A room-temperature blue light topological corner state nanolaser based on a two-dimensional SSH topological lattice and a preparation method thereof

Abstract

Embodiments of the present application disclose a room-temperature blue light topological corner state nanolaser based on a two-dimensional SSH topological lattice and a preparation method thereof. Embodiments of the present application include a supporting substrate; a blue light gain film located on the supporting substrate, the blue light gain film including a nanocolumn array; wherein the nanocolumn array includes a central region and a peripheral region surrounding the central region; a plurality of nanocolumns in the nanocolumn array are arranged according to a two-dimensional SSH lattice, and every four adjacent nanocolumns form a tetramer unit; the spacing between nanocolumns inside the tetramer unit is an intracell spacing, and the spacing between adjacent tetramer units is an intercell spacing; in the central region, the intracell spacing is less than the intercell spacing; in the peripheral region, the intracell spacing is greater than the intercell spacing; a closed domain wall is formed at the junction of the central region and the peripheral region, and a zero-dimensional topological corner state is formed at the internal corner of the closed domain wall. Thus, embodiments of the present application improve the stability of the laser mode.

Description

Technical Field

[0001] This application relates to the field of optoelectronic technology, specifically to a room-temperature blue topological angle state nanolaser based on a two-dimensional SSH topological lattice and its fabrication method. Background Technology

[0002] Blue nanolasers are micro- and nanoscale laser devices capable of generating coherent light output in the blue light band, and they have significant application value in optical communication, on-chip optoelectronic systems, visible light displays, and integrated light sources. Traditional blue nanolasers often employ structures such as microdisk cavities, photonic crystal defect cavities, nanowire cavities, or Fabry-Perot cavities, and their laser modes primarily rely on local geometric resonances. The Su–Schrieffer–Heeger (SSH) model is a topological lattice model that, by adjusting the strength of intracellular and intercellular coupling, can form interface states with topological protection properties at the boundaries of different topological phases, providing a new approach to controlling the stability of the laser mode.

[0003] However, existing blue nanolasers rely on local geometric resonance for their laser modes, which are easily affected by cavity size errors, sidewall roughness, and boundary defects, leading to mode drift, multimode competition, or unstable laser output, resulting in technical problems of insufficient mode stability. Summary of the Invention

[0004] This application provides a room-temperature blue topological angle state nanolaser based on a two-dimensional SSH topological lattice and its fabrication method. By constructing a two-dimensional SSH topological lattice in a nanopillar array, closed domain walls are formed between the central region and the peripheral region. The zero-dimensional topological angle state at the inner corner of the closed domain wall is used as the laser mode, so that the laser mode is determined by the overall topological coupling relationship rather than relying on local geometric resonance, thereby improving the stability of the laser mode.

[0005] This application provides a room-temperature blue topological angular nanolaser based on a two-dimensional SSH topological lattice, the laser comprising:

[0006] Support substrate;

[0007] A blue light gain film is located on a supporting substrate, and the blue light gain film includes an array of nanopillars.

[0008] The nanopillar array includes a central region and an outer region surrounding the central region;

[0009] Multiple nanopillars in the nanopillar array are arranged in a two-dimensional SSH lattice, and every four adjacent nanopillars form a tetramer unit.

[0010] The spacing between nanopillars inside a tetramer unit is the intracellular spacing, and the spacing between adjacent tetramer units is the intercellular spacing.

[0011] In the central region, the intracellular spacing is smaller than the intercellular spacing; in the peripheral region, the intracellular spacing is larger than the intercellular spacing.

[0012] A closed domain wall is formed at the boundary between the central region and the outer region, and a zero-dimensional topological angle state is formed at the inner corner of the closed domain wall.

[0013] On the other hand, a method for fabricating a room-temperature blue topological angular nanolaser based on a two-dimensional SSH topological lattice is provided, the method comprising:

[0014] Provides a blue light multi-quantum-well epitaxial wafer, the epitaxial wafer comprising a primary growth substrate and a blue light gain thin film grown thereon;

[0015] A metal layer for bonding transfer is formed on the side of the blue light gain film facing away from the original growth substrate. The metal layer is formed by evaporation, sputtering or electroplating processes.

[0016] Blue light multi-quantum-well epitaxial wafers are flip-chip bonded to a support substrate using a metal layer;

[0017] The original growth substrate was removed, and the exposed blue light gain film was thinned.

[0018] A two-dimensional SSH lattice pattern is defined on the surface of the thinned blue light gain film, and the pattern is transferred to the blue light gain film by dry etching to form a nanopillar array containing a central region, a peripheral region and closed domain walls.

[0019] The beneficial effects of the technical solution provided in this application include at least the following:

[0020] In the nanolaser provided in this application, the nanopillar array is arranged according to a two-dimensional SSH topological lattice. Through the inversion of the strength of intracellular and intercellular coupling between the central and peripheral regions, a zero-dimensional topological angular state is formed at the inner corner of the closed domain wall. Since the laser mode is determined by the overall topological coupling relationship rather than relying on local geometric resonance, it is less susceptible to the effects of cavity size errors, sidewall roughness, and boundary defects. Compared with traditional blue nanolasers that use local resonance structures such as microdisk cavities and photonic crystal defect cavities, the nanolaser provided in this application has higher mode stability.

