Semiconductor laser and method of manufacture

Abstract

The disclosure provides a semiconductor laser and a preparation method. The semiconductor laser comprises a substrate; a negative electrode is arranged on the bottom surface of the substrate; an active layer is arranged on the top surface of the substrate; a grating layer and a waveguide layer are both arranged on the active layer; a ridge waveguide is arranged on the grating layer and the waveguide layer; a first positive electrode and a second positive electrode are both arranged on the ridge waveguide, and the second positive electrode is located above the grating layer and is configured to apply alternating current and direct current for adjusting the working state of the semiconductor laser. The semiconductor laser is provided with a partial grating structure, a light feedback structure below the first positive electrode, and a reduced length of the second electrode, so that the semiconductor laser has high bandwidth, improved single mode rate and anti-reflection characteristics; the light feedback structure below the first positive electrode facilitates cleaving and heat dissipation of the semiconductor laser; and the same active layer can simplify the epitaxial growth process, reduce the cost of the semiconductor laser, and improve the yield.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of semiconductor lasers, and more particularly, to a semiconductor laser and a preparation method. BACKGROUND

[0002] The main ways to improve the speed of semiconductor lasers include quantum well optimization, waveguide optimization, and application of effects such as optical-optical resonance or reduction of cavity length, but the condition for realizing optical-optical resonance requires the introduction of a suitable optical feedback structure.

[0003] Traditional optical feedback uses a passive waveguide or a passive grating as a feedback structure, although this structure can realize the enhancement of the bandwidth of the laser, but the existence of the feedback waveguide can reduce the single mode rate of the laser, thereby affecting the yield, and the passive waveguide or passive grating requires the introduction of a passive and active epitaxial butt joint growth process, which has high process complexity. Although reducing the cavity length can improve the bandwidth to a certain extent, but when the cavity length is too short, the bandwidth improvement is limited due to thermal effects, and even the bandwidth is deteriorated, and the shorter cavity length is also not conducive to the cleaving of the chip. SUMMARY

[0004] Therefore, the present disclosure provides a semiconductor laser and a preparation method.

[0005] One aspect of the present disclosure provides a semiconductor laser, comprising:

[0006] a substrate;

[0007] a negative electrode disposed on the bottom surface of the substrate;

[0008] an active layer disposed on the top surface of the substrate;

[0009] a grating layer and at least one waveguide layer, both disposed on the active layer;

[0010] a ridge waveguide disposed on the grating layer and the waveguide layer;

[0011] a first positive electrode and a second positive electrode, both disposed on the ridge waveguide, wherein the second positive electrode is located above the grating layer, and the second positive electrode is configured to apply alternating current for transmitting information and direct current for adjusting the working state of the semiconductor laser.

[0012] According to the embodiments of the present disclosure, the semiconductor laser further comprises:

[0013] two coating layers, respectively disposed on both sides of the semiconductor laser, wherein the first positive electrode is configured to apply an adjustment current to adjust the intensity and phase of the reflected light reflected by one of the coating layers.

[0014] According to an embodiment of the present disclosure, the two above-mentioned coating layers are an anti-reflection film and a high-reflection film respectively.

[0015] According to an embodiment of the present disclosure, an electrically isolated channel is arranged on the ridge waveguide between the first positive electrode and the second positive electrode, and the electrically isolated channel is used to reduce the leakage current.

[0016] According to an embodiment of the present disclosure, when the number of the waveguide layers is multiple, the grating layer is arranged between the multiple waveguide layers.

[0017] According to an embodiment of the present disclosure, the active region includes a multi-quantum well active region, and the multi-quantum well active region is used to provide optical gain.

[0018] According to an embodiment of the present disclosure, the active layer includes AlGaInAs or InGaAsP.

[0019] According to an embodiment of the present disclosure, the length of the second positive electrode is greater than the length of the grating layer.

