Double-layer optical cipher device and method based on room temperature polariton condensation

Abstract

The invention discloses a double-layer optical cipher device and method based on room temperature polariton condensation. The device mainly comprises a pump light path, a room temperature exciton polariton condensation carrier and a signal acquisition terminal, the first part mainly comprises a femtosecond pulse laser, an optical parameter amplifier and a spatial light modulator, the second part mainly comprises an introduction light path and a sample bin, and the third part mainly comprises an image and spectrum analysis terminal. Firstly, a pump light path part generates femtosecond pulse pump light with specific wavelength, repetition frequency and light field intensity distribution; then, pumping light is introduced to a sample with a disc-shaped potential well structure, and an exciton polariton condensed state is generated; and finally, obtaining the intensity distribution and spectral distribution of the condensed light through an image and spectral analysis terminal. A group of specific corresponding relations can be formed by the intensity distribution and the spectrum distribution of the condensed state, and a double-layer password function is realized. The device is special in principle, can be simply realized by regulating and controlling a light field, and is a novel optical password form.

Description

Technical Field

[0001] The present invention mainly relates to the fields of halide perovskite materials, condensed matter physics, semiconductor microcavities, spectral space and signal processing, especially the formation of room temperature exciton-polariton Bose-Einstein condensate in semiconductor microcavities, the detection of stimulated radiation images, the regulation technology of light field intensity distribution and other methods. Technical Background

[0002] Exciton polaritons are quasiparticles generated by strong coupling of excitons and photons in semiconductor microcavities. It combines the properties of photons and particles to form a unique hybrid state of half light and half matter. This quasiparticle plays an important role in basic science and new optoelectronic and quantum technologies. In the exploration of fundamental physics, due to its low effective mass and the interaction between bosons, exciton polaritons are regarded as ideal objects for studying room temperature Bose-Einstein condensation (BEC) phenomena. Since Hopfield first proposed the concept of exciton polaritons in the 1950s, research on this quasiparticle in microcavities has made significant progress. In 1992, Weisbuch and his team successfully experimentally confirmed the existence of cavity excitons in a GaAs planar quantum well (QW) microcavity, and this discovery injected new vitality into this field. Summary of the invention

[0003] The technical problem solved by the present invention is: in view of the problem that traditional cryptographic devices are easy to crack, are fully digital and have low security factors, the present invention proposes a double-layer optical cryptographic device based on exciton polaritons. The present invention aims to design an optical path so that the sample produces Bose-Einstein condensation and emits light under femtosecond pulse laser pumping with a specific light field intensity distribution, and analyzes the code "carried" in the sample of the disk-type potential well structure through a spectrometer and a charge-coupled sensor.

[0004] The technical solution of the present invention is: the present invention relates to a double-layer optical cryptographic device based on exciton polaritons, such as Figure 1As shown, its main components include: femtosecond pulse laser (1), laser and spatial light modulator control computer (2), optical parametric amplifier (3), plane mirror 1 (4), plane mirror 2 (5), plane mirror 3 (6), beam splitter 1 (7), achromatic plano-convex lens 1 (8), sample chamber (9), microscope objective (10), beam splitter 2 (11), achromatic plano-convex lens 2 (12), square aperture (13), achromatic plano-convex lens 3 (14), charge coupled sensor (15), image acquisition and processing terminal (16), achromatic plano-convex lens 4 (17), spectrometer (18), Beam splitter 3 (19), white light source (20), spatial light modulator (21); first, use white light source (20) to generate illumination white light, the illumination light passes through beam splitter 1 (7), achromatic plano-convex lens 1 (8), beam splitter 2 (11) and microscope objective (10) and then irradiates the sample surface of sample chamber (9), and adjusts the sample in sample chamber (9) to the field of view of charge coupled sensor (15), then turns on femtosecond pulse laser (1) and optical parametric amplifier (3), and controls the laser to generate femtosecond pulse laser through laser and spatial light modulator control computer (2), and modulates the femtosecond pulse laser. After being modulated to a suitable wavelength, the light is irradiated onto the liquid crystal display screen of the spatial light modulator (21) via the plane reflector 1 (4) and the plane reflector 2 (5). At this time, the computer (2) is controlled by the laser and the spatial light modulator to load a series of different holograms onto the spatial light modulator (21). Through software control, the light intensity distribution of the diffraction spot after passing through the spatial light modulator (21) can be adjusted. The modulated femtosecond pulse laser passes through the reflector 3 (6), the beam splitter 1 (7), the achromatic plano-convex lens 1 (8), the beam splitter 2 (11) and the microscope objective (10) and then irradiates the sample surface of the sample chamber (9). The sample is excited to produce a specific pattern of fluorescence on the sample surface; the fluorescence pattern first passes through a 4f system composed of an achromatic plano-convex lens 2 (12) and an achromatic plano-convex lens 3 (14), and is separated into two beams by a beam splitter 3 (19) after the stray light is filtered out by a square aperture (13) between the two. One beam is focused by an achromatic plano-convex lens 4 (17) and then collected by a charge coupled sensor (15) for real-space luminescence pattern, and the other beam is sent to a spectrometer (18) for spectral distribution detection. An image acquisition and processing terminal (16) processes the real-space and spectral space signals collected by the charge coupled sensor (15) and the spectrometer (18). The laser and spatial light modulator control computer (2) controls the femtosecond pulse laser (1) and the optical parametric amplifier (3) to output a femtosecond pulse laser of a certain wavelength and repetition frequency, and adjusts the output energy so that the sample in the sample chamber reaches the pump threshold, thereby generating Bose-Einstein condensation at room temperature.

