阅读说明：本技术 一种激子极化激元载体的系统损耗参数检测装置 (System loss parameter detection device of exciton polarization excimer carrier ) 是由 任元 吴昊 刘通 高廷阁 傅百恒 王元钦 丁友� 于 2019-09-24 设计创作，主要内容包括：本发明涉及一种激子极化激元载体的系统损耗参数检测装置。它主要包括涡旋和泵浦光制备、载体自发辐射信号采集与图像分析终端两部分,前者主要包含激光器、空间光调制器和可调衰减器,后者主要包括采集光路和图像分析终端。首先,激光器产生高斯光束,经空间光调制器制备轨道角动量分别为±l的涡旋光,同时制备受可调衰减器控制光强的泵浦光；随后,涡旋光与泵浦光同时照射到载体表面；然后,利用电荷耦合传感器相机采集载体受激自发辐射干涉图样光信号；最后,利用图像信号处理终端判别干涉图样的稳定区间,通过区间对应的泵浦光强度计算出载体的系统损耗参数。本装置结构简单,操作方便,开辟了一种激子极化激元载体的系统损耗实验测量新方法。(The invention relates to a system loss parameter detection device for an exciton polarization excimer carrier. The device mainly comprises two parts, namely vortex and pump light preparation, carrier spontaneous radiation signal acquisition and an image analysis terminal, wherein the vortex and pump light preparation mainly comprises a laser, a spatial light modulator and an adjustable attenuator, and the image analysis terminal mainly comprises an acquisition light path and an image analysis terminal. Firstly, a laser generates a Gaussian beam, vortex rotation with orbital angular momentum of +/-l is prepared by a spatial light modulator, and pumping light with light intensity controlled by an adjustable attenuator is prepared at the same time; then, simultaneously irradiating vortex rotation and pumping light to the surface of the carrier; then, acquiring a carrier stimulated spontaneous emission interference pattern optical signal by using a charge coupled sensor camera; and finally, distinguishing a stable interval of the interference pattern by using the image signal processing terminal, and calculating the system loss parameter of the carrier according to the pump light intensity corresponding to the interval. The device has simple structure and convenient operation, and develops a new method for measuring the system loss experiment of the exciton polarization excimer carrier.)

1. The invention relates to a system loss parameter detection device of an exciton polarization excimer carrier, which comprises: the device comprises a laser 1(1), a horizontal polaroid (2), a beam expanding lens group (3), a spectroscope 1(4), a spatial light modulator SLM1(5), a spatial light modulator SLM2(6), a plane mirror 1(7), a plane mirror 2(8), a spectroscope 2(9), a spectroscope 3(10), a laser 2(11), a controllable attenuator (12), a plane mirror 3(13), a collimating lens group 1(14), a spectroscope 4(15), an objective lens (16), a sample bin (17), a collimating lens group 2(18), a focusing spatial filter (19), a charge coupled sensor camera (20) and an image processing terminal (21).

2. A process according to claim 1The system loss parameter detection device of the exciton polarization excimer carrier is characterized in that a spatial light modulator is utilized to generate two beams of vortex light with topological charge numbers which are opposite to each other, the vortex light is used as signal light and is irradiated to the surface of a semiconductor-based exciton polarization excimer carrier material together with pump light with light intensity adjusted by a controllable attenuator after passing through a specific light path, so that the carrier is excited to spontaneously radiate to generate a vortex superposition state interference pattern; scanning and adjusting the controllable attenuator to enable the pumping light intensity to change within a certain range, collecting interference pattern signals through a specific light path consisting of a spectroscope, a lens group and a focusing space filter and a charge coupled sensor camera, processing the light spot pattern of the interference pattern signals in real time by using an image signal processing terminal, and obtaining the critical states of dissipation and divergence of the excited radiation of the exciton polariton carrier through criteria; then, the lower limit value pump of the pumping light intensity corresponding to the two critical states is obtained_minAnd an upper limit value pump_maxThe difference between the upper and lower boundaries can be expressed as "pump_max-pump_minAnd the system loss parameter γ can be expressed as γ ═ Δ pump-0.3 by this difference Δ pump.

Technical Field

The invention mainly relates to the fields of condensed state, photoelectricity and signal processing, in particular to technical methods for forming a wave particle vortex superposed state, modulating the phase of a light beam, detecting a spontaneous radiation image and the like.