[0021] Furthermore, the closed domain walls are preferably closed square domain walls, with zero-dimensional topological corner states formed at the four interior corners of the closed square domain walls, spatially overlapping with multiple quantum wells to provide optical gain. Due to the high spatial locality of the zero-dimensional topological corner states, they exhibit strong mode selectivity, enabling them to preferentially reach the laser threshold and generate laser output. This allows for single-mode, narrow-linewidth blue laser output with a wavelength in the range of 430 nm to 480 nm and a linewidth less than 0.1 nm. Moreover, by adjusting the lattice constant, the radius of the nanopillars, the height of the nanopillars, or the ratio of intracellular to intercellular spacing, the output wavelength of the blue laser can be flexibly controlled, facilitating device design according to different application requirements.

[0022] Furthermore, the nanopillars allow for processing deviations such as sidewall taper, non-ideal morphology where the top dimension is smaller than the bottom dimension, or slight local dimensional deviations. As long as these processing deviations are non-destructive, and the nanopillar array as a whole maintains the strong-weak inversion relationship between intracellular and intercellular couplings and the closed domain walls remain continuous, zero-dimensional topological angular states can still exist and generate laser output. Therefore, the nanolaser provided in this application has a certain tolerance for non-destructive processing deviations in actual fabrication, which helps improve the device's process adaptability.

[0023] Furthermore, the blue light gain film is an indium gallium nitride / gallium nitride multiple quantum well, comprising quantum well nanopillars and a quantum well cladding. The quantum well nanopillars form a nanopillar array, and the quantum well cladding is located below and connected to the quantum well nanopillars. Both the quantum well nanopillars and the quantum well cladding are formed by alternating layers of indium gallium nitride and gallium nitride, and both provide blue light gain. The blue light gain film also includes a gallium nitride cladding in the thickness direction. The gallium nitride cladding does not provide blue light gain and is not part of the multiple quantum well. Since the optical field of the zero-dimensional topological angular state and the multiple quantum well, which is the active region, are spatially fully overlapped, it helps to improve the optical gain coupling efficiency. The blue light gain film is a substrate transfer film with the original growth substrate removed. The supporting substrate is bonded to the bottom of the blue light gain film through a metal layer. The metal layer has both optical reflection and structural support functions, which helps to improve the optical gain utilization and structural stability of the device. The etch gaps between adjacent nanopillars are filled with air or a low-refractive-index medium to create a refractive index contrast, which helps to enhance the lateral confinement of the light field and further improve the spatial locality of the topological angular states.

[0024] Furthermore, the nanopillar array can contain multiple closed domain walls arranged in a one-dimensional or two-dimensional array. The zero-dimensional topological angular states at the inner corners of each closed domain wall are optically independent and generate blue laser output independently, thereby forming a multi-channel emission array. This is beneficial for improving device integration and is suitable for applications such as multi-channel blue light sources, on-chip displays, optical communication, or integrated photonic chips.

[0025] Furthermore, the nanolaser provided in this application can operate using optical pumping or electric pumping. Optical pumping uses ultraviolet or near-ultraviolet pulsed lasers in the range of 320nm to 380nm as the pump source, which is suitable for device performance characterization. Electric pumping achieves excitation by injecting current into the blue light gain film, which facilitates the practical application and integrated application of the device, thereby broadening the application range of the nanolaser provided in this application. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of a room-temperature blue topological angular nanolaser based on a two-dimensional SSH topological lattice provided in the embodiments of this application;

[0028] Figure 2 This is a simulation diagram of the angular state mode of the room-temperature blue topological angular state nanolaser provided in the embodiments of this application;

[0029] Figure 3 This is a full scanning electron microscope image of a physical object processed by the room-temperature blue light topological angle state nanolaser provided in the embodiments of this application;

[0030] Figure 4 This is a magnified scanning electron microscope image of a physical object processed by the room-temperature blue light topological angle state nanolaser provided in the embodiments of this application;

[0031] Figure 5 This is a schematic diagram showing the photoluminescence spectrum and output intensity of a topological laser in angular mode as a function of pump energy density, provided in an embodiment of this application.

[0032] Figure 6 This is a flowchart illustrating the fabrication method of a room-temperature blue topological angular nanolaser based on a two-dimensional SSH topological lattice, as provided in the embodiments of this application. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0034] The following embodiments of this application provide a room-temperature blue topological angular nanolaser based on a two-dimensional SSH topological lattice. Figure 1 This is a schematic diagram of the structure of a room-temperature blue topological angular nanolaser based on a two-dimensional SSH topological lattice provided in an embodiment of this application, as shown below. Figure 1As shown, the room-temperature blue topological angle nanolaser 10 may include a supporting substrate S1011 and a blue light gain film S1014, wherein the blue light gain film S1014 includes a nanopillar array S10142.