[0005] By controlling the hologram loaded on the spatial light modulator (21), the light field intensity distribution of the pump light at the sample surface in the sample chamber (9) is adjusted, and the adjusted pump light generates different modes of exciton polaritons condensation in the same disk-shaped sample, and these different condensation modes show one-to-one correspondence in real space and spectral space, and are repeatable. Based on this, a double-layer password device is designed, the first layer of the double-layer password device is a pattern layer, the real space distribution images of different exciton polaritons condensation modes are collected, and the pattern with specific characteristics of the petal distribution in the image is set as the first layer of password; the second layer is a spectral space layer, the spectral space fluorescence signals of different exciton polaritons condensation modes are collected, and the central wavelength of the strongest emission peak is set as the second layer of password, thereby forming a double-layer password device to realize the optical password function.

[0006] The principle of the present invention is:

[0007] (1) Generation of exciton-polaritons (BECs)

[0008] The concept of Bose-Einstein condensate (BEC) was first developed and proposed by Einstein based on Bose's previous work, pointing out that an infinite number of bosons can gather in the lowest energy state of the system. In a non-interacting boson system with a dimension greater than two, at a certain temperature, when the density of bosons reaches a critical density (ncrit), all states are filled, and the bosons that continue to be added to the system will all gather in the ground state of the system to form a BEC. Alternatively, at a certain particle density, when the temperature drops to a critical temperature (Tcrit), the number of states of the system decreases to saturation, and the excess particles form a BEC after further cooling. BEC is a macroscopic coherent state composed of microscopic particles of the same state, which can be regarded as a matter wave composed of a large number of particles. ncrit and Tcrit increase and decrease respectively with the increase of boson mass, that is, in a boson system with a smaller mass, it is easier to achieve BEC. In 1995, Cornell, Wieman and Ketterle first observed the BEC phenomenon experimentally by cooling dilute atomic vapor to a temperature of about 100nK, and won the 2001 Nobel Prize in Physics. Excitons have an effective mass much smaller than atoms, and theoretically BEC can be achieved at higher temperatures or even room temperature. However, excitons are dissipative systems. The excited bright excitons annihilate and radiate photons before they have time to cool to the temperature of the lattice, and thermal equilibrium cannot be reached. Dark excitons are difficult to detect because they do not emit light. Exciton BEC was eventually realized in an indirect exciton system. Microcavity exciton polaritons have an effective mass much smaller than excitons, so it is possible to achieve BEC at higher temperatures.

[0009] (2) Bose-Einstein condensation based on the lower-branch exciton-polaritons

[0010] Exciton polaritons are quasi-particles formed by the mutual coupling of exciton fields and photon fields. Since the exciton-photon coupling problem is quadratic, the Hamiltonian H of the diagonalized exciton polaritons can be analytically obtained as:

[0011]

[0012] in, is the reduced Planck 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 exciton and the photon can be expressed by the element Ω in the matrix R Description, called Rabi cleavage.

