阅读说明：本技术 一种基于全介质超表面的激光发射器及参数确定方法 (Laser transmitter based on all-dielectric super surface and parameter determination method ) 是由 方明 徐珂 黄志祥 吴杰 杨利霞 任信钢 刘瑜 于 2019-11-06 设计创作，主要内容包括：本发明公开一种基于全介质超表面的激光发射器。所述激光发射器从底部到顶部依次包括：第一反射镜、有源层和第二反射镜；所述第一反射镜和所述第二反射镜均由周期性排列的硅圆柱粒子组成。本发明的第一反射镜和第二反射镜通过采用周期性排列的硅圆柱粒子的结构,大大降低了反射镜的厚度,有效减小了激光发射器的整体体积。(The invention discloses a laser transmitter based on an all-dielectric super surface. The laser emitter comprises the following components in sequence from bottom to top: a first mirror, an active layer, and a second mirror; the first reflecting mirror and the second reflecting mirror are each composed of periodically arranged silicon cylindrical particles. The first reflector and the second reflector of the invention greatly reduce the thickness of the reflector and effectively reduce the whole volume of the laser emitter by adopting the structure of silicon cylindrical particles which are periodically arranged.)

1. A laser transmitter based on all-dielectric super surface is characterized in that,

the laser emitter comprises the following components in sequence from bottom to top: a first mirror, an active layer, and a second mirror;

the first reflecting mirror and the second reflecting mirror are each composed of periodically arranged silicon cylindrical particles.

2. The all-dielectric super surface based laser transmitter according to claim 1, further comprising: a first confinement layer and a second confinement layer;

the first confinement layer is disposed between the first mirror and the active layer; the second confinement layer is disposed between the active layer and the first mirror; the first limiting layer and the second limiting layer are used for limiting carriers and adjusting resonance wavelength to enable the resonance wavelength to be equal to laser wavelength.

3. The all-dielectric super surface based laser transmitter according to claim 1, further comprising: a substrate;

the substrate is located below the first mirror.

4. The all-dielectric super surface based laser transmitter according to claim 1, further comprising: a first metal contact layer and a second metal contact layer;

the first metal contact layer is positioned below the substrate and is in ohmic contact with the substrate;

the second metal contact layer is located on the second mirror, and the second metal contact layer is in ohmic contact with the second mirror.

5. The all-dielectric-based super-surface laser emitter according to claim 1, wherein the silicon cylindrical particles of the first mirror are doped with trivalent elements; and pentavalent elements are doped into the silicon cylindrical particles of the second reflector.

6. The all-dielectric-based super-surface laser emitter according to claim 1, wherein a light outlet is formed on each of the second reflector and the second metal contact layer; the light outlet is used for outputting laser beams.

7. The all-dielectric-based super surface laser transmitter according to claim 6, wherein the active layer comprises a plurality of quantum well layers.

8. The all-dielectric-super-surface-based laser transmitter according to claim 7, wherein a plurality of the quantum well layers are filled with a gain medium.

9. A method for determining parameters of silicon cylindrical particles applied to the laser emitter of any one of claims 1 to 8, wherein the method for determining parameters comprises:

determining the diameter of silicon cylindrical particles of the reflector according to the working wavelength of the laser;

determining the aspect ratio of the silicon cylindrical particles when the reflectivity of the reflector is the preset reflectivity through an experiment;

determining the thickness of the silicon cylindrical particles of the reflector according to the aspect ratio and the diameter of the silicon cylindrical particles;

obtaining a relation curve diagram of the reflectivity of the reflecting mirror and the period of the silicon cylindrical particle arrangement and a relation curve diagram of the modulation bandwidth of the reflecting mirror and the period of the silicon cylindrical particle arrangement through experiments;

and determining the period of the silicon cylindrical particle arrangement when the reflectivity of the reflector is a preset reflectivity according to a relation line graph of the modulation bandwidth of the reflector and the period of the silicon cylindrical particle arrangement.