[0035] The supporting substrate S1011 is located at the bottom of the device and provides mechanical support for the entire device. A metal layer S1012 is also disposed between the supporting substrate S1011 and the blue light gain film S1014. This metal layer S1012 can be a metal reflective layer or a metal bonding layer, serving both optical reflection and structural support functions. Optionally, the material of the metal layer can include a single metal, an alloy metal, or a multilayer metal stack structure. For example, it can include one or more of Ni, Ag, Au, Ti, and Al, or an alloy of the above metals, or a multilayer metal stack structure composed of the above metals.

[0036] The blue light gain film S1014 is located above the metal layer S1012. The blue light gain film S1014 is a multi-quantum well, which includes quantum well nanopillars (i.e., nanopillar array S10142) and a quantum well cladding S10141 located below and connected to the quantum well nanopillars. Both the quantum well nanopillars and the quantum well cladding S10141 are formed by alternating layers of indium gallium nitride (i.e., InGaN) and gallium nitride (i.e., GaN) layers and both provide blue light gain. The blue light gain film S1014 also includes a gallium nitride (i.e., GaN) cladding S1013 located below the quantum well cladding S10141 in the thickness direction. The gallium nitride cladding S1013 is a gallium nitride layer that does not provide gain, does not belong to the multi-quantum well, and is a different film layer from the multi-quantum well. The blue light gain film S1014 is a substrate transfer film with the original growth substrate removed. A supporting substrate S1011 is bonded to the bottom of the blue light gain film S1014 via a metal layer S1012. The thickness of the blue light gain film S1014 ranges from 200 nm to 800 nm, and can be further selected as 300 nm to 600 nm. This thickness design allows the optical field of the topological angle states to fully overlap with the multiple quantum wells in space, thereby achieving effective optical gain.

[0037] The nanopillar array S10142 consists of quantum well nanopillars within the blue light gain film S1014. It is formed by patterned etching of the blue light gain film S1014 (i.e., indium gallium nitride / gallium nitride multiple quantum wells, InGaN / GaN), with multiple nanopillars arranged in a two-dimensional SSH topological lattice. The nanopillar array S10142, along with the underlying quantum well cladding S10141, belongs to the indium gallium nitride / gallium nitride multiple quantum well family and provides blue light gain, ensuring sufficient overlap between the light field of the zero-dimensional topological angular states and the multiple quantum wells, thereby achieving effective optical gain. Etched gaps exist between adjacent nanopillars; these gaps are photonic crystal air holes filled with air or a low-refractive-index medium, which helps enhance the lateral confinement of the light field and improve the spatial localization of the topological angular states.

[0038] It should be noted that the blue light gain film S1014, namely the indium gallium nitride / gallium nitride multiple quantum wells, includes quantum well nanopillars and a quantum well cladding S10141. The quantum well nanopillars form a nanopillar array S10142, and the quantum well cladding S10141 is located below and connected to the nanopillar array S10142. Both the quantum well nanopillars and the quantum well cladding S10141 are formed by alternating layers of indium gallium nitride (InGaN) and gallium nitride (GaN), and both serve as active regions providing blue light gain. The gallium nitride cladding S1013 located below the quantum well cladding S10141 is a gallium nitride layer that does not provide gain; it is not part of the multiple quantum wells, and the gallium nitride cladding S1013 and the multiple quantum wells are different films. The optical field of the zero-dimensional topological angular state fully overlaps with the multiple quantum wells, thereby obtaining effective optical gain.

[0039] Optionally, the support substrate S1011 can be made of silicon, silicon carbide, alumina, or other materials with good thermal conductivity and mechanical strength. The support substrate S1011 needs to have sufficient mechanical strength to support the blue light gain film S1014 and the nanopillar array S10142, while its thermal conductivity helps to dissipate the heat generated during device operation quickly, avoiding heat accumulation that could affect the gain characteristics of the multi-quantum well.

[0040] Figure 2 This is a simulation diagram of the angular mode of the room temperature blue light topological angular state nanolaser provided in the embodiments of this application, wherein (a) is a conical nanopillar and (b) is a cylindrical nanopillar. Figure 3 This is a full scanning electron microscope image of a physical object processed by the room temperature blue light topological angular nanolaser provided in the embodiments of this application. Figure 4 This is a magnified scanning electron microscope image of a physical object processed by the room-temperature blue light topological angular nanolaser provided in the embodiments of this application. For example... Figures 2 to 4 As shown, the nanopillar array includes a central region and an outer region surrounding the central region, with each four adjacent nanopillars forming a tetramer unit.

