surrounded by the second waveguide 174 of the first portion 170 in plan view. On the other hand, in the light emitting device 200, the second opening 132 is surrounded by the second waveguide 174 of the first portion 170 in a plan view as shown in FIG. 10. That is, the entire inner surface of the second opening 132 is in contact with the second waveguide 174 in plan view.

  In the light emitting device 200, since the second opening 132 is surrounded by the second waveguide 174 in plan view, the light guided through the second waveguide 174 travels so as to surround the second opening 132. To do. As a result, part of the light guided through the second waveguide 174 also oozes out to the waveguide portion blocked in the second opening 132, and the light guided through the second waveguide 174 is the optical waveguide 160. Amplified within. Accordingly, the area of the region where light is guided in plan view is increased. As a result, the light emitting device 200 can give a large gain to light.

3.2. Second Modified Example Next, a light emitting device according to a second modified example of the present embodiment will be described with reference to the drawings. FIG. 11 is a plan view schematically showing a light emitting device 300 according to a second modification of the present embodiment. Hereinafter, in the light emitting device 300 according to the second modification of the present embodiment, members having the same functions as those of the constituent members of the light emitting device 100 according to the present embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. To do.

  In the light emitting device 100, as shown in FIG. 1, the first portion 170 and the second portion 180 were orthogonal to the first side surface 105 in plan view. On the other hand, in the light emitting device 300, as shown in FIG. 11, the first portion 170 and the second portion 180 are connected to be inclined at an angle θ with respect to the perpendicular P of the first side surface 105 in plan view. . Specifically, the waveguide portions 172 and 176 and the second portion 180 are provided to be inclined at an angle θ with respect to the normal line P of the first side surface 105 in plan view. The angle θ is an acute angle that is smaller than the critical angle. The waveguide portions 172 and 176 and the second portion 180 are connected to the second waveguide portion 174 at an angle.

  Compared with the light emitting device 100, the light emitting device 300 can reduce the multiple reflection of light generated in the optical waveguide 160 directly between the light emitting units 140, 142, and 144 more reliably. As a result, speckle noise can be reduced more reliably.

4). Next, the projector according to the present embodiment will be described with reference to the drawings. FIG. 12 is a diagram schematically showing a projector 800 according to the present embodiment. For the sake of convenience, in FIG. 12, the housing constituting the projector 800 is omitted, and the light source 100 is simplified.

  As shown in FIG. 12, the projector 800 includes a red light source 100R that emits red light, green light, and blue light, a green light source 100G, and a blue light source 100B. The red light source 100R, the green light source 100G, and the blue light source 100B are light emitting devices according to the present invention. Hereinafter, an example in which the light emitting device 100 is used as the light emitting device according to the present invention will be described.

  The projector 800 further includes lens arrays 802R, 802G, and 802B, transmissive liquid crystal light valves (light modulation devices) 804R, 804G, and 804B, and a projection lens (projection device) 808.

  Light emitted from the light sources 100R, 100G, and 100B is incident on the lens arrays 802R, 802G, and 802B. Light emitted from the light sources 100R, 100G, and 100B becomes light whose illuminance distribution is made uniform by the lens arrays 802R, 802G, and 802B.

  Light emitted from the lens arrays 802R, 802G, and 802B is incident on the liquid crystal light valves 804R, 804G, and 804B. Each of the liquid crystal light valves 804R, 804G, and 804B modulates incident light according to image information. The projection lens 808 enlarges and projects an image (image) formed by the liquid crystal light valves 804R, 804G, and 804B onto a screen (display surface) 810.

  Further, the projector 800 can include a cross dichroic prism (color light combining means) 806 that combines the light emitted from the liquid crystal light valves 804R, 804G, and 804B and guides the light to the projection lens 808.

