High-power narrow-linewidth hybrid integrated laser

Abstract

The invention relates to the field of semiconductor lasers, in particular to a high-power narrow-linewidth hybrid integrated laser, which comprises a wide waveguide laser gain chip and a silicon-based external cavity photon chip, and is characterized in that the silicon-based external cavity photon chip comprises a tip multi-section edge coupler, a bus waveguide, at least three cascaded micro-ring resonators and a feedback assembly; the tip multi-section edge coupler comprises a tip waveguide array and a conical combined waveguide, the tip waveguide array is composed of inverted conical waveguides arranged side by side, and the width of the input end face of each inverted conical waveguide is smaller than that of the output end face of each inverted conical waveguide; and the width of the conical combined waveguide is gradually reduced from the input end to the output end. The invention solves the industrial problem that high power and narrow linewidth are difficult to consider in the hybrid integrated laser, has the advantages of high output power, extremely narrow linewidth, wide tuning range, high coupling efficiency, good process tolerance, high integration level and the like, and provides a high-performance light source for the next generation of coherent optical communication, laser radar and precision measurement system.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor laser technology, and particularly relates to a high-power narrow-linewidth hybrid integrated laser. Background Technology

[0002] The hybrid integration of III-V active laser gain chips and silicon-based external cavity photonic chips provides a promising technological path for realizing high-performance III-V active photonic integrated circuits (PICs) such as narrow-linewidth lasers, optical frequency combs, optical interconnects, and photonic computing. Active PICs are widely used in coherent optical communication, lidar, precision measurement, and microwave photonics. In these applications, the demand for high-power, narrow-linewidth lasers is increasing to support long-distance transmission and detection, overcome high link losses, improve signal-to-noise ratio (SNR), and achieve strong nonlinear optical effects. The necessary laser output power ranges from tens of milliwatts to several watts, and the linewidth requirement ranges from hundreds of kHz to Hz.

[0003] However, there is a significant mismatch in the mode field distribution between III-V group active laser gain chips and silicon-based external cavity photonic chips, resulting in high end-face coupling losses. In existing technologies, edge couplers with inverted conical, Y-shaped tip, or trident-shaped structures can effectively couple the optical power of single-mode or small-mode-field-diameter laser chips to silicon-based external cavity photonic chips. However, these edge couplers are suitable for laser chips with small mode fields and are insufficient for high-power requirements.

[0004] To improve output power, wide-waveguide laser gain chips (such as wide strip chips or tapered amplification structures) have been introduced, with larger mode field sizes. However, this also exacerbates the mode field mismatch with silicon-based photonic chips, further reducing coupling efficiency. Traditional wide-tapered edge couplers attempt to solve this problem, but due to the limitations of silicon-based waveguide thickness, the matching degree between the mode field at the coupling end face and the mode field of the wide-waveguide laser chip spot is still not high. Furthermore, mode perturbations and diffraction effects easily occur during light transmission in wide waveguides, typically requiring longer coupler lengths (e.g., over 1500 μm), increasing manufacturing and packaging complexity and cost.

[0005] In terms of external cavity design, existing hybrid integrated lasers often employ silicon-based photonic chips with cascaded dual microring resonators integrated with Sagnac ring mirrors to narrow the laser linewidth to the kHz level. However, this approach has a limited effective cavity length, making it difficult to further narrow the linewidth. Furthermore, the feedback light from the Sagnac ring mirror must pass through the microring resonators, resulting in significant feedback power loss and making it difficult to achieve strong feedback while maintaining high output power. Summary of the Invention

[0006] In view of this, the present invention aims to provide a high-power narrow-linewidth hybrid integrated laser to solve the technical problems of existing technologies in terms of efficient coupling between high-power wide-waveguide laser chips and silicon-based photonic chips, as well as linewidth narrowing with long effective cavity length and high feedback utilization.