[0041] The spacing between nanopillars within a tetramer unit is the intracellular spacing, while the spacing between adjacent tetramer units is the intercellular spacing. In the central region, the intracellular spacing is smaller than the intercellular spacing, corresponding to a topologically nontrivial state; in the peripheral region, the intracellular spacing is larger than the intercellular spacing, corresponding to a topologically trivial state. Closed domain walls are formed at the boundary between the central and peripheral regions, and zero-dimensional topological angular states are formed at the interior corners of these closed domain walls. These zero-dimensional topological angular states are spatially localized optical modes, with their light field mainly concentrated near the interior corners of the closed domain walls. The laser mode is determined by the overall topological coupling relationship rather than relying on local geometric resonance, thus making it less susceptible to cavity size errors, sidewall roughness, and boundary defects.

[0042] It should be noted that in the above structure, the central region corresponds to a topologically nontrivial state, while the outer region corresponds to a topologically trivial state; the two have different topological properties. A closed domain wall is formed at the boundary between them, and a zero-dimensional topological angular state is formed at the interior corner of the closed domain wall. The optical field of this zero-dimensional topological angular state is highly localized near the interior corner, exhibiting strong spatial locality and mode selectivity. After gain is provided by multiple quantum wells, it can preferentially reach the laser threshold and generate laser output.

[0043] Additionally, it should be noted that in this application, "interior angle" refers to the corner point of the apex of a closed domain wall that faces the central region. Taking a closed square domain wall as an example, the square domain wall has four apex angles, and the corner point of each apex facing the central region is the interior angle. The light field of the zero-dimensional topological angular state is localized in the vicinity of these four interior angles.

[0044] Optionally, the closed domain wall is a closed square domain wall, and the zero-dimensional topological corner state is formed at the four interior corners of the closed square domain wall and spatially overlaps with the multiple quantum wells to provide optical gain. Due to the high spatial locality of the zero-dimensional topological corner state, it has strong mode selectivity, which enables the zero-dimensional topological corner state to preferentially reach the laser threshold and generate laser output, thereby realizing blue single-mode, narrow linewidth laser output with a laser wavelength in the range of 430nm to 480nm and a linewidth of less than 0.1nm.

[0045] Tetramer units constitute the basic unit of a two-dimensional SSH lattice. The lattice constant of the basic unit can be designed according to the target blue light wavelength, preferably 180nm to 280nm, and more preferably 200nm to 250nm. For example, the lattice constant can be selected as 210nm, 220nm or 230nm to achieve blue light angular state laser output in different wavelength ranges.

[0046] For example, a laser peak of approximately 462.55 nm can be obtained when the lattice constant is 220 nm; a laser peak of approximately 472.7 nm can be obtained when the lattice constant is 230 nm, and the linewidths are both within the narrow linewidth range. By adjusting the lattice constant, the radius of the nanopillars, the height of the nanopillars, or the ratio of intracellular to intercellular spacing, the output wavelength of the blue laser can be flexibly controlled, facilitating device design according to different application requirements.

[0047] The base radius of the nanopillar ranges from 40 nm to 100 nm, further preferably from 50 nm to 90 nm, and more preferably about 70 nm; the top radius of the nanopillar ranges from 10 nm to 60 nm, further preferably from 15 nm to 45 nm, and more preferably about 26 nm; the height of the nanopillar ranges from 100 nm to 300 nm, further preferably from 120 nm to 250 nm, and more preferably about 170 nm. Through this dimensional design, the optical field of the topological angle state can fully overlap with the active region of blue light gain, thereby obtaining effective optical gain.

[0048] The nanopillars can be cylindrical or frustum-shaped with tapered sidewalls. Specifically, cylindrical structures can be cylinders, elliptical cylinders, etc.; frustum-shaped structures can be frustums of a cone, truncated cone, or elliptical truncated cone, etc., with a top cross-sectional area smaller than the bottom cross-sectional area. In actual fabrication, due to limitations of dry etching processes, nanopillars are often not ideal cylinders but may exhibit a frustum-shaped morphology with tapered sidewalls. This application does not require the nanopillars to be ideal cylinders; processing deviations such as tapered sidewalls, reduced top size, slight surface contamination, or slight local dimensional deviations are permissible for each nanopillar in the nanopillar array. As long as these processing deviations are non-destructive, and the nanopillar array as a whole maintains the inverted relationship of stronger intercellular coupling than intracellular coupling in the central region and stronger intracellular coupling than intercellular coupling in the peripheral region, and the nanopillars constituting the closed domain walls are continuously arranged without gaps, zero-dimensional topological angular states can still exist and generate laser output. Conversely, when there are severe pillar defects at the domain walls, the domain wall continuity is disrupted, or key nanopillars at the inner corners are missing, the corner localization conditions may be disrupted, and the device may degenerate into a common defect mode or a Fabry-Perot-like mode.

[0049] It should be noted that, as Figure 2 As shown, simulation results for frustum-shaped nanopillars with sidewall tapers (a) and ideal cylindrical nanopillars (b) indicate that the actual frustum-shaped nanopillar structure will cause certain changes in the angular state frequency and field distribution, but will not change the higher-order topological origin of the angular state.