[0020] Another aspect of the embodiment of the present disclosure provides a preparation method of a semiconductor laser, comprising:

[0021] The active layer and the waveguide layer are epitaxially grown on a first surface of a substrate in sequence, and a negative electrode is prepared on a second surface of the substrate;

[0022] The waveguide layer is etched to obtain a grating layer;

[0023] A ridge waveguide is epitaxially grown and etched on the surface of the grating layer and the waveguide layer;

[0024] A first positive electrode and a second positive electrode are prepared on both sides of a third surface of the ridge waveguide respectively to obtain the semiconductor laser, and the second positive electrode is located above the grating layer.

[0025] According to the embodiment of the present disclosure, by arranging a partial grating structure in the semiconductor laser, arranging a shorter second electrode length, and arranging a light feedback structure below the first electrode, the semiconductor laser has higher bandwidth, improved single mode rate, and anti-reflection characteristics; by arranging a waveguide feedback structure below the first electrode, the cavity length of the semiconductor laser is increased, thereby facilitating cleaving and heat dissipation of the semiconductor laser; using the same active layer can simplify the epitaxial growth process, reduce the cost of the semiconductor laser, and improve the yield. BRIEF DESCRIPTION OF DRAWINGS

[0026] The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments of the present disclosure taken in conjunction with the accompanying drawings, in which:

[0027] Figure 1 schematic cross-sectional view of a semiconductor laser according to an embodiment of the present disclosure is shown;

[0028] Figure 2 a top view of a semiconductor laser according to an embodiment of the present disclosure is shown;

[0029] Figure 3 a simulated small signal response curve of a semiconductor laser according to an embodiment of the present disclosure under different injection currents is shown;

[0030] Figure 4 a simulated spectrum of a semiconductor laser according to an embodiment of the present disclosure under different injection currents is shown;

[0031] Figure 5 a schematic cross-sectional view of a semiconductor laser according to another embodiment of the present disclosure is shown; and

[0032] Figure 6 a flow chart of a fabrication process of a semiconductor laser according to an embodiment of the present disclosure is shown.

[0033] In the above drawings, the meaning of the reference signs is as follows:

[0034] 100 - substrate; 200 - negative electrode; 300 - active layer; 400 - grating layer; 500 - waveguide layer; 600 - ridge waveguide; 610 - electrically isolated channel; 710 - first positive electrode; 720 - second positive electrode; 800 - coating layer. DETAILED DESCRIPTION

[0035] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood, however, that the description which follows is merely exemplary and is not intended to limit the scope of the present disclosure. In the following detailed description of the embodiments of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it would be apparent to one skilled in the art that the present disclosure can be practiced without these specific details. In other instances, well-known structures and functions have not been described in detail in order to avoid obscuring aspects of the present disclosure.

[0036] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the term "includes" and tautological expressions thereof, such as "including", "includes", "include", "including", etc., mean the term "comprises", "comprising", "comprises", "comprising", etc.

[0037] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0038] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0039] Figure 1 A schematic cross-sectional view of a semiconductor laser according to an embodiment of the present disclosure is shown.

[0040] Figure 2 A schematic top view of a semiconductor laser according to an embodiment of the present disclosure is shown.

[0041] like Figure 1 and Figure 2 As shown, the semiconductor laser includes a substrate 100, a negative electrode 200, an active layer 300, a grating layer 400, and at least one waveguide layer 500, a ridge waveguide 600, a first positive electrode 710, and a second positive electrode 720.

[0042] A negative electrode 200 is disposed on the bottom surface of the substrate 100; an active layer 300 is disposed on the top surface of the substrate 100; a grating layer 400 and at least one waveguide layer 500 are both disposed on the active layer 300; a ridge waveguide 600 is disposed on the grating layer 400 and the waveguide layer 500; a first positive electrode 710 and a second positive electrode 720 are both disposed on the ridge waveguide 600, wherein the second positive electrode 720 is located above the grating layer 400, and the second positive electrode 720 is configured to apply alternating current for transmitting information and direct current for adjusting the operating state of the semiconductor laser.

[0043] According to an embodiment of the present disclosure, an electrical isolation channel 610 is provided on the ridge waveguide 600 located between the first positive electrode 710 and the second positive electrode 720. The electrical isolation channel 610 is used to reduce leakage current.

