Semiconductor laser based on periodic surface microstructure
By etching periodic surface microstructures on the ridge waveguide surface of a semiconductor laser, the problems of beam quality and spectral brightness difference were solved, and a semiconductor laser with high power, high beam quality and high spectral brightness was realized.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHANGCHUN INST OF OPTICS FINE MECHANICS & PHYSICS CHINESE ACAD OF SCI
- Filing Date
- 2024-10-18
- Publication Date
- 2026-04-21
AI Technical Summary
Existing semiconductor lasers suffer from poor beam quality due to the influence of the gain region area on output power, making them unsuitable for wavelength-sensitive applications and resulting in poor spectral width.
Periodic surface microstructures are etched on the surface of the ridge waveguide. The transverse and longitudinal modes of the device are selected by the periodic surface microstructures, forming alternating or concentrated microstructure regions and no microstructure regions, thereby controlling carrier injection and mode distribution.
It improves the beam quality and spectral brightness of semiconductor lasers, enhances single-mode characteristics, improves heat dissipation characteristics, and achieves high power output.
Smart Images
Figure CN121906231A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor optoelectronic device technology and relates to a semiconductor laser based on a periodic surface microstructure. Background Technology
[0002] Semiconductor lasers offer advantages such as small size, light weight, high energy conversion efficiency, long lifespan, and high reliability, making them widely used in displays, communications, sensing, pumping, medical, and military fields. However, due to the structural characteristics of semiconductor lasers, the area of their gain region affects the output power of the device. Increasing the width of the laser's ridge waveguide generates higher-order modes, and with increasing injection current, the number of higher-order modes also increases. This leads to rapid deterioration of the device's far-field (Far-Field Bloom-FFB effect). Furthermore, widening the mesa enhances the lateral carrier accumulation effect (Lateral Carrier Accumulation-LCA), ultimately resulting in poor beam quality and consequently, reduced brightness, significantly limiting the application prospects of semiconductor lasers. Additionally, the spectral width of wide-area devices is typically several to tens of nanometers, and the poor spectral brightness prevents their application in wavelength-sensitive fields such as communications and sensing. Currently, semiconductor lasers combining high power, high beam quality, and high spectral brightness are a key focus of industry research. Summary of the Invention
[0003] In view of this, the object of the present invention is to provide a novel semiconductor laser based on periodic surface microstructures. The semiconductor laser of the present invention achieves high power, high beam quality, and high spectral brightness by etching periodic surface microstructures on the surface of a ridge waveguide, thereby simultaneously selecting the transverse and longitudinal modes of the device through the periodic surface microstructures.
[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:
[0005] A semiconductor laser based on a periodic surface microstructure includes a chip structure;
[0006] The chip structure, from bottom to top, includes: a substrate, a buffer layer, an N-type cladding, an N-type waveguide, an active region, a P-type waveguide, a P-type cladding, and a P-type capping layer; wherein, the N-type waveguide, the active region, and the P-type waveguide constitute the optical confinement layer of the laser, and the refractive index of the optical confinement layer is greater than the refractive index of the N-type cladding and the P-type cladding;
[0007] Its features are,
[0008] The chip structure is formed by etching multiple ridge waveguides downward on the P-type capping layer, with etched trenches on both sides of each ridge waveguide; periodic microstructures are etched on the surface of the ridge waveguides, the etched microstructures are called microstructure regions, and the unetched microstructures are called microstructure-free regions.
[0009] The ridge waveguide, microstructure, etched trenches, and non-injection region constitute the surface waveguide region;
[0010] The chip structure has an N-side electrode on the underside of the substrate, and an insulating layer and a P-side electrode are sequentially disposed on the P-type capping layer.
[0011] In the above technical solution, the size of each basic unit of the periodic microstructure is such that the length of the major axis does not exceed one-quarter of the width of the ridge waveguide, and the length of the minor axis is not less than 1 μm.
[0012] In the above technical solution, the periodic surface microstructures are arranged periodically along a direction parallel to the ridge waveguide, and the period is: Λ=mλ / 2n eff Where m is a positive integer and n eff λ is the equivalent refractive index of the device, and λ is the target wavelength.
[0013] In the above technical solution, no insulating layer is provided on the microstructure region.
