JP2013045803A - Semiconductor laser and optical transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser that is easily coupled to an optical component.SOLUTION: A semiconductor laser 10 has a light-emitting part 20 and a light control part 30 formed in a monolithic manner. An n-type lower DBR 102, an active region 104, a current constriction layer 106, and a p-type upper DBR are laminated on an n-type GaAs substrate 100. The light control part 30 propagates light emitted by the light-emitting part 20 in a direction substantially parallel to a principal plane of the substrate, and absorbs or amplifies the propagated light. Also, a reflection part 124 is formed on a surface of the light control part 30, and the reflection part 124 converges the light incident from an upper DBR 108 and reflects it in a certain direction.

Description

  The present invention relates to a semiconductor laser and an optical transmission device.

  In recent years, the optical link transmission capacity has been increasing at an accelerating rate, and a light source capable of high-speed transmission of about 100 Gbs and low power consumption is required. In order to use a surface emitting semiconductor laser for such a light source, the modulation speed of the surface emitting semiconductor laser must be further increased. One method for high-speed modulation of a surface emitting semiconductor laser is to form a surface emitting semiconductor laser and a lateral waveguide monolithically on a substrate and inject light into the surface emitting semiconductor laser from the lateral waveguide. There is one that switches or modulates light emitted from a surface emitting semiconductor laser (Patent Document 1). Furthermore, the increase in optical transmission capacity requires higher output of the surface emitting semiconductor laser. For example, by forming a light confinement region surrounded by a recess on the light emitting surface of a surface emitting semiconductor laser, the number of modes is reduced and high output is achieved (Patent Document 2).

  Patent Document 3 relates to a mode-locked edge-emitting semiconductor laser, and relates to a light absorber section that absorbs light by applying a reverse bias voltage and changing the refractive index of a modulation element, and a forward bias voltage. Is applied to form an active section that generates optical gain, enabling high-speed modulation and high output.

JP-A-11-274640 JP 2007-189033 A JP 2010-3930 A

  An object of the present invention is to provide a semiconductor laser that can be easily coupled to an optical transmission member such as an optical fiber.

According to a first aspect of the present invention, a drive current is supplied to the substrate, the first active region formed on the substrate, and configured to sandwich the first active region, and the first active region. A light-emitting unit including a first electrode for supply; and light emitted from the light-emitting unit formed on the substrate in a direction substantially parallel to the main surface of the substrate; A light control unit that absorbs or amplifies the second active region, a second vertical resonator configured to sandwich the second active region, and for supplying a control current A second electrode, and a reflection part formed on the second vertical resonator, wherein the reflection part receives light from the second vertical resonator and reflects the incident light in a certain direction. , Semiconductor laser.
According to a second aspect of the present invention, the reflecting unit includes an incident surface on which light from the second vertical resonator is incident, a reflective surface that reflects incident light, and an output surface that emits reflected light in the predetermined direction. The semiconductor laser according to claim 1, wherein the reflecting surface is inclined with respect to the incident surface.
According to a third aspect of the present invention, in the semiconductor laser according to the first or second aspect, the reflecting section converges the light incident from the incident surface and emits the converged light from the emission surface.
According to a fourth aspect of the present invention, in the semiconductor laser according to any one of the first to third aspects, the reflecting portion is a semiconductor layer crystal-grown on the second vertical resonator.
According to a fifth aspect of the present invention, the semiconductor layer has a first end and a second end facing the first end, and the first end includes the first film thickness and the first thickness. The second end has a second film thickness greater than the first film thickness and a second width narrower than the first width, and the second end is The semiconductor laser according to claim 1, wherein an emission surface of the reflection portion is formed.
The light control unit includes a low equivalent refractive index region having an equivalent refractive index smaller than an equivalent refractive index of the light emitting unit, and a high equivalent refractive index region having an equivalent refractive index higher than that of the low equivalent refractive index region. The semiconductor laser according to claim 1, wherein the reflection portion extends in a direction in which the high equivalent refractive index region extends.
7. The semiconductor laser according to claim 1, wherein the reflecting portion is formed at a position overlapping the high equivalent refractive index region.
The semiconductor laser according to claim 6, wherein the low equivalent refractive index region is a groove formed in the second vertical resonator.
The semiconductor laser according to claim 9, wherein the emission surface is substantially circular or substantially square.
10. The semiconductor laser according to claim 1, wherein the light control unit amplifies the propagated light when a forward bias control current is supplied to the second electrode. .
11. The semiconductor laser according to claim 1, wherein the light control unit absorbs the propagated light when a reverse device control current is supplied to the second electrode.
A twelfth aspect of the present invention is an optical transmission device comprising: the semiconductor laser according to any one of the first to eleventh aspects; and an optical transmission member that is coupled with light emitted from an emission surface of the reflecting portion.
The optical transmission device according to claim 12, further comprising a driving unit that supplies a driving current to the first electrode and supplies a control current to the second electrode.

