A super-symmetry loss type semiconductor laser and a preparation method thereof

Abstract

The application discloses a kind of supersymmetry loss type semiconductor laser and preparation method, comprising: ridge waveguide and tapered gain waveguide integrated on the same epitaxial structure;Tapered gain waveguide is located at the output end of ridge waveguide;Tapered gain waveguide is provided with left supersymmetry waveguide and right supersymmetry waveguide, left supersymmetry waveguide and right supersymmetry waveguide are asymmetrically arranged on the two sides of tapered gain waveguide central axis, to divide tapered gain waveguide into three parts;The starting width of central amplification area between left supersymmetry waveguide and right supersymmetry waveguide is the same as the width of ridge waveguide;Left supersymmetry waveguide and right supersymmetry waveguide have unequal lateral width, the propagation constant of base transverse mode or high-order mode generated by the two respectively matches the high-order transverse mode propagation constant generated in ridge waveguide, and the high-order transverse mode in directional dispersion loss transmission process is dispersed by refractive index coupling mechanism, to realize base transverse mode single-mode laser output.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser technology, and specifically to a supersymmetric loss semiconductor laser and its fabrication method. Background Technology

[0002] Semiconductor lasers possess advantages such as compact size, high electro-optic conversion efficiency, and a wide lasing wavelength range, leading to their widespread applications in optical communication, laser processing, laser ranging, and biomedical equipment. Among these, tapered semiconductor lasers, compared to traditional bar lasers, offer higher beam quality under high-power output conditions. Furthermore, their monolithic integrated structure results in a more compact and simpler overall design. This structure not only facilitates packaging and integration but also helps reduce manufacturing costs and improve production efficiency. In addition, the tapered structure reduces filamentary emission, further enhancing the device's output power and stability.

[0003] However, as the gain of a conical laser continues to increase, both the ridge waveguide and the tapered gain waveguide may excite higher-order transverse modes, leading to a deterioration in the laser beam quality. To address this issue, a common current method is to deeply etch both sides of the ridge waveguide to form a leakage groove structure, thereby filtering out higher-order transverse modes. However, this method may cause light leakage in the laser, reducing its stability, and the leakage groove structure has a large aspect ratio, making the manufacturing process complex and requiring advanced technology. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a supersymmetric loss semiconductor laser and its fabrication method.

[0005] This invention discloses a supersymmetric loss semiconductor laser, comprising: a ridge waveguide and a tapered gain waveguide integrated on the same epitaxial structure; the tapered gain waveguide is located at the output end of the ridge waveguide; a left supersymmetric waveguide and a right supersymmetric waveguide are disposed within the tapered gain waveguide, the left and right supersymmetric waveguides being asymmetrically arranged on both sides of the central axis of the tapered gain waveguide to divide the tapered gain waveguide into three parts; the initial width of the central amplification region between the left and right supersymmetric waveguides is the same as the width of the ridge waveguide, the ridge waveguide generates a seed laser, and the tapered gain waveguide is used to amplify the power of the seed laser for output; The left and right supersymmetric waveguides have unequal transverse widths. The propagation constants of the fundamental transverse mode or higher-order mode generated by the two waveguides are matched with the propagation constants of the higher-order transverse mode generated in the ridge waveguide. The higher-order transverse mode in the transmission process is dissipated in a directional manner through the refractive index coupling mechanism to achieve single-mode laser output of the fundamental transverse mode.

[0006] As a further improvement of the present invention, the epitaxial structure includes, from bottom to top, an N-type substrate, an N-type confinement layer, an N-type waveguide layer, an active region, a P-type waveguide layer, a P-type confinement layer, and a P-type ohmic contact layer. An N-type electrode is formed on the back side of the N-type substrate, and an insulating layer and a P-type electrode are formed on the upper surface of the P-type ohmic contact layer. The ridge waveguide is etched vertically downward from the top to the P-type waveguide layer, and the tapered gain waveguide is etched vertically downward from the top to the P-type confinement layer. The left supersymmetric waveguide and the right supersymmetric waveguide are shallowly etched in the tapered gain waveguide.

