CN113008839B - Organic semiconductor microcavity vitreous color-Einstein condensation vortex generation device - Google Patents

Abstract

The invention relates to an organic semiconductor microcavity Bose-Einstein condensed vortex generating device. It mainly includes three parts: excitation light generation, Bose-Einstein condensate vortex generation and acquisition and detection terminal. The first part mainly includes femtosecond laser, optical parametric amplifier and vortex wave plate, and the second part mainly includes excitation light path and organic matter The sample chamber, the third part mainly includes the acquisition optical path and the image analysis terminal. First, the femtosecond laser generates a femtosecond laser, the wavelength of the femtosecond laser is modulated to 405 nm after being controlled by the laser control terminal, and converted into a femtosecond vortex beam by a vortex wave plate; then, the beam is irradiated on the surface of the sample, and the excitation produces Bose-Einstein condensate; then, the stimulated spontaneous emission light signal of the sample is collected by the charge-coupled sensor camera and the spectrometer; finally, according to the lasing phenomenon produced by the organic sample observed by the charge-coupled sensor camera, and the spectrometer is used to Determining the Generation of Bose-Einstein Condensation Excitation in Organic Semiconductor Microcavities. The device has simple structure and convenient operation, and opens up a new device for generating organic semiconductor microcavity Bose-Einstein condensed vortex.

Description

An organic semiconductor microcavity Bose-Einstein condensate vortex generator

technical field

The invention mainly relates to the fields of organic semiconductor microcavity, condensed matter, optoelectronics and signal processing, in particular to the formation of Bose-Einstein condensation excitation in organic semiconductor microcavity, generation of vortex beam, detection of spontaneous radiation image and other technologies method.

technical background

Bose–Einstein condensate (BEC) is a gas condensate proposed by Bose and Einstein in the 1920s. The Institute succeeds in realizing a true BEC. In recent years, it has been discovered that the exciton polariton system in the organic semiconductor microcavity can realize BEC at room temperature. Flow properties show great scientific and application value, but the research on photon-exciton coupling in new organic semiconductors is still in its infancy. In organic semiconductors, the Rabi splitting of exciton polaritons can reach hundreds of meV, so the emission wavelength range of organic exciton polaritons is also very large, strong coupling, low cost, and wavelength tunable. Organic semiconductor exciton polaritons have important application prospects in Bose-Einstein condensation. In addition, due to the gyroscopic effect of exciton polariton, the use of exciton polariton generated by vortex light excitation with orbital angular momentum is also of great significance for the study of new gyroscopes.

SUMMARY OF THE INVENTION

The technical problem solved by the present invention is: in view of the difficulty of direct and simple preparation of exciton polarized vortex in the current organic semiconductor microcavity, the present invention has designed an experimental optical path to make the preparation of vortex light and exciton polarized vortex. The excitation device of the exciton is organically combined, and the generation of the exciton polariton is verified by a spectrometer.

