Semiconductor hexagonal micro-disk laser with double triangular whispering gallery optical resonance mode

Abstract

The present invention belongs to the field of semiconductor microcavity lasers. In order to solve the problems of low quality factor of hexagonal whispering gallery mode and difficult emission of triangular whispering gallery mode, a semiconductor hexagonal micro-disk laser with double triangular whispering gallery optical resonance mode is disclosed. The device uses the stimulated radiation physical characteristics of high refractive index gain materials, and provides light reflection on the bottom surface through a reflective substrate to reduce the vertical optical loss of the microcavity laser. The semiconductor hexagonal micro-disk is used as an optical resonant cavity and laser gain material, and the laser is used as an optical pump source to provide optical gain. When the pump source power exceeds the threshold of the microcavity laser, laser emission is generated; by controlling the pump source laser spot to be located at the corner of the hexagonal micro-disk, laser emission of double triangular whispering gallery optical resonance mode is generated after stimulated radiation. Compared with conventional hexagonal and triangular whispering gallery optical resonance mode lasers, the present invention has the advantages of high quality factor and easy laser emission.

Description

Technical Field

[0001] The invention relates to the field of semiconductor microcavity lasers, and in particular to a semiconductor hexagonal micron-disk laser in a double-triangle whispering gallery optical resonance mode. Background Art

[0002] Semiconductor materials have broad application value in the field of micro-nano light-emitting devices and optoelectronic integration and have thus attracted widespread attention from scientists. In particular, semiconductors with high refractive index and direct band gap, such as GaN, ZnO, GaAs, InP, perovskite, etc., can be directly used as gain materials and resonant cavities to make microcavity lasers. In addition, detectors and light-emitting devices made of compounds such as GaInN, AlGaN, and GaInAs can also cover a wide band of ultraviolet, visible light, and near-infrared. Whispering-gallery mode microcavity lasers are widely studied because they use the principle of periodic resonance formed by total reflection of light on the surface of the medium. Compared with the Fabry-Pérot mode, they have the advantages of small size, high quality factor, low threshold, and easy integration. Whispering-gallery mode microcavity lasers based on semiconductor materials can be used in optical communications, optical storage, chemical and biological detection, and other fields.

[0003] Currently reported research on semiconductor whispering gallery mode microcavity lasers mainly uses microdisk structures, among which hexagonal microdisks are widely studied. This is because most wide-bandgap, direct-bandgap semiconductors have a wurtzite structure, resulting in the microdisk obtained by epitaxial growth having a hexagonal prism geometry. At the same time, in the study of optical modes of hexagonal resonant cavities, most of the reported are hexagonal and triangular whispering gallery modes, for example: hexagonal whispering gallery mode scheme (see [Rui Chen and BoLing,”Room Temperature Excitonic Whispering Gallery Mode Lasing from High-Quality Hexagonal ZnO Microdisks”, Advanced Materials, vol. 23, no. 19. pp. 2199+, 2011]) and triangular whispering gallery mode scheme (see [Kouno T,”Lasing Action on WhisperingGallery Mode of Self-Organized GaN Hexagonal Microdisk Crystal Fabricated by RF-Plasma-Assisted Molecular Beam Epitaxy”, Ieee Journal of Quantum Electronics, vol. 47, no. 12, pp. 1565-1570, 2011]). Theoretical research by Wiersig, J. (see ["Hexagonaldielectric resonators and microcrystal lasers", Physical Review A, vol. 67, no. 2, pp. 12, 2003]) shows that the light path of the hexagonal whispering gallery mode is located at the edge of the resonant cavity. Due to the principle of optical diffraction, the light can be emitted from the corner, but its quality factor is much lower than that of the triangular whispering gallery mode. On the other hand, the reflection area of ​​the light in the triangular whispering gallery mode is located at the center of each side of the hexagon, making it difficult for the light circulating inside to be emitted, thereby reducing the light extraction efficiency of the laser. Therefore, these two problems reduce the performance of semiconductor hexagonal micro-disk lasers. Summary of the invention

[0004] In view of this, the main purpose of the present invention is to provide a semiconductor hexagonal micro-disk laser with a double triangular whispering gallery optical resonance mode to solve the shortcomings of existing solutions that are limited by the low quality factor of the hexagonal whispering gallery mode and the difficulty in emitting the triangular whispering gallery mode, while having the advantages of both high quality factor and easy emission.