Technical Field

Bose-Einstein condensate (BEC) was the gaseous condensate proposed by Bose and Einstein in the last 20 th century, and cornell and wilman and their assistants succeeded in achieving a true BEC in 1995 at the institute of astronomical physics laboratories. In recent years, people find that an exciton polarization system in a semiconductor microcavity can realize BEC at normal temperature, the research enthusiasm of people on the exciton polarization of the semiconductor microcavity is greatly stimulated, and the normal-temperature superflow characteristic of the semiconductor microcavity shows great scientific research and application values. The current worldwide research on exciton polaritons in semiconductor microcavities mainly focuses on three aspects of photon-exciton coupling, exciton polariton spontaneous radiation and exciton polariton evolution characteristics. Because an exciton polariton system in the semiconductor microcavity material is a non-Hermite dissipation system, the loss coefficient of the semiconductor material must be determined through theoretical and experimental researches in the three aspects. However, a direct and simple loss factor measurement method and measurement device are still lacking.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: aiming at the problem that the loss characteristic parameters of the prior exciton polarization excimer carrier material with a semiconductor microcavity structure are difficult to directly and simply measure, the invention aims to realize the transfer of vortex rotation Sagnac interference effect to the semiconductor microcavity exciton polarization excimer carrier material by utilizing the spontaneous radiation characteristic of the semiconductor microcavity exciton polarization excimer, extract key parameters by utilizing image information generated by the spontaneous radiation of the carrier material and realize the measurement of the system loss characteristic gamma of the exciton polarization excimer carrier material with the semiconductor microcavity structure by simple calculation.

The technical solution of the invention is as follows: the invention relates to a device for detecting loss characteristics of an exciton polariton carrier system based on wave particle vortex, which comprises the following main components as shown in figure 1: the device comprises a laser 1(1), a horizontal polaroid (2), a beam expanding lens group (3), a spectroscope 1(4), a spatial light modulator SLM1(5), a spatial light modulator SLM2(6), a plane mirror 1(7), a plane mirror 2(8), a spectroscope 2(9), a spectroscope 3(10), a laser 2(11), a controllable attenuator (12), a plane mirror 3(13), a collimating lens group 1(14), a spectroscope 4(15), an objective lens (16), a sample bin (17), a collimating lens group 2(18), a focusing spatial filter (19), a CCD (20) and an image processing terminal (21). First, a laser (1) generates a laser beam, the laser beam is changed into horizontal polarized light after passing through a polaroid (2), the horizontal polarized light is changed into a Gaussian beam with a required diameter through a beam expanding lens (3), the Gaussian beam is divided into two beams through a spectroscope (4), the two beams are respectively irradiated on a spatial light modulator 1(5) and a spatial light modulator 2(6) to respectively modulate two vortex beams with orbital angular momentum of opposite numbers, one of the two vortex beams passes through a plane mirror 1(7) and a plane mirror 2(8), and then is optically merged with the other vortex beam at a spectroscope (9). Meanwhile, a laser 2(11) generates a pumping laser beam, and the pumping laser beam passes through a controllable attenuator (12) and a plane mirror (13) and then is merged with the other two vortex light beams at a spectroscope 3 (10). Then, the light beam passes through the collimating lens group 1(14), the beam splitter 4(15) and the objective lens (16) and irradiates the surface of the exciton polarization excimer sample fixed on the sample chamber (17). At this time, the sample surface generates an interference pattern of spontaneous emission. The interference pattern passes through an objective lens (16) and a spectroscope (4) (15), then pump light is filtered out sequentially through a collimating lens group (2) (18) and a focusing space filter (19), exciton polarized excimer spontaneous radiation facula image signals are collected by a charge coupled sensor camera (20), and finally real-time processing and result calculation are carried out by an image information processing terminal (21). By adjusting the controllable attenuator (12), when the attenuation value of the controllable attenuator is larger than a certain value, the light spot cannot be formed, and when the attenuation value of the controllable attenuator is smaller than a certain value, the light spot presents a divergence characteristic. And searching the moment corresponding to the starting of the formation and the starting of the divergence of the light spots by using the image information processing terminal, thereby successfully calculating the system loss parameter gamma by using the corresponding controllable attenuation value.

