Semiconductor laser with loss-enhanced super-symmetric structure and preparation method thereof

Abstract

The invention relates to the technical field of semiconductor lasers, in particular to a semiconductor laser with a loss-enhanced super-symmetric structure and a preparation method thereof, and the laser comprises a main gain waveguide and a loss waveguide array which are arranged on an epitaxial structure; the loss waveguide array is positioned beside the main gain waveguide; the loss waveguide array comprises a plurality of loss waveguides, and grooves are formed between the main gain waveguide and the loss waveguides and between the adjacent loss waveguides; a loss enhancing structure is etched on the surface of each loss waveguide. The loss enhancement structure enables a high-order lateral mode to obtain higher loss, and improves the excitation threshold of the high-order lateral mode, thereby achieving a smaller slow axis divergence angle under a higher working current, and optimizing the quality of a light beam.

Description

Technical Field

[0001] This application relates to the field of semiconductor laser technology, and in particular to a loss-enhanced supersymmetric semiconductor laser and its fabrication method. Background Technology

[0002] Semiconductor lasers possess a range of advantages, including small size, low power consumption, high efficiency, and long lifespan, leading to their widespread application in numerous fields such as optical communication systems, optical networks, and optical storage. However, with the continuous development of these applications, higher demands are being placed on the performance of semiconductor lasers, necessitating the ability to increase power while ensuring a small divergence angle in the output beam.

[0003] To increase output power, traditional semiconductor lasers typically employ large gain areas, but this can lead to multi-mode lasing, resulting in an increased far-field divergence angle. To address this issue, curved or tilted waveguides have been developed to suppress higher-order modes, thereby maintaining a smaller slow-axis divergence angle while increasing power. However, these structures inevitably increase the complexity of fabrication processes.

[0004] To address the issue of increased far-field divergence angle caused by increased output power, a new theory has emerged. In recent years, the concept of supersymmetry in atomic quantum systems has been introduced into laser systems to control the optical field distribution. Supersymmetry theory was initially used for bosons and fermions in correlated quantum field theory; given the similarities between quantum and optical systems, it has also been applied to wave optics. Based on supersymmetry theory, a supersymmetric waveguide structure has been successfully designed and fabricated, enabling semiconductor lasers to achieve increased power while maintaining a small divergence angle.

[0005] Since supersymmetric structures are passive waveguide structures, relying solely on the intrinsic loss of the material to suppress higher-order modes, their loss capability is insufficient under high-current injection conditions. When the current exceeds a certain value, supersymmetric lasers can still exhibit higher-order side-mode lasing, indirectly leading to an increase in the divergence angle, which is a problem that urgently needs to be solved. Summary of the Invention

[0006] This application provides a loss-enhanced supersymmetric semiconductor laser and its fabrication method. Based on a conventional supersymmetric semiconductor laser, a loss-enhancing structure is etched onto the loss waveguides on both sides, covering all loss waveguides on both sides. This structure enables higher losses in higher-order side modes, increases the excitation threshold of higher-order side modes, and thus achieves a smaller slow-axis divergence angle at higher operating currents, optimizing the laser's beam quality.

[0007] To address the aforementioned technical problems, in a first aspect, embodiments of this application provide a semiconductor laser with a loss-enhanced supersymmetric structure, comprising: a main gain waveguide and a loss waveguide array disposed on an epitaxial structure; the loss waveguide array is located beside the main gain waveguide; the loss waveguide array includes a plurality of loss waveguides, and trenches are formed between the main gain waveguide and the loss waveguides, and between adjacent loss waveguides; a loss-enhancing structure is etched on the surface of each loss waveguide.

[0008] In some exemplary embodiments, the main gain waveguide is located in the middle of the epitaxial structure; the main gain waveguide is used to confine the optical field and achieve gain.

[0009] In some exemplary embodiments, a plurality of loss waveguides are located on both sides of the main gain waveguide; the loss waveguide array is used to couple higher-order modes.