[0005] To achieve the above-mentioned object, the present invention provides a semiconductor hexagonal micro-disk laser in a double-triangular whispering gallery optical resonance mode, comprising: a reflective substrate, a semiconductor hexagonal micro-disk, and a laser; wherein: the semiconductor hexagonal micro-disk is arranged on the reflective substrate; the output light of the laser is perpendicular to the surface of the semiconductor hexagonal micro-disk and irradiates any one of the six corners of the semiconductor hexagonal micro-disk; the laser in the double-triangular whispering gallery optical resonance mode is horizontally emitted from one of the six side walls of the semiconductor hexagonal micro-disk.

[0006] A better solution: the laser is a single-mode high-power laser, the wavelength of the emitted laser is smaller than the bandgap emission wavelength of the semiconductor material used, the semiconductor hexagonal micro-disk is a regular hexagonal surface, the side of which is perpendicular to the surface and smooth, and the surface of the reflective substrate is a smooth plane. This reduces the loss of optical resonant strong light and enhances the stability of the emitted laser spectrum.

[0007] Furthermore, by adjusting the output power of the laser, the intensity and line width of the output light of the micro-disk laser can be changed.

[0008] Furthermore, the size of the excitation area where the laser irradiates the corner of the semiconductor hexagonal micro-disk is smaller than the surface size of the semiconductor hexagonal micro-disk.

[0009] Furthermore, by adjusting the irradiation spot size of the laser, the stability of the double-triangle whispering gallery mode laser can be adjusted.

[0010] Due to the adoption of the above technical scheme, the beneficial effects of the present invention are as follows: the semiconductor hexagonal micro-disk laser with a double triangular whispering gallery optical resonance mode proposed by the present invention has the advantages of high quality factor and easy emission compared with the existing hexagonal whispering gallery mode laser and triangular whispering gallery mode laser schemes. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 A schematic diagram of a semiconductor hexagonal micron-disk laser provided by the present invention;

[0012] Figure 2 This is a scanning electron microscope image of a gallium nitride microdisk;

[0013] Figure 3 Output spectrum for GaN laser;

[0014] Figure 4 This is the simulated light field diagram of the double triangle whispering gallery mode;

[0015] Figure 5 This is the function diagram of the number of reflections and quality factor of the double triangle whispering gallery mode;

[0016] Figure 6aThis is the simulated light field diagram when the ratio of the excitation area to the resonant cavity area is 5%;

[0017] Figure 6b This is the simulated light field diagram when the ratio of the excitation area to the resonant cavity area is 15%;

[0018] Figure 6c This is the simulated light field diagram when the ratio of the excitation area to the resonant cavity area is 20%;

[0019] Figure 6d This is the simulated light field diagram when the ratio of the excitation area to the resonant cavity area is 30%;

[0020] in, Figure 1 Middle: 1. Reflective substrate, 2. Semiconductor hexagonal microdisk, 3. Laser. DETAILED DESCRIPTION

[0021] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0022] Embodiment 1

[0023] A semiconductor hexagonal micro-disk laser with double triangular whispering gallery optical resonance mode, such as Figure 1 As shown, it includes: a reflective substrate 1, a semiconductor hexagonal micron dish 2, and a laser 3; wherein: the semiconductor hexagonal micron dish is arranged on the reflective substrate; the output light of the laser is perpendicular to the surface of the semiconductor hexagonal micron dish, and irradiates any one of the six corners of the semiconductor hexagonal micron dish; the laser of the double-triangular whispering gallery optical resonance mode is horizontally emitted from one of the six side walls of the semiconductor hexagonal micron dish.