According to invention of Claim 1, compared with the structure which is not provided with the reflection part, a coupling | bonding with an optical transmission member can be made easy.
According to the second aspect of the present invention, it is possible to easily reflect the incident light.
According to invention of Claim 3, the coupling efficiency with an optical transmission member can be improved.
According to invention of Claim 4, formation of a reflection part can be made easy.
According to invention of Claim 5, selection of the shape of the output surface of a reflection part can be made easy.
According to the sixth and seventh aspects of the invention, the light from the second vertical resonator can be efficiently incident on the reflecting portion.
According to invention of Claim 8, the light of a light emission part can be easily propagated to a light control part.
According to the ninth aspect of the present invention, the coupling with the optical transmission member can be facilitated.
According to invention of Claim 10, the light quantity of a laser beam can be increased.
According to the invention of claim 11, the laser beam can be modulated.

1A is a schematic plan view of a semiconductor laser according to a first embodiment of the present invention, and FIG. It is a figure which shows the equivalent refractive index and optical confinement distribution of the semiconductor laser which concerns on a 1st Example. It is a graph which shows the calculation result of the light distribution of the semiconductor laser which concerns on a 1st Example. FIG. 4A is a diagram illustrating a configuration example of the reflecting portion, and FIG. 4B is a diagram illustrating an example of a manufacturing method of the reflecting portion. It is a figure which shows the other structural example of the reflection part which concerns on the Example of this invention. It is a graph which shows the optical amplification amount of the semiconductor laser which concerns on the Example of 1st invention. It is a block diagram which shows the electrical constitution of the optical transmission apparatus using the semiconductor laser which concerns on the Example of this invention. It is sectional drawing which shows one structural example of the optical transmission apparatus using the semiconductor laser which concerns on the Example of this invention.

  Next, a semiconductor laser according to an embodiment of the present invention will be described with reference to the drawings. It should also be noted that the scale of the drawings is emphasized to make the features of the invention easier to understand and is not necessarily the same as the actual device scale.

  FIG. 1A is a schematic plan view of a semiconductor laser according to a first embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA. As shown in the figure, the semiconductor laser 10 of this embodiment functions as a light emitting unit 20 that emits light and a lateral waveguide that propagates light emitted from the light emitting unit 20 in the lateral direction and absorbs or absorbs light. A light control unit 30 that controls amplification and the like is included on the substrate.

  The light emitting unit 20 is configured in the same manner as a typical surface emitting semiconductor laser (Vertical-Cavity Surface-Emitting Laser diode: VCSEL). That is, the light emitting unit 20 includes an n-type lower distributed black reflector (hereinafter referred to as DBR) 102 and a lower DBR 102 in which AlGaAs layers having different Al compositions are alternately stacked on an n-type GaAs substrate 100. An active region 104 including a quantum well layer sandwiched between upper and lower spacer layers formed above, and a p-type upper DBR 108 in which AlGaAs layers having different Al compositions formed on the active region 104 are alternately stacked are stacked. Configured. The planar shape of the light emitting unit 20 is substantially semicircular as shown in FIG.

