Vertical Cavity Surface Emitting Semiconductor Laser with Meander-Shaped Resonant Cavity

Abstract

The present invention relates to the field of semiconductor laser technology, and in particular to a vertical cavity surface emitting semiconductor laser of a meander-shaped resonant cavity, comprising a bottom VCSEL structure and two side VCSEL structures with the same structure, insulating layers are arranged on both sides of the bottom VCSEL structure, the two side VCSEL structures are respectively bonded and fixed to the insulating layers on both sides of the bottom VCSEL structure, the placement direction of the two side VCSEL structures is perpendicular to the placement direction of the bottom VCSEL structure, a transparent substrate is arranged at one end of the two side VCSEL structures, a top DBR structure is arranged on the transparent substrate, and the top DBR structure, the bottom VCSEL structure and the two side VCSEL structures form a meander-shaped resonant cavity. The present invention can achieve high-power fundamental transverse mode output.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor lasers, and in particular relates to a vertical cavity surface emitting semiconductor laser with a meander-shaped resonant cavity. Background Art

[0002] Semiconductor lasers have become a research hotspot in the field of optoelectronic technology due to their advantages of high photoelectric conversion efficiency, small size, light weight, and low cost. Vertical-Cavity Surface-Emitting Laser (VCSEL) in semiconductor lasers has been widely used in optical communications, laser printing, laser mouse, medical cosmetology, atomic clock light sources and other fields due to its advantages of low loss and good single longitudinal mode characteristics. With the popularization of smart devices and the rapid development of fields such as communications, higher demands have been put forward for VCSELs, and improving the fundamental mode output power of VCSELs has become a research hotspot. The commonly used method at present is usually to increase the oxidation restriction structure. When the oxidation aperture is less than 3μm, the laser mode output by the VCSEL is the fundamental transverse mode, but it will limit the output power of the VCSEL. How VCSEL can achieve high-power stable output of the fundamental transverse mode under the oxidation aperture is a technical problem that needs to be solved urgently in the industry.

[0003] In order to solve the above problems, complex mode filtering structures such as photonic crystal structures are usually integrated on the surface of VCSEL to achieve high-order mode filtering. The photon localization characteristics of photonic crystals are used to etch photonic crystal structures on the surface of the upper DBR (Distributed Bragg Reflector). The refractive index difference between the photonic crystal pattern and the defect area is used to confine the light to the defect area of ​​the photonic crystal, change the lateral mode distribution in the cavity, and achieve fundamental lateral mode output under large oxidation aperture. However, the etching difficulty of this photonic crystal structure is high and the preparation process is complex. Summary of the invention

[0004] In view of this, the present invention aims to provide a vertical cavity surface emitting semiconductor laser with a meander-shaped resonant cavity. By adopting a meander-shaped structure, the light beam can oscillate multiple times in the meander-shaped cavity, thereby achieving stable output of a high-power fundamental transverse mode.

[0005] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0006] A vertical cavity surface emitting semiconductor laser of a meander-shaped resonant cavity comprises a bottom VCSEL structure and two side VCSEL structures with the same structure, wherein the two side VCSEL structures are arranged at both sides of the bottom VCSEL structure, and the light emitting directions of the two side VCSEL structures are perpendicular to the light emitting direction of the bottom VCSEL structure, a transparent substrate is arranged at one end of the two side VCSEL structures, a top DBR structure is arranged on the transparent substrate, and the top DBR structure, the bottom VCSEL structure and the two side VCSEL structures form a meander-shaped resonant cavity.

[0007] Furthermore, a surface microstructure is provided on the top DBR structure.

[0008] Furthermore, the surface microstructure is any one of a surface relief, an inverted surface relief, a surface grating, and a microlens.

[0009] Furthermore, the side VCSEL structure includes a side substrate, a side N-type electrode is arranged on the back side of the side substrate, and a side N-type DBR layer and a side active layer are arranged in sequence on the front side of the side substrate.

[0010] Furthermore, a current diffusion layer is arranged on the side active layer.

[0011] Furthermore, the bottom VCSEL structure includes a bottom substrate, a bottom N-type electrode is arranged on the back side of the bottom substrate, and a bottom N-type DBR layer, a bottom active layer, a bottom oxide layer, a bottom P-type DBR layer and a bottom P-type electrode are arranged in sequence on the front side of the bottom substrate.

[0012] Furthermore, insulating layers are provided on both sides of the bottom VCSEL structure to achieve insulation between the bottom N-type electrode and the bottom P-type electrode, and the bottom P-type electrode is in contact with the current diffusion layer.