10. The method for determining the parameters of the silicon cylindrical particle of the all-dielectric-super-surface-based laser emitter according to claim 9, wherein the determining the thickness of the silicon cylindrical particle of the reflector according to the aspect ratio and the diameter of the silicon cylindrical particle comprises:

according to the aspect ratio and the diameter of the silicon cylindrical particles, using a formula

wherein, α_iAspect ratio of silicon cylindrical particles, S, as a mirror_iThickness of silicon cylindrical particle as mirror, D_iThe diameter of the silicon cylinder particle is 1 or 2, and when 1, the mirror is the first mirror, and when 2, the mirror is the second mirror.

Technical Field

The invention relates to the technical field of computational electromagnetic metamaterials and multi-physics simulation, in particular to a laser transmitter based on an all-dielectric super surface and a parameter determination method.

Background

The super surface is a two-dimensional sheet-like metamaterial, and the thickness of the super surface is several times smaller than the working wavelength. Their subwavelength structures propagate in a two-dimensional space in a periodic or non-periodic manner. The super-surface can be used to provide special optical properties to the device that some natural material films cannot achieve. In recent years, all-dielectric metamaterials and metamaterials have been considered to be more efficient counterparts to plasmonic materials. The core principle of all-dielectric metamaterials and metamaterials is the optical response of high-index-of-refraction dielectric nanoparticles. At present, because of the existence of electric resonance and magnetic resonance in the visible light range, the dielectric nanoparticles with high refractive index can effectively control light scattering and strength enhancement, and have the advantages of negligible extinction coefficient and extremely low loss. The all-dielectric super-surface is applied to the fields of wavefront engineering, electromagnetic induction transparency, high transmittance, broadband perfect mirrors, beam collimators and the like, particularly the broadband perfect mirrors, and provides a new unique opportunity for designing optical lenses, particularly semiconductor laser resonators.

The semiconductor laser has the advantages of small size, high efficiency, long service life, easy integration and the like. The semiconductor laser with high beam quality and narrow linewidth has higher beam quality, smaller slow axis divergence angle and narrower spectral linewidth, and is more suitable for shaping and combining large-scale semiconductor laser. Has wider application prospect in the aspects of industry, military, medical treatment and the like. The production of high power, high beam quality, narrow linewidth semiconductor lasers has been a goal of pursuit. However, although the conventional laser with the distributed bragg grating structure has the characteristic of easy operation in terms of preparation process and design, in the conventional distributed bragg reflector, a reflector is composed of a layer of high-refractive-index medium and a layer of low-refractive-index medium alternately, and incident light enters a dielectric layer and is reflected layer by the dielectric layer. Therefore, the method of controlling the reflectivity of the mirror in the bragg reflector is to increase or decrease the number of the reflective layers of the entire period, which is very inconvenient for controlling the thickness of the mirror and the size of the laser.

Disclosure of Invention

The invention aims to provide a laser transmitter based on an all-dielectric super-surface and a parameter determination method, which greatly reduce the thickness of a reflector and effectively reduce the overall volume of the laser transmitter.

In order to achieve the purpose, the invention provides the following scheme:

a laser transmitter based on a full-medium super surface,

the laser emitter comprises the following components in sequence from bottom to top: a first mirror, an active layer, and a second mirror;

the first reflecting mirror and the second reflecting mirror are each composed of periodically arranged silicon cylindrical particles.

Optionally, the laser transmitter further includes: a first confinement layer and a second confinement layer;

the first confinement layer is disposed between the first mirror and the active layer; the second confinement layer is disposed between the active layer and the first mirror; the first limiting layer and the second limiting layer are used for limiting carriers and adjusting resonance wavelength to enable the resonance wavelength to be equal to laser wavelength.

Optionally, the laser transmitter further includes: a substrate;

the first mirror the substrate is located below the first mirror.

Optionally, the laser transmitter further includes: a first metal contact layer and a second metal contact layer;

the first metal contact layer is positioned below the substrate and is in ohmic contact with the substrate;

the second metal contact layer is located on the second mirror, and the second metal contact layer is in ohmic contact with the second mirror.

Optionally, trivalent elements are doped into the silicon cylindrical particles of the first reflector; and pentavalent elements are doped into the silicon cylindrical particles of the second reflector.