[0013] The eigenvalues ​​of this matrix are given by the following equation:

[0014]

[0015] Obviously, from the above formula, we can get the two dispersion relations of exciton polaritons, namely:

[0016]

[0017] In the above formula, ω UP (k) and ω LP (k) represent the upper and lower branch dispersion relations of exciton polaritons respectively. The Bose-Einstein condensation of exciton polaritons refers to the condensation of lower branch exciton polaritons, and the vortex superposition state of exciton polaritons is also formed by the lower branch exciton polaritons.

[0018] (3) Vortex light preparation based on spatial light modulator

[0019] A spatial light modulator (SLM) is an optical modulation device that can change the phase, amplitude, and polarization state of an incident light beam. The principle is to first use a computer to simulate a hologram of the target light beam, and then convert the grayscale of the hologram into a voltage signal and load it onto a liquid crystal display. The external voltage will change the orientation of the liquid crystal molecules, thereby controlling the birefringence of the liquid crystal to achieve phase modulation of the light wave. When the initial incident light enters the display, the outgoing light is the target light beam. The phase adjustment angle of each pixel on the surface of the spatial light modulator is proportional to the distance that the light beam passes through the liquid crystal layer, and the adjustment angle of each liquid crystal molecule in the liquid crystal layer is equal to the product of the voltage and distance of the pixel. Therefore, the total phase modulation of each pixel (x, y) can be expressed as:

[0020]

[0021] Where the phase modulation parameter Δφ x,y (V) = φ x,y (V)-φ x,y (0), depends on the position of the pixel and its corresponding control voltage; Is a constant representing the phase compensation of each pixel.

[0022] The following is an example of the working principle of SLM using Gaussian beam as an example:

[0023] If the waist radius of a Gaussian beam is ω 0 , when ω=ω 0 The amplitude expression of the Gaussian beam is:

[0024]

[0025] In the formula, r 0 ,θ 0 is the beam polar coordinate parameter. The amplitude expression of the holographic pattern loaded on the SLM liquid crystal screen can be expressed as:

[0026]

[0027] When the hologram obtained by the above formula is loaded onto the SLM surface, the grayscale value of each pixel in the image will be converted into the voltage of the corresponding pixel on the screen of the spatial light modulator, thereby realizing precise angle control of the liquid crystal molecules and achieving the goal of adjusting the phase of the light beam.

[0028] The main advantages of the present invention are:

[0029] (1) The structure of the device is simple. The positions of the components in the optical path are fixed, and the only variables are the power, frequency and light field intensity distribution of the femtosecond pulse laser at the laser and spatial light modulator control end, which are easy to control. By using a beam splitter, the radiation light is divided into two paths, which are collected by the charge coupled sensor camera and the spectrometer respectively and the data is transmitted to the image acquisition and processing terminal for analysis and processing, so that the device can detect the real space pattern and the spectral space signal at the same time, reducing the influence of the complexity of the optical path on the detection equipment.

[0030] (2) The device has a wide range of applications. Different passwords can be constructed by designing different sample potential well structures. At the same time, the intensity of the pump light field can be flexibly changed by the spatial light modulator. The diversity of the sample structure design and the light field intensity distribution determines the diversity of the password, which can be applied to various occasions requiring encryption.

[0031] (3) The device has high confidentiality and security. First, a sample with a special potential well structure is required. Figure 1Only by using the optical path shown and adjusting the special intensity distribution of the laser can the code "carried" by the sample be parsed, and a double-layer code combining pattern and number is designed based on real space and k-space, which further improves security. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic diagram of the detection device;

[0033] Figure 2 Schematic diagram of a disc-shaped perovskite sample under a microscope;

[0034] Figure 3 The lasing pattern of the first excitation mode;

[0035] Figure 4 Spectrum of the first excitation mode;

[0036] Figure 5 The lasing pattern of the second excitation mode;

[0037] Figure 6 Spectrum of the second excitation mode;

[0038] Figure 7 The lasing pattern of the third excitation mode;

[0039] Figure 8 Spectrum of the third excitation mode; Specific implementation plan

[0040] The present invention uses the spontaneous emission interference pattern formed by the coupling of pulsed laser and exciton polaritons in the semiconductor microcavity as the measurement carrier, and the specific implementation steps are as follows:

[0041] First, a white light source (20) is used to generate illuminating white light. The illuminating light passes through a beam splitter 1 (7), an achromatic plano-convex lens 1 (8), a beam splitter 2 (11) and a microscope objective (10) and then irradiates the sample surface of a sample chamber (9). The sample in the sample chamber (9) is adjusted to be within the field of view of a charge coupled sensor (15). Subsequently, a femtosecond pulse laser (1) and an optical parametric amplifier (3) are turned on. A laser and a spatial light modulator control computer (2) are used to control the laser to generate a femtosecond pulse laser. The femtosecond pulse laser is modulated to a suitable wavelength and then irradiated onto a liquid crystal display screen of a spatial light modulator (21) via a plane reflector 1 (4) and a plane reflector 2 (5). At this time, a series of different holograms are loaded onto the spatial light modulator (21) via a laser and a spatial light modulator control computer (2). After software control, the light intensity distribution of the diffraction spot after passing through the spatial light modulator (21) can be adjusted.

[0042] Subsequently, the modulated femtosecond pulse laser passes through a reflector 3 (6), a beam splitter 1 (7), an achromatic plano-convex lens 1 (8), a beam splitter 2 (11) and a microscope objective lens (10) and then irradiates the sample surface in the sample chamber (9), thereby stimulating the sample to generate a specific pattern of fluorescence on the sample surface. The fluorescence pattern first passes through a 4f system composed of an achromatic plano-convex lens 2 (12) and an achromatic plano-convex lens 3 (14), and is filtered out of stray light by a square aperture (13) between the two, and then is divided into two beams by a beam splitter 3 (19), one of which is focused by an achromatic plano-convex lens 4 (17) and then collected by a charge coupled sensor (15) for real-space luminous pattern, and the other is sent to a spectrometer (18) to detect spectral distribution, and an image acquisition and processing terminal (16) processes the real-space and spectral space signals collected by the charge coupled sensor (15) and the spectrometer (18). A computer (2) controls a femtosecond pulse laser (1) and an optical parametric amplifier (3) through a laser and a spatial light modulator to output a femtosecond pulse laser with a certain wavelength and repetition frequency, and adjusts the output energy so that the sample in the sample chamber reaches a pumping threshold, thereby generating Bose-Einstein condensation at room temperature.

[0043] By controlling the hologram loaded on the spatial light modulator (21), the light field intensity distribution of the pump light at the sample surface in the sample chamber (9) is adjusted, and the adjusted pump light will generate different modes of exciton-polaritons condensation in the same disk-shaped sample, and these different condensation modes show one-to-one correspondence in real space and spectral space and are repeatable.

[0044] First, the cryptographic features of this device are defined here: real-space distribution images of different exciton-polaritons condensation modes are collected, such as Figure 3 , 5 As shown in Figure 7, the password features are the angular petal number l and radial layer number p of the petal-shaped luminescence. The petal distribution in this image is set as the first layer of password; the spectral spatial fluorescence signals of different exciton-polariton condensation modes are collected, such as Figure 4 , 6 As shown in 8, the password feature is the spectral peak of petal-shaped luminescence. Note that the number of radial layers in the first layer of password corresponds to the number of spectral peaks in the second layer of password. The central wavelength λ of the emission peak is set as the second layer of password. For example, according to the setting, Figure 3 and Figure 4 The corresponding first password is l=2, p=1, λ=533.932nm, Figure 5 and Figure 6 The corresponding second password is l=14, p=2, λ1=533.499nm, λ2=539.132nm, Figure 7 and Figure 8The corresponding second set of passwords is l=14, p=4, λ1=532.609nm, λ2=533.579nm, λ3=538.066nm, λ4=538.031nm.

[0045] When implementing the double-layer password device, the password characteristic values, i.e., l, p, and λ parameters, are set in advance. When a set of data to be tested is input, the parameters l and p of the input data image layer are first verified to see if they are the same as the set values. If they are exactly the same, it is true and the next step is carried out; otherwise, it is false and the password input is wrong. If the first layer of password passes, check whether the number of emission peaks and the corresponding wavelengths are the same as the set values. If they are, the output is true and the password is correct; otherwise, the output is false and the password is wrong.

[0046] The contents not described in detail in this specification belong to the prior art known to the professionals in this field.