[0013] Compared with the prior art, the invention can achieve the following beneficial effects:

[0014] 1. Based on the traditional VCSEL structure, the present invention adds half-VCSEL structures on the left and right sides to form a toroidal resonant cavity. The top DBR structure increases the cavity length of the resonant cavity, which can narrow the line width of the output laser and realize fundamental transverse mode output. At the same time, the laser oscillates multiple times in the resonant cavity, which can optimize the mode characteristics of the high-order mode, thereby realizing high-power fundamental transverse mode output.

[0015] 2. The surface microstructure can further increase the loss of high-order modes and further improve the single-mode characteristics of VCSEL. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0017] Figure 1 It is a schematic structural diagram of a vertical cavity surface emitting semiconductor laser with a meander-shaped resonant cavity according to an embodiment of the invention.

[0018] Explanation of the reference numerals: bottom VCSEL structure 10, bottom substrate 100, bottom N-type DBR layer 101, bottom active layer 102, bottom oxide layer 103, bottom P-type DBR layer 104, oxide holes 105, bottom P-type electrode 106, bottom N-type electrode 107, side VCSEL structure 20, side substrate 200, side N-type DBR layer 201, side active layer 202, side N-type electrode 203, current diffusion layer 204, insulating layer 30, transparent substrate 40, top DBR structure 50, surface microstructure 60. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the invention more clear, the invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the invention and do not constitute a limitation of the invention.

[0020] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0021] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0022] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0023] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0024] like Figure 1 As shown, the vertical cavity surface emitting semiconductor laser of the meander-shaped resonant cavity provided by the embodiment of the present invention comprises a bottom VCSEL structure 10 and two side VCSEL structures 20 with the same structure, the two side VCSEL structures 20 with the same structure are respectively arranged on both sides of the bottom VCSEL structure 10, the light emitting directions of the two side VCSEL structures 20 are perpendicular to the light emitting direction of the bottom VCSEL structure 10, a transparent substrate 40 is arranged at one end of the two side VCSEL structures 10, the transparent substrate 40 and the bottom VCSEL structure 10 are distributed at both ends of the side VCSEL structure 20, a top DBR structure 50 is arranged on the transparent substrate 40, and the top DBR structure 50, the bottom VCSEL structure 10 and the two side VCSEL structures 20 form a meander-shaped resonant cavity.

[0025] The material system of the bottom VCSEL structure 10 includes but is not limited to SiC, AlN, GaN, etc. The bottom VCSEL structure 10 includes a bottom substrate 100, on which an epitaxial structure is grown, the epitaxial structure including a bottom N-type DBR layer 101, a bottom active layer 102, a bottom oxide layer 103, and a bottom P-type DBR layer 104. Specifically, a metal-organic chemical vapor deposition process is used. Deposition, MOCVD) alternately grows N-doped AlGaAs with different components to form a bottom N-type DBR layer 101, grows quantum well material on the bottom N-type DBR layer 101 to form a bottom active layer 102, grows a layer of AlAs material on the bottom active layer 102 to form a bottom oxide layer 103, then alternately grows P-doped AlGaAs on the bottom oxide layer 103 to form a bottom P-type DBR layer 104, etches the epitaxial structure to form a mesa, and performs side oxidation on the bottom oxide layer 103 to form an oxide hole 105, performs photolithography on the surface of the epitaxial structure to form a central light-emitting hole, then evaporates metal around the central light-emitting hole to form a bottom P-type electrode 106, and finally thins and polishes the bottom surface of the bottom substrate 100, and deposits metal to form a bottom N-type electrode 107.

[0026] The side VCSEL structure 20 includes a side substrate 200, a side N-type DBR layer 201 is grown on the side substrate 200, a quantum well material is grown on the side N-type DBR layer 201 to form a side active layer 202, and a metal-shaped side N-type electrode 203 is deposited after the bottom surface of the side substrate 200 is thinned and polished. The side active layers 202 of the two side VCSEL structures 20 face each other, and the side N-type electrodes 203 of the two side VCSEL structures 20 face away from each other.

[0027] The bottom P-type electrode 106 of the bottom VCSEL structure 10 is also in contact with the side active layer 202. When the bottom P-type electrode 106 is deposited, it is directly deposited between the side active layer 202 and the bottom P-type electrode 106 to serve as the P-type electrode of the side VCSEL structure 20, that is, the bottom VCSEL structure 10 and the side VCSEL structure 20 share a common P-type electrode.

[0028] In order to prevent the bottom P-type electrode 106 from directly contacting the bottom N-type electrode 107 , an insulating layer 30 is disposed between the bottom P-type electrode 106 and the bottom N-type electrode 107 to achieve insulation between the bottom P-type electrode 106 and the bottom N-type electrode 107 .