[0024] The specific working principle of the semiconductor hexagonal micro-disk laser in the double-triangular whispering gallery optical resonance mode involved in the present invention is as follows:

[0025] The present invention mainly performs optical excitation on a part of a semiconductor micro-disk to control the output of the laser mode. The laser excitation method reported in the past is that the laser spot fully covers the micro-disk. Under this condition, only the hexagonal whispering gallery mode and the triangular whispering gallery mode can be stimulated. The semiconductor micro-disk described in the present invention has a larger diameter, so that the spot of the conventional laser pump source can only cover a part of the micro-disk. Since the stimulated radiation characteristic is spatial, that is, the particle number inversion will only occur in the stimulated working material area and only the light path of this area will be enhanced. Therefore, when the excitation light spot is only located at the corner of the hexagonal micro-disk, only the optical mode whose light path is located under the light spot will resonate. The light path of this double triangular whispering gallery mode is located at the corner of the hexagonal micro-disk, so this optical mode can obtain effective stimulated radiation amplification.

[0026] Then through the formula Where m is the number of reflections, r is the radius of the hexagonal circumscribed circle, and R is the effective reflectivity. It can be obtained that under the same effective reflectivity conditions, the quality factor of the double-triangular whispering gallery mode is similar to that of the triangular whispering gallery mode, but is significantly higher than that of the hexagonal whispering gallery mode. Figure 4 The light field simulation diagram of the double triangle whispering gallery mode is shown. The white frame is the excitation area, the regular hexagon is the semiconductor resonant cavity, the outer periphery is air, the outermost frame is the perfect matching layer as the absorption layer, and the bright area in the hexagon is the area with high light intensity density, that is, the light path. At the same time, the light path of the double triangle whispering gallery mode is located at the corners of the hexagonal micro-dish. Due to the optical diffraction effect of the corners, the resonant light of the double triangle whispering gallery mode is easier to emit.

[0027] Embodiment 2

[0028] A semiconductor hexagonal micron-disk laser with a double-triangular whispering gallery optical resonance mode, wherein the reflective substrate, the semiconductor hexagonal micron-disk, and the laser are sequentially configured as a single crystal silicon reflective substrate, a gallium nitride hexagonal micron-disk, and an ultraviolet pulse laser, wherein the ultraviolet pulse laser has a wavelength of 325nm, a line width of 100fs, a frequency of 1kHz, and a spot diameter of 10μm; the gallium nitride hexagonal micron-disk has a diameter of 25μm; and the excitation area irradiated at any one of the six corners of the gallium nitride hexagonal micron-disk is a square. The excitation area is a special term in this field. In this embodiment, the ultraviolet pulse laser irradiates the gallium nitride hexagonal micron-disk, and the excitation area is the area where the ultraviolet pulse laser produces an excitation effect on gallium nitride.

[0029] Comsol Multiphysics simulation software is used to find the most suitable conditions for the emission of double-triangular whispering gallery mode light. A hexagonal resonant cavity model is constructed, with the periphery set as air, the edge area set as a perfect matching layer, and electric field excitation set at the corner of the hexagonal resonant cavity, and the excitation area is a square.

[0030] By changing the area of ​​the square in the excitation region, that is, adjusting the ratio of the excitation area to the hexagonal area, the change in light field distribution can be observed from the light field simulation result diagram, that is, the optical mode inside the hexagonal resonant cavity has changed.

[0031] In order to verify the effect of the technical solution of the present invention, an experimental verification was carried out. In the experiment, the wavelength of the ultraviolet pulse laser was 325nm, the line width was 100fs, the frequency was 1kHz, and the spot diameter was 10μm. Figure 2 This is a scanning electron microscope image of a gallium nitride microdisk. It can be seen that the diameter of the gallium nitride hexagonal microdisk in the experiment is 25μm. Figure 3 is the GaN laser output spectrum, through the formula Δλ=λ 2 / [L(n-λdn / dλ)], where λ is the emission wavelength of the micro-disk laser, Figure 3 As shown, λ is about 375nm, L is the total length of the optical path cycle, and the double triangle whispering gallery mode interval is 0.35nm, which is very close to the experimental result of 0.36nm, confirming that the result is double triangle whispering gallery mode laser emission. At the same time, the quality factor is calculated by the formula Q = λ / Δλ, and the Q value is as high as 3049. Figure 4 This is the simulated light field diagram of the double-triangular whispering gallery mode, which also confirms that the laser mode is a double-triangular whispering gallery mode. Figure 5 The figure is a function diagram of the number of reflections of the double triangular whispering gallery mode and the quality factor, in which the corresponding values ​​of the quality factors of the three whispering gallery modes in the same resonant cavity are marked. It can be seen that the quality factor corresponding to the double triangular whispering gallery mode (D3-WGM) is higher than that of the hexagonal whispering gallery mode (6-WGM). Figures 6a to 6d The simulated light field diagrams correspond to the ratio of the excitation area to the resonant cavity area of ​​5%, 15%, 20% and 30% respectively; from the simulation results, it is found that the ratio of the excitation area to the hexagonal resonant cavity area that is most suitable for the stable and efficient output of the double-triangular whispering gallery mode laser is 20%. This is because when the area ratio is further increased, it can be seen that Figure 6d The double-triangular whispering gallery mode is gradually destroyed, so the optimal solution can be obtained while ensuring the maximum excitation area ratio and the stability of the double-triangular whispering gallery mode.

