Synchrotron orthogonally linearly polarized light resonant cavity light emitting diode

Abstract

The application discloses a kind of synchrotron orthogonal linear polarization light resonant cavity light-emitting diode.The device, from bottom to top, is metal substrate, lower mirror, parallel plane resonant cavity, upper electrode, upper mirror;The epitaxial layer of the parallel plane resonant cavity includes n-type layer, p-type layer and active region;Wherein n-type layer, p-type layer and active region are made of birefringent semiconductor material, and the active region is birefringent quantum well structure.The application has the characteristics of simple structure, high integration, narrow spectral line width, adjustable spectral mode and the like, and has wide application prospect in the fields of precision measurement, microscopic tissue imaging, visual imaging, three-dimensional display, optical communication, quantum communication and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of diode, in particular to a synchrotron radiation orthogonal linearly polarized light resonant cavity light emitting diode. BACKGROUND

[0002] Linearly polarized light source has important applications in the fields of visual imaging, microscopic tissue observation, optical communication, quantum communication, etc. In order to obtain more information at the same time, it is a highly feasible scheme to replace the single-direction linearly polarized light source with orthogonal dual-polarized light source. For example, the dual-frequency orthogonal laser can be used to accurately measure the distance between objects, the moving speed of objects, and the rotation angle, and has been widely used in precision machining instruments. At present, the main way to obtain orthogonal polarized light source is to rely on the Zeeman dual-frequency orthogonal laser. However, the laser needs to apply a magnetic field with a certain direction and intensity when working, which makes it difficult to realize the optical path integration in a small space.

[0003] Birefringent semiconductor material refers to the crystal structure in which there are different refractive indices in two directions, generally being orthorhombic and close-packed hexagonal. Or the crystal structure of the material is deformed by external stress to obtain birefringence. When a beam of light passes through the birefringent semiconductor material, a set of orthogonal polarized light is formed. It is reported that Seoul University in Korea epitaxially grows c-GaN wafer and quantum well on a patterned stripe sapphire substrate to make it have significant anisotropy, and the linear polarization degree of the photoluminescence spectrum reaches 0.74. In addition, since the semi-polar surface of GaN (r-GaN) has a certain anisotropy, the Jun Han team of Yale University in the United States uses epitaxially grown r-GaN to prepare a green LED, and the linear polarization degree of the electroluminescence spectrum of the device is 0.3, and the 3dB bandwidth of the visible light communication reaches 756MHz, and the transmission rate reaches 1.5Gbit / s. However, the linearly polarized light in the above two cases is in a single direction. The main reason is that the refractive index difference of the material in the orthogonal direction is too small, and it is difficult to clearly observe the birefringence phenomenon, and the linearly polarized light cannot be separated in the orthogonal direction. SUMMARY

[0004] Therefore, the present application aims to provide a synchrotron radiation orthogonal linearly polarized light resonant cavity light emitting diode, which can obtain a synchrotron radiation orthogonal linearly polarized light resonant cavity light emitting diode. The present application has the characteristics of simple structure, high integration, narrow spectral linewidth, adjustable spectral mode, etc., and has a wide application prospect in the fields of precision measurement, microscopic tissue imaging, visual imaging, three-dimensional display, optical communication, quantum communication, etc.

[0005] According to one aspect of the present application, there is provided a synchrotron radiation orthogonal linearly polarized light resonant cavity light emitting diode, which adopts a vertical internal cavity contact structure, and from bottom to top, there are a metal substrate, a lower mirror, a parallel plane resonant cavity, an upper electrode and an upper mirror; the epitaxial layer of the parallel plane resonant cavity comprises an n-type layer, a p-type layer and an active region; wherein the n-type layer, the p-type layer and the active region are all made of a birefringent semiconductor material, and the active region is a corresponding quantum well structure.

[0006] It can be found that, according to the above scheme, the active region of the semiconductor material with birefringent properties provided in the present application provides anisotropic refractive index in orthogonal directions, so that the device generates orthogonal linearly polarized light. The parallel plane cavity structure further improves the polarization degree of the device spectrum and forms clear orthogonal dual-polarized light. On the one hand, the present application has the characteristics of simple structure and high integration; on the other hand, the mode selection function of the resonant cavity and the birefringent properties of the semiconductor material generate orthogonal linearly polarized light, and the single-direction polarization degree is close to 1.0. BRIEF DESCRIPTION OF DRAWINGS

[0007] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0008] Figure 1 Structure schematic diagram of one embodiment of the synchrotron radiation orthogonal linearly polarized light resonant cavity light emitting diode of the present application;

