High-power semiconductor laser with high-order transverse mode loss and preparation process thereof
By introducing linearly increasing lateral grating structures on both sides of the ridge waveguide, the problem of multi-mode lasing in wide-area semiconductor lasers under high driving current is solved, achieving high power output and improved beam quality, suitable for applications such as laser pumping, laser ranging, and materials processing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-26
- Publication Date
- 2026-03-13
Smart Images
Figure CN121663331A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor laser technology, and more specifically to a high-power semiconductor laser with high-order transverse mode loss and its fabrication process. Background Technology
[0002] Wide-area edge-emitting diode lasers have been widely used in laser pumping, laser ranging, materials processing, and medical displays due to their high power and efficiency. However, the wide transverse waveguide size of wide-area semiconductor lasers typically leads to drastic changes in the optical field under high drive currents, exciting multiple transverse modes and causing a "multi-lobed" phenomenon in the near-field beam. This significantly degrades the transverse beam quality of the laser and also results in problems such as increased lateral far-field divergence angle and reduced brightness, thus affecting its application prospects in various fields.
[0003] Numerous methods have been proposed to suppress higher-order lasing modes and reduce transverse far-field expansion. In epitaxial structure design, asymmetric ultra-large optical cavity structures are employed to expand the vertical optical field area, thereby reducing vertical laser divergence. However, this cannot suppress the non-uniform refractive index distribution of internal materials caused by the increased device temperature due to increased current. Introducing mode filters, such as in a cone laser (MOPA), can achieve high beam quality and optical amplification, resulting in high output power; however, efficiency issues cannot be ignored. External cavity techniques and phase modulation structures can also effectively improve transverse beam quality, but these methods either increase the system integration size or are technically complex and costly, limiting the direct application of these devices in certain areas. Summary of the Invention
[0004] In view of this, the present invention provides a high-power semiconductor laser with high-order transverse mode loss and its fabrication process, which achieves high power while improving the beam quality of the laser.
[0005] To achieve the above objectives, the present invention provides a fabrication process for a high-power semiconductor laser with high-order transverse mode loss, comprising the following steps: S1. A lower capping layer, a lower waveguide layer, an active layer, an upper waveguide layer, and an upper capping layer are epitaxially grown sequentially on a substrate to obtain a wafer containing an epitaxial structure. S2. Perform photolithography on the surface of the wafer containing the epitaxial structure, form the ridge waveguide structure by dry etching, remove the mask layer by BOE, clean, and obtain the wafer containing the ridge waveguide. S3. Perform secondary photolithography on the wafer surface containing the ridge waveguide, and prepare lateral grating structures symmetrically distributed on both sides of the ridge waveguide by dry etching process. Perform BOE to remove the mask layer, clean, and obtain a wafer containing the ridge waveguide and grating. S4. An insulating layer is grown on the wafer surface containing the ridge waveguide and grating, and then three photolithography steps are performed. The electrode injection structure is prepared by dry etching, and then the top electrode layer is grown. S5. Grow a bottom electrode layer on the back side of the substrate, then anneal to form an ohmic contact, cleave to obtain the chip.
[0006] The technical solution provided by this invention introduces lateral gratings on both sides of the ridge waveguide with a linearly increasing distance from the ridge waveguide width. The lateral gratings are formed by dry etching, which enhances the loss of the laser's transverse higher-order modes, achieving high power while improving the laser's beam quality.
[0007] Optionally, when the emission wavelength is 600~1200 nm, gallium arsenide material system is used; when the emission wavelength is 1300~1600 nm, indium phosphide material system is used.