[0007] To achieve the above objectives, the technical solution created by this invention is implemented as follows: A high-power, narrow-linewidth hybrid integrated laser, comprising: Wide waveguide laser gain chip, used to provide optical gain; A silicon-based external cavity photonic chip, coupled with a wide-waveguide laser gain chip, is used to form a laser resonant cavity and provide optical feedback; wherein the silicon-based external cavity photonic chip includes: A multi-segment edge coupler with a pointed tip is connected to the output of a wide waveguide laser gain chip to receive and couple optical signals. Bus waveguide, which connects to the output of a tip multi-segment edge coupler, is used to transmit optical signals; At least three cascaded microring resonators are coupled to a bus waveguide for mode selection and to extend the effective cavity length of the silicon-based external cavity photonic chip. The feedback component is located on the output side of the bus waveguide and is used to feed back part of the output light of the cascaded micro-ring resonator to the bus waveguide and transmit it to the wide waveguide laser gain chip. Tip-type multi-segment edge couplers include: The pointed waveguide array is composed of inverted conical waveguides arranged side by side. The width of the input end face of the inverted conical waveguide is smaller than the width of the output end face. It is used to interface with the output end of the wide waveguide laser gain chip and improve the end face coupling efficiency between the beam mode field of the wide waveguide laser gain chip. The tapered combined waveguide has a width that gradually decreases from the input end to the output end. The input end of the tapered combined waveguide is connected to the output end of the tip waveguide array, and the output end of the tapered combined waveguide is connected to the bus waveguide. The tapered combined waveguide is used to compress the beam mode field of the wide waveguide laser gain chip into a single mode and transmit it to the bus waveguide.

[0008] Furthermore, the inverted conical waveguides in the tip waveguide array are arranged side by side at equal intervals, and the length, input end face width, and output end face width of each inverted conical waveguide are all the same.

[0009] Furthermore, there are 62 inverted conical waveguides, each with a length of 40 μm, an input end face width of 0.26 μm, an output end face width of 0.5 μm, and a center-to-center distance of 0.8 μm between two adjacent inverted conical waveguides.

[0010] Furthermore, the tapered composite waveguide is composed of tapered waveguides connected end to end, with the width of each tapered waveguide gradually decreasing from the input end to the output end.

[0011] Furthermore, the tapered waveguide is composed of three tapered waveguide segments connected end to end. The width of the input end face of the first tapered waveguide is greater than the width of the output end face. The width of the input end face of the second tapered waveguide is the same as the width of the output end face of the first tapered waveguide, and the width of the input end face of the second tapered waveguide is greater than the width of the output end face. The width of the input end face of the third tapered waveguide is the same as the width of the output end face of the second tapered waveguide, and the width of the input end face of the third tapered waveguide is greater than the width of the output end face.

[0012] Furthermore, the first tapered waveguide has a length of 350 μm, a width of 50 μm at its input end face, and a width of 30 μm at its output end face; the second tapered waveguide has a length of 200 μm, a width of 30 μm at its input end face, and a width of 15 μm at its output end face; the third tapered waveguide has a length of 60 μm, a width of 15 μm at its input end face, and a width of 1 μm at its output end face.

[0013] Furthermore, the number of cascaded microring resonators is three. The difference between the radii of the first microring resonator and the second microring resonator is the first difference value. The radius of the third microring resonator is greater than the radii of the first microring resonator and the second microring resonator. The difference between the radius of the third microring resonator and the radius of the first or second microring resonator is the second difference value. The second difference value is greater than the first difference value.

[0014] Furthermore, the wide waveguide laser gain chip is a multimode wide straight waveguide structure or a tapered amplification waveguide structure.

[0015] Furthermore, the feedback components include: The coupled waveguide is placed in parallel with the output of the cascaded microring resonator, and the light output from the cascaded microring resonator is coupled into the input of the coupled waveguide. The feedback waveguide connects to the output of the coupled waveguide and to the bus waveguide. The feedback waveguide is used to feed back a portion of the output light coupled from the coupled waveguide to the wide waveguide laser gain chip via the bus waveguide.

[0016] Furthermore, the silicon-based external cavity photonic chip includes a silicon substrate and a silicon dioxide lower cladding, a silicon nitride waveguide layer, and a silicon dioxide upper cladding deposited sequentially from bottom to top on the silicon substrate. A tip-type multi-segment edge coupler, a bus waveguide, a cascaded micro-ring resonator, and a feedback component are respectively fabricated on the silicon nitride waveguide layer. Heating electrodes for phase modulation are deposited on the silicon dioxide upper cladding at positions corresponding to the bus waveguide and the cascaded micro-ring resonator.

[0017] Compared with the prior art, the present invention can achieve the following beneficial effects: 1. This invention uses a wide-waveguide laser gain chip as the gain medium, which can provide higher output power compared to traditional single-mode or small-mode-field laser chips. The wider waveguide structure of the wide-waveguide laser chip can support higher optical power output, meeting the high-power laser requirements of high-performance optoelectronic devices.