[0009] Figure 2 It is a schematic diagram of a close-packed hexagonal crystal structure and a corresponding crystal direction index schematic diagram;

[0010] Figure 3 It is a synchrotron radiation orthogonal linearly polarized light resonant cavity light emitting diode spectrum diagram obtained by the present application at different polarization angles. DETAILED DESCRIPTION

[0011] The present application will be described in further detail below in combination with the drawings and embodiments. It is particularly pointed out that the following embodiments are only used to illustrate the present application, but do not limit the scope of the present application. Similarly, the following embodiments are only some embodiments of the present application, but not all embodiments, and all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0012] The application provides a kind of synchrotron orthogonal linear polarization light resonant cavity light emitting diode, which can obtain synchrotron orthogonal linear polarization light resonant cavity light emitting diode.The application has the characteristics of simple structure, high integration, narrow spectral line width, adjustable spectral mode, etc., and has wide application prospect in the fields of precision measurement, microscopic tissue imaging, visual imaging, three-dimensional display, optical communication, quantum communication, etc.

[0013] Please refer to Figure 1 , Figure 1 is the structural schematic diagram of an embodiment of the synchrotron orthogonal linear polarization light resonant cavity light emitting diode of the application.

[0014] The device adopts a vertical internal cavity contact structure, and from bottom to top, it is a metal substrate 1, a lower mirror 2, a parallel plane resonant cavity 3, an upper electrode 4, and an upper mirror 5.

[0015] The epitaxial layer of the parallel plane resonant cavity 3 includes an n-type layer 3.1, a p-type layer 3.3, and an active region 3.2; wherein the n-type layer 3.1, the p-type layer 3.3, and the active region 3.2 are all made of a birefringent semiconductor material, and the active region is a corresponding quantum well structure.

[0016] In this embodiment, the vertical internal cavity contact structure refers to a typical device structure in which the resonant cavity is inside the overall device structure and is wrapped by the metal substrate. The advantage is that it can alleviate the current congestion effect. In this case, two basic conditions of the light-emitting semiconductor with a resonant cavity and birefringent properties are met, and other structures can also produce orthogonal polarization phenomena, which are not limited by the application.

[0017] In this embodiment, the birefringent semiconductor material refers to a crystal structure in which there are different refractive indices in two directions (generally orthogonal directions), thereby producing a birefringent phenomenon. When a beam of light passes through the birefringent semiconductor material, due to the different refractive indices, the refraction angles are different, resulting in two different refracted light beams. One of the refracted light beams is always in the plane of the incident light and follows the refraction law, i.e., the ratio of the sine of the incident angle to the sine of the refraction angle is a constant, which is usually referred to as the ordinary light or o light. The other refracted light beam is not in the same plane as the incident light, and the ratio of the sine of the incident angle to the sine of the refraction angle is not a constant, which does not follow the refraction law, and is usually referred to as the extraordinary light or e light.

[0018] There are mainly two factors that cause the material to have birefringent properties. One is that the material's inherent crystal structure has anisotropy, i.e., the atomic arrangement spacing, the number of atoms, and the types of atoms are different in two directions. Taking a hexagonal close-packed crystal structure as an example, please refer to Figure 2There is a significant difference in the atomic arrangement in the direction parallel to the c-axis

[0001] and the direction perpendicular to the c-axis (x-axis [2-1-10] or y-axis [-12-10]), which leads to a difference in the refractive index parallel to the c-axis and the refractive index in the x-axis or y-axis. Secondly, external stress causes deformation of the crystal structure of the material, resulting in changes in the two directions where the atoms were originally aligned. Generally, in the direction of tensile stress, the interatomic spacing increases; in the direction of compressive stress, the interatomic spacing decreases, thus causing a change in the refractive index in both directions. There are two main methods to generate anisotropy in quantum wells: 1) epitaxially growing quantum well structures using patterned substrates with anisotropy; 2) growing quantum well materials with anisotropic crystal structures. The main reason why existing technologies have not achieved orthogonal double-polarized light is that the refractive index difference of most birefringent semiconductor materials is too small, about 0.01, making it difficult to clearly observe the birefringence phenomenon. The purpose of using birefringent semiconductor materials in this case is twofold: first, to emit light under injected current; and second, to generate linear polarization.