Optionally, a light outlet is correspondingly formed on the second reflector and the second metal contact layer respectively; the light outlet is used for outputting laser beams.

Optionally, the active layer comprises a plurality of quantum well layers.

Optionally, a gain medium is filled between the quantum well layers.

A parameter determination method of a silicon cylindrical particle applied to a laser emitter, the parameter determination method comprising:

determining the diameter of silicon cylindrical particles of the reflector according to the working wavelength of the laser;

determining the aspect ratio of the silicon cylindrical particles when the reflectivity of the reflector is the preset reflectivity through an experiment;

determining the thickness of the silicon cylindrical particles of the reflector according to the aspect ratio and the diameter of the silicon cylindrical particles;

obtaining a relation curve diagram of the reflectivity of the reflecting mirror and the period of the silicon cylindrical particle arrangement and a relation curve diagram of the modulation bandwidth of the reflecting mirror and the period of the silicon cylindrical particle arrangement through experiments;

determining the period range of the silicon cylindrical particle arrangement when the reflectivity of the reflector is a preset reflectivity according to a relation curve graph of the reflectivity of the reflector and the period of the silicon cylindrical particle arrangement;

and determining the period of the silicon cylindrical particle arrangement when the reflectivity of the reflector is a preset reflectivity according to a relation line graph of the modulation bandwidth of the reflector and the period of the silicon cylindrical particle arrangement.

Optionally, the determining the thickness of the silicon cylindrical particle of the mirror according to the aspect ratio and the diameter of the silicon cylindrical particle includes:

according to the aspect ratio and the diameter of the silicon cylindrical particles, using a formulaCalculating to obtain the thickness of the silicon cylindrical particles of the reflector;

wherein, α_iAspect ratio of silicon cylindrical particles, S, as a mirror_iThickness of silicon cylindrical particle as mirror, D_iThe diameter of the silicon cylinder particle, i-1 or i-2, of the mirror, which is the first mirror when i-1,when i is 2, the mirror is a second mirror.

According to the specific embodiment provided by the invention, the invention discloses the following technical effects:

the first reflector and the second reflector in the laser emitter provided by the invention are both of periodically arranged silicon cylindrical particle structures, and the periodically arranged silicon cylindrical particles have high reflectivity and nanoscale thickness, so that the thickness of the reflector in the laser emitter is greatly reduced on the premise of ensuring the high reflectivity, and the overall volume of the laser emitter is effectively reduced.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

FIG. 1 is a block diagram of a laser transmitter provided by the present invention;

FIG. 2 is a block diagram of a mirror provided by the present invention;

FIG. 3 is a plan view of a reflector provided by the present invention;

FIG. 4 is a diagram illustrating the relationship between the reflectivity of the mirror and the frequency of the mirror according to the present invention;

FIG. 5 is a schematic diagram of the relationship between reflectivity and aspect ratio provided by the present invention;

FIG. 6 is a graph of reflectivity versus period provided by the present invention;

FIG. 7 is a line graph of bandwidth versus period provided by the present invention;

FIG. 8 is a schematic diagram of a four-level system provided by the present invention;

FIG. 9 is a diagram illustrating the relationship between the quality factor and the wavelength of a conventional DBG laser transmitter;

FIG. 10 is a diagram illustrating the relationship between the quality factor and the wavelength of a laser transmitter according to the present invention;

FIG. 11 is a laser time domain diagram of a laser transmitter provided by the present invention;

FIG. 12 is a frequency domain plot corresponding to FIG. 11;

description of the symbols: 1-first mirror, 2-second mirror, 3-active layer, 4-substrate, 5-first confinement layer, 6-second confinement layer, 7-first metal contact layer, 8-second metal contact layer.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention aims to provide a laser transmitter based on an all-dielectric super-surface and a parameter determination method, which greatly reduce the thickness of a reflector and effectively reduce the overall volume of the laser transmitter.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

The embodiment of the invention provides a laser transmitter based on an all-dielectric super surface, which sequentially comprises the following components from bottom to top: a first mirror 1, an active layer 3 and a second mirror 2. Preferably, the Laser transmitter is a VCSEL (Vertical Cavity Surface Emitting Laser).