[0050] Furthermore, it should be noted that in this application, "non-destructive deviation" refers to a processing deviation that does not disrupt the following two key conditions: First, the nanopillar array as a whole maintains the inverted relationship of intercellular coupling being stronger than intracellular coupling in the central region and intracellular coupling being stronger than intercellular coupling in the peripheral region; that is, the relationship between the magnitude of any intracellular spacing and intercellular spacing in each region does not reverse. Second, the nanopillars constituting the closed domain walls are continuously arranged without any gaps, and the continuity of the closed domain walls remains intact. Processing deviations that satisfy the above two conditions are considered non-destructive deviations, and zero-dimensional topological angular states can still exist and generate laser output under these conditions. Conversely, if either of the above conditions is disrupted, it is considered a destructive deviation, and the device may degenerate into a common defect mode or a Fabry-Perot type mode.

[0051] Optionally, the nanopillar array may contain multiple closed domain walls, which are arranged in a one-dimensional or two-dimensional array to form a multi-channel emission array. In the multi-channel emission array, each closed domain wall independently forms a zero-dimensional topological angle state at its interior corner. These zero-dimensional topological angle states are optically independent of each other and independently generate blue laser output, which is beneficial for improving device integration and is suitable for applications such as multi-channel blue light sources, on-chip displays, optical communication, or integrated photonic chips.

[0052] Figure 5 This diagram illustrates the photoluminescence spectrum and output intensity variation with pump energy density of the topological laser angular mode provided in this embodiment. The nanolaser provided in this embodiment can operate using either optical or electrical pumping. When optical pumping is used, the pump source is an ultraviolet or near-ultraviolet pulsed laser with a wavelength range of 320 nm to 380 nm, for example, a 355 nm pulsed laser. When the pump light irradiates near the inner corner of the closed domain wall, stimulated emission occurs in the blue light gain film, and the zero-dimensional topological angular state gains gain and generates blue laser output. Figure 5 As shown, the excitation threshold is approximately 850 nanojoules / square centimeter. Above this threshold, the output intensity is significantly enhanced, and the linewidth remains within a narrow range. When using an electric pumping method, injecting current into the blue light gain film excites it, enabling the zero-dimensional topological angular state to gain gain and generate blue laser output, facilitating the practical application and integration of the device.

[0053] It should be noted that the above laser output characteristics are typical results measured under optical pumping conditions. With increasing pump energy density, the device output intensity exhibits a significant nonlinear enhancement near the excitation threshold, and the linewidth narrows significantly, indicating that the device has entered a laser oscillation state. The aforementioned single-mode narrow-linewidth laser output characteristics originate from the high spatial locality and mode selectivity of the zero-dimensional topological angular state, rather than relying on cavity geometric resonance, thus exhibiting good output stability.

[0054] In some embodiments, the linewidth of the single-mode blue laser is preferably less than 0.1 nm, and more preferably less than 0.06 nm. Different wavelengths of blue topological angle state laser output can be achieved by adjusting the lattice constant. For example, when the lattice constant is 220 nm, a laser peak of approximately 462.55 nm can be obtained; when the lattice constant is 230 nm, a laser peak of approximately 472.7 nm can be obtained, and the laser linewidth in both cases is within the aforementioned narrow linewidth range.

[0055] This application combines a multi-quantum-well blue light gain film with a two-dimensional SSH high-order topological lattice to construct closed domain walls between topologically nontrivial and topologically trivial regions, and utilizes the zero-dimensional topological angular states formed at the interior corners of the closed domain walls as laser modes, which can bring the following beneficial effects:

[0056] 1) This application breaks through the limitation of existing topological lasers, which are mostly concentrated in the infrared band, and extends high-order topological angular state lasers to the blue light band. By providing blue light gain through multiple quantum wells and using a two-dimensional SSH topological lattice to form angular state modes, blue nanolaser output can be realized at room temperature.

[0057] 2) Traditional blue nanolasers typically rely on local geometric resonance, making them susceptible to factors such as cavity size errors, sidewall roughness, and boundary defects. The laser mode in this application originates from the global coupling inversion relationship between topological non-trivial and topological trivial regions, thus exhibiting better mode stability compared to traditional local resonance structures.

[0058] 3) This application utilizes the zero-dimensional topological angle state at the inner corner of the closed domain wall as the laser mode. This mode is highly localized in space and has strong mode selectivity, which enables the zero-dimensional topological angle state to preferentially reach the laser threshold and generate laser output, thereby realizing blue single-mode, narrow linewidth laser output.

[0059] 4) In actual fabrication, nanopillars may exhibit sidewall taper, reduced top size, or slight local dimensional deviations. This application does not rely on an ideal cylindrical structure. As long as the nanopillar array as a whole maintains the strong-weak reversal relationship between intracellular and intercellular coupling and keeps the closed domain walls continuous, a stable topological angular state can still be formed, thereby improving the device's tolerance to non-destructive fabrication deviations.