  The three color lights modulated by the liquid crystal light valves 804R, 804G, and 804B are incident on the cross dichroic prism 806. This prism is formed by bonding four right-angle prisms, and a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are arranged in a cross shape on the inner surface thereof. These dielectric multilayer films combine the three color lights to form light representing a color image. The synthesized light is projected onto the screen 810 by the projection lens 808 which is a projection optical system, and an enlarged image is displayed.

  The projector 800 can include the light emitting device 100 that can suppress a decrease in yield even when the number of light emitting portions is increased.

  In the above example, a transmissive liquid crystal light valve is used as the light modulation device. However, a light valve other than liquid crystal may be used, or a reflective light valve may be used. Examples of such a light valve include a reflection type liquid crystal light valve and a digital micromirror device (Digital Micromirror Device). Further, the configuration of the projection optical system is appropriately changed depending on the type of light valve used.

  Further, the light source 100 can be applied to a light source device of a scanning type image display device (projector) that displays an image of a desired size on a screen by scanning light from the light source 100. is there.

  The above-described embodiments and modifications are merely examples, and the present invention is not limited to these. For example, it is possible to appropriately combine each embodiment and each modification.

The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

DESCRIPTION OF SYMBOLS 10, 12, 14, 16, 20, 22, 24 ... light, 100 ... light-emitting device, 102 ... board | substrate, 104 ... 1st clad layer, 105 ... 1st side surface, 106 ... active layer, 107 ... 2nd side surface, 108 DESCRIPTION OF SYMBOLS ... 2nd clad layer, 110 ... Contact layer, 111 ... Columnar part, 112 ... Insulating layer, 120 ... 1st electrode, 122 ... 2nd electrode, 130 ... 1st opening part, 131 ... Inner surface, 132 ... 2nd opening part 133, 134 ... inner surface, 136 ... third opening, 137 ... inner surface, 140 ... first light emitting portion, 142 ... second light emitting portion, 144 ... third light emitting portion, 150 ... antireflection film, 160 ... 1st optical waveguide, 170 ... 1st part, 172 ... 1st waveguide part, 174 ... 2nd waveguide part, 176 ... 3rd waveguide part, 180 ... 2nd part, 185 ... area | region, 190 ... 1st reflection Part, 192 ... second reflection part, 192a ... part, 194 ... third counter Department, 200, 300 ... light-emitting device, 800 ... projector 802 ... lens array, 804 ... liquid crystal light valve, 806 ... cross dichroic prism 808 ... projection lens 810 ... screen

Claims (6)

An active layer capable of generating light when current is injected;
A first cladding layer and a second cladding layer sandwiching the active layer;
Including
The active layer constitutes an optical waveguide that guides light generated in the active layer,
The optical waveguide is
A first portion connecting a first light emitting portion and a second light emitting portion located on a side surface of the active layer;
A second part connecting the first part and a third light emitting part located on a side surface of the active layer between the first light emitting part and the second light emitting part;
A reflector that reflects the light guided through the first portion toward the second portion;
A light emitting device characterized by comprising: The second portion extends linearly from the third light emitting portion to the first portion,
2. The light emitting device according to claim 1, wherein the reflection portion is provided only in a region where the first portion and the second portion overlap when viewed from the extending direction of the second portion. . The reflective portion is configured by an inner surface of an opening provided in the active layer,
3. The light emitting device according to claim 1, wherein the opening is surrounded by the first portion when viewed from a stacking direction of the active layer and the first cladding layer.   The first portion and the second portion are inclined with respect to a normal to the side surface of the active layer when viewed from the stacking direction of the active layer and the first cladding layer, and are connected to the side surface of the active layer. The light emitting device according to claim 1, wherein the light emitting device is a light emitting device.   The light-emitting device according to claim 1, wherein an antireflection film is provided on a side surface of the active layer. A light emitting device according to any one of claims 1 to 5,
A light modulation device that modulates light emitted from the light emitting device according to image information;
A projection device for projecting an image formed by the light modulation device;
Including a projector.

Images