[0018] 2. The tip-type multi-segment edge coupler designed in this invention significantly improves the end-face coupling efficiency between wide-waveguide laser gain chips and silicon-based external cavity photonic chips by extending the vertical mode field through a tip waveguide array. Simulation results show that the coupling efficiency reaches 88% at a wavelength of 1550nm, with a corresponding coupling loss of only 0.56dB, comparable to the coupling performance of single-mode or small-mode-field laser chips. Furthermore, the tip-type multi-segment edge coupler achieves a horizontal alignment tolerance of ±8.5μm with an additional 1dB loss. Compared to edge couplers designed for single-mode or small-mode-field laser gain chips, this edge coupler relaxes the alignment accuracy requirements of the bonding process, providing higher yield and lower cost for mass production.

[0019] 3. The advanced multi-segment edge coupler also boasts excellent broadband performance, covering the long-wavelength portion of the O-band to the L-band, with coupling loss of less than 1dB. This ultra-wideband characteristic enables the laser to operate efficiently across multiple wavelength ranges, making it suitable for a variety of applications.

[0020] 4. Compared to traditional wide-tapered edge couplers, this invention optimizes the coupler length to 650μm through a three-stage tapered combination structure, significantly shortening the coupler length and reducing modal perturbations and diffraction effects. This not only improves transmission efficiency but also reduces manufacturing and packaging complexity, thereby increasing production yield.

[0021] 5. This invention employs three cascaded microring resonators of different radii to design a photonic external cavity chip. The radius of the third microring resonator is much larger than that of the first two, significantly increasing the effective cavity length. Combined with a feedback waveguide designed using coupled-mode theory, the feedback optical power is maximized, further narrowing the laser linewidth to achieve linewidths in the kHz range or even narrower.

[0022] 6. Three cascaded microring resonators achieve a wider wavelength tuning range through the vernier effect, offering a broader tuning range compared to traditional dual-microring resonator structures. Combined with the thermal phase tuning function of the heating electrode, fast and precise wavelength tuning can be achieved, meeting the needs of various application scenarios. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 A schematic diagram of the structure of the high-power narrow-linewidth hybrid integrated laser described in the embodiments of the present invention; Figure 2 A schematic diagram of the structure of the tip multi-segment edge coupler described in the embodiment of the present invention; Figure 3 A schematic diagram of the fundamental mode spot mode field distribution of the wide waveguide laser gain chip described in the embodiment of the present invention; Figure 4 A schematic diagram of the mode field distribution of the tip waveguide array described in the embodiment of the present invention; wherein, Figure 4 (a) shows the mode field distribution at the injection end face of a single inverted conical waveguide; Figure 4 (b) shows the mode field distribution after coupling of all inverted conical waveguides to the injection end face; Figure 5 The simulation results illustrate the impact of the lengths of each segment of the tip-four-segment edge coupler described in the embodiments of the present invention on the overall coupling efficiency between the wide waveguide laser gain chip and the tip-four-segment edge coupler; wherein, Figure 5 (a) shows the relationship between the tip waveguide array length L1 and the total coupling efficiency; Figure 5 (b) shows the relationship between the length L2 of the first tapered waveguide and the overall coupling efficiency; Figure 5 (c) shows the relationship between the length L3 of the second tapered waveguide and the overall coupling efficiency; Figure 5 (d) shows the relationship between the length L4 of the third tapered waveguide and the overall coupling efficiency; Figure 6 This is a schematic diagram illustrating the mode evolution of the optical field propagating in a 650 μm-long tip-four-segment edge coupler, as described in an embodiment of the present invention; wherein, Figure 6(a) shows the optical field distribution in the YZ plane at the starting position (x=0μm) of the tip four-segment edge coupler; Figure 6 (b) shows the optical field distribution in the YZ plane at a distance of 41 micrometers (x=41μm) from the starting position within the tip four-segment edge coupler; Figure 6 (c) shows the optical field distribution in the YZ plane at a distance of 215 micrometers (x=215μm) from the starting position within the tip four-segment edge coupler; Figure 6 (d) shows the optical field distribution in the YZ plane at a distance of 390 micrometers (x=390μm) from the starting position within the tip four-segment edge coupler; Figure 6 (e) shows the optical field distribution in the YZ plane at a distance of 490 micrometers (x=490μm) from the starting position within the tip four-segment edge coupler; Figure 6 (f) shows the optical field distribution in the YZ plane at a distance of 590 micrometers (x=590μm) from the starting position within the tip four-segment edge coupler; Figure 6 (g) shows the optical field distribution in the YZ plane at a distance of 620 micrometers (x=620μm) from the starting position within the tip four-segment edge coupler; Figure 6 (h) shows the optical field distribution in the YZ plane at a distance of 650 micrometers (x=650μm) from the starting position within the tip four-segment edge coupler; Figure 7 A schematic diagram illustrating the dependence of the total coupling efficiency on wavelength between the wide waveguide laser gain chip and the 650μm long tip-type four-segment edge coupler described in the embodiment of the present invention.