[0014] In the above technical solution, the two types of regions, namely the microstructure region and the non-microstructure region, are arranged alternately or concentratedly; the total proportion of the microstructure region is 20%-100%, and the proportion of the non-microstructure region is 0%-80%; the graphic part in the microstructure region is concentrated on both sides of the ridge waveguide, accounting for 30%-70% of the width of the ridge waveguide.
[0015] In the above technical solution, the etching depth H of the periodic surface microstructure ranges from the P-type cladding to the N-type cladding, and the microstructure etching duty cycle is 5% to 50%.
[0016] In the above technical solution, the end face width of the ridge waveguide is 10-400μm and the length is 200-6000μm; the spacing between each unit device is 200-1000μm, and the end face width of the ridge waveguide is smaller than the spacing between the unit devices.
[0017] In the above technical solution, the width of the etched trench is less than half the difference between the unit device spacing and the ridge waveguide width, and the length is the same as that of the ridge waveguide.
[0018] In the above technical solution, the non-injection region is located outside the etching trench, its width is less than half the difference between the unit device spacing and the ridge waveguide width, and its length is the same as that of the ridge waveguide.
[0019] In the above technical solutions, the gain medium of the active region is any one or a combination of multiple quantum wells, quantum dots, quantum bands, quantum cascades, and interband cascade structures, either singly or in complexly.
[0020] The beneficial effects of this invention are:
[0021] The semiconductor laser based on periodic surface microstructures of this invention, through etching periodic surface microstructures on the ridge waveguide surface, effectively suppresses higher-order lateral modes, alters the mode distribution within the device cavity, and controls carrier injection, weakening the lateral carrier accumulation effect, thus improving the beam quality. Simultaneously, due to their periodic distribution along the longitudinal direction of the device, they selectively target specific longitudinal modes within the cavity, significantly improving the single-mode characteristics, narrowing the spectral range, increasing the side-mode suppression ratio, and thereby enhancing the spectral brightness. The etched microstructures provide a larger heat dissipation area, shorten the heat dissipation distance from the active region to the surface, and allow for temperature distribution control by adjusting the distribution of the microstructures and the etching depth, ultimately improving heat dissipation characteristics.
[0022] The semiconductor laser based on periodic surface microstructures of the present invention selects both transverse and longitudinal modes of the device simultaneously through periodic surface microstructures, thereby realizing a semiconductor laser with high power, high beam quality, and high spectral brightness. Attached Figure Description
[0023] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of specific embodiments or examples will be briefly introduced below. Obviously, the accompanying drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0024] Figure 1 This is a schematic diagram of the cross-sectional structure of the semiconductor laser of the present invention.
[0025] Figure 2 This is a schematic diagram of the surface waveguide region of the semiconductor laser of the present invention.
[0026] Figure 3 This is a schematic diagram of the constituent units of the periodic microstructure of the semiconductor laser of the present invention.
[0027] Figure 4 This is a schematic diagram illustrating the composition of the periodic microstructure of the semiconductor laser of the present invention.
[0028] Figure 5 This is a cross-sectional view of the periodic microstructure of the semiconductor laser of the present invention.
[0029] Figure 6 This is a schematic diagram of the chip structure of a semiconductor laser according to a first embodiment of the present invention.
[0030] Figure 7 This is a schematic diagram of the chip structure of a second embodiment of the semiconductor laser of the present invention.
[0031] Figure 8 This is a schematic diagram of the chip structure of the semiconductor laser of the present invention, embodiment three.