[0008] Optionally, when using gallium arsenide material systems, the following materials may be included: The substrate is N-type GaAs; The lower capping layer is an N-type capping layer with a thickness of 0.1 μm to 3 μm. The material is AlGaAs, with an Al molar fraction of 0.2-0.6. The dopant is Si, with a doping concentration of 1 × 10⁻⁶. 17 ~1×10 19 / cm 3 ; The lower waveguide layer is an N-type waveguide layer with a thickness ranging from 0.1 μm to 10 μm. It is made of AlGaAs with an Al molar fraction of 0.05–0.7 and is doped with Si at a concentration of 1 × 10⁻⁶. 16 ~8×10 18 / cm 3 ; The active layer is a barrier / quantum well / barrier structure with a barrier thickness of 1 nm to 200 nm and a quantum well thickness of 1 nm to 20 nm. The emission wavelength is 700 nm to 1200 nm. The material is AlGaAs / InGaAs / AlGaAs with a molar fraction of 0-0.5 for both In and Al components. The upper waveguide layer is a P-type waveguide layer with a thickness ranging from 0.1 μm to 10 μm. It is made of AlGaAs with an Al molar fraction of 0.05–0.7 and is doped with C at a concentration of 1 × 10⁻⁶. 16 ~8×10 18 / cm 3 ; The upper capping layer is a P-type capping layer with a thickness of 0.1 μm to 3 μm. The material is AlGaAs with an Al molar fraction of 0.4–0.6 and the dopant is C with a doping concentration of 1 × 10⁻⁶. 17 ~1×10 19 / cm 3 ; The insulating layer material is SiO2 or Si3N4, with a thickness of 50 nanometers to 1000 nanometers; The contact layer material is GaAs, the dopant is C, and the doping concentration is 1×10⁻⁶. 17 ~1×10 19 / cm 3 Thickness 20-500nm; The electrode layer material is an alloy material with a thickness of 200 nanometers to 500 nanometers. The alloy material is an alloy material formed by combining titanium, platinum, gold, nickel and germanium.
[0009] To achieve the above objectives, the present invention also provides a semiconductor laser fabricated by the above process, comprising, from bottom to top, a bottom electrode layer, a substrate layer, a lower capping layer, a lower waveguide layer, an active layer, an upper waveguide layer, an upper capping layer, an insulating layer, a contact layer, and a top electrode layer; a ridge waveguide structure is disposed on the epitaxial structure formed by the lower capping layer, the lower waveguide layer, the active layer, the upper waveguide layer, and the upper capping layer; a lateral grating is disposed on the epitaxial structure, the lateral gratings being symmetrically distributed on both sides of the ridge waveguide structure, and the lateral grating on one side of the ridge waveguide structure including multiple sets of trenches, each set of trenches including multiple trenches at the same distance from the ridge waveguide structure, the distance of each set of trenches from the ridge waveguide structure increasing linearly, and the width and length of each individual trench being the same.
[0010] Optionally, the waveguide width of the ridge waveguide structure ranges from 5 to 200 μm, and the cavity length ranges from 0.5 to 5 μm.
[0011] Optionally, the lateral grating on one side of the ridge waveguide structure includes 1-100 groups of grooves, each group of grooves including 5 grooves at the same distance from the ridge waveguide structure; the width of a single groove is 0.5-5μm and the length is 1-50µm; the distance between the grooves is 0.5-10μm, and the distance between each group of grooves and the ridge waveguide structure is (n-1)×5μm, where n represents the group number.
[0012] The technical solution provided by this invention introduces lateral gratings on both sides of the ridge waveguide with a linearly increasing distance from the ridge waveguide width. By optimizing the grating length, the spacing between the grating and the ridge waveguide, and the etching depth, the loss of the laser's lateral higher-order modes is enhanced, thereby achieving high power while improving the laser's beam quality.