[0007] As a further improvement of the present invention, the width of the ridge waveguide is 12~14μm, and its width satisfies the fundamental transverse mode of the three transverse modes. First-order transverse mode Second-order transverse mode The conditions for its existence.

[0008] As a further improvement of the present invention, the etching depth of the ridge waveguide is 0.8~1.0μm; the longitudinal dimension of the ridge waveguide is determined by the longitudinal single-mode cutoff condition. Obtain; among them, d For the ridge waveguide etching depth, λ The wavelength of light in free space. n 1 The equivalent refractive index of the P-type confinement layer. n 2 is the equivalent refractive index of the P-type waveguide layer.

[0009] As a further improvement of the present invention, the cone angle of the tapered gain waveguide should be less than or equal to the fundamental mode diffraction angle. The cone angle of the tapered gain waveguide is in the range of 3~5°, and the shallow etching depth is 0.1~0.8μm.

[0010] As a further improvement to the present invention, the width is w The fundamental transverse mode propagation constant in the left supersymmetric waveguide of 1 corresponds to the propagation constant of the first-order transverse mode in the ridge waveguide; the width is w The propagation constant of the first transverse mode in the right supersymmetric waveguide of 2 is equal to the propagation constant of the second transverse mode in the ridge waveguide.

[0011] As a further improvement of the present invention, the width of the left supersymmetric waveguide... w 1 is (5.3±0.5) μm, and the width of the right supersymmetric waveguide is... w 2 is (7.7±0.5) μm; the etching depth range of the left and right supersymmetric waveguides is 0.8~1.0 μm.

[0012] As a further improvement of the present invention The insulating layer includes one of silicon dioxide and silicon nitride; The P-type electrode includes one or more of gold, platinum, and titanium; The N-type electrode includes one or more of germanium, niobium, and gold.

[0013] This invention also discloses a method for fabricating a high-power single-mode supersymmetric loss semiconductor laser, comprising: Step 1: Select an N-type substrate; Step 2: Epitaxial growth is performed using metal-organic chemical vapor deposition (MOCVD) technology. From bottom to top, an N-type confinement layer, an N-type waveguide layer, an active region, a P-type waveguide layer, a P-type confinement layer, and a P-type ohmic contact layer are grown on the surface of the N-type substrate to form an epitaxial structure.

[0014] Step 3: Using ultraviolet exposure technology and inductively coupled plasma dry etching technology, deeply etch the ridge waveguide and the left and right supersymmetric waveguides on the upper surface of the epitaxial structure; Step 4: Using ultraviolet exposure technology and inductively coupled plasma dry etching technology, a tapered gain waveguide is shallowly etched on the upper surface of the epitaxial structure; Step 5: Deposit an insulating layer on the upper surface of the epitaxial structure using plasma-enhanced chemical vapor deposition (PECVD). Step 6: Using photolithography, etch the P-type electrode windows of the ridge waveguide and the tapered gain waveguide on the upper surface of the epitaxial structure; Step 7: Sputter a P-type electrode onto the epitaxial structure using magnetron sputtering technology; Step 8: Thinning and polishing the N-type substrate; Step 9: Sputter an N-type electrode on the back side of the N-type substrate using magnetron sputtering technology; Step 10: Cleave, wire bond, and package the supersymmetric loss semiconductor laser.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: When the gain operation is applied only to the ridge waveguide, the left and right supersymmetric waveguides increase the loss of higher-order transverse modes, raising the threshold at the corresponding propagation constant and making them difficult to lasing. In contrast, the loss experienced by the fundamental transverse mode in the ridge waveguide is smaller, so the fundamental transverse mode dominates in the mode competition of the laser, achieving single transverse mode output. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the supersymmetric loss semiconductor laser disclosed in this invention; Figure 2 This is an epitaxial structure diagram of the supersymmetric loss semiconductor laser disclosed in this invention; Figure 3This is a diagram of the optical field mode of the supersymmetric loss semiconductor laser disclosed in this invention.