[0010] In some exemplary embodiments, the semiconductor laser includes a front end as an output end face and a rear end opposite to the front end; a loss enhancement structure is disposed close to the front end; and the loss enhancement structure is disposed at an angle of 1° to 90° with the laser output direction, and the width of the loss enhancement structure is 5μm to 30μm.

[0011] In some exemplary embodiments, the ridge width of the main gain waveguide is 10 μm to 50 μm; the width of a single loss waveguide in the loss waveguide array is 2 μm to 20 μm.

[0012] In some exemplary embodiments, the width of the groove is 1 μm to 7 μm.

[0013] In some exemplary embodiments, the etching depth of the main gain waveguide and the loss waveguide is 0.4 μm to 1.5 μm.

[0014] In some exemplary embodiments, the cavity length of the semiconductor laser tube is 0.5 mm to 5 mm, the width of the semiconductor laser tube is 100 μm to 800 μm, and the thickness of the semiconductor laser tube is 150 μm to 450 μm.

[0015] In some exemplary embodiments, the epitaxial structure includes a substrate and an N-confinement layer, an N-waveguide layer, a quantum well active layer, a P-waveguide layer, and a P-confinement layer sequentially stacked on the substrate.

[0016] Secondly, this application also provides a method for fabricating a loss-enhanced supersymmetric semiconductor laser. This method is used to fabricate a loss-enhanced supersymmetric semiconductor laser as described in the above embodiments. The method includes the following steps: First, a substrate is provided, and an N-confinement layer, an N-waveguide layer, a quantum well active layer, a P-waveguide layer, and a P-confinement layer are sequentially formed on the substrate to obtain an epitaxial structure; then, a main gain waveguide and a loss waveguide array are formed on the P-confinement layer by spin-coating photoresist, photolithography, development, etching, and photoresist removal; the loss waveguide array is positioned... The loss waveguide array comprises several loss waveguides, and trenches are formed between the main gain waveguide and the loss waveguides, as well as between adjacent loss waveguides. Next, the loss waveguides are etched to form a loss enhancement structure. An insulating layer is formed on the surface of the P-confinement layer and the trenches. A P-plane metal electrode is formed on the insulating layer. Then, the surface of the substrate away from the P-plane metal electrode is thinned and polished, and an N-plane metal electrode is deposited on the thinned and polished side of the substrate to form an N-plane metal electrode. Finally, the wafer is cleaved and packaged to prepare a semiconductor laser.

[0017] The technical solution provided in this application has at least the following advantages: This application provides a loss-enhanced supersymmetric semiconductor laser and its fabrication method. The semiconductor laser includes: a main gain waveguide and a loss waveguide array disposed on an epitaxial structure; the loss waveguide array is located beside the main gain waveguide; the loss waveguide array includes a plurality of loss waveguides, and trenches are formed between the main gain waveguide and the loss waveguides, and between adjacent loss waveguides; a loss-enhancing structure is etched on the surface of each loss waveguide. This application provides a loss-enhanced supersymmetric semiconductor laser and its fabrication method, which introduces a loss-enhanced supersymmetric structure to solve the problem of poor loss capability of passive waveguide supersymmetric structures. This structure can generate higher losses in higher-order side modes, increase the excitation threshold of higher-order side modes, and thus achieve a smaller slow-axis divergence angle at higher operating currents, further optimizing beam quality. Attached Figure Description One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments, and unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0018] Figure 1 This is a three-dimensional structural diagram of a loss-enhanced supersymmetric semiconductor laser provided in an embodiment of this application.

[0019] Figure 2 This is a definition diagram of a loss-enhanced supersymmetric semiconductor laser provided in an embodiment of this application.

[0020] Figure 3 This is a front view along the Z-direction of a semiconductor laser with a loss-enhanced supersymmetric structure, provided as an embodiment of this application.

[0021] Figure 4 This is a top view of a loss-enhanced supersymmetric semiconductor laser provided in an embodiment of this application.

[0022] Figure 5 This is a simulation diagram of the scattering of higher-order modes by the loss-enhanced structure in a semiconductor laser with a loss-enhanced supersymmetric structure provided in an embodiment of this application.