As shown in fig. 2, the first mirror 1 and the second mirror 2 are each composed of periodically arranged silicon cylindrical particles; preferably, the reflectivity of the first mirror 1 is almost 100%; the reflectivity of the second mirror 2 is between 99% and 100%, as shown in fig. 4, the first and second mirrors constituting the output coupler. The diameter and period of the silicon cylindrical particle of the first reflector 1 and the silicon cylindrical particle of the second reflector 2 are the same, and the thickness of the silicon cylindrical particle of the second reflector 2 is greater than the thickness of the silicon cylindrical particle of the first reflector 1, wherein the period refers to the distance a (shown in fig. 3) between the central axes of two adjacent silicon cylindrical particles, and the diameter and period of the silicon cylindrical particle, the thickness of the silicon cylindrical particle of the first reflector 1 and the thickness of the silicon cylindrical particle of the second reflector 2 are determined according to the following method, specifically comprising:

determining the diameter of the silicon cylindrical particles according to the working wavelength of the laser; preferably, the working wavelength of the laser is 1500 nm; electric resonance is a basis for laser emitters capable of generating laser light, and the prior art has been disclosedGenerating electric resonance, wherein lambda is the working wavelength, and D is the diameter of the silicon cylindrical particle; in the embodiment of the present application, the silicon cylindrical particles of the reflector are periodically arranged, when the silicon cylindrical particles are periodically arranged, the obtained reflector resonates at a wavelength higher than that of a single silicon cylindrical particle, and experimental simulation shows that when the diameter of the silicon cylindrical particle of the reflector is 400nm, electrical resonance is generated.

The aspect ratio at which the reflectance is the preset reflectance is determined through experiments, as shown in fig. 5.

Determining the thickness of the silicon cylindrical particle of the mirror according to the aspect ratio and the diameter of the silicon cylindrical particle, comprising: using the formula of diameter and aspect ratio of silicon cylindrical particles

Calculating to obtain the thickness of the silicon cylindrical particle, wherein α_iAspect ratio of silicon cylindrical particles, S, as a mirror_iThickness of silicon cylindrical particle as mirror, D_iThe diameter of the silicon cylinder particle is 1 or 2, and when 1, the mirror is the first mirror 1, and when 2, the mirror is the second mirror 2.

Graphs of the reflectance of the mirror with respect to the period of the silicon cylindrical particle arrangement and line graphs of the modulation bandwidth of the mirror with respect to the period of the silicon cylindrical particle arrangement were obtained through experiments, as shown in fig. 6 and 7.

Determining the periodic range of the silicon cylindrical particle arrangement when the reflectivity of the reflector is a preset reflectivity according to a relation curve graph of the reflectivity of the reflector and the period of the silicon cylindrical particle arrangement; when the reflectivity of the reflector is close to 1, the period range is 630-660 nm.

Determining the period of the silicon cylindrical particle arrangement when the reflectivity of the reflector is the preset reflectivity according to a relation line graph of the modulation bandwidth of the reflector and the period of the silicon cylindrical particle arrangement; when the period is 630nm, the bandwidth is much larger than the other bandwidths, and therefore, the period width is selected to be 630 nm.

The laser transmitter further includes: a first confinement layer 5 and a second confinement layer 6; a first confinement layer 5 is arranged between the first mirror 1 and the active layer 3; the second confinement layer 6 is arranged between the active layer 3 and the first mirror 1; the first confinement layer 5 and the second confinement layer 6 serve to confine carriers and to adjust the resonance wavelength to be equal to the laser wavelength.

The laser transmitter further includes: a substrate 4; the first mirror 1 is located between the active layer 3 and the substrate 4.

The laser transmitter further includes: a first metal contact layer 7 and a second metal contact layer 8; the first metal contact layer 7 is arranged at the bottom of the laser emitter, the first metal contact layer 7 is in contact with the substrate 4, and the first metal contact layer 7 is in ohmic contact with the substrate 4; the second metal contact layer 8 is arranged on top of the laser emitter, the second metal contact layer 8 is in contact with the second mirror 2, and the second metal contact layer 8 is in ohmic contact with the second mirror 2.