The technical solution of the present invention is: the present invention relates to an organic semiconductor microcavity Bose-Einstein condensed vortex generating device, as shown in FIG. 1 , the main components of which include: a femtosecond laser (1), a laser control terminal (2), optical parametric amplifier (3), plane mirror (4), linear polarizer 1 (5), quarter wave plate (6), vortex wave plate (7), linear polarizer 2 (8) ), beam splitter 1 (9), sample chamber (10), microscope objective lens (11), beam splitter 2 (12), collimating lens 1 (13), short-wave pass filter (14), collimating lens 2 ( 15), a charge-coupled sensor camera (16), an image acquisition and processing terminal (17), a notch plate (18), a spectrometer (19), a beam splitter 3 (20), and a white light source (21). First, by using a white light source (21), adjust the sample in the sample chamber (10) to an appropriate position in the field of view of the charge-coupled sensor camera (16), turn off the white light source (21), and turn on the femtosecond laser (1) to generate The femtosecond laser beam, through the laser control terminal (2), controls the femtosecond laser (1) and the optical parametric amplifier (2) so that the femtosecond laser beam is converted into a femtosecond laser beam with a set power and frequency, and the beam passes through the plane mirror (4) After passing through the linear polarizer 1 (5), the quarter wave plate (6) and the vortex wave plate (7), the outgoing beam is converted into a femtosecond vortex beam through the linear polarizer 2 (8). The light beam passes through the beam splitter 2 (12) and then is irradiated on the organic sample chamber (10) through the microscope objective lens (11). At this time, a spontaneous emission pattern will be generated on the surface of the sample. The pattern passes through the microscope objective lens (11) and the beam splitter 2 (12), and then passes through the collimating lens 1 (13), the collimating lens 2 (14) and the filter (15) in order to filter out the pump light, and then passes through the beam splitting The mirror 3 (20) is divided into two beams, which are respectively collected by a charge-coupled sensor camera (16) and a spectrometer (19) and transmit data to an image collection and processing terminal (17) for analysis and processing. The power and frequency of the excitation light are adjusted in real time by controlling the parameters of the laser control terminal (2). When the power is lower than the threshold for generating Bose-Einstein condensation, only fluorescence is observed in the sample; when the power is further increased, the sample will A lasing phenomenon occurs, and a significant change in light intensity is observed; and when the power continues to increase, the sample will be destroyed by ablation. The device not only generates vortex light and irradiates the sample through the optical path, but also can use the information of the image acquisition and processing terminal to observe the phenomenon of Bose-Einstein condensation excitation in real time.

The principle of the present invention is:

(1) Generation of exciton polaritons based on supercurrent properties

Super fluidity is a quantum effect on a macroscopic scale. Superfluidity is a concrete manifestation of this phenomenon, in which atoms form a tight group due to Bose-Einstein condensation. The research on superfluid and quantum vortex in the field of physics has lasted for nearly a century, and the development of ultracold atomic condensation provides an ideal platform for research in this field. P.Kapitza first observed the superfluid phenomenon of Bose liquid, and won the Nobel Prize in Physics in 1978; L.Landau proposed the quantum theory of superfluid, explained and predicted many important properties of superfluid, won the 1962 Nobel Prize in Physics; A.A.Abrikosov discovered by solving the Ginzburg–Landau equation that quantum vortices follow the principle of the lowest energy and are arranged in a periodic lattice structure; A. Leggett proposed a new quantum theory, revealing liquid helium -3 Mechanism of Fermi superfluid, they shared the 2003 Nobel Prize in Physics.

Unlike macroscopic objects, microscopic particles have an "internal" angular momentum, namely spin, in addition to the momentum in the coordinate space. Particles with half-integer spins are called fermions, such as electrons, quarks, neutrinos, and their spin is 1/2. Particles with integer spins are called bosons, such as gluons, photons, gravitons, W and Z bosons, and their spin is 1. For fermions, due to the Pauli exclusion principle, only one particle is allowed to fill each state. For bosons, however, there is no limit to the number of particles that fill each state. After the temperature drops to a certain value, more and more bosons are in the lowest energy state, that is, their momentum is zero, and this phenomenon is called Bose-Einstein condensation.

(2) Bose-Einstein Condensation Based on Lower Branch Exciton Polariton

The exciton polariton is a quasiparticle formed by the mutual coupling of the exciton field and the photon field. Since the exciton-photon coupling problem is quadratic, the diagonalized exciton polariton can be obtained analytically. The Hamilton quantity H is:

为约化普朗克常量，k表示波矢，ω_X(k)和ω_C(k)分别表示激子场和光子场的色散，而激子与光子间的耦合就可以用矩阵中的元素Ω_R描述，称之为Rabi劈裂。in,

In order to reduce Planck's constant, k represents the wave vector, ω _X (k) and ω _C (k) represent the dispersion of the exciton field and the photon field, respectively, and the coupling between the excitons and photons can be determined by the elements in the matrix Ω _R description, called Rabi splitting.