[0032] The reference numerals in the figure are:
[0033] 101-Substrate, 102-Buffer layer, 103-N-type cladding, 104-N-type waveguide, 105-Active region, 106-P-type waveguide, 107-P-type cladding, 202-Insulating layer, 108-P-type capping layer;
[0034] 201-Microstructure, 202-Insulating layer, 203-N-surface electrode, 204-P-surface electrode, 205-Ridge waveguide, 206-Etched trench, 207-Non-injection region;
[0035] 301 - Optical confinement layer, 302 - Surface waveguide region, 303 - Microstructure region, 304 - Region without microstructure. Detailed Implementation
[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0037] like Figure 1 and Figure 2As shown, the semiconductor laser based on a periodic surface microstructure of the present invention comprises, from bottom to top, an N-type electrode 203, a substrate 101, a buffer layer 102, an N-type cladding 103, an N-type waveguide 104, an active region 105, a P-type waveguide 106, a P-type cladding 107, a P-type capping layer 108, an insulating layer 202, and a P-type electrode 204. The substrate 101 is a III-V group compound, such as GaAs, InP, GaSb, or GaN, etc., including but not limited to these materials, typically N-type doped, but in some cases, P-type doped. The buffer layer 102 is made of the same material as the substrate 101 and is used to bury defects in the substrate 101 itself. The N-type waveguide 104, the active region 105, and the P-type waveguide 106 constitute the optical confinement layer 301 of the laser. The active region 105 is located between the N-type waveguide 104 and the P-type waveguide 106. The active region 105 can be a single-layer or multi-layer quantum well, quantum dot, quantum cascade, interband cascade, or a combination of the above structures, serving as the gain region of the laser. The optical confinement layer 301 is flanked by an N-type cladding 103 and a P-type cladding 107, respectively. The refractive index of the optical confinement layer 301 is usually greater than that of the N-type cladding 103 and the P-type cladding 107, thus forming a total internal reflection waveguide. The optical modes propagating in the laser resonant cavity are confined within the optical confinement layer 301. However, due to the evanescent wave effect, some light will still propagate in the N-type cladding 103 and the P-type cladding 107. Therefore, by controlling some characteristics of the N-type cladding 103 and the P-type cladding 107, the optical field characteristics propagating in the optical confinement layer 301 can be affected. A P-type capping layer 108 is grown on top of a P-type cladding layer 107 and is heavily doped to facilitate ohmic contact. A P-side electrode 204 is deposited on the top surface of the P-type capping layer 108, and an N-side electrode 203 is deposited on the bottom surface of the substrate 101. Both serve as electrodes for current injection in the laser.
[0038] The semiconductor laser based on periodic surface microstructures of the present invention has multiple ridge waveguides 205 formed by etching downwards on a P-type capping layer 108, each ridge waveguide 205 having etched trenches 206 on both sides; periodic microstructures 201 are etched on the surface of the ridge waveguides 205, the etched area of the microstructures 201 is the microstructure region 303, and the unetched area of the microstructures 201 is the non-microstructure region 304; the ridge waveguides 205, microstructures 201, etched trenches 206 and non-injection region 207 constitute the surface waveguide region 302.
[0039] In this invention, the periodic surface microstructure 201 has two composition forms. One type of structure is an arbitrary pattern, where the size of each basic unit is such that the major axis length does not exceed one-quarter of the width of the ridge waveguide 205, and the minor axis length is not less than 1 μm. The second type of structure is a combination of a trench of the same width as the ridge waveguide 205 and the first type of structure (see [link]). Figure 3 and 4 ).
[0040] In this invention, the periodic surface microstructures 201 are arranged periodically along a direction parallel to the ridge waveguide 205, and their period is: Λ=mλ / 2n eff Where m is a positive integer and n eff λ is the equivalent refractive index of the device, and λ is the target wavelength (see [reference]). Figure 5 ).
[0041] In this invention, the arrangement of the periodic surface microstructures 201 along the parallel direction of the ridge waveguide 205 can be a single type of structure, or a combination of type one and type two structures as described above.
[0042] In this invention, periodic surface microstructures 201 form microstructure regions 303 and non-microstructure regions 304 on the ridge waveguide 205. These two types of regions can be arranged alternately or concentrated in one area. The total proportion of microstructure regions 303 is 20%-100%, and the corresponding proportion of non-microstructure regions 304 is 0%-80%. The patterned portions of the microstructure regions 303 are concentrated on both sides of the ridge waveguide 205, occupying 30%-70% of the width of the ridge waveguide 205.
[0043] In this invention, the periodic surface microstructure 201 has an etching depth H ranging from the bottom of the P-type cladding 107 to the N-type cladding 103. The etching duty cycle of the microstructure 201 is 5% to 50% (see [reference]). Figure 5 ).
[0044] In this invention, the ridge waveguide 205 has a strip width of 10-400 μm (referring to the end face width) and a length of 200-6000 μm. The spacing between each unit device is 200-1000 μm, and the strip width of the ridge waveguide 205 is smaller than the spacing between the unit devices.