[0060] 5) This application can adjust the angular resonant wavelength by changing the lattice constant, nanopillar size and coupling spacing of the two-dimensional SSH lattice. Different blue light band laser outputs can be obtained by using different lattice constants, which has good wavelength design flexibility and is convenient for designing blue laser devices according to different application requirements.

[0061] 6) This application clarifies the key conditions for maintaining blue topological corner laser output, including the strong-weak coupling reversal between topological non-trivial and topological trivial regions, the continuity of closed domain walls, the integrity of corner key nanopillar structures, and the lattice size adapted to the blue light band, which helps guide device optimization, mass production and defect control.

[0062] 7) The laser mode of this application is localized at the inner corner of the closed domain wall, resulting in a small mode volume, which is beneficial for realizing small-sized blue nanolasers. Furthermore, this device is based on a gallium nitride material platform, making it compatible with existing group III nitride optoelectronic processes and suitable for further development of integrated blue light sources, visible light topological laser arrays, and on-chip optoelectronic systems.

[0063] 8) The basic unit of this application is a two-dimensional SSH topology nanocavity, which can be repeatedly arranged to form a one-dimensional or two-dimensional blue light topology angular state nanolaser array, which helps to improve the device integration and is suitable for applications such as multi-channel blue light source, on-chip display, optical communication or integrated photonic chip.

[0064] In summary, the room-temperature blue topological angle state nanolaser based on a two-dimensional SSH topological lattice provided in this application embodiment uses a nanopillar array arranged according to a two-dimensional SSH topological lattice. Through the inversion of the strength of intracellular and intercellular coupling between the central and peripheral regions, zero-dimensional topological angle states are formed at the inner corners of closed domain walls. Since the laser mode is determined by the overall topological coupling relationship rather than relying on local geometric resonance, it is less susceptible to cavity size errors, sidewall roughness, and boundary defects, exhibiting higher mode stability compared to traditional blue nanolasers. Furthermore, due to the high spatial locality of the zero-dimensional topological angle state, it possesses strong mode selectivity, enabling room-temperature blue single-mode narrow-linewidth laser output. In addition, the nanolaser provided in this application embodiment has a certain tolerance for non-destructive processing deviations in actual fabrication, which helps improve the device's process adaptability and is suitable for further development of integrated blue light sources, visible light topological laser arrays, and on-chip optoelectronic systems.

[0065] Figure 6 This is a flowchart illustrating a method for fabricating a room-temperature blue topological angular nanolaser based on a two-dimensional SSH topological lattice, as provided in an embodiment of this application. This method can be used to fabricate... Figure 1 Lasers. For example... Figure 6 As shown, the method may include:

[0066] Step 601: Provide a blue light multi-quantum-well epitaxial wafer, the epitaxial wafer including a raw growth substrate and a blue light gain film grown thereon.

[0067] For example, suppliers of the various components can directly provide blue light multi-quantum-well epitaxial wafers. It is understood that the epitaxial wafer, in the thickness direction, may specifically include a primary growth substrate, a gallium nitride (GaN) cladding, a multi-quantum-well layer formed by alternating layers of indium gallium nitride (InGaN) and gallium nitride (GaN), and a p-GaN layer. The multi-quantum-well layer serves as the active region for blue light gain, while the gallium nitride (GaN) cladding does not provide gain and is not part of the multi-quantum-well layer.

[0068] Step 602: On the side of the blue light gain film facing away from the original growth substrate, a metal layer for bonding transfer is formed. The metal layer is formed by evaporation, sputtering or electroplating processes.

[0069] For example, a metal layer can be deposited on the surface of the blue light gain film facing away from the original growth substrate using evaporation, sputtering, or electroplating processes. This metal layer can be a metal reflective layer or a metal bonding layer, combining optical reflection and bonding functions. Optionally, the metal layer can be made of one or more of Ni, Ag, Au, Ti, and Al, or an alloy of these metals, or a multilayer metal stack structure composed of these metals. The specific material and thickness of the metal layer can be selected according to the optical reflection and bonding requirements of the device.

[0070] Step 603: The blue light multi-quantum well epitaxial wafer is flip-bonded to the support substrate through the metal layer.

[0071] For example, a blue light multi-quantum well epitaxial wafer with a metal layer can be inverted so that one side of the metal layer faces the supporting substrate. The epitaxial wafer can be fixed to the supporting substrate by means of thermo-press bonding or eutectic bonding, so that the metal layer is bonded between the bottom of the blue light gain film and the supporting substrate, thereby completing the transfer of the epitaxial wafer to the supporting substrate.

[0072] Step 604: Remove the original growth substrate and thin the exposed blue light gain film.

[0073] For example, after flip bonding is completed, the original growth substrate can be removed by laser lift-off, chemical mechanical polishing, or wet etching to expose the blue light gain film. The exposed blue light gain film is then thinned to a thickness that meets the requirements for angular state light field distribution and gain coupling. Optionally, the thickness of the thinned blue light gain film ranges from 200 nm to 800 nm, and more preferably from 300 nm to 600 nm.