[0044] According to embodiments of this disclosure, the grating layer 400 is partially distributed above the active layer 300, and its function is to provide wavelength selectivity. Alternating current for transmitting information and direct current required to provide optical gain enter the semiconductor laser through the second positive electrode 720, and the ridge waveguide 600 is used to confine the optical field.

[0045] According to an embodiment of the present disclosure, the active layer 300 located below the second electrode can be reduced to less than 200 um, which is beneficial to improve the response bandwidth, while the length of the whole laser can be greater than or equal to 250 um, which is conducive to heat dissipation and cleaving.

[0046] According to an embodiment of the present disclosure, the length of the second positive electrode 720 is 200 um, the length of the first positive electrode 710 is 40 um, the length of the electrically isolated channel 610 is 10 um, the thickness of the waveguide layer 500 is 1.8 um, the thickness of the whole semiconductor laser is 100 um, and the length of the grating layer 400 is 80 um.

[0047] Figure 3 The simulation small signal response curve of the semiconductor laser according to an embodiment of the present disclosure under different injection currents is schematically shown.

[0048] Figure 4 The simulation spectrum of the semiconductor laser according to an embodiment of the present disclosure under different injection currents is schematically shown.

[0049] According to an embodiment of the present disclosure, when the second positive electrode 720 is connected to a current of 60 mA, a high-frequency signal (i.e. alternating current for transmitting information) is injected into the semiconductor laser through the second positive electrode 720, and the first positive electrode 710 is connected to currents of 0 mA, 5 mA, 10 mA and 15 mA respectively, the simulation response curve of the semiconductor laser is as shown in Figure 3 , and the corresponding spectrum is as shown in Figure 4 It can be seen that the semiconductor laser with such a structure has excellent side mode suppression ratio and high response bandwidth, and since the total cavity length is 250 um, the cleaving is also easy to handle.

[0050] According to an embodiment of the present disclosure, by setting a partial grating structure in the semiconductor laser, setting a shorter second electrode length, and setting a light feedback structure located below the first electrode, the semiconductor laser has higher bandwidth, improved single mode rate and anti-reflection characteristics; by setting the waveguide feedback structure below the first electrode, the cavity length of the semiconductor laser is increased, which is conducive to the cleaving and heat dissipation of the semiconductor laser; the same active layer 300 can simplify the epitaxial growth process, reduce the cost of the semiconductor laser, and improve the yield.

[0051] According to an embodiment of the present disclosure, the semiconductor laser further comprises two coating layers 800.

[0052] The two coating layers 800 are respectively arranged on both sides of the semiconductor laser, and the first positive electrode 710 is configured to apply direct current to adjust the intensity and phase of the reflected light reflected by the coating layer 800 on the side of the first positive electrode 710.

[0053] According to an embodiment of the present disclosure, the two coating layers 800 are an antireflection coating and a high-reflection coating respectively.

[0054] According to an embodiment of the present disclosure, the first positive electrode 710 adjusts the intensity and phase of the reflected light on the high-reflection coating by injecting a suitable current.

[0055] Figure 5 A cross-sectional view of a semiconductor laser according to another embodiment of the present disclosure is schematically shown.

[0056] According to an embodiment of the present disclosure, as shown in Figure 5 In the case where the number of waveguide layers 500 is multiple, the grating layer 400 is located between the multiple waveguide layers 500.

[0057] According to an embodiment of the present disclosure, the active region comprises a multiple quantum well active region for providing optical gain.

[0058] According to an embodiment of the present disclosure, the active layer 300 comprises AlGaInAs or InGaAsP.

[0059] According to an embodiment of the present disclosure, the length of the second positive electrode 720 is greater than the length of the grating layer 400.

[0060] Figure 6 A flow chart of a preparation process of a semiconductor laser according to an embodiment of the present disclosure is schematically shown.

[0061] As shown in Figure 6 The preparation method of the semiconductor laser comprises operations S601-S604.