In the n-type lower DBR 102, for example, a plurality of pairs of an Al _0.92 Ga _0.08 As layer and an Al _0.16 Ga _0.84 As layer are stacked as a stack of a high refractive index layer and a low refractive index layer. The thickness of each layer is λ / 4n _r (where λ is the oscillation wavelength and n _r is the refractive index of the medium), and these are alternately stacked in 40 cycles. The carrier concentration after doping silicon which is an n-type impurity is, for example, 3 × 10 ¹⁸ cm ⁻³ . The lower spacer layer of the active region 104 is an undoped Al _0.6 Ga _0.4 As layer, the quantum well active layer is an undoped GaAs quantum well layer and an undoped Al _0.3 Ga _0.7 As barrier layer, and the upper spacer The layer is an undoped Al _0.6 Ga _0.4 As layer. The p-type upper DBR 108 is formed by stacking a plurality of pairs of, for example, an Al _0.92 Ga _0.08 As layer and an Al _0.16 Ga _0.84 As layer as a stack of a high refractive index layer and a low refractive index layer. The thickness of each layer is lambda / 4n _r, to 24 cycles are alternately stacked. The carrier concentration after doping with carbon which is a p-type impurity is, for example, 3 × 10 ¹⁸ cm ⁻³ .

A current confinement layer 106 made of a p-type Al _0.98 Ga _0.02 As layer (or AlAs layer) is formed in the lowermost layer of the upper DBR 108 or in the inside thereof. Further, a contact layer having a high impurity concentration (for example, 1 × 10 ¹⁹ cm ⁻³ ) made of p-type GaAs may be formed on the uppermost layer of the upper DBR 108. The current confinement layer 106 has an Al composition higher than that of the lower DBR 102 and the upper DBR 108, and oxidation proceeds faster in the oxidation process. When a semi-cylindrical post as shown in FIG. 1A is oxidized, the current confinement layer 106 has an oxidized region 106A (FIG. 1B hatched selectively) oxidized selectively from the side wall of the post. Part) is formed. As a result, a non-oxidized region 106B surrounded by the oxidized region 106A is formed. The planar shape of the non-oxidized region 106B substantially reflects the planar shape of the post structure. A broken line 106C shown in FIG. 1A indicates a boundary between the oxidized region 106A and the non-oxidized region 106B.

The diameter of the semicircular portion of the non-oxidized region 106B is large enough to cause fundamental transverse mode oscillation, for example, about 3 microns or less. The refractive index of the oxidized region 106A is about 1.7, the refractive index of the non-oxidized region (Al _0.98 Ga _0.02 As) 106B is about 3.0, and light enters the non-oxidized region 106B having a high refractive index. It becomes possible to confine. Further, since the oxidized region 106A is a high-resistance region, carriers injected from the electrode pass through the non-oxidized region 106B that is a conductive region, whereby the carrier density is increased and injected into the active region 104.

  On the upper DBR 108, for example, a metal semicircular p-side electrode 110 made of a metal in which Au or Ti / Au is laminated is formed, and the p-side electrode 110 is electrically connected to the upper DBR 108. Is done. Preferably, the p-side electrode 110 is formed so as to cover, ie, overlap with, the non-oxidized region 106B of the current confinement layer 106. More preferably, the p-side electrode 110 is formed of the upper DBR 108 of the light emitting unit 20. It is formed so as to cover substantially the entire area. Therefore, it should be noted that the light emitting unit 20 does not emit laser light from the uppermost layer of the upper DBR 108, unlike a normal VCSEL. An n-side electrode 112 is formed on the back surface of the substrate 100. The n-side electrode 112 is also common to the light control unit 30.

  Thus, the light emitting unit 20 having a vertical resonator structure is formed on the substrate 100, and a forward drive signal is applied between the p-side electrode 110 and the n-side electrode 112, so that light from the active region 104 can be obtained. Is generated, and the laser beam is excited. However, since the surface of the upper DBR 108 is covered with the p-type electrode 110 as described above, the laser light is reflected to the inside by the p-side electrode 110.