[0024] Figure labeling: 1. Wide waveguide laser gain chip; 2. Silicon-based external cavity photonic chip; 21. Tip multi-segment edge coupler; 22. Bus waveguide; 23. First micro-ring resonator; 24. Second micro-ring resonator; 25. Third micro-ring resonator; 26. Coupled waveguide; 27. Feedback waveguide. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0027] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0028] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "assembly," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0029] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] like Figure 1 As shown, an embodiment of the present invention provides a high-power narrow-linewidth hybrid integrated laser, including a wide-waveguide laser gain chip 1 and a silicon-based external cavity photonic chip 2. The wide-waveguide laser gain chip 1 is used to provide optical gain; the silicon-based external cavity photonic chip 2 is coupled to the wide-waveguide laser gain chip 1 to form a laser resonant cavity and provide optical feedback.

[0031] To achieve higher output power in the hybrid integrated laser, this invention employs a wide-waveguide laser gain chip 1 to provide gain for the hybrid integrated laser. The wide-waveguide laser gain chip 1 utilizes a multimode wide straight waveguide structure or a tapered amplifying waveguide structure, exhibiting very high optical gain and a large beam mode field, such as above 40μm / 50μm. The center wavelength of the wide-waveguide laser gain chip 1 can be any band, such as the 1310nm, 1060nm, or 1550nm bands. The end of the wide-waveguide laser gain chip 1 facing away from the silicon-based external cavity photonic chip 2 is coated with a high-reflection film, while the end facing the silicon-based external cavity photonic chip 2 is coated with an anti-reflection film.

[0032] The silicon-based external cavity photonic chip 2 includes a silicon substrate and, from bottom to top, a silicon dioxide lower cladding layer, a silicon nitride waveguide layer, and a silicon dioxide upper cladding layer deposited on the silicon substrate. A pointed multi-segment edge coupler 21, a bus waveguide 22, at least three cascaded microring resonators, and a feedback component are fabricated on the silicon nitride waveguide layer. The input end of the pointed multi-segment edge coupler 21 is connected to the output end of the wide waveguide laser gain chip for receiving and coupling optical signals. The bus waveguide 22 is connected to the output end of the pointed multi-segment edge coupler 21 for transmitting optical signals. The cascaded microring resonators are coupled to the bus waveguide 22 for mode selection and extending the effective cavity length of the silicon-based external cavity photonic chip 2. The feedback component is located on one side of the output end of the bus waveguide 22 and is used to feed back a portion of the output light from the cascaded microring resonators to the bus waveguide 22 and transmit it to the wide waveguide laser gain chip 1.

[0033] Because silicon nitride material has low optical loss, high nonlinear coefficient, wide transparency window and excellent light field confinement capability, silicon nitride waveguide is used to design silicon-based external cavity photonic chips2.

[0034] Because the mode field of the wide-waveguide laser gain chip 1 is much larger than that of the single-mode silicon nitride waveguide, the efficiency of direct coupling between the two is extremely low. Therefore, this invention designs a novel tip-multi-segment edge coupler 21 to achieve coupling between the wide-waveguide laser gain chip 1 and the silicon-based external cavity photonic chip 2. The coupling end of the tip-multi-segment edge coupler 21 uses a tip waveguide array to extend the vertical mode field, improving the end-face coupling efficiency with the wide-waveguide laser gain chip 1. The transmission region of the tip-multi-segment edge coupler 21 uses tapered combined waveguides with gradually decreasing widths, significantly shortening the length of the tip-multi-segment edge coupler 21, thereby suppressing mode perturbations and diffraction effects, and further reducing the transmission loss of the tip-multi-segment edge coupler 21. This design enables the tip-multi-segment edge coupler 21 to achieve higher coupling efficiency with a shorter length. Therefore, this tip-multi-segment edge coupler 21 can efficiently couple and integrate the wide-waveguide laser gain chip 1 and the silicon-based external cavity photonic chip 2, ultimately achieving high-power output of the hybrid integrated laser.