[0017] In the picture: 1. Ridge waveguide; 2. Tapered gain waveguide; 3. Left supersymmetric waveguide; 4. Right supersymmetric waveguide; 5. N-type electrode; 6. N-type substrate; 7. N-type confinement layer; 8. N-type waveguide layer; 9. Active region; 10. P-type waveguide layer; 11. P-type confinement layer; 12. P-type ohmic contact layer; 13. Insulating layer; 14. P-type electrode; 15. Side cladding region; 16. Under-ridge waveguide region. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0019] The present invention will now be described in further detail with reference to the accompanying drawings: like Figure 1 , Figure 2 As shown, the present invention provides a supersymmetric loss semiconductor laser, including a ridge waveguide 1 integrated on the same epitaxial structure and a tapered gain waveguide 2 located at the output end of the ridge waveguide 1; a left supersymmetric waveguide 3 and a right supersymmetric waveguide 4 are disposed within the tapered gain waveguide 3, the left supersymmetric waveguide 3 and the right supersymmetric waveguide 4 are asymmetrically arranged on both sides of the central axis of the tapered gain waveguide 2 to divide the tapered gain waveguide 2 into three parts, isolating the tapered region to form a central amplification region with the same width as the ridge waveguide 1. The left supersymmetric waveguide 3 and the right supersymmetric waveguide 4 are respectively located on both sides of the central axis of the tapered gain waveguide 2, and the starting width of the central amplification region between the left supersymmetric waveguide 3 and the right supersymmetric waveguide 4 is the same as the width of the ridge waveguide 1.

[0020] Among them, the left supersymmetric waveguide 3 and the right supersymmetric waveguide 4 have unequal transverse widths. The propagation constants of the fundamental transverse mode or higher-order mode generated by the two are matched with the propagation constants of the higher-order transverse mode generated in the ridge waveguide 1, respectively. The higher-order transverse mode in the transmission process is dissipated in a directional manner through the refractive index coupling mechanism to realize the fundamental transverse mode single-mode laser output.

[0021] like Figure 3 As shown, the higher-order modes of the ridge waveguide 1 of this invention exhibit a one-to-one correspondence with the modes in the left supersymmetric waveguide 3 and the right supersymmetric waveguide 4. Specifically, the propagation constant of the first-order transverse mode in the ridge waveguide 1 corresponds to a width of... w 1The fundamental transverse mode within the left supersymmetric waveguide 3 TE 0 Propagation constant; while the propagation constant of the second-order transverse mode in ridge waveguide 1 is equal to the width of w 2 The first transverse mode within the right supersymmetric waveguide 4 TE 1 Propagation constant. Based on this characteristic, when gain operation is applied only to ridge waveguide 1, the left supersymmetric waveguide 3 and right supersymmetric waveguide 4 increase the loss of higher-order transverse modes, raising the threshold at the corresponding propagation constant and making them difficult to lasing; in contrast, the fundamental transverse mode in ridge waveguide 1 experiences less loss, so the fundamental transverse mode dominates in the mode competition of the laser, achieving single transverse mode output.

[0022] Specifically: The lateral dimension of the ridge waveguide 1 of the present invention is greater than the lateral single-mode cutoff condition. This allows it to exist as a basic transverse mode. TE 0 First-order transverse mode TE 1 Second-order transverse mode TE 2 The three horizontal mode patterns; among them, w For a ridge waveguide of width 1, λ The wavelength of light in free space. The equivalent refractive index of waveguide region 15 under the ridge. 16 is the equivalent refractive index of the side cladding region.

[0023] The longitudinal dimension of the ridge waveguide 1 of the present invention is determined by the longitudinal single-mode cutoff condition. Obtain; among them, d The etching depth of ridge waveguide 1. λ The wavelength of light in free space. n 1 The equivalent refractive index of the P-type confinement layer 11, n 2 is the equivalent refractive index of the P-type waveguide layer 10.

[0024] The dimensional parameters of the ridge waveguide 1 of the present invention are: width of 12~14μm and etching depth of 0.8~1.0μm.