[0045] In this invention, the etched trench 206 is located on both sides of the ridge waveguide 205, separating the ridge waveguide 205 from the non-injection region 207. Its width is less than half the difference between the unit device spacing and the width of the ridge waveguide 205, and its length is equivalent to that of the ridge waveguide 205.
[0046] In this invention, the non-injection region 207 is located outside the etched trench 206 and its width is less than half the difference between the unit device spacing and the width of the ridge waveguide 205, and its length is equivalent to that of the ridge waveguide 205.
[0047] In this invention, the gain medium in the gain material region, i.e. the active region 105, in the vertical z-direction can be a single or multiple quantum wells, quantum dots, quantum bands, quantum cascades, interband cascade structures, or any combination of any number of types.
[0048] The semiconductor laser based on periodic surface microstructures of the present invention has the following general fabrication steps:
[0049] Step 1: On substrate 101, a buffer layer 102, an N-type cladding layer 103, an N-type waveguide 104, an active region 105, a P-type waveguide 106, a P-type cladding layer 107, and a P-type capping layer 108 are grown sequentially using molecular beam epitaxy (MBE) or metal-organic chemical vapor deposition (MOCVD) techniques to obtain the chip structure.
[0050] Step two: Photoresist is uniformly coated onto the P-type capping layer 108. Using an optical mask, a ridge waveguide 205 and a periodic surface microstructure 201 are fabricated on the chip structure using ultraviolet exposure and etching techniques. The ridge waveguide 205 and the periodic surface microstructure 201 can be etched simultaneously, or they can be fabricated in two separate steps depending on the situation. (In some cases, the periodic surface microstructure 201 can also be fabricated using electron beam lithography or nanoimprint lithography.)
[0051] Step 3: An insulating layer 202 is grown on the P-type capping layer 8. Ohmic contact areas are etched on the surface of the ridge waveguide 205 using optical masks, ultraviolet exposure, and dry / wet etching techniques.
[0052] The microstructure region 303 can be configured to retain the insulating layer 202, and the ohmic contact area within the region can be of any shape or a combination of shapes.
[0053] Step four: After depositing a layer of P-type ohmic contact metal, namely P-side electrode 204, using a metal growth device, the P-side electrode 204 is rapidly annealed to improve the device conductivity.
[0054] Step 5: Thin and polish the substrate 101. After completion, clean the chip and grow N-side electrode 203 on the polished surface of the substrate 101 (that is, the bottom surface of the substrate 101).
[0055] Step six: Disassemble the device, coat it with a film, and encapsulate it.
[0056] The semiconductor laser of the present invention is characterized by a periodic surface microstructure, which simultaneously selects the transverse and longitudinal modes of the device, thereby realizing a semiconductor laser with high power, high beam quality, and high spectral brightness.
[0057] Example 1
[0058] See Figure 6 This embodiment is a GaAs-based high-power near-infrared semiconductor laser. The device structure and manufacturing steps are as follows:
[0059] Step 1: On a GaAs substrate 101, a GaAs buffer layer 102 with a thickness of 300-1000 nm, an AlGaAs N-type cladding layer 103 with a thickness of 1-5 μm, an AlGaAs N-type waveguide 104 with a thickness of 200-1000 nm, an InGaAs active region 105 with a PL range of 700-1100 nm, an AlGaAs P-type waveguide 106 with a thickness of 200-1000 nm, an AlGaAs P-type cladding layer 107 with a thickness of 1-5 μm, and a GaAs P-type capping layer 108 with a thickness of 200-300 nm are grown sequentially to obtain a chip structure.
[0060] Step two: Photoresist is uniformly coated on the P-type capping layer 108. Using an optical mask, a ridge waveguide 205 and a periodic surface microstructure 201 are fabricated on the chip structure using ultraviolet exposure and etching techniques. The ridge waveguide 205 and the periodic surface microstructure 201 can be etched simultaneously, or they can be fabricated in two separate steps depending on the situation. (In some cases, the periodic surface microstructure 201 can also be fabricated using electron beam lithography or nanoimprinting). The periodic microstructure 201 is etched onto the surface of the ridge waveguide 205. The etched area of the microstructure 201 is the microstructure region 303, and the unetched area of the microstructure 201 is the non-microstructure region 304. The two sides of the laser are non-injection regions 207. The ridge waveguide 205, microstructure 201, etched trenches 206, and non-injection regions 207 constitute the surface waveguide region 302.