[0029] In order to ensure uniform current distribution in the side active layer 202 , a current diffusion layer 204 is grown on the side active layer 202 . At this time, the bottom P-type electrode 106 is deposited between the current diffusion layer 204 and the table of the bottom VCSEL structure 10 , and the bottom P-type electrode 106 wraps the insulating layer 30 .

[0030] By adjusting the thickness of the insulating layer 30 , the distance between the side N-type DBR layers 201 of the two side VCSEL structures 20 is changed, and a reasonable design is performed according to the emission wavelength of the VCSEL.

[0031] The bottom N-type DBR layer 101 of the bottom VCSEL structure 10, the top DBR structure 50 and the side N-type DBR layers 201 of the two side VCSEL structures 20 form a meandering resonant cavity. The light beams emitted by the two side VCSEL structures 20 and the light beam emitted by the bottom VCSEL structure oscillate together in the meandering cavity. The light beams emitted by the two half VCSEL structures 20 ultimately increase the output power of the VCSEL.

[0032] The light beam oscillates in the meander cavity, increasing the optical path of the light beam. The light beam with a large divergence angle is reflected multiple times between the bottom N-type DBR layer 101, the top DBR structure 50 and the side N-type DBR layer 201 of the two side VCSEL structures 20, extending the propagation distance of the light beam in the meander cavity. During the multiple reflections, the divergence degree of the light beam gradually decreases, thereby reducing the divergence angle of the output light beam. Due to its complex light field distribution, the high-order mode will suffer greater losses during the reflection process between the bottom N-type DBR layer 101, the top DBR structure 50 and the side N-type DBR layer 201 of the two side VCSEL structures 20, and thus be suppressed. Through multiple oscillations and filtering of high-order modes, more photons can be effectively confined in the meander cavity and participate in the stimulated radiation process, which increases the opportunity for photons to interact with the gain medium, thereby increasing the output power of the VCSEL.

[0033] Since the arrangement of the meander-shaped resonant cavity can achieve high-power fundamental transverse mode output, the size of the oxidation hole 105 of the bottom VCSEL structure 10 can be increased, thereby further improving the output power of the VCSEL.

[0034] In order to further filter out high-order modes, a surface microstructure 60 is provided on the top DBR structure 50. The surface microstructure 60 includes but is not limited to surface relief (protruding from the surface of the top DBR structure 50), inverted surface relief (recessed in the surface of the top DBR structure 50), surface grating, microlens and other structures, which are used to lose high-order modes and further improve the single-mode characteristics of the VCSEL.

[0035] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the disclosure of the present invention can be performed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.

[0036] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A vertical cavity surface emitting semiconductor laser with a meander-shaped resonant cavity, characterized in that: It includes a bottom VCSEL structure and two side VCSEL structures with the same structure. The two side VCSEL structures are arranged on both sides of the bottom VCSEL structure. The light emitting directions of the two side VCSEL structures are perpendicular to the light emitting direction of the bottom VCSEL structure. A transparent substrate is arranged at one end of the two side VCSEL structures, and a top DBR structure is arranged on the transparent substrate. The top DBR structure, the bottom VCSEL structure and the two side VCSEL structures form a meandering resonant cavity.

2. The vertical cavity surface emitting semiconductor laser with a meander-shaped resonant cavity according to claim 1, characterized in that: A surface microstructure is provided on the top DBR structure.

3. The vertical cavity surface emitting semiconductor laser with a meander-shaped resonant cavity according to claim 2, characterized in that: The surface microstructure is any one of a surface relief protruding from the surface of the top DBR structure, an inverted surface relief recessed in the surface of the top DBR structure, a surface grating, and a microlens.

4. The vertical cavity surface emitting semiconductor laser with a meander-shaped resonant cavity according to claim 1, characterized in that: The side VCSEL structure includes a side substrate, a side N-type electrode is arranged on the back side of the side substrate, and a side N-type DBR layer and a side active layer are arranged in sequence on the front side of the side substrate.

5. The vertical cavity surface emitting semiconductor laser with a meander-shaped resonant cavity according to claim 4, characterized in that: A current spreading layer is disposed on the side active layer.

6. The vertical cavity surface emitting semiconductor laser with a meander-shaped resonant cavity according to claim 5, characterized in that: The bottom VCSEL structure includes a bottom substrate, a bottom N-type electrode is arranged on the back side of the bottom substrate, and a bottom N-type DBR layer, a bottom active layer, a bottom oxide layer, a bottom P-type DBR layer and a bottom P-type electrode are arranged in sequence on the front side of the bottom substrate.

7. The vertical cavity surface emitting semiconductor laser with a meander-shaped resonant cavity according to claim 6, characterized in that: Insulating layers are arranged on both sides of the bottom VCSEL structure to achieve insulation between the bottom N-type electrode and the bottom P-type electrode, and the bottom P-type electrode is in contact with the current diffusion layer.

Images