  In the semiconductor laser 10, a light control unit 30 as a lateral waveguide is formed monolithically on the side of the light emitting unit 20. The light control unit 30 includes a low equivalent refractive index region 120 having a relatively small equivalent refractive index for guiding the laser light generated by the light emitting unit 20, and a higher level for propagating light derived from the low equivalent refractive index region 120. It has a slow light part 122 in the valence index region and a reflection part 124 formed on the slow light part 122. Preferably, the light control unit 30 is configured using the same semiconductor layer as the light emitting unit 20. Note that the equivalent refractive index used in this specification is an effective refractive index of a semiconductor multilayer film having a different refractive index laminated in a direction perpendicular to the substrate (the refractive index of the multilayer film is a single layer). (Referred to as a refractive index) is obtained by an equivalent refractive index method.

  Preferably, the low equivalent refractive index region 120 is formed by a trench 120 formed in the upper DBR 108. The trench 120 is preferably formed inside the boundary 106C between the oxidized region 106A and the non-oxidized region 106B shown in FIG. 1A, that is, at a position overlapping the non-oxidized region 106, and is constant in a direction substantially perpendicular to the substrate. Has depth. More preferably, the trench 120 is formed adjacent to the end of the p-side electrode 110. Thus, the reason why the trench 120 is formed at the position overlapping the non-oxidized region 106B inside the boundary 106C is to easily guide the light generated in the light emitting unit 20 to the slow light unit 122. The light emitting unit 20 is formed at a position, depth, and width (D2) such that light from the light emitting unit 20 is efficiently leaked to the slow light unit 122. The shape of the trench 120 does not matter, but in this embodiment, it is formed in a rectangular shape. Further, the substantial diameter D1 of the non-oxidized region 106B of the light emitting portion 20 is 2 μm, the width D2 of the trench 120 is 1 μm, and the distance D3 extending in the longitudinal direction of the slow light portion 122 is 6 μm.

  FIG. 2 shows the relationship between the equivalent refractive index of the semiconductor laser 10 and the optical confinement distribution. In the figure, a step-like line indicates an equivalent refractive index, and a curve indicates a light confinement distribution. A region D0 having a low equivalent refractive index NL (see FIG. 1A) corresponds to the oxidized region 106A of the light emitting unit 20, and a region D1 having a high equivalent refractive index NH corresponds to the non-oxidized region 106B of the light emitting unit 20. To do. The region D2 having a low equivalent refractive index NL corresponds to the trench 120 of the light control unit 30, and the region D3 having a high equivalent refractive index NH corresponds to the non-oxidized region 106B of the slow light unit 122 of the light control unit 30.

  By continuously forming the regions D0, D1, D2, and D3 that become the high and low equivalent refractive indexes NL and NH, the light generated in the light emitting unit 20 is not emitted from the uppermost layer of the upper DBR 108, It is confined in the region D1. Although the fundamental transverse mode light Lin confined in the region D1 has a Gaussian distribution, the trench 120 (region D2) does not completely confine the light Lin, but instead uses a portion of the light at the base of the slow light portion. Lead to 122. Even in the case of laser light that is vertically resonated in the light emitting unit 20, the laser light has a slight inclination angle or spread angle from the vertical direction. For this reason, the light leaking from the base is guided to the region D3 having the high equivalent refractive index NH via the region D2 having the low equivalent refractive index. The light guided to the slow light part 122 is confined in the non-oxidized region 106B of the slow light part 122 and is resonated in the direction of the inclination angle in the direction of the inclination angle in a substantially horizontal direction with the main surface of the substrate. Propagated.

  Since the light propagated through the slow light part 122 travels while being reflected between the lower DBR 102 and the upper DBR 108, even if the horizontal distance D3 of the slow light part 122 is small, the distance that the light actually travels (the optical path length). ) Corresponds to several hundred times the distance D3. For this reason, the speed of light propagating through the slow light unit 122 in the horizontal direction appears to be slow light as if the speed of light was delayed.