[0061] The ridge waveguide 205 has a width of 10-400 micrometers, the individual etched trench 206 has a width of 5-150 micrometers, the individual non-injection region 207 has a width of 0-240 micrometers, and the unit device spacing is 250-500 micrometers. The width of each region is dynamically adjusted according to the unit device spacing to maintain a consistent width. Figure 2 The distribution relationship is shown. The etching depth of the trenches 206 and microstructures 201 stops at 200-500 nm from the P-type waveguide 106. The microstructures 201 are periodically distributed on the ridge waveguide 205 of the device, and their period is:
[0062] Λ=mλ / 2n eff
[0063] Where, n eff λ is the equivalent refractive index of the device, λ is the target wavelength, and m is a positive integer.
[0064] The periodic surface microstructure 201 has two composition forms. One type is an arbitrary pattern, where each basic unit has a major axis length not exceeding one-quarter of the width of the ridge waveguide 205 and a minor axis length not less than 1 μm. The second type is a combination of a trench of the same width as the ridge waveguide 205 and the first type of structure (see [link]). Figure 3 and 4The periodic surface microstructures 201 arranged along the parallel direction of the ridge waveguide 205 can be a single type I structure, or a combination of type I and type II structures as described above. The microstructure region 303 and the unstructured region 304 can be arranged alternately or concentratedly, with the total proportion of the microstructure region 303 being 20%-100%, and the corresponding proportion of the unstructured region 304 being 0%-80%. The patterned portions of the microstructure region 303 are concentrated on both sides of the ridge waveguide 205, occupying 30%-70% of the width of the ridge waveguide 205. The etching duty cycle of the microstructure 201 is 5% to 50%.
[0065] Step 3: An insulating layer 202 is grown on the P-type capping layer 8. Ohmic contact areas are etched on the surface of the ridge waveguide 205 using optical masks, ultraviolet exposure, and dry / wet etching techniques.
[0066] The microstructure region 303 can be configured to retain the insulating layer 202, and the ohmic contact area within the region can be of any shape or a combination of shapes.
[0067] Step four: After depositing a layer of P-type ohmic contact metal, namely P-side electrode 204, using a metal growth device, the P-side electrode 204 is rapidly annealed to improve the device conductivity.
[0068] Step 5: Thin and polish the substrate 101. After completion, clean the chip and grow N-side electrode 203 on the polished surface of the substrate 101 (that is, the bottom surface of the substrate 101).
[0069] Step six: Disassemble the device, coat it with a film, and encapsulate it.
[0070] The insulating layer 202 is usually SiO2 or Si3N4 with a thickness of 150-300nm; the P-side electrode 204 is usually Ti-Pt-Au with a thickness of 200-300nm; and the N-side electrode 203 is usually AuGe-Ni-Au with a thickness of 200-300nm.
[0071] Example 2
[0072] See Figure 7 This embodiment is an InP-based near-infrared semiconductor laser, and the device structure and manufacturing steps are as follows:
[0073] Step 1: On an InP substrate 101, sequentially grow an InP buffer layer 102 with a thickness of 300-1000 nm, an InP N-type cladding layer 103 with a thickness of 0-5 μm, an AlGaInAs / AlInAs N-type waveguide 104 with a thickness of 50-300 nm, an active region 105 of InGaAsP / AlGaInAs material with a PL range of 1250-1700 nm, an AlGaInAs / AlInAs P-type waveguide 106 with a thickness of 50-300 nm, an InP P-type cladding layer 107 with a thickness of 1-5 μm, and an InGaAs / InGaAsP P-type capping layer 108 with a thickness of 200-300 nm to obtain the chip structure.