[0023] Figure 6 The horizontal far-field distribution diagrams of the loss-enhanced supersymmetric semiconductor laser and the conventional wide-strip semiconductor laser provided in the embodiments of this application are shown.

[0024] Figure 7 These are mode matching diagrams of various loss-enhanced supersymmetric semiconductor laser structures in the embodiments of this application.

[0025] Among them, 1. N-plane metal electrode; 2. Substrate; 3. N-confinement layer; 4. N-waveguide layer; 5. Quantum well active layer; 6. P-waveguide layer; 7. P-confinement layer; 8. Insulating layer; 9. Left waveguide array; 10. Right waveguide array; 11. Trench; 12. Main gain waveguide; 13. P-plane metal electrode; 14. Loss enhancement structure. Detailed Implementation

[0026] As can be seen from the background technology, supersymmetric waveguide structures prepared based on supersymmetric theory suffer from insufficient loss capability under high current injection conditions.

[0027] To address the aforementioned technical problems, this application provides a loss-enhanced supersymmetric semiconductor laser and its fabrication method. The semiconductor laser includes: a main gain waveguide and a loss waveguide array disposed on an epitaxial structure; the loss waveguide array is located beside the main gain waveguide; the loss waveguide array includes several loss waveguides, and trenches are formed between the main gain waveguide and the loss waveguides, and between adjacent loss waveguides; a loss-enhancing structure is etched on the surface of each loss waveguide. This loss-enhancing structure enables higher-order side modes to achieve higher losses, increases the excitation threshold of higher-order side modes, thereby achieving a smaller slow-axis divergence angle at higher operating currents and optimizing beam quality.

[0028] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0029] See Figures 1 to 3 This application provides a semiconductor laser with a loss-enhanced supersymmetric structure, comprising: a main gain waveguide 12 and a loss waveguide array disposed on an epitaxial structure; the loss waveguide array is located beside the main gain waveguide 12; the loss waveguide array includes a plurality of loss waveguides, and trenches 11 are formed between the main gain waveguide 12 and the loss waveguides and between adjacent loss waveguides; a loss-enhancing structure 14 is etched on the surface of each loss waveguide.

[0030] In some embodiments, the main gain waveguide 12 is located in the middle of the epitaxial structure; the main gain waveguide 12 is used to confine the optical field and achieve gain.

[0031] In some embodiments, a plurality of loss waveguides are located on both sides of the main gain waveguide 12; the number of loss waveguides on each side is 1 to 5. The loss waveguide array is used to perform phase matching on the higher-order modes in the main gain waveguide 12 to achieve effective coupling loss.

[0032] like Figure 3 As shown, the main gain waveguide 12 is located in the middle of the epitaxial structure, and the loss waveguide array includes a left waveguide array 9 and a right waveguide array 10, which are located on both sides of the loss waveguide array.

[0033] Please continue reading. Figure 3 In some embodiments, the epitaxial structure includes a substrate 2 and an N-confinement layer 3, an N-waveguide layer 4, a quantum well active layer 5, a P-waveguide layer 6, and a P-confinement layer 7 sequentially stacked on the substrate 2; the upper part of the P-confinement layer 7 consists of a left waveguide array 9, a main gain waveguide 12, and a right waveguide array 10, and trenches 11 are formed between the main gain waveguide 12 and the loss waveguides at both ends and between adjacent loss waveguides; after forming the main gain waveguide 12, the loss waveguide array, and the trenches 11, an insulating layer 8 and a P-plane metal electrode 13 are formed on the main gain waveguide 12, the loss waveguide array, and the trenches 11; and an N-plane metal electrode 1 is formed on the back side of the substrate 2 (the side surface of the substrate 2 away from the P-plane metal electrode 13).

[0034] In some embodiments, the thickness of the N-confining layer 3 is 1 μm to 3 μm, and the thickness of the N-waveguide layer 4 is 100 to 600 nm.

[0035] In some embodiments, the thickness of the quantum well active layer 5 is 1 nm to 50 nm.

[0036] In some embodiments, the thickness of the P-waveguide layer 6 is 100 nm to 600 nm; the thickness of the P-confining layer 7 is 1 μm to 3 μm.