[0013] The above-described technical solution of the present invention has at least the following beneficial effects: Unlike traditional edge-emitting semiconductor lasers in existing technologies, which typically support multiple transverse modes operating simultaneously and significantly degrade beam quality, this invention introduces a novel periodic lateral grating structure to suppress higher-order transverse modes based on the FP cavity structure. The lateral gratings are parallel to the device cavity surface and located on both sides of the ridge waveguide, with the distance between the grating and the ridge waveguide increasing linearly. Based on the calculated distribution of transverse mode spots in the transverse direction of the device, the optical field of the fundamental transverse mode is mainly concentrated at the waveguide center, and is less affected by disturbances from the gratings on both sides, resulting in very low loss. The optical field of higher-order transverse modes is closer to the waveguide edge or both sides. By optimizing parameters such as grating etching depth, grating length, and grating spacing, higher-order transverse modes are coupled with the periodic grating structure. These higher-order transverse modes are scattered out of the waveguide or converted into radiation modes, thus experiencing significant loss. This means that the lateral grating structure provides additional loss in the transverse direction, with higher-order modes exhibiting even higher loss, while the fundamental mode suffers almost no loss, greatly improving the beam quality of the laser. Attached Figure Description
[0014] Figure 1 A three-dimensional structural diagram of a high-power semiconductor laser with high-order transverse mode loss provided by the present invention; Figure 2 A planar structural diagram of a high-power semiconductor laser with high-order transverse mode loss provided by the present invention; Figure 3 This is a lateral mode distribution diagram of a 50 μm waveguide width in Embodiment 1 of the present invention.
[0015] Figure 1 In the middle: 101, substrate layer; 102, lower capping layer; 103, lower waveguide layer; 104, active layer; 105, upper waveguide layer; 106, upper capping layer; 107, contact layer; 108, top electrode layer; 109, side grating; 110, bottom electrode layer; 111, insulating layer.
[0016] Figure 2 In the diagram: 201, transverse mode filter grating region; 202, ridge waveguide region; 203, equivalent light field distribution diagram; the arrow on the left side of the diagram indicates the light output direction of the device.
[0017] Figure 3 In the middle: 302, first-order modulus distribution; 303, second-order modulus distribution; 304, third-order modulus distribution; 305, fourth-order modulus distribution; 306, fifth-order modulus distribution; 307, sixth-order modulus distribution. Detailed Implementation
[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will be described in conjunction with the accompanying drawings of the embodiments of the present invention. Figures 1-3The technical solutions of the embodiments of the present invention will be clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.
[0019] This invention proposes a high-power semiconductor laser with high-order lateral mode loss. Lateral gratings with linearly increasing distances from the ridge waveguide width are introduced on both sides of a wide ridge waveguide via dry etching. By optimizing the grating length and the spacing between the grating and the ridge waveguide, the high-order lateral modes overlap more with the grating structure, providing additional loss for the high-order modes in the lateral direction. This achieves high power while improving the laser beam quality, providing a novel technical solution for applications requiring high power and high beam quality, such as laser pumping, laser ranging, and materials processing.
[0020] This invention provides a high-power semiconductor laser with high-order lateral mode loss, comprising, from bottom to top, a bottom electrode layer 110, a substrate layer 101, a lower capping layer 102, a lower waveguide layer 103, an active layer 104, an upper waveguide layer 105, an upper capping layer 106, an insulating layer 111, a contact layer 107, and a top electrode layer 108; a ridge waveguide structure is disposed on the epitaxial structure formed by the lower capping layer 102, the lower waveguide layer 103, the active layer 104, the upper waveguide layer 105, and the upper capping layer 106; a lateral grating 109 is disposed on the epitaxial structure, the lateral grating 109 being symmetrically distributed on both sides of the ridge waveguide structure, each lateral grating on one side of the ridge waveguide structure including multiple sets of trenches, each set of trenches including multiple trenches at the same distance from the ridge waveguide structure, the distance of each set of trenches from the ridge waveguide structure increasing linearly, and the width and length of each individual trench being the same.
[0021] In some embodiments, the waveguide width of the ridge waveguide structure ranges from 5 to 200 μm, and the cavity length ranges from 0.5 to 5 μm.
[0022] In some embodiments, the lateral grating on one side of the ridge waveguide structure includes 1-100 groups of trenches, each group of trenches including 5 trenches at the same distance from the ridge waveguide structure; the width of a single trench is 0.5-5μm and the length is 1-50µm; the distance between trenches is 0.5-10μm, and the distance between each group of trenches and the ridge waveguide structure is (n-1)×5μm, where n represents the group number.