[0074] Step two: Photoresist is uniformly coated on the P-type capping layer 108. Using an optical mask, a ridge waveguide 205 and a periodic surface microstructure 201 are fabricated on the chip structure using ultraviolet exposure and etching techniques. The ridge waveguide 205 and the periodic surface microstructure 201 can be etched simultaneously, or they can be fabricated in two separate steps depending on the situation. (In some cases, the periodic surface microstructure 201 can also be fabricated using electron beam lithography or nanoimprinting). The periodic microstructure 201 is etched onto the surface of the ridge waveguide 205. The etched area of the microstructure 201 is the microstructure region 303, and the unetched area of the microstructure 201 is the non-microstructure region 304. The two sides of the laser are non-injection regions 207. The ridge waveguide 205, microstructure 201, etched trenches 206, and non-injection regions 207 constitute the surface waveguide region 302.
[0075] The ridge waveguide 205 has a width of 2-200 micrometers, a single etched trench width of 5-150 micrometers, a single non-injection region width of 0-240 micrometers, and a unit device spacing of 200-500 micrometers. The width of each region is dynamically adjusted according to the unit device spacing to maintain a consistent width. Figure 2 The distribution relationship is shown. The microstructure etching depth stops at 106 nm from the P-type waveguide, at a depth of 200-500 nm. The microstructures are periodically distributed on the ridge waveguide of the device, with the period being:
[0076] Λ=mλ / 2n eff
[0077] Where n eff λ is the equivalent refractive index of the device, λ is the target wavelength, and m is a positive integer.
[0078] The periodic surface microstructure 201 has two composition forms. One type is an arbitrary pattern, where each basic unit has a major axis length not exceeding one-quarter of the width of the ridge waveguide 205 and a minor axis length not less than 1 μm. The second type is a combination of a trench of the same width as the ridge waveguide 205 and the first type of structure (see [link]). Figure 3 and4 The periodic surface microstructures 201 arranged along the parallel direction of the ridge waveguide 205 can be a single type I structure, or a combination of type I and type II structures as described above. The microstructure region 303 and the unstructured region 304 can be arranged alternately or concentratedly, with the total proportion of the microstructure region 303 being 20%-100%, and the corresponding proportion of the unstructured region 304 being 0%-80%. The patterned portions of the microstructure region 303 are concentrated on both sides of the ridge waveguide 205, occupying 30%-70% of the width of the ridge waveguide 205. The etching duty cycle of the microstructure 201 is 5% to 50%.
[0079] Step 3: An insulating layer 202 is grown on the P-type capping layer 8. Ohmic contact areas are etched on the surface of the ridge waveguide 205 using optical masks, ultraviolet exposure, and dry / wet etching techniques.
[0080] The microstructure region 303 can be configured to retain the insulating layer 202, and the ohmic contact area within the region can be of any shape or a combination of shapes.
[0081] Step four: After depositing a layer of P-type ohmic contact metal, namely P-side electrode 204, using a metal growth device, the P-side electrode 204 is rapidly annealed to improve the device conductivity.
[0082] Step 5: Thin and polish the substrate 101. After completion, clean the chip and grow N-side electrode 203 on the polished surface of the substrate 101 (that is, the bottom surface of the substrate 101).
[0083] Step six: Disassemble the device, coat it with a film, and encapsulate it.
[0084] The insulating layer 202 is usually SiO2 or Si3N4 with a thickness of 150-300nm; the P-side electrode 204 is usually Ti-Pt-Au with a thickness of 200-300nm; and the N-side electrode 203 is usually AuGe-Ni-Au with a thickness of 200-300nm.
[0085] Example 3
[0086] See Figure 8 This embodiment is a quantum cascade laser, and the device structure and manufacturing steps are as follows:
[0087] Step 1: Sequentially grow an InP buffer layer 102 with a thickness of 300-1000 nm and an InP N-type cladding layer 103 with a thickness of 1-5 μm on an InP substrate 101. Figure 8 The lower cladding layer 103), and the 200-500nm thick InGaAs N-type waveguide 104 (i.e. Figure 8The lower waveguide 104), the active region 105 of InGaAs / InAlAs material with an EL range of 3-11 μm, and the P-type waveguide 106 of InGaAs with a thickness of 200-500 nm (i.e., the lower waveguide 104), the active region 105 of InGaAs material with an EL range of 3-11 μm, and the P-type waveguide 106 of InGaAs with a thickness of Figure 8 The upper waveguide 106), and the 1-5 μm thick InP P-type cladding 107 (i.e. Figure 8 The chip structure is obtained by adding an upper cladding layer 107 and a P-type capping layer 108 of InP material with a wavelength of 300-700 nm.