The eigenvalues of this matrix are given by the following equations, namely:

Obviously, from the above formula, we can obtain the two-branch dispersion relation of the exciton polariton, namely:

In the above formula, ω _UP (k) and ω _LP (k) represent the dispersion relation of the upper branch and the lower branch of the exciton polariton, respectively, and the Bose-Einstein condensation of the exciton polariton refers to the lower branch excitation. The condensation of the subpolariton, the vortex superposition state of the exciton polariton is also formed by the lower branch exciton polariton.

(3) Preparation of vortex light based on vortex wave plate

Vortex light is a light beam with a vortex-shaped light field distribution. The propagation of vortex light has cylindrical symmetry, and the optical field intensity is zero in the central region of the beam, which is called the beam singularity or phase singularity. During the propagation of vortex light, the light intensity at the singularity always remains zero. The wavefront of vortex light is spiral, and its wave vector has an azimuth term, and it rotates around the center of the vortex, and because of the existence of this rotation, the vortex light wave carries orbital angular momentum. The special properties of orbital angular momentum carried by vortex light make it not only have a wide range of applications in the field of physics, but also have broad application prospects in the biological and medical fields. Vortex wave plate is an optical element that can generate vortex beam. Vortex wave plate can be realized by using liquid crystal, liquid crystal polymer and advanced optical matching technology. Vortex beams generated by vortex wave plates have good application prospects in the fields of quantum optics, light field manipulation, super-resolution imaging, beam trapping, and laser processing.

The Jones matrix M of the vortex plate can be expressed as:

where R(θ) is the rotation matrix:

E₀表示光场强度，则出射光场为：When the incident light is left-handed circularly polarized light, the incident light field is

E ₀ represents the intensity of the light field, then the outgoing light field is:

则出射光场为：When the incident light is left-handed circularly polarized light, the incident light field is

Then the outgoing light field is:

Among them, exp(i2θ(x,y)) and exp(-i2θ(x,y)) are the helical phase factors. It can be seen that when the incident is left-handed circularly polarized light, it becomes right-handed circularly polarized after passing through the vortex wave plate. Vortex beam; when the incident is right-handed circularly polarized light, it becomes a left-handed circularly polarized vortex beam after passing through the vortex wave plate.

The main advantages of the present invention:

(1) The structure is simple, the position of each component is fixed, and the variable is only controlled by the laser control end to control the power and frequency of the femtosecond beam, which is easy to control.

(2) The device has a wide range of applications. According to the designed device, it can be seen that the wavelength of the femtosecond laser used in the experiment is adjustable, and the pump light of each wavelength can be used to excite the Bose-Einstein condensation, and it can be used to study the excitation threshold of the pump light of different wavelengths.

(3) The device is flexible in the preparation of vortex light, and different vortex wave plates can be replaced in the optical path to form vortex lights with different topological charge numbers, thereby realizing exciton polarization excitation generated by vortex light excitation of different topological charge numbers. Formation of meta-agglomerates and effects of vortex preparation.

Description of drawings

1 is a schematic diagram of a detection device;

Figure 2. The intensity map of the vortex light field;

Figure 3 is a schematic diagram of organic matter samples;

Fig. 4 Schematic diagram of exciton polariton lasing;

Figure 5 is a schematic diagram of a lasing spectrum;

specific implementation

The present invention uses the spontaneous emission interference pattern formed by the coupling of the vortex light and the exciton polariton in the semiconductor microcavity as the measurement carrier, and the specific implementation steps are as follows:

First, place the sample in the sample chamber, use the white light source (21) and the charge-coupled sensor camera (16) to observe the spatial position of the sample, and adjust the sample to the position shown in Figure 3 in conjunction with the image acquisition and processing terminal (17), so that After the sample has a good observation area within the field of view, turn off the white light source (21), turn on the femtosecond laser (1), and control the femtosecond laser (1) and the optical parametric amplifier (3) through the laser control terminal (2), The fundamental light emitted from the femtosecond laser is converted into a femtosecond beam of a specific power and frequency.