[0023] The three-dimensional structural diagram of the high-power semiconductor laser with high-order transverse mode loss provided by this invention is shown below. Figure 1 See the planar structure diagram. Figure 2 .
[0024] A fabrication process for a high-power semiconductor laser with high-order transverse mode loss includes the following steps: S1. A lower capping layer, a lower waveguide layer, an active layer, an upper waveguide layer, and an upper capping layer are epitaxially grown sequentially on a substrate to obtain a wafer containing an epitaxial structure. S2. Perform photolithography on the surface of the wafer containing the epitaxial structure, form the ridge waveguide structure by dry etching, remove the mask layer by BOE, clean, and obtain the wafer containing the ridge waveguide. S3. Perform secondary photolithography on the wafer surface containing the ridge waveguide, fabricate the lateral grating structure by dry etching process, perform BOE to remove the mask layer, clean, and obtain the wafer containing the ridge waveguide and grating. S4. An insulating layer is grown on the wafer surface containing the ridge waveguide and grating, and then three photolithography steps are performed. The electrode injection structure is prepared by dry etching, and then the top electrode layer is grown. S5. Grow a bottom electrode layer on the back side of the substrate, then anneal to form an ohmic contact, cleave to obtain the chip.
[0025] It should be noted that the material composition, thickness and doping concentration of each layer in the epitaxial structure of the laser described in this invention are basically the same as those in the mature epitaxial structure design of edge-emitting semiconductor lasers in the prior art, and each process parameter can be selected according to the needs of those skilled in the art.
[0026] Example 1 The high-power semiconductor laser with high-order lateral mode loss provided by this invention includes, from bottom to top, a bottom electrode layer, a substrate layer, a lower capping layer, a lower waveguide layer, an active layer, an upper waveguide layer, an upper capping layer, an insulating layer, a contact layer, and a top electrode layer. A ridge waveguide structure is disposed on the epitaxial structure formed by the lower capping layer, lower waveguide layer, active layer, upper waveguide layer, and upper capping layer. The waveguide width of the ridge waveguide structure is 50 μm, and the cavity length is 2 μm. Lateral gratings are disposed on the epitaxial structure, symmetrically distributed on both sides of the ridge waveguide structure. Each lateral grating on one side of the ridge waveguide structure includes 10 groups of trenches, each group of trenches including 5 trenches at the same distance from the ridge waveguide structure. The width of a single trench is 5 μm, and the length is 10 μm. The distance between trenches is 5 μm, and the distance from each group of trenches to the ridge waveguide structure is (n-1) × 5 μm, where n represents the group number. The width and length of a single trench are the same.
[0027] The lateral mode distribution diagram of the 50 μm waveguide width in Example 1 is shown below. Figure 3 . Figure 3 In the diagram, 301 represents the fundamental mode distribution; 302 represents the first-order mode distribution; 303 represents the second-order mode distribution; 304 represents the third-order mode distribution; 305 represents the fourth-order mode distribution; 306 represents the fifth-order mode distribution; and 307 represents the sixth-order mode distribution.
[0028] Example 2 This invention provides a fabrication process for a high-power semiconductor laser with high-order transverse mode loss, comprising the following steps: Step 1: Design the photolithography pattern for etching to form the ridge waveguide structure, the photolithography pattern for the lateral grating structure, and the photolithography pattern for the electrode structure.
[0029] Step 2: On an N-type GaAs substrate, an N-type capping layer, an N-type waveguide layer, an active layer, a P-type waveguide layer, and a P-type capping layer are sequentially prepared by epitaxial growth to obtain a wafer containing an epitaxial structure.