  FIG. 3 is a graph showing the calculation result of the light distribution of the light propagated from the light emitting unit 20 to the light control unit 30. The horizontal axis is distance (μm), and the vertical axis is relative intensity. In the figure, the range of 0-2 μm corresponds to the diameter D1 of the non-oxidized region 106B, and laser oscillation with a Gaussian distribution having a large relative intensity occurs. The range of 2-3 μm corresponds to the width D2 of the trench 120, and here, light having a small relative intensity is generated. The range of 3-9 μm corresponds to the distance D3 of the slow light part 122, and indicates the laser light that is confined in the slow light part 122 and propagates. However, FIG. 3 shows the light distribution when the light control unit 30 does not amplify or absorb light.

  As illustrated in FIG. 1, the light control unit 30 includes a reflection unit 124 on the upper surface of the slow light unit 122, that is, on the upper DBR 108. The reflection unit 124 receives the light from the slow light unit 122 and reflects the incident light in a direction substantially parallel to the main surface of the substrate. As shown in FIG. 1A, the reflecting portion 124 extends in a direction in which the non-oxidized region 106B of the slow light portion 122 extends. Preferably, the reflecting portion 124 overlaps with substantially the entire oxidized region 106B. It is formed in the position to do. In the example shown in FIG. 1A, the reflecting portion 124 is formed somewhat shorter than the distance D3 of the slow light portion 122, but the reflecting portion 124 has a length of the distance D3 so as to be adjacent to the trench 120. Or may be longer than the distance D3.

  FIG. 4A is a perspective view schematically showing the reflecting portion 124. As shown in the figure, the reflection unit 124 includes an incident surface 124A on which light from the slow light unit 122 is incident, a reflection surface 124B that reflects incident light, and an output that emits light reflected on the reflection surface 124. 124C. Here, one end portion of the reflecting portion 124 has a width W1 and a film thickness H1, and the other end portion has a width W2 and a film thickness H2, and W1> W2 and H1 <H2. The width W1 of the reflecting part 124 is preferably larger than the width of the non-oxidized region 106B of the slow light part 122, and the width W2 is preferably equal to or slightly larger than the width of the non-oxidized region 106B. The reflecting surface 124B is inclined with respect to the incident surface 124A, and reflects incident light toward the emitting surface 124. Further, the reflecting surface 124B converges the light incident from the width W2 toward the width W1.

FIG. 4B is a diagram for explaining an example of a manufacturing method of the reflecting portion 124. As shown in the figure, a dielectric film such as a silicon oxide film (SiO ₂ ) or a silicon nitride film (SiN) is applied to the surface of the slow light portion 122 on the GaAs wafer (substrate) W, that is, the uppermost layer of the upper DBR 108. A pair of patterns 130 is formed using a known photolithography process. The pattern 130 has a certain film thickness, and its planar shape is appropriately selected according to the shape of the reflective film 124 to be formed, but the trapezoidal reflective portion 124 as shown in FIG. For example, a pattern 130 having a triangular plane shape is juxtaposed, and a trapezoidal opening having a width W1 and a width W2 is formed between both patterns. The surface of the upper DBR 108 is exposed through this opening.

  Next, when the compound semiconductor layer is recrystallized and grown on the slow light portion 122 by MOCVD (metal organic chemical vapor deposition), the compound semiconductor layer is pattern-grown on the opening of the pattern 130, thereby A trapezoidal reflecting portion 124 having W1 and width W2 is formed. Here, because of the relationship of W2 <W1, the thickness H2 of the width W2 is larger than the thickness H1 of the width W1. The film thicknesses H1 and H2 are adjusted by appropriately adjusting the widths W1 and W2, the inclination angle of the opposite side surface (edge) of the pattern 130 with respect to the substrate, the recrystallization growth time, and the like. The shape of the exit surface 124C can be adjusted.

  When the reflecting portion 124 is formed by pattern growth, a material whose lattice constant matches or approximates that of the underlying semiconductor layer is preferably used. In addition, for the reflection unit 124, a material that absorbs less light from the slow light unit 122 and has a refractive index that reflects incident light on the reflection surface 124B is selected. For example, when the laser beam emitted from the light emitting unit 20 has a wavelength of 850 nm, the reflecting unit 124 is made of GaInP, AlGaAs, GaAs, or the like. Of these, GaInP, which absorbs less light and hardly oxidizes, is more preferable.