The generated femtosecond beam is reflected by the plane mirror (4) and then successively passes through the linear polarizer 1 (5), the quarter wave plate (6), the vortex wave plate (7) and the linear polarizer 2 (8) and then converted into a The femtosecond vortex beam as shown in Figure 2 enters the microscope objective lens (11) after passing through the beam splitter 1 (9) and the beam splitter 2 (12), and the beam converges and irradiates the sample in the sample chamber (10), Bose-Einstein condensates that generate organic semiconductor microcavities are excited and emit lasing light.

The laser light enters the collection optical path after passing through the microscope objective lens (11) and the beam splitter 2 (12), wherein the collimating lens 1 (13) and the collimating lens 2 (15) collimate the optical path, and the short-wave pass filter (14) The reflected stray wave is filtered out, and after passing through the beam splitter 3 (20), one beam of light passes through the notch filter (18) to filter out the pump light and is received by the CCD camera (16), and the other beam of light is received by the CCD camera (16). It is sensed and received by the spectrometer (19), and the generated lasing is observed through the image acquisition and processing terminal (17). The image obtained by the charge-coupled sensor camera is shown in Figure 4, and the generation of the lasing region can be clearly seen; the image obtained by the spectrometer is shown in Figure 5, and the appearance of lasing is observed near 490 nm, which further verifies the exciton pole. The generation of excimer condensation.

Contents not described in detail in the present invention belong to the prior art known to those skilled in the art.

Claims (2)

1. An organic semiconductor micro-cavity glass-Einstein condensation vortex generating device, comprising: the device comprises a femtosecond laser (1), a laser control end (2), an optical parametric amplifier (3), a plane reflector (4), a linear polarizer 1 (5), a quarter-wave plate (6), a vortex wave plate (7), a linear polarizer 2 (8), a beam splitter 1 (9), a sample bin (10), a microscope objective (11), a beam splitter 2 (12), a collimating lens 1 (13), a short-wave-pass filter (14), a collimating lens 2 (15), a charge coupled sensor camera (16), an image acquisition processing terminal (17), a trap plate (18), a spectrometer (19), a beam splitter 3 (20) and a white light source (21); the method comprises the steps that a femtosecond laser is utilized to generate a beam of femtosecond pulse laser, the generated femtosecond beam is reflected by a plane reflector (4) to be converted into a femtosecond vortex beam through a linear polarizer 1 (5), a quarter wave plate (6), a vortex wave plate (7) and a linear polarizer 2 (8), the femtosecond vortex beam enters a microscope objective (11) through a beam splitter 1 (9) and a beam splitter 2 (12), the beam is converged and then irradiated on a sample in a sample bin (10), and the vitrescence-einstein coagulation of an organic semiconductor microcavity is generated through excitation and emitted laser light is emitted; laser light enters a collection light path after passing through a microscope objective (11) and a beam splitter 2 (12), wherein the light path is collimated by a collimating lens 1 (13) and a collimating lens 2 (15), reflected stray waves are filtered by a short wave pass filter (14), after passing through a beam splitter 3 (20), one beam of light is received by a charge coupled sensor camera (16) after being filtered by pump light by a trap wave plate (18), the other beam of light is sensed and received by a spectrometer (19), and the generated laser is observed by an image collection processing terminal (17).

2. The organic semiconductor microcavity vitreous color-einstein condensed vortex generating device according to claim 1, wherein the device is characterized in that: the power and the frequency of the emergent femtosecond laser are changed by continuously changing the control coefficient of the laser control end, so that the femtosecond laser with different power and frequency is irradiated on the surface of a sample to generate stimulated radiation; the radiation light passes through the collection light path and passes through the beam splitter, one beam of the radiation light is collected by the charge coupled sensor camera, the other beam of the radiation light is collected by the spectrometer, the image collection processing terminal is used for carrying out real-time analysis processing on the collected signals, and whether the sample is stimulated to radiate or not and generate glass color-Einstein condensation is judged in real time by combining the spectrometer.

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