Trivalent elements are doped into silicon cylindrical particles of the first reflector 1, and the first reflector 1 is an n-type reflector based on a full-medium super surface; the second reflector 2 is a p-type all-dielectric super-surface based reflector, and pentavalent elements are doped in the silicon cylindrical particles of the second reflector 2.

A light outlet is correspondingly arranged on the second reflector 2 and the second metal contact layer 8 respectively; the light outlet is used for outputting laser beams. Preferably, the light outlet is a circular light outlet and outputs a circular laser beam.

The active layer 3 includes a plurality of quantum well layers. Preferably, the active layer 3 is composed of 1 to 3 quantum wells.

The gain medium is filled among the quantum well layers, the gain medium is described by a universal four-level system in simulation, and the simulation method is FDTD (Finite-Difference Time-Domain). For isotropic media, the expression of maxwell's equations in the time domain is as follows:

wherein, B ═ mu₀H represents magnetic induction, mu represents magnetic permeability, mu₀Denotes the permeability in vacuum, the intensity of the magnetic field H, the intensity of the electric field E, the dielectric constant E, and₀denotes the air dielectric constant, t denotes time, P ═ Sigma_i＝a,bP_iRepresenting the electrical polarization density of the gain material.

As shown in FIG. 8, P_aIs a second energy level N₂And a first energy level N₁The induced polarization density of atomic transitions between. P_bAt a third energy level N₃And the ground state energy level N₀The induced polarization density of atomic transitions between. The electrons being from the ground level N₀To a third energy level N₃At pumping frequency omega_bPumping, wherein the pumping frequency

E₃Is the energy level represented by the third energy level, E₀The magnitude of the energy represented by the ground state energy level,

is Planck constant. Second energy level N₂Is the upper energy level of a metastable laser. Over a short time t₃₂After that, the particles are at a third energy level N₃Upper is rapidly transferred to the second energy level N by non-radiative transition₂Second energy level N₂Being metastable, having a longer lifetime, the particle may be at a second energy level N₂Upper accumulation to realize three electric energy levels N₃And a firstTwo energy level N₂Population inversion of (2). When electrons radiate from high to low, they are at a central frequency ω_aThe photons of the radiation are, among other things,

E₂: the magnitude of the energy represented by the second energy level, E₁: the magnitude of the represented energy of the first energy level,is Planck constant. Finally, the electron goes from the first energy level N₁Upper rapid radiationless transfer to ground level N₀. The atomic population density follows the following rate equation:

wherein, tau₃₂Denotes the particles from N₃Decline to N₂Time of (d), τ₂₁Denotes the particles from N₂Decline to N₁Time of (d), τ₁₀Denotes the particles from N₁Decline to N₀Time of (d).

In optically pumping electrons from the ground level N0 to the third level N3 without using external electromagnetic waves, equations (2) and (5) can be obtained by pumping at a uniform pumping speed f_pumpPumping electrons to simplify and uniform pumping speed f_pumpProportional to the optical pumping intensity in the experiment. Based on this simplification, the following equation is derived:

the embodiment of the invention also provides a parameter determination method of the silicon cylindrical particles applied to the laser emitter, which comprises the following steps:

determining the diameter of the silicon cylindrical particles according to the working wavelength of the laser; preferably, the working wavelength of the laser is 1500 nm; electric resonance is a basis for laser emitters capable of generating laser light, and the prior art has been disclosedGenerating electric resonance, wherein lambda is the working wavelength, and D is the diameter of a silicon cylindrical particle; in the embodiment of the present application, the silicon cylindrical particles of the reflector are periodically arranged, when the silicon cylindrical particles are periodically arranged, the obtained reflector resonates at a wavelength higher than that of a single silicon cylinder, and experimental simulation shows that when the diameter of the silicon cylindrical particles of the reflector is 400nm, electrical resonance is generated.

The aspect ratio at which the reflectance is the preset reflectance is determined through experiments.