[0035] This invention employs multiple cascaded microring resonators of varying radii to design a silicon-based external cavity photonic chip 2. The radii of the microring resonators gradually increase, with the radius of the last microring resonator being significantly larger than the others. This greatly increases the effective cavity length of the external cavity. The multiple cascaded microring resonators act as filters for mode selection in the hybrid integrated laser, and the longer effective cavity length narrows the laser linewidth. Furthermore, the different radii of the multiple microring resonators generate a vernier effect, enabling the hybrid integrated laser to achieve a wider tuning range. Figure 1 The diagram shows three microring resonators. The radius of the second microring resonator 24 is slightly larger than that of the first microring resonator 23. The radii of the first microring resonator 23 and the second microring resonator 24 are very similar. However, the radius of the third microring resonator 25 is much larger than that of the second microring resonator 24 and the first microring resonator 23. This greatly extends the effective cavity length of the external cavity photonic chip and further narrows the laser linewidth. The reason for choosing to cascade three microring resonators in this invention is that the vernier effect of three cascaded microring resonators can achieve a larger wavelength tuning range than that of two cascaded microring resonators.

[0036] This invention designs a feedback component based on coupled-mode theory, including a coupling waveguide 26 and a feedback waveguide 27. The coupling waveguide 26 is a straight waveguide section, placed in parallel with the output of a cascaded microring resonator. Light output from the cascaded microring resonator is coupled into the coupling waveguide 26 from its input. The input of the feedback waveguide 27 is connected to the output of the coupling waveguide 26, and its output is connected to a bus waveguide 22. The feedback waveguide 27 is used to feed back a portion of the output light coupled from the coupling waveguide 26 to the wide-waveguide laser gain chip 1 via the bus waveguide 22, maximizing the utilization of the feedback light power. This longer effective cavity length and stronger feedback effect further narrow the laser linewidth.

[0037] Heating electrodes for phase tuning are deposited on the silicon dioxide cladding at positions corresponding to the bus waveguide 22 and the cascaded microring resonators, respectively. By thermally controlling the phase of the bus waveguide 22 and the cascaded microring resonators, faster and finer wavelength tuning can be achieved.

[0038] The tip-type multi-segment edge coupler 21 includes a tip waveguide array and a tapered combined waveguide. The tip waveguide array consists of multiple inverted tapered waveguides arranged side by side. The width of the input end face of the inverted tapered waveguide is smaller than the width of the output end face. It is used to interface with the output end of the wide waveguide laser gain chip 1 and improve the end face coupling efficiency between the light spot mode field and the wide waveguide laser gain chip 1. The tapered combined waveguide consists of tapered waveguides connected end to end. The width of each tapered waveguide segment gradually decreases from the input end to the output end. The overall width of the tapered combined waveguide gradually decreases from the input end to the output end. The input end of the tapered combined waveguide is connected to the output end of the tip waveguide array. The output end of the tapered combined waveguide is connected to the bus waveguide 22. The tapered combined waveguide is used to compress the light spot mode field of the wide waveguide laser gain chip 1 into a single mode and transmit it to the bus waveguide 22.

[0039] Each inverted conical waveguide has a small mode field. The tip waveguide array synthesizes a larger effective mode field in the vertical direction through the spatial superposition of the small mode fields of each inverted conical waveguide. This matches the beam mode field distribution of the wide waveguide laser gain chip 1, increases the mode overlap efficiency with the mode field of the wide waveguide laser gain chip 1, and thus improves the end-face coupling efficiency between the two modes. If the tip waveguide array is removed and only the conical combined waveguide is retained, the vertical mode field of the tip multi-segment edge coupler 21 is limited by the waveguide thickness and cannot expand the vertical mode field. This reduces the mode overlap efficiency between the tip multi-segment edge coupler 21 and the wide waveguide laser gain chip 1, resulting in a decrease in coupling efficiency and making it difficult to improve the coupling efficiency.