[0019] In this embodiment, the birefringent semiconductor material includes ZnO, GaN, and CdS, and the doping ratios of x and y range from 0 ≤ x ≤ 1 to 0 ≤ y ≤ 1. Preferably, the birefringent semiconductor material is semi-polar GaN or non-polar GaN, and the active region is In. x Ga (1-x) N / Al y Ga (1-y) N-quantum well structure; where x and y represent In and Al respectively in In x Ga (1-x) N and Al y Ga (1-y) The doping ratio of N. By changing the doping ratio of In and Al in the active region between 0 and 1, the wavelength of the light-emitting diode can be changed, covering the 200-1700nm wavelength range. The principle is that by changing the doping ratio, the band gap of the semiconductor material can be changed, and the band gap determines the radiation wavelength. It should be noted that GaN material, as a third-generation semiconductor material, is widely used in light-emitting devices. GaN material is mainly grown by metal-organic vapor deposition (MOCVD). Moreover, GaN grown along different crystal planes can be divided into polar, semi-polar, and non-polar. Only semi-polar and non-polar GaN have birefringence properties. At present, most devices still use polar GaN, that is, (1000) plane GaN, which does not have birefringence properties and therefore cannot achieve orthogonal linear polarization.

[0020] In this embodiment, to further improve the polarization degree of the device spectrum and form clean orthogonally double-polarized light, the resonant cavity adopts a parallel planar structure. In the parallel planar resonant cavity, the mode distribution of the optical field strictly obeys the following formula:

[0021]

[0022] Where Δν is the frequency difference between adjacent modes, c is the speed of light, n is the refractive index within the resonant cavity, and L is the physical length of the resonant cavity. In other words, if different refractive indices exist within the same resonant cavity, different modes will be distributed at intervals, thus producing clearly linearly polarized light. Unlike ordinary resonant cavity light-emitting diodes used in lighting applications, the main innovation of this invention lies in the synergistic use of the mode selection function of the resonant cavity and semiconductor materials with birefringent properties to fabricate a resonant cavity light-emitting diode capable of synchronously radiating orthogonally linearly polarized light. The electrical injection spectrum of the device changes periodically with the observation angle, and the degree of polarization can reach 1.00. This invention is of great significance for the integration of orthogonally polarized light paths and the miniaturization of devices.

[0023] In this embodiment, the mode distribution mainly refers to the spacing between modes and the location of modes. The mode distribution primarily depends on the refractive index and cavity length of the resonant cavity. That is, for a specific resonant cavity, the refractive index and cavity length are constant, resulting in a corresponding mode distribution. This is also known as the mode selection function of the resonant cavity. In this case, due to the use of a birefringent material, there are two different refractive indices n, resulting in two different mode distributions.

[0024] In this embodiment, the reflector comprises a distributed Bragg reflector (DBR) composed of alternating layers of dielectric films with two different refractive indices. The thickness of each dielectric film layer is 1 / 4 of the center wavelength. The dielectric film combination uses SiO2 and any one of TiO2, Ta2O5, or Ti3O5. Preferably, the reflector is a DBR composed of alternating layers of dielectric films with two different refractive indices, with each dielectric film layer having a thickness of 1 / 4 of the center wavelength. The dielectric film combination uses TiO2 / SiO2. It should be understood that the reason for each dielectric film layer having a thickness of 1 / 4 of the center wavelength is to reduce reflection loss on the optical reflector and improve device performance. According to the principles of optical propagation, the optical thickness of a single dielectric film must be 1 / 4 of the center wavelength to minimize loss, increase reflectivity, and improve the quality of the resonant cavity. The reason for using TiO2 / SiO2 in the dielectric film combination is that it has a large refractive index difference, making it easy to obtain higher reflectivity; it has low absorption of visible light, which helps to improve the optical output power of the device; and the fabrication process is mature, readily available, and low-cost. The two emission wavelengths of the device are located within the high-reflectivity band formed by the upper and lower distributed Bragg mirrors, and the reflectivity of both mirrors must reach 99% or higher. It is important to note that the spectrum of the electrically injected device should be located within the high-reflectivity band (high-reflectivity region) to achieve a significant resonance effect. For dielectric film mirrors, the greater the difference in refractive index between the two dielectric film materials, the easier it is to achieve high reflectivity. Higher reflectivity results in less light loss during reflection and a more pronounced resonance effect; therefore, the reflectivity of both the upper and lower distributed Bragg mirrors must reach 99% or higher.

[0025] This embodiment uses 529nm and 536nm synchrotron radiation orthogonally linearly polarized light-emitting diodes (LEDs) with resonant cavities. From bottom to top, the diode comprises: a Cu substrate, a lower electrode (Cr / Au), a lower distributed Bragg mirror (12 pairs of TiO2 / SiO2), a parallel-plane resonant cavity, an upper electrode (Cr / Au), and an upper distributed Bragg mirror (8 pairs of TiO2 / SiO2). The lower distributed Bragg mirror (12 pairs of TiO2 / SiO2) is used to obtain higher reflectivity and reduce losses. The upper distributed Bragg mirror (8 pairs of TiO2 / SiO2) is used to balance reflectivity and light output. If the reflectivity of the upper distributed Bragg mirror (8 pairs of TiO2 / SiO2) is too high, light cannot escape from the resonant cavity, and the device's light output power will decrease; if the reflectivity of the upper distributed Bragg mirror (8 pairs of TiO2 / SiO2) is too low, it will be difficult to form a good resonance effect.