Claims

1. A double-layer optical cryptographic device and method based on room temperature polaritons condensation, comprising: Femtosecond pulse laser (1), laser and spatial light modulator control computer (2), optical parametric amplifier (3), plane mirror 1 (4), plane mirror 2 (5), plane mirror 3 (6), beam splitter 1 (7), achromatic plano-convex lens 1 (8), sample chamber (9), microscope objective (10), beam splitter 2 (11), achromatic plano-convex lens 2 (12), square aperture (13), achromatic plano-convex lens 3 (14), charge coupled sensor ( 15), an image acquisition and processing terminal (16), an achromatic plano-convex lens 4 (17), a spectrometer (18), a beam splitter 3 (19), a white light source (20), and a spatial light modulator (21); first, the white light source (20) is used to generate illuminating white light, and the illuminating light is irradiated to the sample surface of the sample chamber (9) after passing through the beam splitter 1 (7), the achromatic plano-convex lens 1 (8), the beam splitter 2 (11) and the microscope objective (10), and the sample in the sample chamber (9) is modulated. The laser beam is adjusted to the field of view of the charge coupled sensor (15), and then the femtosecond pulse laser (1) and the optical parametric amplifier (3) are turned on. The laser and the spatial light modulator control computer (2) are used to control the laser to generate a femtosecond pulse laser. The femtosecond pulse laser is modulated to a suitable wavelength and then irradiated onto the liquid crystal display screen of the spatial light modulator (21) via the plane reflector 1 (4) and the plane reflector 2 (5). At this time, the laser and the spatial light modulator control computer (2) load a series of different holograms onto the spatial light modulator (21), and the light intensity distribution of the diffraction spot after passing through the spatial light modulator (21) can be adjusted through software control. The modulated femtosecond pulse laser passes through the reflector 3 (6), the beam splitter 1 (7), the achromatic plano-convex lens 1 (8), the beam splitter 2 (11) and the microscope objective (10) and then irradiates onto the sample surface of the sample chamber (9), thereby stimulating the sample to produce a specific pattern of fluorescence on the sample surface. The fluorescence pattern first passes through a 4f system composed of an achromatic plano-convex lens 2 (12) and an achromatic plano-convex lens 3 (14), and is separated into two beams by a beam splitter 3 (19) after stray light is filtered out by a square aperture (13) between the two. One beam is focused by an achromatic plano-convex lens 4 (17) and then collected by a charge coupled sensor (15) for real-space luminescence pattern, and the other beam is sent to a spectrometer (18) for spectrum distribution detection. An image acquisition and processing terminal (16) processes the real-space and spectral space signals collected by the charge coupled sensor (15) and the spectrometer (18). A laser and spatial light modulator control computer (2) controls a femtosecond pulse laser (1) and an optical parametric amplifier (3) to output a femtosecond pulse laser of a certain wavelength and repetition frequency, and adjusts the output energy so that the sample in the sample chamber reaches the pump threshold, thereby generating Bose-Einstein condensation at room temperature.

2. The double-layer optical cryptographic device according to claim 1, characterized in that The pump light source is femtosecond pulse light, the energy corresponding to the selected wavelength is higher than the exciton energy of the sample in the sample chamber, and the spot diameter of the pump light is about 40μm.

3. The double-layer optical cryptographic device according to claim 1 or 2, characterized in that The sample in the sample chamber is CsPbBr3 material, and a disk-shaped area with a diameter of 6 μm is etched by positive photoresist.

4. A method for realizing a double-layer optical cryptographic device based on room temperature exciton-polariton condensation, characterized in that: By controlling the hologram loaded on the spatial light modulator (21), the light field intensity distribution of the pump light at the sample surface in the sample chamber (9) is adjusted, and the adjusted pump light will generate different modes of exciton polaritons condensation in the same disk-shaped sample, and these different condensation modes show one-to-one correspondence in real space and spectral space, and are repeatable. The first layer of the double-layer encryption device is a pattern layer, which collects real-space distribution images of different exciton polaritons condensation modes, and sets the pattern with specific characteristics of the petal distribution in the image as the first layer of encryption; the second layer is a spectral space layer, which collects spectral space fluorescence signals of different exciton polaritons condensation modes, and sets the central wavelength of the strongest emission peak as the second layer of encryption, thereby forming a double-layer encryption device to realize the optical encryption function.

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