[0037] In some embodiments, the insulating layer 8 is made of silicon dioxide and has a thickness of 50 nm to 400 nm; the P-side metal electrode 13 has a thickness of 50 nm to 200 nm.

[0038] like Figure 4 As shown, in some embodiments, loss enhancement structures 14 are etched on individual loss waveguides of the left waveguide array 9 and the right waveguide array 10.

[0039] like Figure 1 As shown, the semiconductor laser is divided into a front end and a back end, wherein the front end is the laser output end face; the loss enhancement structure 14 is disposed close to the front end; and the loss enhancement structure 14 is disposed at an angle, that is, the loss enhancement structure 14 and the laser output direction have a certain angle, the angle between the loss enhancement structure and the laser output direction is 1°~90°. Furthermore, the loss enhancement structure 14 has a certain width, which is 5μm~30μm.

[0040] like Figure 2 As shown, the width of the main gain waveguide 12 is d. M , θ L With θ R d is the angle between the loss-enhancing structure and the laser output direction. L d represents the waveguide width of the left waveguide array 9. R d represents the waveguide width of the right-side waveguide array 10. Slot The etching depth of the main gain waveguide 12 and the loss waveguide array, d G The width d of the trench 11 between the main gain waveguide 12 and the loss waveguide array. LES The width of the loss-enhancing structure 14.

[0041] It should be noted that, based on the existing supersymmetric semiconductor laser, this application etches loss enhancement structures 14 on the loss waveguides on both sides of the main gain waveguide 12. These loss enhancement structures 14 cover all the loss waveguides on both sides of the main gain waveguide 12. Both the left waveguide array 9 and the right waveguide array 10 are provided with loss enhancement structures 14, and the tilt angles of the left and right loss enhancement structures 14 can be the same or different. These loss enhancement structures 14 enable higher losses in higher-order side modes, increase the excitation threshold of higher-order side modes, and thus achieve a smaller slow-axis divergence angle at higher operating currents, optimizing the laser beam quality.

[0042] In some embodiments, the width of the main gain waveguide 12 is 10 μm to 50 μm, and the widths of the two side loss waveguide arrays (left waveguide array 9 and right waveguide array 10) are 2 μm to 20 μm. Preferably, the width of the main gain waveguide is 30 μm, the width of the left loss waveguide array 9 is 12 μm, and the width of the right waveguide array 10 is 6 μm.

[0043] In some embodiments, the number of loss waveguides is 1 to 5, and the width of the trench 11 between the main gain waveguide 12 and the loss waveguide is 1 to 7 μm, the same as the width of the trench 11 between adjacent loss waveguides. Preferably, the number of loss waveguides is 3, and the width of the trench between the main gain waveguide 12 and the loss waveguide is 5 μm.

[0044] In some embodiments, the depth of the trench 11 between the main gain waveguide 12 and the loss waveguide is 0.4~1.5μm, preferably, the depth of the trench 11 between the main gain waveguide 12 and the loss waveguide is 0.5μm.

[0045] In some embodiments, the cavity length of the semiconductor laser tube is 0.5 mm to 5 mm, the width of the semiconductor laser tube is 100 μm to 800 μm, and the thickness of the semiconductor laser tube is 150 μm to 450 μm. Preferably, the cavity length of the semiconductor laser tube is 2 mm, the width of the semiconductor laser tube is 800 μm, and the thickness of the semiconductor laser tube is 150 μm.

[0046] Compared to wide-strip semiconductor lasers, loss-enhanced supersymmetric semiconductor lasers are characterized by effective loss of higher-order modes and are simple to design and easy to fabricate.

[0047] Figure 5 A simulation diagram of the scattering of higher-order modes by the loss-enhanced structure in a loss-enhanced supersymmetric semiconductor laser provided in this application embodiment; from Figure 5 As can be seen, the loss-enhancing structure causes a deflection effect on the light field propagating within it, increasing the loss of higher-order modes.