[0088] Step two: Photoresist is uniformly coated on the P-type capping layer 108. Using an optical mask, a ridge waveguide 205 and a periodic surface microstructure 201 are fabricated on the chip structure using ultraviolet exposure and etching techniques. The ridge waveguide 205 and the periodic surface microstructure 201 can be etched simultaneously, or they can be fabricated in two separate steps depending on the situation. (In some cases, the periodic surface microstructure 201 can also be fabricated using electron beam lithography or nanoimprinting). The periodic microstructure 201 is etched onto the surface of the ridge waveguide 205. The etched area of the microstructure 201 is the microstructure region 303, and the unetched area of the microstructure 201 is the non-microstructure region 304. The two sides of the laser are non-injection regions 207. The ridge waveguide 205, microstructure 201, etched trenches 206, and non-injection regions 207 constitute the surface waveguide region 302.
[0089] The ridge waveguide 205 has a width of 5-400 micrometers, the individual etched trench 206 has a width of 5-150 micrometers, the individual non-injection region 207 has a width of 0-240 micrometers, and the unit device spacing is 250-500 micrometers. The width of each region is dynamically adjusted according to the unit device spacing to maintain a consistent width. Figure 2 The distribution relationship is shown. The etching depth of microstructure 201 stops at 200-500 nm in the P-type waveguide 106, and the etching depth of the trench 206 exceeds the active region, reaching as deep as the N-type cladding 103. The microstructures are periodically distributed on the ridge waveguide of the device, with the period being:
[0090] Λ=mλ / 2n eff
[0091] Where n eff λ is the equivalent refractive index of the device, λ is the target wavelength, and m is a positive integer.
[0092] The periodic surface microstructure 201 has two composition forms. One type is an arbitrary pattern, where each basic unit has a major axis length not exceeding one-quarter of the width of the ridge waveguide 205 and a minor axis length not less than 1 μm. The second type is a combination of a trench of the same width as the ridge waveguide 205 and the first type of structure (see [link]). Figure 3 and 4The periodic surface microstructures 201 arranged along the parallel direction of the ridge waveguide 205 can be a single type I structure, or a combination of type I and type II structures as described above. The microstructure region 303 and the unstructured region 304 can be arranged alternately or concentratedly, with the total proportion of the microstructure region 303 being 20%-100%, and the corresponding proportion of the unstructured region 304 being 0%-80%. The patterned portions of the microstructure region 303 are concentrated on both sides of the ridge waveguide 205, occupying 30%-70% of the width of the ridge waveguide 205. The etching duty cycle of the microstructure 201 is 5% to 50%.
[0093] Step 3: An insulating layer 202 is grown on the P-type capping layer 8. Ohmic contact areas are etched on the surface of the ridge waveguide 205 using optical masks, ultraviolet exposure, and dry / wet etching techniques.
[0094] The microstructure region 303 can be configured to retain the insulating layer 202, and the ohmic contact area within the region can be of any shape or a combination of shapes.
[0095] Step four: After depositing a layer of P-type ohmic contact metal, namely P-side electrode 204, using a metal growth device, the P-side electrode 204 is rapidly annealed to improve the device conductivity.
[0096] Step 5: Thin and polish the substrate 101. After completion, clean the chip and grow N-side electrode 203 on the polished surface of the substrate 101 (that is, the bottom surface of the substrate 101).
[0097] Step six: Disassemble the device, coat it with a film, and encapsulate it.
[0098] The insulating layer 202 is usually SiO2 or Si3N4 with a thickness of 150-300nm; the P-side electrode 204 is usually Ti-Pt-Au with a thickness of 200-300nm; and the N-side electrode 203 is usually AuGe-Ni-Au with a thickness of 200-300nm.