[0032] In the experiment, it was also found that the semiconductor hexagonal micro-disk material is selected from one or more combinations of GaN, AlN, GaAs, InAs, ZnO, InP, CdS, and perovskite. The use of this solution can achieve double-triangular whispering gallery optical resonance mode laser output, and the quality factor is greatly improved. The listed materials all have the characteristics of high refractive index. The stimulated radiation physical characteristics of their high refractive index gain materials are used to reduce the vertical optical loss of the microcavity laser by providing light reflection on the bottom surface through the reflective substrate. The semiconductor hexagonal micro-disk is used as an optical resonant cavity and laser gain material, and the laser is used as an optical pump source to provide optical gain. When the pump source power exceeds the threshold of the microcavity laser, laser emission is generated; by controlling the pump source laser spot to be located at the corner of the hexagonal micro-disk, laser emission in the double-triangular whispering gallery optical resonance mode is generated after stimulated radiation. Compared with conventional hexagonal and triangular whispering gallery optical resonance mode lasers, the present invention has the advantages of high quality factor and easy laser emission.

[0033] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. Semiconductor hexagonal micro-disk laser with double triangular whispering gallery optical resonance mode, including: A reflective substrate, a semiconductor hexagonal micron disk, and a laser; the semiconductor hexagonal micron disk is arranged on the reflective substrate; the characteristics are as follows: the laser light is perpendicular to the surface of the semiconductor hexagonal micron disk and irradiates any one of the six corners of the semiconductor hexagonal micron disk; the laser light in the double triangle whispering gallery light resonance mode is horizontally emitted from one of the six side walls of the semiconductor hexagonal micron disk; The laser emission wavelength of the laser is smaller than the forbidden band emission wavelength of the semiconductor hexagonal micro-disk material used, and the semiconductor hexagonal micro-disk has a regular hexagonal surface; The size of the excitation area at the corner of the semiconductor hexagonal micro-disk irradiated by the laser is smaller than the surface size of the semiconductor hexagonal micro-disk.

2. The semiconductor hexagonal micro-disk laser in double triangular whispering gallery optical resonance mode according to claim 1, characterized in that: The intensity and line width of the output light of the hexagonal micron-disk laser are controlled by the output power of the laser.

3. The semiconductor hexagonal micro-disk laser in double triangular whispering gallery optical resonance mode according to claim 1, characterized in that: The stability of the double-triangular whispering gallery mode laser is controlled by the illumination spot size of the laser.

4. The semiconductor hexagonal micro-disk laser in double triangular whispering gallery optical resonance mode according to claim 1, characterized in that: The reflective substrate, semiconductor hexagonal micron disk, and laser are sequentially configured as a single crystal silicon reflective substrate, a gallium nitride hexagonal micron disk, and an ultraviolet pulse laser; The wavelength of the ultraviolet pulse laser is 325nm, the line width is 100fs, the frequency is 1kHz, and the spot diameter is 10μm; the diameter of the gallium nitride hexagonal micron disk is 25μm.

5. The semiconductor hexagonal micro-disk laser in double triangular whispering gallery optical resonance mode according to claim 1, characterized in that: The semiconductor hexagonal micro-disk material is selected from one or more combinations of GaN, AlN, GaAs, InAs, ZnO, InP, and CdS.

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