[0048] Figure 6 These are the horizontal far-field distribution diagrams of the loss-enhanced supersymmetric semiconductor laser and the conventional wide-strip semiconductor laser in the embodiments of this application; from Figure 6 As can be seen, compared with traditional wide-strip lasers, the far-field divergence angle of the loss-enhanced supersymmetric semiconductor laser of this application is significantly reduced.

[0049] Figure 7 These are mode matching diagrams of various loss-enhanced supersymmetric semiconductor laser structures in the embodiments of this application; from Figure 7As can be seen from this, the fundamental mode of the main gain waveguide is not coupled, its first and third modes are coupled by the left loss waveguide array, and its second mode is coupled by the right loss waveguide array.

[0050] This application also provides a method for fabricating a loss-enhanced supersymmetric semiconductor laser. This method, used to fabricate a loss-enhanced supersymmetric semiconductor laser as described in the above embodiments, includes the following steps: Step 1: Provide a substrate, and sequentially form an N-confinement layer, an N-waveguide layer, a quantum well active layer, a P-waveguide layer, and a P-confinement layer on the substrate to obtain an epitaxial structure.

[0051] Step 2: On the P-confined layer, a main gain waveguide and a loss waveguide array are formed by spin coating photoresist, photolithography, development, etching and photoresist removal. The loss waveguide array is located next to the main gain waveguide. The loss waveguide array includes several loss waveguides, and trenches are formed between the main gain waveguide and the loss waveguide, as well as between adjacent loss waveguides.

[0052] Step 3: Etch the loss waveguide to form a loss enhancement structure.

[0053] Step 4: Form an insulating layer on the surface of the P-confining layer and the trench.

[0054] Step 5: Form a P-side metal electrode on the insulating layer.

[0055] Step 6: Thin and polish the surface of the substrate away from the P-side metal electrode, and deposit the N-side metal electrode on the thinned and polished side of the substrate to form the N-side metal electrode.

[0056] Step 7: Cleave and package the wafer to prepare the semiconductor laser.

[0057] Specifically, in step one, the resulting epitaxial structure is as follows: Figure 1 As shown, the N-confinement layer 3, the N-waveguide layer 4, the quantum well active layer 5, the P-waveguide layer 6, and the P-confinement layer 7 are sequentially stacked on the substrate 2.

[0058] In step two, photoresist is spin-coated onto the surface of the P-confined layer, followed by ultraviolet contact lithography, development, coating, post-baking, magnetron sputtering, and lift-off to preserve the shape of multiple waveguides on the P-confined layer and create alignment marks.

[0059] Then, photoresist is spin-coated onto the surface of the P-confining layer again, followed by step lithography, development, coating, and post-baking. The waveguide array and loss enhancement structure are then etched by ICP according to the preset structural pattern.

[0060] The developed pattern is hardened, and then transferred to the wafer using ICP etching, followed by resist removal.

[0061] The patterned wafer is coated with an insulating layer (SiO2), then photoresist is applied again, and ultraviolet lithography is performed to overlay the electrode windows.

[0062] Then, a P-side metal electrode is deposited on the P-confinement layer and then stripped off.

[0063] Next, the back side of the substrate (the surface of the substrate away from the P-side metal electrode) is thinned and polished to reduce the thickness of the substrate to 100~150μm, and the N-side metal electrode is deposited on the thinned and polished side.

[0064] Semiconductor lasers are fabricated by cleaving and packaging wafers.