[0040] Multiple inverted conical waveguides are arranged at equal intervals, and each inverted conical waveguide has the same length, input end-face width, and output end-face width. The number of inverted conical waveguides, their lengths, the widths of their input end-faces, and the center-to-center spacing between adjacent inverted conical waveguides mainly affect the mode overlap efficiency with the wide-waveguide laser gain chip 1. A higher mode overlap efficiency indicates a higher end-face coupling efficiency between the tip multi-segment edge coupler 21 and the wide-waveguide laser gain chip 1, meaning more light is coupled from the wide-waveguide laser gain chip 1 into the tip multi-segment edge coupler 21. In practical applications, based on the different mode field dimensions of the wide waveguide laser gain chip 1, the number of inverted conical waveguides, the length of the inverted conical waveguides, the width of the input end face of the inverted conical waveguides, and the center spacing between two adjacent inverted conical waveguides can be determined by simulation using the FDE and FDTD modules in the Lumerical simulation software. The goal is to achieve the maximum mode overlap efficiency (i.e., end face coupling efficiency) between the tip multi-segment edge coupler 21 and the wide waveguide laser gain chip 1.

[0041] The width of the rear face of the inverted conical waveguide, the length of the conical composite waveguide, and the widths at both ends of the conical composite waveguide primarily affect the transmission efficiency of the tip multi-segment edge coupler 21, and consequently, its overall coupling efficiency. In practical applications, these factors can be determined through simulation using the EME and FDTD modules in Lumerical simulation software, with the goal of maximizing the overall coupling efficiency of the tip multi-segment edge coupler 21.

[0042] The following explanation uses a four-segment tip-type edge coupler as an example. A tip waveguide array is used as the first segment of the edge coupler, and three tapered waveguide segments are used as the second to fourth segments.

[0043] like Figure 2 As shown, I is a pointed waveguide array with a length of L1; pointed waveguide array I consists of a row of equally spaced inverted conical waveguides, W a W is the width of the incident end face of each inverted conical waveguide. b The width of the exit face of each inverted conical waveguide is W, and the width of the incident face of the inverted conical waveguide is W. a smaller than the width W of the exit end face b W c N is the center-to-center distance between two adjacent inverted conical waveguides. tip The number of inverted conical waveguides. These parameters of the aforementioned tip waveguide array depend on the beam pattern size of the wide waveguide laser gain chip 1.

[0044] The three-segment tapered waveguide consists of three interconnected segments: a first segment (T-2), a second segment (T-3), and a third segment (T-4). The lengths of T-2, T-3, and T-4 are L2, L3, and L4, respectively. T-2 is connected to the tip waveguide array I. The width of the incident face of T-2 is W1, and the width of the exit face is W2. T-3 connects T-2 and T-4. The width of the incident face of T-3 is W2, and the width of the exit face is W3. The exit face of T-4 connects to the bus waveguide 22. The width of the incident face of T-4 is W3, and the width of the exit face is W4.

[0045] Fixed center-to-center spacing W between adjacent inverted conical waveguides cBy simulating and optimizing the number and width of the inverted conical waveguides, the mode overlap efficiency between the tip-shaped four-segment edge coupler and the wide-waveguide laser gain chip 1 can be increased, thereby improving the end-face coupling efficiency between the two. By simulating and optimizing the lengths of the tip-shaped waveguide array I and the first conical waveguide II, the second conical waveguide III, and the third conical waveguide IV, the transmission loss of light in the tip-shaped four-segment edge coupler can be reduced, thereby increasing the overall coupling efficiency of the tip-shaped four-segment edge coupler.

[0046] The simulation verification of the tip-type four-segment edge coupler is as follows: like Figure 3 As shown, the fundamental mode spot diameter of the wide waveguide laser gain chip 1 is approximately 50 μm (Y-axis direction, i.e., the horizontal direction of the light field) × 2.5 μm (Z-axis direction, i.e., the vertical direction of the light field).

[0047] This invention uses the FDE and FDTD modules in Lumerical simulation software to simulate and determine the structural parameters of an inverted conical waveguide for a wide waveguide laser gain chip with a fundamental mode spot diameter of approximately 50 μm × 2.5 μm. The parameters include the width W of the incident end face of the inverted conical waveguide. a Width W of the exit end face b The center-to-center spacing W between the inverted conical waveguides is 0.26 μm and 0.5 μm, respectively. c The wavelength is 0.8 μm, and the number of inverted conical waveguides is 62. At this point, the end-face coupling efficiency between the wide-waveguide laser gain chip 1 and the tip-type four-segment edge coupler is approximately 0.92. The mode field distribution of a single inverted conical waveguide input end face and the mode field distribution after coupling of all inverted conical waveguide input end faces are shown below. Figure 4 As shown in (a) and (b), Figure 4 (b) shows the optical field morphology of the entire coupling end face composed of all 62 inverted conical waveguides. The shape and size of this synthesized optical field match the large spot mode field of 50μm×2.5μm output by the wide waveguide laser gain chip 1.