  Note that the reflection portion 124 may be formed by a method other than pattern growth by MOCVD. For example, a reflection part 124 having a desired shape may be obtained by forming a material having a small refractive index and a constant refractive index on the surface of the slow light part 122 and etching the material. .

  In the above example, an example in which the inclination of the reflecting surface 124B changes linearly is shown. However, the present invention is not limited thereto, and the inclination of the reflecting surface 124B has a curve or a curved surface as shown in FIG. It may be changed, or may be changed stepwise as shown in FIG. In short, the reflection surface 124B may have any shape that can reflect the light from the incidence surface 124A toward the emission surface 124C.

  In addition, the shape of the exit surface 124C is preferably a shape having no anisotropy, and for example, as shown in FIG. Further, when the shape of the emission surface 124C is a rectangular shape as shown in FIG. 4A, it is desirable that the width W2 = H2. Furthermore, as shown in FIG. 5D, the emission surface 124C may have a semicircular shape or a dome shape in which the top is a semicircle. In short, the shape (or width W2, film thickness H2) of the exit surface 124C is selected so that the anisotropy of the profile of the light incident from the entrance surface 124A is suppressed or reduced. Further, the size of the exit surface 124C is selected so that the converged laser beam can be easily coupled to an optical transmission component such as an optical fiber.

  Referring to FIG. 1 again, the light control unit 30 includes a pair of p-side electrodes 210 on the upper surface of the slow light unit 122. The pair of p-side electrodes 210 are preferably arranged so as to sandwich the reflecting portion 124 and are electrically connected to the upper DBR 108 of the slow light portion 122. The light control unit 30 and the light emitting unit 20 are electrically connected via a part of the upper DBR 108, but carriers injected from the p-side electrode 110 of the light emitting unit 20 are optically controlled due to the presence of the trench 120. Since most of it does not flow into the portion 30 and is injected into the active region 104 via the non-oxidized region 106B directly below, the operations of the light emitting portion 20 and the light control portion 30 do not substantially interfere. . In addition, if necessary, the resistance value between the light control unit 30 and the light emitting unit 20 is increased by extending the width of the trench 120 in the vertical direction, or an electrical operation using an ion implantation (injection) or the like. It is also possible to break up.

  In addition to functioning as a lateral waveguide, the light control unit 30 has a function of externally modulating light from the light emitting unit 20. In the first preferred embodiment, an example will be described in which the light control unit 30 functions as a light absorber that selectively absorbs light. A forward-bias drive current is always applied between the p-side electrode 110 and the n-side electrode 112 of the light emitting unit 20, and the laser-oscillated light in the light emitting unit 20 is reflected by the p-side electrode 110. Therefore, more light is guided to the light control unit 30.

  On the other hand, a drive pulse signal having a reverse bias frequency f is applied between the p-type electrode 210 and the n-side electrode of the light control unit 30. When a reverse bias voltage is applied to the slow light unit 122, the refractive index of the active region 104 changes and light passing therethrough is absorbed. Such a light absorption principle is known as an electro absorption (EA) modulator. The EA modulator performs modulation using the property that the absorption edge shifts to the long wavelength side when an electric field is applied to a quantum well formed of a semiconductor heterojunction.

  The laser light Lm guided laterally from the light emitting unit 20 is propagated in the horizontal direction while being reflected from the lower DBR 102 of the slow light unit 122 in the vertical resonator of the upper DBR 108. For this reason, even if the horizontal distance D3 of the slow light portion 122 is small, the laser light Lm passes through the active region 104 a number of times corresponding to several hundred times the distance, and thereby the laser light Lm. Is absorbed more effectively. Thus, the laser light Ln switched or modulated according to the frequency f of the drive pulse signal is incident on the incident surface 124A of the reflecting portion 124 from the surface of the slow light portion 122 (an area corresponding to the boundary 106C). The light is reflected by the reflecting surface 124B, and the laser light Ln converged from the emitting surface 124C is emitted in a direction substantially parallel to the main surface of the substrate.