[0065] Based on the above technical solutions, embodiments of this application provide a semiconductor laser with a loss-enhanced supersymmetric structure and its fabrication method. The semiconductor laser includes: a main gain waveguide and a loss waveguide array disposed on an epitaxial structure; the loss waveguide array is located beside the main gain waveguide; the loss waveguide array includes several loss waveguides, and trenches are formed between the main gain waveguide and the loss waveguides, as well as between adjacent loss waveguides; a loss-enhancing structure is etched on the surface of each loss waveguide. Embodiments of this application provide a semiconductor laser with a loss-enhanced supersymmetric structure and its fabrication method. To solve the problem of poor loss capability in passive waveguide supersymmetric structures, a loss-enhanced supersymmetric structure is introduced. This structure enables higher-order side modes to generate higher losses, increases the excitation threshold of higher-order side modes, and thus achieves a smaller slow-axis divergence angle at higher operating currents, further optimizing beam quality. Those skilled in the art will understand that the above-described embodiments are specific implementations of this application, and in practical applications, various changes can be made in form and detail without departing from the spirit and scope of this application. Any person skilled in the art can make their own modifications and alterations without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A semiconductor laser with a loss-enhanced supersymmetric structure, characterized in that, include: A main gain waveguide and a loss waveguide array mounted on an epitaxial structure; The loss waveguide array is located beside the main gain waveguide; The loss waveguide array includes several loss waveguides, and grooves are formed between the main gain waveguide and the loss waveguides, as well as between adjacent loss waveguides. Each of the loss waveguides has a loss enhancement structure etched on its surface.

2. The semiconductor laser with a loss-enhanced supersymmetric structure according to claim 1, characterized in that, The main gain waveguide is located in the middle of the epitaxial structure; The main gain waveguide is used to confine the optical field and achieve gain.

3. The semiconductor laser with a loss-enhanced supersymmetric structure according to claim 1, characterized in that, Several loss waveguides are located on both sides of the main gain waveguide; The lossy waveguide array is used to couple higher-order modes.

4. The semiconductor laser with a loss-enhanced supersymmetric structure according to claim 1, characterized in that, A semiconductor laser includes a front end that serves as an output end face and a rear end opposite to the front end; The loss enhancement structure is positioned close to the front end; and the loss enhancement structure is inclined, with an angle of 1° to 90° between the loss enhancement structure and the laser output direction, and a width of 5μm to 30μm.

5. The semiconductor laser with a loss-enhanced supersymmetric structure according to claim 1, characterized in that, The ridge width of the main gain waveguide is 10μm~50μm; The width of a single loss waveguide in the loss waveguide array is 2μm to 20μm.

6. The semiconductor laser with a loss-enhanced supersymmetric structure according to claim 1, characterized in that, The width of the groove is 1μm to 7μm.

7. The semiconductor laser with a loss-enhanced supersymmetric structure according to claim 1, characterized in that, The etching depth of the main gain waveguide and the loss waveguide is 0.4μm~1.5μm.

8. The semiconductor laser with a loss-enhanced supersymmetric structure according to claim 1, characterized in that, The cavity length of a single semiconductor laser tube is 0.5mm to 5mm, the width of a single semiconductor laser tube is 100μm to 800μm, and the thickness of a single semiconductor laser tube is 150μm to 450μm.

9. The semiconductor laser with a loss-enhanced supersymmetric structure according to claim 1, characterized in that, The epitaxial structure includes a substrate and an N-confinement layer, an N-waveguide layer, a quantum well active layer, a P-waveguide layer, and a P-confinement layer sequentially stacked on the substrate.

10. A method for fabricating a loss-enhanced supersymmetric semiconductor laser, the method being used to fabricate a loss-enhanced supersymmetric semiconductor laser as described in any one of claims 1 to 9, characterized in that, The method includes the following steps: A substrate is provided, and an N-confinement layer, an N-waveguide layer, a quantum well active layer, a P-waveguide layer, and a P-confinement layer are sequentially formed on the substrate to obtain an epitaxial structure. A main gain waveguide and a loss waveguide array are formed on the P-confining layer by spin coating photoresist, photolithography, development, etching and resist removal. The loss waveguide array is located next to the main gain waveguide. The loss waveguide array includes a plurality of loss waveguides, and trenches are formed between the main gain waveguide and the loss waveguide, and between adjacent loss waveguides. The loss waveguide is etched to form a loss enhancement structure; An insulating layer is formed on the surface of the P-limiting layer and the trench; A P-plane metal electrode is formed on the insulating layer; The surface of the substrate away from the P-side metal electrode is thinned and polished, and the N-side metal electrode is deposited on the thinned and polished side of the substrate to form the N-side metal electrode. Semiconductor lasers are fabricated by cleaving and packaging the wafer.

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