[0025] The cone angle of the tapered gain waveguide 2 of the present invention should be less than or equal to the fundamental mode diffraction angle, the cone angle range of the tapered gain waveguide 2 is 3~5°, and the shallow etching depth is 0.1~0.8μm.

[0026] The dimensional parameters of the supersymmetric waveguide of this invention are as follows: the width of the left supersymmetric waveguide 3 w 1 The width of the right supersymmetric waveguide 4 is (5.3 ± 0.5) μm.w 2 The etching depth ranges from 0.8 to 1.0 μm for both the left supersymmetric waveguide 3 and the right supersymmetric waveguide 4, which is (7.7 ± 0.5) μm.

[0027] The epitaxial structure of the supersymmetric loss semiconductor laser of the present invention includes, from bottom to top, an N-type substrate 6, an N-type confinement layer 7, an N-type waveguide layer 8, an active region 9, a P-type waveguide layer 10, a P-type confinement layer 11, and a P-type ohmic contact layer 12. An N-type electrode 5 is formed on the back side of the N-type substrate 6, and an insulating layer 13 and a P-type electrode 14 are formed on the upper surface of the P-type ohmic contact layer 12. The ridge waveguide 1 is etched vertically downward from the top to the P-type waveguide layer 10, the tapered gain waveguide 2 is etched vertically downward from the top to the P-type confinement layer 11, and the left supersymmetric waveguide 3 and the right supersymmetric waveguide 4 are shallowly etched in the tapered gain waveguide 2.

[0028] The insulating layer 13 of the present invention includes, but is not limited to, one of silicon dioxide and silicon nitride; the P-type electrode 14 includes, but is not limited to, one or more of gold, platinum, and titanium; and the N-type electrode 5 includes, but is not limited to, one or more of germanium, niobium, and gold.

[0029] This invention provides a method for fabricating a supersymmetric loss semiconductor laser, comprising: Step 1: Select an N-type substrate 6; Step 2: Epitaxial growth is performed using metal-organic chemical vapor deposition (MOCVD) technology. From bottom to top, an N-type confinement layer 7, an N-type waveguide layer 8, an active region 9, a P-type waveguide layer 10, a P-type confinement layer 11, and a P-type ohmic contact layer 12 are grown on the upper surface of the N-type substrate 6 to form an epitaxial structure.

[0030] Step 3: Using ultraviolet exposure technology and inductively coupled plasma dry etching technology, deeply etch the ridge waveguide 1, the left supersymmetric waveguide 3 and the right supersymmetric waveguide 4 on the upper surface of the epitaxial structure; Step 4: Using ultraviolet exposure technology and inductively coupled plasma dry etching technology, a tapered gain waveguide 2 is shallowly etched on the upper surface of the epitaxial structure; Step 5: Using plasma-enhanced chemical vapor deposition (PECVD), an insulating layer 13 is deposited on the upper surface of the epitaxial structure. Step 6: Using photolithography, etch the P-type electrode windows of the ridge waveguide 1 and the tapered gain waveguide 2; Step 7: Sputter a P-type electrode 14 on the top of the upper surface of the epitaxial structure using magnetron sputtering technology; Step 8: Thinning and polishing the N-type substrate 6; Step 9: Sputter an N-type electrode 5 onto the back side of the N-type substrate 6 using magnetron sputtering technology; Step 10: Cleave, wire bond, and package the supersymmetric loss semiconductor laser.

[0031] Example: Taking a supersymmetric loss semiconductor laser with an operating wavelength of 808 nm as an example, its fabrication method includes: S1. Select a GaAs substrate with a thickness of 300μm~600μm.