[0048] After selecting W1, W2, W3, and W4 as 50μm, 30μm, 15μm, and 1μm respectively, this invention used the EME module in Lumerical software to simulate the influence of the length of each segment of the tip-type four-segment edge coupler on the overall coupling efficiency between the wide waveguide laser gain chip 1 and the tip-type four-segment edge coupler. The results are as follows: Figure 5As shown in (a)-(d) in the figure. Based on the simulation results, the final selected lengths are: L1 of the tip waveguide array is 40 μm, L2 of the first tapered waveguide segment is 350 μm, L3 of the second tapered waveguide segment is 200 μm, and L4 of the third tapered waveguide segment is 60 μm. The total length of the corresponding four-segment tip edge coupler is 650 μm, and its total coupling efficiency is approximately 0.88.

[0049] Traditional edge couplers based on a single wide tapered waveguide require increasing their length (generally above 1500 μm) to reduce transmission loss by suppressing mode perturbations and diffraction effects, in order to ensure high coupling efficiency. This invention optimizes the overall length of the four-segment tip edge coupler to 650 μm through a three-segment tapered waveguide design, which can suppress mode perturbations and diffraction effects, thereby reducing the transmission loss of the edge coupler. This design enables the edge coupler to achieve higher coupling efficiency with a shorter length.

[0050] This invention illustrates the evolution of the beam pattern field when the light field propagates in a 650 μm long tip-four-segment edge coupler, such as... Figure 6 As shown in (a)-(h).

[0051] For the starting position: such as Figure 6 As shown in (a), x=0μm corresponds to the incident end face position of the light field at the tip waveguide array, showing a broadened mode field that matches the large-size light spot of the wide waveguide laser gain chip 1, thus achieving high end face coupling efficiency.

[0052] For intermediate processes: such as Figure 6 As shown in (b) to (g), light propagates in a three-segment tapered waveguide. Figure 6 Figures (b) to (g) clearly demonstrate how the optical field is gradually constrained and compressed without significant mode distortion or scattering. This directly proves the effectiveness of the present invention in suppressing mode perturbations and diffraction effects, and is key to achieving high transmission efficiency in the tip-type four-segment edge coupler.

[0053] For the destination location: such as Figure 6 As shown in (h), x=650μm corresponds to the optical field being perfectly compressed into a small, regular spot, which matches the fundamental mode of bus waveguide 22, indicating that the optical field is ready to efficiently enter the subsequent photonic circuit.

[0054] Furthermore, this invention simulates the dependence of the total coupling efficiency on wavelength between the wide waveguide laser gain chip 1 and the 650μm long tip-type four-segment edge coupler using the FDTD module in Lumerical software. The results are as follows: Figure 7As shown, this tip-based four-segment edge coupler exhibits ultra-wideband performance with less than 1 dB coupling loss from the O-band long-wavelength portion to the L-band, and a horizontal alignment tolerance of ±8.5 μm for the 1 dB additional loss. Simulation results show that this tip-based four-segment edge coupler achieves a coupling efficiency of up to 88% at a wavelength of 1550 nm on a wide-waveguide laser chip, with a corresponding coupling loss of only 0.56 dB. This coupling performance is comparable to that of edge couplers designed for single-mode or small-mode-field-size laser chips.