[0026] The active region of the parallel planar resonant cavity is In. 0.3The GaN / Al0GaN quantum well structure has an In doping ratio of 0.3 and an Al doping ratio of 0. The active region of the parallel-planar resonant cavity provides anisotropic refractive index in orthogonal directions, enabling the device to generate orthogonally linearly polarized light. This invention utilizes a parallel-planar cavity structure and a birefringent semiconductor material to obtain a resonant cavity light-emitting diode capable of synchronously emitting orthogonally linearly polarized light. It features simple structure, high integration, narrow spectral linewidth, and tunable spectral modes, showing broad application prospects in precision measurement, microscopic tissue imaging, visual imaging, 3D display, optical communication, and quantum communication. By changing the In and Al doping ratios in the active region between 0 and 1, the wavelength of the light-emitting diode can be changed, covering the 200–1700 nm wavelength range. Please refer to [link to relevant documentation]. Figure 3 The image shows the spectra of a synchrotron radiation orthogonally linearly polarized resonant cavity light-emitting diode obtained at different polarization angles according to an example of the present invention. It can be observed that when the polarization angle is 0°, the device spectrum contains only Peak1; as the polarization angle rotates, Peak1 gradually weakens, while Peak2 gradually strengthens. When the polarization angle is 90°, Peak1 completely disappears, leaving only Peak2. This indicates that the device can synchronously radiate two sets of peaks, Peak1 and Peak2, in two orthogonal directions.

[0027] It can be observed that, in the above scheme, the active region of the semiconductor material with birefringence properties provides anisotropic refractive index in orthogonal directions, enabling the device to generate orthogonally linearly polarized light. The parallel planar cavity structure further enhances the polarization degree of the device spectrum and forms clear orthogonally bipolarized light. On the one hand, the present invention features simple structure and high integration; on the other hand, the mode selection function of the resonant cavity and the birefringence property of the semiconductor material generate orthogonally linearly polarized light, with a single-direction polarization degree approaching 1.0.

[0028] The above description is only a part of the embodiments of the present invention and does not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made based on the content of the present invention specification and drawings, or direct or indirect application in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A synchrotron radiation orthogonally linearly polarized light resonator light-emitting diode, characterized in that, The diode, from bottom to top, consists of a metal substrate, a lower reflector, a parallel plane resonant cavity, an upper electrode, and an upper reflector; The epitaxial layer of the parallel planar resonant cavity includes an n-type layer, a p-type layer, and an active region; wherein the n-type layer, p-type layer, and active region are all made of birefringent semiconductor material, and the active region is In... x Ga (1-x) N / Al y Ga (1-y) N-birefringent quantum well structure, wherein 0≤x≤1, 0≤y≤1; the birefringent semiconductor material includes ZnO, GaN, or CdS; In a parallel-plane resonant cavity, the mode distribution of the optical field follows a certain pattern. in ν is the frequency difference between adjacent modes, c is the speed of light, n is the refractive index inside the resonant cavity, and L is the physical length of the resonant cavity.

2. The synchrotron radiation orthogonally linearly polarized light resonator light-emitting diode as described in claim 1, characterized in that, The reflector includes a distributed Bragg reflector composed of alternating layers of two dielectric films with different refractive indices, wherein the thickness of each dielectric film is 1 / 4 of the center wavelength, and the dielectric film combination adopts a combination of SiO2 dielectric film and any one of TiO2, Ta2O5 or Ti3O5 dielectric film.

3. A synchrotron radiation orthogonally linearly polarized light resonator light-emitting diode as described in claim 2, characterized in that, The two emission wavelengths of the light-emitting diode are located in the high-reflection band formed by the upper and lower distributed Bragg mirrors, and the reflectivity of both the upper and lower distributed Bragg mirrors must reach more than 99%.

4. A synchrotron radiation orthogonally linearly polarized light resonator light-emitting diode as described in claim 1, characterized in that, The upper electrode is Cr / Au.

5. A synchrotron radiation orthogonally linearly polarized light resonator light-emitting diode as described in claim 1, characterized in that, The substrate is a metallic conductive substrate.

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