[0074] Step 605: Define a two-dimensional SSH lattice pattern on the surface of the thinned blue light gain film, and transfer the pattern to the blue light gain film by dry etching to form a nanopillar array containing a central region, a peripheral region and closed domain walls.

[0075] For example, a hard mask layer can be first formed on the surface of the thinned blue light gain film. A two-dimensional SSH topological lattice pattern can then be defined on the hard mask layer using electron beam lithography, deep ultraviolet lithography, nanoimprint lithography, or other high-resolution patterning processes. This pattern includes the spatial distribution information of the central region, peripheral regions, and closed domain walls. Subsequently, an inductively coupled plasma (ICP) etching process is used to etch downwards in the vertical direction, transferring the pattern into the blue light gain film until the etching gaps between adjacent nanopillars are completely exposed, forming photonic crystal air holes filled with air or a low-refractive-index medium. This ultimately yields a nanopillar array containing a central region, peripheral regions, and closed domain walls. It should be noted that during the actual etching process, the nanopillars may exhibit a frustum-shaped morphology with tapered sidewalls due to process limitations. As long as the overall nanopillar array maintains the strong-weak inversion relationship between intracellular and intercellular coupling and the closed domain walls remain continuous, a topological angular state can be formed and maintained, achieving blue laser output.

[0076] In some embodiments, a two-dimensional SSH lattice pattern is defined on the surface of the thinned blue light gain film, including:

[0077] A hard mask layer is formed on the surface of a blue light gain film, and a pattern is formed on the hard mask layer by electron beam lithography, deep ultraviolet lithography, nanoimprinting or other high-resolution patterning processes.

[0078] It should be noted that, since the required structural dimensions in the blue light band are on the order of hundreds of nanometers, the resolution of the patterning process directly determines the dimensional accuracy of the nanopillar array, which in turn affects whether the strong / weak inversion relationship between intracellular and intercellular coupling can be accurately achieved. Electron beam lithography has high pattern resolution and is suitable for precisely defining the spatial distribution of the nanopillar array, while deep ultraviolet lithography and nanoimprint lithography are suitable for mass production scenarios.

[0079] In some embodiments, transferring a pattern to a blue light gain film by dry etching includes:

[0080] An inductively coupled plasma etching process is used to etch downwards in a vertical direction until gaps are formed between the nanopillars.

[0081] It should be noted that inductively coupled plasma etching (ICP-C) is characterized by strong anisotropy and controllable etching depth, enabling the formation of nanopillar structures with relatively steep sidewalls in blue light gain films. This helps ensure the spacing accuracy between adjacent nanopillars, thereby maintaining the strong-weak coupling reversal relationship between topologically non-trivial and topologically trivial regions. The etching endpoint is defined as the complete exposure of the etching gaps between adjacent nanopillars. The resulting etching gaps are filled with air or a low-refractive-index medium, forming an air-hole structure in the photonic crystal.

[0082] It should be noted that in the embodiments of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "multiple" refers to two or more unless otherwise expressly defined. "Approximately" and "substantially" mean that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect. In the accompanying drawings, the dimensions of layers and regions may be exaggerated for clarity of illustration. It is also understood that when an element or layer is referred to as being "on" another element or layer, it can be directly on other elements, or there may be intermediate layers. Similar reference numerals throughout indicate similar elements. The term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone.

[0083] The laser embodiments in this application can be referenced in conjunction with the laser fabrication method embodiments. The above descriptions are merely optional embodiments of this application and are not intended to limit the application. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A room-temperature blue topological angular nanolaser based on a two-dimensional SSH topological lattice, characterized in that, include: Support substrate; A blue light gain film is located on the supporting substrate, and the blue light gain film includes an array of nanopillars. The nanopillar array includes a central region and a peripheral region surrounding the central region; The nanopillars in the nanopillar array are arranged in a two-dimensional SSH lattice, and every four adjacent nanopillars form a tetramer unit. The spacing between the nanopillars inside the tetramer unit is the intracellular spacing, and the spacing between adjacent tetramer units is the intercellular spacing. In the central region, the intracellular spacing is smaller than the intercellular spacing; in the peripheral region, the intracellular spacing is larger than the intercellular spacing. A closed domain wall is formed at the boundary between the central region and the peripheral region, and a zero-dimensional topological angle state is formed at the interior corner of the closed domain wall.

2. The room-temperature blue topological angular nanolaser as described in claim 1, characterized in that, The closed domain wall is a closed square domain wall, and the zero-dimensional topological angular state is formed at the four interior corners of the closed square domain wall; The blue light gain film is a multi-quantum well, which is formed by alternating layers of indium gallium nitride and gallium nitride. The blue light gain film includes quantum well nanopillars and a quantum well cladding. The quantum well nanopillars form the nanopillar array, and the quantum well cladding is located below the quantum well nanopillars and connected to them. Both the quantum well nanopillars and the quantum well cladding provide blue light gain. The optical field of the zero-dimensional topological angle state is concentrated at the interior corner of the closed square domain wall and spatially overlaps with the multiple quantum wells to provide optical gain; The multiple quantum wells generate single-mode blue laser light based on the optical gain, wherein the wavelength of the single-mode blue laser light is 430nm to 480nm and the linewidth is less than 0.1nm.