[0032] S2. Epitaxial growth is performed on GaAs substrate 6 using metal-organic chemical vapor deposition. The epitaxial structure, from bottom to top, consists of an N-type confinement layer 7, an N-type waveguide layer 8, an active region 9, a P-type waveguide layer 10, a P-type confinement layer 11, and a P-type ohmic contact layer 12; wherein, the N-type confinement layer 7 is Al 0.52~0.55 Ga 0.48~0.45 As, Si doping concentration is 1.0 × 10⁻⁶ 19 ~1.5×10 19 / cm -3 The thickness is 1.0μm~1.5μm; the N-type waveguide layer 8 is made of Al. 0.35~0.55 Ga 0.65~0.45 As, Si doping concentration is 1.0 × 10⁻⁶ 17 ~1.0×10 18 / cm -3 The thickness is 0.4 μm to 0.6 μm; in active region 9, the quantum well is GaAs with a thickness of 0.004 μm, and the quantum barrier layer is Al. 0.15 Ga 0.85 As, with a thickness of 0.006 μm; P-type waveguide layer 10 is Al 0.35~0.55 Ga 0.65~0.45 As, with a Be doping concentration of 1.0 × 10⁻⁶. 17 ~1.0×10 18 / cm -3 The thickness is 0.4μm~0.6μm; the P-type confinement layer 11 is Al 0.52~0.55 Ga 0.48~0.45 As, with a Be doping concentration of 1.0 × 10⁻⁶. 19 ~1.5×10 19 / cm -3 The thickness is 1.0 μm to 1.5 μm; the P-type ohmic contact layer 12 is GaAs with a doping concentration of 1.0 × 10⁻⁶. 19 / cm -3 The thickness is 0.15μm~0.2μm.

[0033] S3. Using ultraviolet exposure technology and inductively coupled plasma dry etching technology, ridge waveguide 1, left supersymmetric waveguide 3 and right supersymmetric waveguide 4 are deeply etched on the upper surface of the epitaxial structure, with an etching depth of 0.8~1.0μm.

[0034] S4. Using ultraviolet exposure technology and inductively coupled plasma dry etching technology, a tapered gain waveguide 2 is shallowly etched on the upper surface of the epitaxial structure, with an etching depth of 0.2~0.5μm.

[0035] S5. Using plasma-enhanced chemical vapor deposition (PECVD), an insulating layer 13 with a thickness of 0.13 μm is deposited on the upper surface of the epitaxial structure.

[0036] S6. Using photolithography, the P-type electrode windows of the ridge waveguide 1 and the tapered gain waveguide 2 are etched to a depth of 0.13 μm.

[0037] S7. Using magnetron sputtering technology, P-type electrode 14 is sputtered on the epitaxial structure in sequence, with Ti, Pt and Au sputtered to a thickness of 30 nm, 50 nm and 300 nm respectively.

[0038] S8, thinning and polishing GaAs substrate 6, with the remaining substrate thickness being 100μm~150μm.

[0039] S9. Using magnetron sputtering technology, an N-type electrode 5 is sputtered on the back side of the GaAs substrate 6, and Ge, Ni and Au are sputtered sequentially with thicknesses of 100 nm, 10 nm and 150 nm, respectively.

[0040] S10. The supersymmetric loss semiconductor laser is cleaved, wire-bonded, and packaged.

[0041] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A supersymmetric loss semiconductor laser, characterized in that, include: A ridge waveguide and a tapered gain waveguide are integrated on the same epitaxial structure; the tapered gain waveguide is located at the output end of the ridge waveguide; a left supersymmetric waveguide and a right supersymmetric waveguide are disposed within the tapered gain waveguide, and the left and right supersymmetric waveguides are asymmetrically arranged on both sides of the central axis of the tapered gain waveguide to divide the tapered gain waveguide into three parts; the initial width of the central amplification region between the left and right supersymmetric waveguides is the same as the width of the ridge waveguide, the ridge waveguide generates seed laser, and the tapered gain waveguide is used to amplify the power of the seed laser output; The left and right supersymmetric waveguides have unequal transverse widths. The propagation constants of the fundamental transverse mode or higher-order mode generated by the two waveguides are matched with the propagation constants of the higher-order transverse mode generated in the ridge waveguide. The higher-order transverse mode in the transmission process is dissipated in a directional manner through the refractive index coupling mechanism to achieve single-mode laser output of the fundamental transverse mode.