  When the reflection part 124 is not formed on the surface of the slow light part 122, the surface of the slow light part 122 has an anisotropic property according to the planar shape of the non-oxidized region 106B, that is, the planar shape of the boundary 106C. Laser light having an elliptical profile is emitted. Even if the laser beam having an elliptical profile with a large anisotropy is coupled to an optical fiber, the loss of the light amount is large and the coupling efficiency is lowered, so that it is coupled with an optical transmission member such as an optical fiber. Not suitable. On the other hand, in the present embodiment, the reflection portion 124 is provided on the surface of the slow light portion 122, and the laser light emitted from the slow light portion 122 is converged to the laser light having a profile with less anisotropy, The coupling between the semiconductor laser 10 and an optical transmission member such as an optical fiber can be facilitated.

  Next, the 2nd preferable aspect of the light control part 30 is demonstrated. In the second preferred embodiment, the light control unit 30 functions as an optical amplification unit. In the second preferred embodiment, a forward bias drive current is applied between the p-side electrode 210 and the n-side electrode 112 of the slow light part 122 to amplify the laser light Lm guided from the light emitting part 20. . An optical amplifier is known as a semiconductor optical amplifier (SOA).

  When a forward bias drive current is applied between the p-side drive electrode 210 and the n-side electrode 112, carriers are injected from the electrode, and the gain of the laser light in the slow light unit 122 is amplified. Since the laser light Lm injected from the light emitting unit 20 is propagated in the horizontal direction while being reflected in the vertical resonator of the slow light unit 122, it passes through the active region 104 many times. As a result, the laser light Lm The gain is amplified, and the high-power laser beam Ln is incident on the reflection unit 124 from the surface of the slow light unit 112. If a drive pulse signal having a frequency f is applied, the laser light Ln modulated according to the frequency f is emitted from the emission surface 124C in the horizontal direction.

  FIG. 6 is a graph showing the amount of light amplification when the light control unit 30 functions as an optical amplifier. The vertical axis represents gain, and the horizontal axis represents current density. As can be seen from the figure, the gain increases as the current density increases. That is, as the injection amount from the carrier from the light control unit 30 increases, the gain increases.

  In the above-described embodiment, an example in which the light control unit 30 functions as an optical absorber or an optical amplifier is shown. However, two light control units are formed on the side of the light emitting unit 20 and light is emitted by the two light control units. You may make it implement | achieve the function of an absorber and an optical amplifier. For example, the laser light Lm injected from the light emitting unit 20 can be amplified with a constant gain by the first light control unit, and the amplified laser light can be selectively absorbed (modulated) by the second optical amplifier. . In this case, for example, the p-side electrode is overlapped with the non-oxidized region 106B so that the light is not emitted from the surface of the first light control unit, and the reflection unit 124 is formed on the surface of the second light control unit. On the contrary, the light injected from the light emitting unit 20 is selectively absorbed (modulated) by the first light control unit, and the modulated laser light is amplified by the second light control unit. May be. Also in this case, light is not emitted from the surface of the first light control unit, and the reflection unit 124 is formed on the surface of the second light control unit. If two light control units can be formed for light absorption and light amplification, it is necessary to form p-side drive electrodes separately.

  FIG. 7 is a block diagram showing a configuration of an optical transmission device using the semiconductor laser of the present embodiment. The optical transmission apparatus 300 of this embodiment includes a drive unit 310 that generates a drive signal S1 for driving the light emitting unit 20 and a drive signal S2 for driving the light control unit 30. The drive signal S2 is changed according to whether the light control unit 30 functions as an optical absorber or an optical amplifier. Furthermore, as described above, when the first and second light control units 30A and 30B are formed, the drive unit 310 sends the drive signal S2 to the first and second light control units 30A and 30B, respectively. S3 is supplied.