3. The room-temperature blue topological angular nanolaser as described in claim 2, characterized in that, The tetramer units constitute the basic units of the two-dimensional SSH lattice, and the lattice constant of the basic units ranges from 180 nm to 280 nm. The bottom radius of the nanopillar ranges from 40 nm to 100 nm, the top radius of the nanopillar ranges from 10 nm to 60 nm, and the height of the nanopillar ranges from 100 nm to 300 nm. The thickness of the blue light gain film ranges from 200 nm to 800 nm; The output wavelength of the single-mode blue laser is controlled by adjusting one or more of the lattice constant, the radius of the nanopillar, the height of the nanopillar, or the ratio of the intracellular spacing to the intercellular spacing.

4. The room-temperature blue topological angular nanolaser as described in claim 1, characterized in that, The nanopillars are in the shape of a straight columnar structure or a frustum structure with tapered sidewalls; When the shape of the nanopillar is the frustum structure, the cross-sectional area of ​​the top of the nanopillar is smaller than the cross-sectional area of ​​its bottom. The individual nanopillars in the nanopillar array are allowed to have processing deviations; Under the condition of the aforementioned processing deviation, the entire nanopillar array satisfies: In the central region, all intracellular spacings are smaller than intercellular spacings; in the peripheral region, all intracellular spacings are larger than intercellular spacings; and the nanopillars constituting the closed domain walls are continuously arranged without any gaps.

5. The room-temperature blue topological angular nanolaser as described in claim 1, characterized in that, A metal layer is also disposed between the supporting substrate and the blue light gain film, wherein the metal layer is a metal reflective layer or a metal bonding layer; The metal layer can be made of a single metal, an alloy metal, or a multilayer metal stack structure.

6. The room-temperature blue topological angular nanolaser as described in claim 1, characterized in that, The nanopillar array contains multiple closed domain walls, which are arranged in a one-dimensional or two-dimensional array to form a multi-channel emission array. In the multi-channel emission array, the zero-dimensional topological angle state is independently formed at the interior corner of each of the closed domain walls. Each of the zero-dimensional topological angle states is optically independent of each other and independently generates blue laser output.

7. The room-temperature blue topological angular nanolaser as described in claim 5, characterized in that, The blue light gain film also includes a gallium nitride cladding layer in the thickness direction, and the gallium nitride cladding layer does not provide blue light gain; The blue light gain film is a substrate transfer film with the original growth substrate removed; The supporting substrate is bonded to the bottom of the blue light gain film via the metal layer; The nanopillar array has etched gaps between adjacent nanopillars, which are photonic crystal air holes filled with air or a low-refractive-index medium.

8. The room-temperature blue topological angular nanolaser as described in claim 1, characterized in that, The room-temperature blue topological angle state nanolaser operates by optical pumping or electrical pumping. When optical pumping is used, the pump source is an ultraviolet or near-ultraviolet pulsed laser with a wavelength range of 320nm to 380nm. The pump light irradiates the vicinity of the inner corner of the closed domain wall, and the blue light gain film generates stimulated emission. The zero-dimensional topological angular state gains gain and generates blue light laser output. When using an electric pumping method, the blue light gain film is excited by injecting current into it, thereby enabling the zero-dimensional topological angle state to gain gain and generate blue laser output.

9. A method for fabricating a room-temperature blue topological angle state nanolaser based on a two-dimensional SSH topological lattice, used to fabricate the nanolaser as described in any one of claims 1 to 8, characterized in that, include: A blue light multi-quantum-well epitaxial wafer is provided, the epitaxial wafer comprising a primary growth substrate and a blue light gain thin film grown thereon; A metal layer for bonding transfer is formed on the side surface of the blue light gain film facing away from the original growth substrate. The metal layer is formed by evaporation, sputtering or electroplating processes. The blue light multi-quantum-well epitaxial wafer is flip-chip bonded to the support substrate through the metal layer; Remove the original growth substrate and thin the exposed blue light gain film; A two-dimensional SSH lattice pattern is defined on the surface of the thinned blue light gain film, and the pattern is transferred to the blue light gain film by dry etching to form a nanopillar array containing the central region, the peripheral region and the closed domain walls.

10. The preparation method according to claim 9, characterized in that, Defining a two-dimensional SSH lattice pattern on the surface of the thinned blue light gain film includes: A hard mask layer is formed on the surface of the blue light gain film, and the pattern is formed on the hard mask layer by electron beam lithography, deep ultraviolet lithography, nanoimprinting or other high-resolution patterning processes. The process of transferring the pattern to the blue light gain film by dry etching includes: An inductively coupled plasma etching process is used to etch downwards in a vertical direction until the gaps between the nanopillars are formed.

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