[0099] The semiconductor laser based on periodic surface microstructures of this invention, through etching periodic surface microstructures on the ridge waveguide surface, effectively suppresses higher-order lateral modes, alters the mode distribution within the device cavity, and controls carrier injection, weakening the lateral carrier accumulation effect, thus improving the beam quality. Simultaneously, due to their periodic distribution along the longitudinal direction of the device, they selectively target specific longitudinal modes within the cavity, significantly improving the single-mode characteristics, narrowing the spectral range, increasing the side-mode suppression ratio, and thereby enhancing the spectral brightness. The etched microstructures provide a larger heat dissipation area, shorten the heat dissipation distance from the active region to the surface, and allow for temperature distribution control by adjusting the distribution of the microstructures and the etching depth, ultimately improving heat dissipation characteristics.
[0100] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A semiconductor laser based on a periodic surface microstructure, comprising a chip structure; The chip structure, from bottom to top, includes: The laser comprises a substrate (101), a buffer layer (102), an N-type cladding (103), an N-type waveguide (104), an active region (105), a P-type waveguide (106), a P-type cladding (107), and a P-type capping layer (108); wherein the N-type waveguide (104), the active region (105), and the P-type waveguide (106) constitute the optical confinement layer (301) of the laser, and the refractive index of the optical confinement layer (301) is greater than that of the N-type cladding (103) and the P-type cladding (107); Its features are, The chip structure is formed by etching multiple ridge waveguides (205) downward on the P-type capping layer (108), and each ridge waveguide (205) has etched trenches (206) on both sides; periodic microstructures (201) are etched on the surface of the ridge waveguides (205), the area with etched microstructures (201) is the microstructure region (303), and the area without etched microstructures (201) is the non-microstructure region (304); The ridge waveguide (205), microstructure (201), etched trench (206), and non-injection region (207) constitute the surface waveguide region (302); The chip structure has an N-side electrode (203) on the underside of the substrate (101), and an insulating layer (202) and a P-side electrode (204) are sequentially disposed on the P-type capping layer (108).
2. The semiconductor laser based on a periodic surface microstructure according to claim 1, characterized in that, The size of each basic unit of the periodic microstructure (201) is such that the length of the major axis does not exceed one-quarter of the width of the ridge waveguide (205), and the length of the minor axis is not less than 1 μm.
3. The semiconductor laser based on a periodic surface microstructure according to claim 1, characterized in that, The periodic surface microstructures (201) are arranged periodically along a direction parallel to the ridge waveguide (205), and their period is: Λ=mλ / 2n eff Where m is a positive integer and n eff λ is the equivalent refractive index of the device, and λ is the target wavelength.
4. The semiconductor laser based on a periodic surface microstructure according to claim 1, characterized in that, No insulating layer (202) is provided on the microstructure region (303).
5. The semiconductor laser based on a periodic surface microstructure according to claim 1, characterized in that, The microstructure region (303) and the non-microstructure region (304) are arranged alternately or concentratedly; the total proportion of the microstructure region (303) is 20%-100%, and the proportion of the non-microstructure region (304) is 0%-80%; the graphic part in the microstructure region (303) is concentrated on both sides of the ridge waveguide (205), accounting for 30%-70% of the width of the ridge waveguide (205).
6. The semiconductor laser based on a periodic surface microstructure according to claim 1, characterized in that, The periodic surface microstructure (201) has an etching depth H ranging from the P-type cladding (107) to the N-type cladding (103) at the bottom, and the etching duty cycle of the microstructure (201) is 5% to 50%.
7. The semiconductor laser based on a periodic surface microstructure according to claim 1, characterized in that, The ridge waveguide (205) has an end face width of 10-400μm and a length of 200-6000μm; the spacing between each unit device is 200-1000μm, and the end face width of the ridge waveguide (205) is smaller than the spacing between the unit devices.
8. The semiconductor laser based on a periodic surface microstructure according to claim 7, characterized in that, The width of the etched trench (206) is less than half the difference between the unit device spacing and the width of the ridge waveguide (205), and the length is the same as that of the ridge waveguide (205).
9. The semiconductor laser based on a periodic surface microstructure according to claim 7, characterized in that, The non-injection region (207) is located outside the etched trench (206), and its width is less than half the difference between the unit device spacing and the width of the ridge waveguide (205), and its length is the same as that of the ridge waveguide (205).
10. The semiconductor laser based on a periodic surface microstructure according to claim 1, characterized in that, The gain medium of the active region (105) is any one or a combination of multiple quantum wells, quantum dots, quantum bands, quantum cascades, and interband cascade structures, either singly or in complexly.