The principle of the invention is as follows:

(1) Gross-Pitaevski equation based on Schrodinger equation

The Gross-Pitaevski (GP equation for short) equation reflects the energy coupling relationship between exciton polaritons and photons and the space-time evolution relationship of field distribution in Bose-Einstein condensation (BEC) in a non-Hermite system. The expression of the GP equation is as follows:

wherein the content of the first and second substances,is normalized Planckian constant, # r is the exciton polariton field distribution wave function, m is the exciton polariton effective mass, V_ext(r) is the barrier distribution in the exciton field; g is a nonlinear correlation coefficient reflecting the degree of coupling between the exciton field and the photon field; p (r) is the pump optical field distribution; η is the system saturation factor; γ is the system loss parameter. In experimental research, loss parameters are the most important system parameters of semiconductor microcavity materials, and reflect the spontaneous emission performance and the stability of the materials in evolution over time. The solution of this equation, i.e., ψ (r, t), reflects the spatio-temporal distribution of the exciton polariton spontaneous emission field, and the system loss γ and the pump p (r) have the greatest influence on this solution, the pump term is in reality a term that is controllable and measurable outside the system, so the GP equation links the externally measurable term with the system loss parameter by the exciton polariton field distribution.

As shown in fig. 5, the numerical calculation result of the relationship can be obtained by the longge stoke method and the real-time evolution method, and the numerical calculation result is statistically processed and then brought into the analysis relationship to be established. Thus, the relationship between system loss and pump intensity can be given by the following relationship:

wherein, P_0maxThe maximum pump light intensity P is the maximum pump light intensity P which keeps the exciton polarization spontaneous radiation to form pattern without diffusion_0minIs the minimum pump light intensity that enables exciton polariton spontaneous emission to form. γ is a dimensionless number, which can be reduced to scale for different usage scenarios. The invention is based on this relationship to measure the system loss parameter of semiconductor-based exciton polariton carrier materials.

(2) Phase imprinting principle based on exciton polarization excimer vortex superposition state

The semiconductor microcavity structure is a flat microcavity structure, as shown in fig. 2(a), where the flat microcavity structure is composed of distributed Bragg reflectors (dbgs), and the dbgs are dielectric periodic structures formed by alternately arranging two dielectric films. The quantum microstructure material is typically embedded in the microcavity where the optical cavity mode has the greatest intensity, as shown in fig. 2 (b). The embedded semiconductor quantum wells provide exciton modes that can couple with optical modes in the slab microcavity, thereby forming their coupled modes-exciton polaritons, as shown in fig. 2 (c). These exciton polaritons are distributed in the semiconductor microcavity and spontaneously emit photons.

If the semiconductor microcavity is irradiated with a specially designed Gauss beam with orbital angular momentum, a vortex state of exciton polarization excimer is excited. In this system, the initial state system energy needs to be non-zero, using the form:

the pump light in the system enables the exciton polariton in the system to be in an excited state all the time. Wherein P is₀Is the pump intensity, e is the natural constant, r is the radial coordinate, r₀Is the pump spot radius. However, at this time, the exciton polariton of the excited spontaneous emission moves from inside to outside on the X-Y plane in the cavity, and the light spot formed by the spontaneous emission is annular, which is not favorable for observationAnd extracting the characteristic signal. If a beam shape is used at this time as:

with orbital angular momentum of l, where P excites exciton polaritons₀' is the vortex intensity, l is the orbital angular momentum, i is the unit complex number, θ is the angular coordinate, ω is the angular frequency, and t is time. At this time, orbital angular momentum of the vortex light beam is transferred between the light beam and the exciton polariton, so that the movement direction of the exciton polariton is changed, and a vortex state is generated. When two vortex beams with orbital angular momentum of +/-l are simultaneously excited, exciton polaritons generate vortex superposed states. As shown in fig. 3, the interference pattern appears macroscopically, and this process is called phase imprinting, i.e., coherent vortex light imprints coherent phases onto the surface of the semiconductor microcavity material. Interference pattern number is l, following circular symmetry, exciton polarization excimer field distribution | psi (r, t)' at coherence²Gaming machine capable of generating light at maximum and cancellation | ψ (r, t)²Approaching to zero, thus creating good conditions for subsequent discrimination and detection.