2. The symmetrical loss semiconductor laser as described in claim 1, characterized in that, The epitaxial structure includes, from bottom to top, an N-type substrate, an N-type confinement layer, an N-type waveguide layer, an active region, a P-type waveguide layer, a P-type confinement layer, and a P-type ohmic contact layer. An N-type electrode is formed on the back side of the N-type substrate, and an insulating layer and a P-type electrode are formed on the upper surface of the P-type ohmic contact layer. The ridge waveguide is etched vertically downwards from the top to the P-type waveguide layer, and the tapered gain waveguide is etched vertically downwards from the top to the P-type confinement layer. The left supersymmetric waveguide and the right supersymmetric waveguide are shallowly etched within the tapered gain waveguide.

3. The symmetrical loss semiconductor laser as described in claim 1, characterized in that, The width of the ridge waveguide is 12~14μm, and its width satisfies the fundamental transverse mode of the three transverse modes. First-order transverse mode Second-order transverse mode The conditions for its existence.

4. The symmetrical loss semiconductor laser as described in claim 2, characterized in that, The etching depth of the ridge waveguide is 0.8~1.0μm; the longitudinal dimension of the ridge waveguide is determined by the longitudinal single-mode cutoff condition. Obtain; among them, d For the ridge waveguide etching depth, λ The wavelength of light in free space. n 1 The equivalent refractive index of the P-type confinement layer. n 2 is the equivalent refractive index of the P-type waveguide layer.

5. The symmetrical loss semiconductor laser as described in claim 1, characterized in that, The cone angle of the tapered gain waveguide should be less than or equal to the fundamental mode diffraction angle. The cone angle of the tapered gain waveguide is in the range of 3~5°, and the shallow etching depth is 0.1~0.8μm.

6. The symmetrical loss semiconductor laser as described in claim 1, characterized in that, Width is w The fundamental transverse mode propagation constant in the left supersymmetric waveguide of 1 corresponds to the propagation constant of the first-order transverse mode in the ridge waveguide; the width is w The propagation constant of the first transverse mode in the right supersymmetric waveguide of 2 is equal to the propagation constant of the second transverse mode in the ridge waveguide.

7. The symmetrical loss semiconductor laser as described in claim 6, characterized in that, The width of the left supersymmetric waveguide w 1 is (5.3±0.5) μm, and the width of the right supersymmetric waveguide is... w 2 is (7.7±0.5) μm; the etching depth range of the left and right supersymmetric waveguides is 0.8~1.0 μm.

8. The symmetrical loss semiconductor laser according to claim 2, characterized in that, The insulating layer includes one of silicon dioxide and silicon nitride; The P-type electrode includes one or more of gold, platinum, and titanium; The N-type electrode includes one or more of germanium, niobium, and gold.

9. A method for fabricating a high-power single-mode supersymmetric loss semiconductor laser as described in any one of claims 1 to 8, characterized in that, include: Step 1: Select an N-type substrate; Step 2: Epitaxial growth is performed using metal-organic chemical vapor deposition (MOCVD) technology. From bottom to top, an N-type confinement layer, an N-type waveguide layer, an active region, a P-type waveguide layer, a P-type confinement layer, and a P-type ohmic contact layer are grown on the surface of the N-type substrate to form an epitaxial structure. Step 3: Using ultraviolet exposure technology and inductively coupled plasma dry etching technology, deeply etch the ridge waveguide and the left and right supersymmetric waveguides on the upper surface of the epitaxial structure; Step 4: Using ultraviolet exposure technology and inductively coupled plasma dry etching technology, a tapered gain waveguide is shallowly etched on the upper surface of the epitaxial structure; Step 5: Deposit an insulating layer on the upper surface of the epitaxial structure using plasma-enhanced chemical vapor deposition (PECVD). Step 6: Using photolithography, etch the P-type electrode windows of the ridge waveguide and the tapered gain waveguide on the upper surface of the epitaxial structure; Step 7: Sputter a P-type electrode onto the epitaxial structure using magnetron sputtering technology; Step 8: Thinning and polishing the N-type substrate; Step 9: Sputter an N-type electrode on the back side of the N-type substrate using magnetron sputtering technology; Step 10: Cleave, wire bond, and package the supersymmetric loss semiconductor laser.

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