[0062] In operation S601, an active layer 300 and a waveguide layer 500 are epitaxially grown on a first surface of a substrate 100 in sequence, and a negative electrode 200 is prepared on a second surface of the substrate 100;

[0063] In operation S602, the waveguide layer 500 is etched to form a grating layer 400;

[0064] In operation S603, a ridge waveguide 600 is epitaxially grown and etched on the surface of the grating layer 400 and the waveguide layer 500;

[0065] In operation S604, a first positive electrode 710 and a second positive electrode 720 are prepared on both sides of a third surface of the ridge waveguide 600 respectively, to obtain a semiconductor laser, wherein the second positive electrode 720 is located above the grating layer 400.

[0066] According to the disclosed embodiment, by setting a partial grating structure in the semiconductor laser, setting a shorter second electrode length, and setting a light feedback structure under the first electrode, the semiconductor laser has higher bandwidth, improved single mode rate, and anti-reflection characteristics; by setting the waveguide feedback structure under the first electrode, the cavity length of the semiconductor laser is increased, thereby facilitating cleaving and heat dissipation of the semiconductor laser; the same active layer 300 is used to simplify the epitaxial growth process, reduce the cost of the semiconductor laser, and improve the yield.

[0067] According to the embodiment of the present disclosure, the preparation method of the semiconductor laser further includes the following operations:

[0068] etching the electrically isolated channel 610 on the third surface of the ridge waveguide 600 between the first positive electrode 710 and the second positive electrode 720;

[0069] preparing a film coating layer 800 on both sides of the semiconductor laser, wherein the two film coating layers 800 are respectively an anti-reflection film and a high-reflection film.

[0070] According to the embodiment of the present disclosure, the first surface can refer to the top surface of the substrate 100, and the second surface can refer to the bottom surface of the substrate 100. The third surface can refer to the top surface of the ridge waveguide 600.

[0071] The above only describes the preferred embodiments of the present disclosure and is not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A semiconductor laser, characterized in that, include: Substrate; The negative electrode is disposed on the bottom surface of the substrate; An active layer is disposed on the top surface of the substrate; A grating layer and at least one waveguide layer are both disposed on the active layer; A ridge waveguide is disposed on the grating layer and the waveguide layer; Both the first positive electrode and the second positive electrode are disposed on the ridge waveguide, wherein only the second positive electrode is located above the grating layer. The second positive electrode is configured to apply alternating current for transmitting information and direct current for adjusting the operating state of the semiconductor laser. The length of the second positive electrode is greater than the length of the grating layer.

2. The semiconductor laser according to claim 1, characterized in that, Also includes: Two coating layers are respectively disposed on both sides of the semiconductor laser, wherein the first positive electrode is configured to apply an adjustment current to adjust the intensity and phase of the reflected light reflected by one of the coating layers.

3. The semiconductor laser according to claim 2, characterized in that, The two coating layers are an antireflection coating and a high reflectivity coating, respectively.

4. The semiconductor laser according to claim 3, characterized in that, An electrically isolated channel is provided on the ridge waveguide located between the first positive electrode and the second positive electrode, the electrically isolated channel being used to reduce leakage current.

5. The semiconductor laser according to claim 1, characterized in that, When there are multiple waveguide layers, the grating layer is located between the multiple waveguide layers.

6. The semiconductor laser according to claim 1, characterized in that, The active layer includes a multi-quantum-well active region, which is used to provide optical gain.

7. The semiconductor laser according to claim 1, characterized in that, The active layer includes AlGaInAs or InGaAsP.

8. A method for fabricating a semiconductor laser, characterized in that, include: An active layer and a waveguide layer are epitaxially grown sequentially on the first surface of the substrate, and a negative electrode is fabricated on the second surface of the substrate. The waveguide layer is etched with a grating to obtain the grating layer; Ridge waveguides are epitaxially grown and etched on the surfaces of the grating layer and the waveguide layer; A first positive electrode and a second positive electrode are respectively fabricated on both sides of the third surface of the ridge waveguide to obtain the semiconductor laser, wherein the second positive electrode is located above the grating layer, the length of the second positive electrode is greater than the length of the grating layer, and only the second positive electrode is located above the grating layer.

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