[0055] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0056] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A high-power, narrow-linewidth hybrid integrated laser, characterized in that, include: Wide waveguide laser gain chip, used to provide optical gain; A silicon-based external cavity photonic chip, coupled with a wide-waveguide laser gain chip, is used to form a laser resonant cavity and provide optical feedback; wherein the silicon-based external cavity photonic chip includes: A multi-segment edge coupler with a pointed tip is connected to the output of a wide waveguide laser gain chip to receive and couple optical signals. Bus waveguide, which connects to the output of a tip multi-segment edge coupler, is used to transmit optical signals; At least three cascaded microring resonators are coupled to a bus waveguide for mode selection and to extend the effective cavity length of the silicon-based external cavity photonic chip. The feedback component is located on the output side of the bus waveguide and is used to feed back part of the output light of the cascaded micro-ring resonator to the bus waveguide and transmit it to the wide waveguide laser gain chip. Tip-type multi-segment edge couplers include: The pointed waveguide array is composed of inverted conical waveguides arranged side by side. The width of the input end face of the inverted conical waveguide is smaller than the width of the output end face. It is used to interface with the output end of the wide waveguide laser gain chip and improve the end face coupling efficiency between the beam mode field of the wide waveguide laser gain chip. The tapered combined waveguide has a width that gradually decreases from the input end to the output end. The input end of the tapered combined waveguide is connected to the output end of the tip waveguide array, and the output end of the tapered combined waveguide is connected to the bus waveguide. The tapered combined waveguide is used to compress the beam mode field of the wide waveguide laser gain chip into a single mode and transmit it to the bus waveguide.

2. The high-power narrow-linewidth hybrid integrated laser according to claim 1, characterized in that, The inverted conical waveguides in the tip waveguide array are arranged side by side at equal intervals, and the length, input end face width, and output end face width of each inverted conical waveguide are the same.

3. The high-power narrow-linewidth hybrid integrated laser according to claim 1, characterized in that, There are 62 inverted conical waveguides, each with a length of 40 μm, an input end face width of 0.26 μm, an output end face width of 0.5 μm, and a center-to-center distance of 0.8 μm between adjacent inverted conical waveguides.

4. The high-power narrow-linewidth hybrid integrated laser according to claim 1, characterized in that, A tapered composite waveguide is composed of tapered waveguides connected end to end, with the width of each tapered waveguide gradually decreasing from the input end to the output end.

5. The high-power narrow-linewidth hybrid integrated laser according to claim 4, characterized in that, The tapered waveguide is composed of three tapered waveguide segments connected end to end. The width of the input end face of the first tapered waveguide is greater than the width of the output end face. The width of the input end face of the second tapered waveguide is the same as the width of the output end face of the first tapered waveguide, and the width of the input end face of the second tapered waveguide is greater than the width of the output end face. The width of the input end face of the third tapered waveguide is the same as the width of the output end face of the second tapered waveguide, and the width of the input end face of the third tapered waveguide is greater than the width of the output end face.

6. The high-power narrow-linewidth hybrid integrated laser according to claim 5, characterized in that, The first tapered waveguide has a length of 350 μm, a width of 50 μm at its input end face, and a width of 30 μm at its output end face. The second tapered waveguide has a length of 200 μm, a width of 30 μm at its input end face, and a width of 15 μm at its output end face. The third tapered waveguide has a length of 60 μm, a width of 15 μm at its input end face, and a width of 1 μm at its output end face.

7. The high-power narrow-linewidth hybrid integrated laser according to claim 1, characterized in that, The number of cascaded microring resonators is 3. The difference between the radii of the first microring resonator and the second microring resonator is the first difference value. The radius of the third microring resonator is greater than the radii of the first microring resonator and the second microring resonator. The difference between the radius of the third microring resonator and the radius of the first microring resonator or the second microring resonator is the second difference value. The second difference value is greater than the first difference value.

8. The high-power narrow-linewidth hybrid integrated laser according to claim 1, characterized in that, Wide waveguide laser gain chips are multimode wide straight waveguide structures or tapered amplification waveguide structures.

9. The high-power narrow-linewidth hybrid integrated laser according to claim 1, characterized in that, The feedback components include: The coupled waveguide is placed in parallel with the output of the cascaded microring resonator, and the light output from the cascaded microring resonator is coupled into the input of the coupled waveguide. The feedback waveguide connects to the output of the coupled waveguide and to the bus waveguide. The feedback waveguide is used to feed back a portion of the output light coupled from the coupled waveguide to the wide waveguide laser gain chip via the bus waveguide.

10. The high-power narrow-linewidth hybrid integrated laser according to claim 1, characterized in that, The silicon-based external cavity photonic chip includes a silicon substrate and a silicon dioxide lower cladding, a silicon nitride waveguide layer, and a silicon dioxide upper cladding, which are deposited sequentially from bottom to top on the silicon substrate. A tip-type multi-segment edge coupler, a bus waveguide, a cascaded micro-ring resonator, and a feedback component are respectively fabricated on the silicon nitride waveguide layer. Heating electrodes for phase modulation are deposited on the silicon dioxide upper cladding at positions corresponding to the bus waveguide and the cascaded micro-ring resonator.

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