[0030] Step 3: Perform a photolithography process and a dry etching process on the photolithography pattern of the ridge waveguide structure on the surface of the grown wafer to prepare the ridge waveguide. Then perform a BOE mask removal process and a cleaning process to obtain a wafer containing the ridge waveguide. Step 4: Perform secondary photolithography on the wafer surface containing the ridge waveguide, fabricate the lateral grating structure using dry etching, perform BOE mask removal process, and clean the wafer to obtain the wafer containing the ridge waveguide and grating. Step 5: Use a PECVD device to grow an insulating layer material on the wafer surface containing the ridge waveguide and grating; Step 6: The electrode implantation structure is prepared by performing a three-stage photolithography process using the photolithography pattern of the electrode structure and a dry etching process.
[0031] Step 7: Grow a P-type electrode in a metal film evaporation device; Step 8: Thin, polish, and clean the N-type substrate; sputter an N-type electrode layer onto the N-type substrate; and perform an annealing process on the wafer to form an ohmic contact. Step 9: Cleave the wafer into bar strips, deposit an anti-reflective coating on the backlight side, and then cleave the bar strips into chips.
[0032] Wherein: the substrate is N-type GaAs; The lower capping layer is an N-type capping layer with a thickness of 0.1 μm to 3 μm. The material is AlGaAs, with an Al molar fraction of 0.2-0.6. The dopant is Si, with a doping concentration of 1 × 10⁻⁶. 17 ~1×10 19 / cm 3 ; The lower waveguide layer is an N-type waveguide layer with a thickness ranging from 0.1 μm to 10 μm. It is made of AlGaAs with an Al molar fraction of 0.05–0.7 and is doped with Si at a concentration of 1 × 10⁻⁶. 16 ~8×10 18 / cm 3 ; The active layer is a barrier / quantum well / barrier structure with a barrier thickness of 1 nm to 200 nm and a quantum well thickness of 1 nm to 20 nm. The emission wavelength is 700 nm to 1200 nm. The material is AlGaAs / InGaAs / AlGaAs with a molar fraction of 0-0.5 for both In and Al components. The upper waveguide layer is a P-type waveguide layer with a thickness ranging from 0.1 μm to 10 μm. It is made of AlGaAs with an Al molar fraction of 0.05–0.7 and is doped with C at a concentration of 1 × 10⁻⁶. 16 ~8×10 18 / cm 3 ; The upper capping layer is a P-type capping layer with a thickness of 0.1 μm to 3 μm. The material is AlGaAs with an Al molar fraction of 0.4–0.6 and the dopant is C with a doping concentration of 1 × 10⁻⁶. 17 ~1×10 19 / cm 3 ; The insulating layer material is SiO2 or Si3N4, with a thickness of 50 nanometers to 1000 nanometers; The contact layer material is GaAs, the dopant is C, and the doping concentration is 1×10⁻⁶. 17 ~1×10 19 / cm 3 Thickness 20-500nm; The electrode layer material is an alloy material with a thickness of 200 nanometers to 500 nanometers. The alloy material is an alloy material formed by combining titanium, platinum, gold, nickel and germanium.
[0033] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A fabrication process for a high-power semiconductor laser with high-order transverse mode loss, characterized in that, Includes the following steps: S1. A lower capping layer, a lower waveguide layer, an active layer, an upper waveguide layer, and an upper capping layer are epitaxially grown sequentially on a substrate to obtain a wafer containing an epitaxial structure. S2. Perform photolithography on the surface of the wafer containing the epitaxial structure, form the ridge waveguide structure by dry etching, remove the mask layer by BOE, clean, and obtain the wafer containing the ridge waveguide. S3. Perform secondary photolithography on the wafer surface containing the ridge waveguide, fabricate the lateral grating structure by dry etching process, perform BOE to remove the mask layer, clean, and obtain the wafer containing the ridge waveguide and grating. S4. An insulating layer is grown on the wafer surface containing the ridge waveguide and grating, and then three photolithography steps are performed. The electrode injection structure is prepared by dry etching, and then the top electrode layer is grown. S5. Grow a bottom electrode layer on the back side of the substrate, then anneal to form an ohmic contact, cleave to obtain the chip.