  FIG. 8 is a cross-sectional view illustrating a configuration example of the optical transmission apparatus according to the present embodiment. The optical transmission device 400 includes a metal stem 420 on which an electronic component 410 on which the semiconductor laser 10 and the driving unit 310 are formed is mounted. The stem 420 is covered with a hollow cap 430, and a ball lens 440 is fixed to the center of the cap 430. ing. A cylindrical housing 450 is further attached to the stem 420, and an optical fiber 470 is fixed to an end of the housing 450 via a ferrule 460. The laser light modulated from the electronic component 410 is collected by the ball lens 440, and the light is incident on the optical fiber 470 and transmitted. In addition to the ball lens, other lenses such as a biconvex lens and a plano-convex lens can be used.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the specific embodiment, and various modifications can be made within the scope of the present invention described in the claims. Deformation / change is possible. In the above embodiment, the semiconductor laser using the AlGaAs compound semiconductor is illustrated, but a semiconductor laser using other III-V group compound semiconductor layers may be used. Furthermore, the shapes of the light emitting unit 20 and the light control unit 30 in the above embodiment are merely examples, and other shapes may be used.

10: Semiconductor laser 20: Light emitting unit 30: Light control unit 100: GaAs substrate 102: Lower DBR
104: Active region 106: Current confinement layer 106A: Oxidized region 106B: Non-oxidized region 106C: Boundary 108: Upper DBR
110, 210: p-side electrode 112: n-side electrode 120: trench (groove)
122: Slow light portion 124: Reflecting portion 124A: Incident surface 124B: Reflecting surface 124C: Outgoing surface

Claims (13)

A substrate,
A first active region formed on the substrate, a first vertical resonator configured to sandwich the first active region, and a first electrode for supplying a driving current to the first active region A light emitting unit including
A light control unit that is formed on the substrate, propagates light emitted from the light emitting unit in a direction substantially parallel to the main surface of the substrate, and absorbs or amplifies the propagated light;
The light control unit includes a second active region, a second vertical resonator configured to sandwich the second active region, a second electrode for supplying a control current, and a second vertical resonator And a reflection part formed on
The said reflection part is a semiconductor laser which injects the light from a 2nd vertical resonator, and reflects the incident light to a fixed direction. The reflection unit has an incident surface on which light from the second vertical resonator is incident, a reflection surface that reflects incident light, and an output surface that emits reflected light in the predetermined direction, and the reflection The semiconductor laser according to claim 1, wherein a surface is inclined with respect to the incident surface. The semiconductor laser according to claim 1, wherein the reflection unit converges light incident from the incident surface and emits the converged light from the emission surface. 4. The semiconductor laser according to claim 1, wherein the reflecting portion is a semiconductor layer crystal-grown on the second vertical resonator. 5. The semiconductor layer has a first end and a second end facing the first end, and the first end has a first film thickness and a first width. The second end portion has a second film thickness larger than the first film thickness and a second width narrower than the first width, and the second end portion is an exit surface of the reflecting portion. The semiconductor laser according to claim 1, wherein the semiconductor laser is formed. The light control unit includes a low equivalent refractive index region whose equivalent refractive index is smaller than an equivalent refractive index of the light emitting unit, and a high equivalent refractive index region whose equivalent refractive index is higher than the low equivalent refractive index region, The semiconductor laser according to claim 1, wherein the reflecting portion extends in a direction in which the high equivalent refractive index region extends. The semiconductor laser according to claim 1, wherein the reflection portion is formed at a position overlapping the high equivalent refractive index region. The semiconductor laser according to claim 6, wherein the low equivalent refractive index region is a groove formed in the second vertical resonator. The semiconductor laser according to claim 1, wherein the emission surface is substantially circular or substantially square. 10. The semiconductor laser according to claim 1, wherein the light control unit amplifies the propagated light when a forward bias control current is supplied to the second electrode. 11. 10. The semiconductor laser according to claim 1, wherein the light control unit absorbs the propagated light when a reverse vise control current is supplied to the second electrode. 11. A semiconductor laser according to any one of claims 1 to 11,
An optical transmission member combined with light emitted from the exit surface of the reflecting portion;
An optical transmission device. The optical transmission device according to claim 12, further comprising a driving unit that supplies a driving current to the first electrode and supplies a control current to the second electrode.

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