The invention has the main advantages that:

(1) the structure is simple, the positions of all components are fixed, the variable is only the attenuation amplitude of the controllable attenuator, and the control is easy.

(2) The device has wide application range. According to the design principle, the dimensionless calculation method is adopted, so that the discrimination method used by the device is suitable for measuring system loss parameters of various semiconductor exciton polariton carriers under the non-Hermite condition.

(3) The device has high measurement sensitivity and large dynamic range. By adopting an image processing mode which takes the maximum and minimum light spot brightness times of the interference fringes as the characteristic value, the characteristic value can be easily extracted, the relative error possibly generated in the characteristic value extraction and analysis processes is small, and the dynamic range of measurement is large.

Drawings

FIG. 1 is a schematic view of a detection apparatus;

FIG. 2 is a diagram of a semiconductor microcavity architecture;

FIG. 3 is a schematic diagram of quantum well and intra-cavity field distributions;

FIG. 4 is a schematic view of a vortex stack configuration;

FIG. 5 is a graph showing pump intensity versus system loss;

detailed description of the preferred embodiments

The invention takes a spontaneous radiation interference pattern formed by coupling vortex rotation and exciton polarization in a semiconductor microcavity as a measurement carrier, and the specific implementation steps are as follows:

firstly, a laser (1) generates a laser beam, the laser beam is changed into horizontal polarized light after passing through a polaroid (2), because the spatial light modulator only has a good modulation effect on the horizontal polarized light, and the light beam emitted by the laser is adjusted through a collimation and beam expansion lens (3) group. Then, the light beam is split into two paths by the beam splitter and irradiated on two spatial light modulators (5) and (6) loaded with holograms as shown in fig. 2(a) and 2(b), respectively, so that vortex light beams as shown in fig. 2(c) and 2(d) can be reflected from the two spatial light modulators, and orbital angular momentum of the two vortex optical rotations are opposite to each other. Then, the two beams are optically rotated to be overlapped by using plane mirrors (7) and (8) and a beam splitter (9).

At the same time, a laser beam is generated by a laser (11), which acts as pump light. The light beam passes through the adjustable attenuator, and the real-time regulation and control of the pump light intensity by the control terminal computer are realized. The regulated and controlled pumping light beam is converged to the spectroscope (10) through the plane reflector (13). The beam splitter (10) is used for realizing the superposition of the two beams of vortex light and the one beam of pump light.

The three superposed laser beams are converged to a spectroscope (15) through a collimating lens group (14), one of the laser beams is collimated and incident to an objective lens, and then a sample bin irradiates the surface of a semiconductor microcavity exciton polariton carrier fixed on the sample bin. At this time, under the energy excitation of the pump light, exciton polarization excimer is generated in the semiconductor microcavity, and then the exciton polarization excimer is coupled with two vortex lights with opposite orbital angular momentum, so that spontaneous radiation occurs. Since the two vortex light beams respectively impress phases to exciton polarization, Sagnac interference occurs in spontaneous radiation, and petaloid interference fringes are formed.

Then the interference fringe enters a focusing space filter (19) through an objective lens (16), a spectroscope (15) and a collimating lens group (18), after reflected pump light interference items are filtered out, the interference fringe is collected by a charge coupled sensor camera (20), and finally a real-time image is transmitted to an image information processing terminal (21) for processing.

The image information real-time processing terminal mainly uses the maximum light intensity value A of interference fringe by image phase processing software_maxAnd a minimum intensity value A_minThe quotient was taken 20lg for processing. As the controllable attenuator continuously increases the attenuation value of the pump light intensity, the exciton polariton system changes from a divergent state to a stable state and then to a dissipative state. At this time, 20lgA_max/A_minWill be gradually increased and then gradually decreased, at which time 20lgA is recorded by the image information real-time processing terminal_max/A_minThe pump light intensity is 2dB twice, that is, the upper/lower limit of the exciton polarization interference pattern in the stable state caused by the pump light is marked as pump_maxAnd pump_minAt this time, according to γ ═ p (pump)_max-pump_min) The loss parameter gamma of the system can be obtained from 2 to 0.3.

Those skilled in the art will appreciate that the details of the present invention not described in detail herein are well within the skill of those in the art.