Determining the thickness of the silicon cylindrical particle of the mirror according to the aspect ratio and the diameter of the silicon cylindrical particle, comprising: using the formula of diameter to aspect ratioCalculating to obtain the thickness of the silicon cylindrical particle, wherein α_iAspect ratio of silicon cylindrical particles, S, as a mirror_iThickness of silicon cylindrical particle as mirror, D_iThe diameter of the silicon cylinder particle is 1 or 2, and when 1, the mirror is the first mirror 1, and when 2, the mirror is the second mirror 2.

A graph of the relationship between the reflectivity of the mirror and the period of the silicon cylindrical particle arrangement and a line graph of the relationship between the modulation bandwidth of the mirror and the period of the silicon cylindrical particle arrangement are obtained through experiments.

Determining the periodic range of the silicon cylindrical particle arrangement when the reflectivity of the reflector is a preset reflectivity according to a relation curve graph of the reflectivity of the reflector and the period of the silicon cylindrical particle arrangement; when the reflectivity of the reflector is close to 1, the period range is 630-660 nm.

Determining the period of the silicon cylindrical particle arrangement when the reflectivity of the reflector is the preset reflectivity according to a relation line graph of the modulation bandwidth of the reflector and the period of the silicon cylindrical particle arrangement; when the period is 630nm, the bandwidth is much larger than the other bandwidths, and therefore, the period width is selected to be 630 nm.

By utilizing the parameter determination method of the silicon cylindrical particles applied to the laser emitter, provided by the embodiment of the invention, the thickness of the silicon cylindrical particles of the first reflector 1 is determined to be 460nm, the diameter is determined to be 400nm, and the period is determined to be 630 nm; the thickness of the silicon cylindrical particles of the second reflector 2 is 465nm, the diameter is 400nm, and the period is 630 nm; preferably, the operating wavelength is 1500nm, and each of the first mirror 1 and the second mirror 2 is composed of 16 periodically arranged silicon cylindrical particles.

The quality factor is an important indicator of laser light. In order to obtain a laser with a higher quality factor, the reflectivity between the two mirrors should be as close as possible. For the laser cavity, the quality factor is:

wherein Q is a quality factor v₀Is the mode frequency, n₀Is the refractive index of the medium in the cavity, c is the speed of light, d is the distance between the pillars, α is the aspect ratio of the silicon cylindrical particles, R₁Is the reflectivity, R, of the first mirror 1₂Is the reflectivity of the second mirror 2.

The reflectance R of the first mirror 1 can be found by the formula (10)₁The reflectivity R of the second mirror 2 can be almost 100%₂The closer to 100%, the higher the quality factor Q, the better the quality of the laser. The reflectivity of the second reflector 2 can be less than 100% but more than 99% by slightly increasing the thickness of the silicon cylindrical particle, that is, the laser emitter provided by the embodiment of the present application achieves a method for controlling the reflectivity of the reflector by only slightly increasing the thickness of the silicon cylindrical particle, thereby showing good micro-control capability for the laser emitter. Compared with the traditional distributed Bragg reflector, the laser transmitter provided by the embodiment of the application is really easy to control, simple to prepare and convenient to produce.

The thickness of the reflector of the laser transmitter provided by the embodiment of the application is only 460nm, and when the reflectivity of the reflector of the distributed Bragg reflector reaches more than 99%, the size of the reflector of the distributed Bragg reflector is at least 1450 nm. When the reflectivity of the reflector of the distributed bragg reflector reaches more than 99% and the working wavelength is 1500nm, the quality factor Q is about 500, as shown in fig. 9; when the working wavelength of the laser transmitter provided by the embodiment of the application is 1500nm (the frequency is 200THz), the maximum quality factor Q is 2505 (as shown in FIG. 10); therefore, the laser transmitter provided by the embodiment of the application effectively reduces the whole volume of the laser, and simultaneously increases the Q value of the laser, so that the laser linewidth is smaller, and the laser transmitter has better single-mode output stability and higher single-mode output power.

A laser time domain diagram and a corresponding laser frequency domain diagram of a laser transmitter provided by an embodiment of the present invention are shown in fig. 11 and 12.

The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.