2. The fabrication process of the high-power semiconductor laser with high-order transverse mode loss according to claim 1, characterized in that, When the emission wavelength is 600~1200 nm, gallium arsenide material system is used; when the emission wavelength is 1300~1600 nm, indium phosphide material system is used.
3. The fabrication process of the high-power semiconductor laser with high-order transverse mode loss according to claim 2, characterized in that, When using gallium arsenide material systems, the following materials are included: The substrate is N-type GaAs; The lower capping layer is an N-type capping layer with a thickness of 0.1 μm to 3 μm. The material is AlGaAs, with an Al molar fraction of 0.2-0.
6. The dopant is Si, with a doping concentration of 1 × 10⁻⁶. 17 ~1×10 19 / cm 3 ; The lower waveguide layer is an N-type waveguide layer with a thickness ranging from 0.1 μm to 10 μm. It is made of AlGaAs with an Al molar fraction of 0.05–0.7 and is doped with Si at a concentration of 1 × 10⁻⁶. 16 ~8×10 18 / cm 3 ; The active layer is a barrier / quantum well / barrier structure with a barrier thickness of 1 nm to 200 nm and a quantum well thickness of 1 nm to 20 nm. The emission wavelength is 700 nm to 1200 nm. The material is AlGaAs / InGaAs / AlGaAs with a molar fraction of 0-0.5 for both In and Al components. The upper waveguide layer is a P-type waveguide layer with a thickness ranging from 0.1 μm to 10 μm. It is made of AlGaAs with an Al molar fraction of 0.05–0.7 and is doped with C at a concentration of 1 × 10⁻⁶. 16 ~8×10 18 / cm 3 ; The upper capping layer is a P-type capping layer with a thickness of 0.1 μm to 3 μm. The material is AlGaAs with an Al molar fraction of 0.4–0.6 and the dopant is C with a doping concentration of 1 × 10⁻⁶. 17 ~1×10 19 / cm 3 ; The insulating layer material is SiO2 or Si3N4, with a thickness of 50 nanometers to 1000 nanometers; The contact layer material is GaAs, the dopant is C, and the doping concentration is 1×10⁻⁶. 17 ~1×10 19 / cm 3 Thickness 20-500nm; The electrode layer material is an alloy material with a thickness of 200 nanometers to 500 nanometers. The alloy material is an alloy material formed by combining titanium, platinum, gold, nickel and germanium.
4. A semiconductor laser fabricated using the fabrication process for a high-power semiconductor laser with high-order transverse mode loss as described in any one of claims 1 to 3, characterized in that, The structure comprises, from bottom to top, a bottom electrode layer, a substrate layer, a lower capping layer, a lower waveguide layer, an active layer, an upper waveguide layer, an upper capping layer, an insulating layer, a contact layer, and a top electrode layer. A ridge waveguide structure is disposed on the epitaxial structure formed by the lower capping layer, the lower waveguide layer, the active layer, the upper waveguide layer, and the upper capping layer. Lateral gratings are disposed on the epitaxial structure and are symmetrically distributed on both sides of the ridge waveguide structure. Each lateral grating on one side of the ridge waveguide structure includes multiple sets of trenches. Each set of trenches includes multiple trenches at the same distance from the ridge waveguide structure. The distance from each set of trenches to the ridge waveguide structure increases linearly, and the width and length of each individual trench are the same.
5. The high-power semiconductor laser with high-order transverse mode loss according to claim 4, characterized in that, The waveguide width of the ridge waveguide structure ranges from 5 to 200 μm, and the cavity length ranges from 0.5 to 5 μm.
6. The high-power semiconductor laser with high-order transverse mode loss according to claim 4, characterized in that, The lateral grating on one side of the ridge waveguide structure includes 1-100 sets of grooves, each set of grooves including 5 grooves at the same distance from the ridge waveguide structure; the width of a single groove is 0.5-5μm and the length is 1-50µm; The distance between the trenches is 0.5-10μm, and the distance between each group of trenches and the ridge waveguide structure is (n-1)×5μm, where n represents the group number.