Momentum filtering system and method for measuring exciton-polariton interaction constant

Abstract

The present invention discloses a momentum filtering system, which includes a pulsed laser. The laser of the pulsed laser passes through a first semi-reflective semi-transmissive lens, a first silver-plated plane mirror, a second silver-plated plane mirror, a second semi-reflective semi-transmissive lens, and an ultraviolet microscope objective lens and then reaches a zinc oxide single crystal micro-rod; a light blocking plate is arranged between the second silver-plated plane mirror and the second semi-reflective semi-transmissive lens; the laser of the pulsed laser passes through the first semi-reflective semi-transmissive lens, the second semi-reflective semi-transmissive lens, and the ultraviolet microscope objective lens and then reaches the zinc oxide single crystal micro-rod; the signal on the zinc oxide single crystal micro-rod is transmitted to a data processing system through the ultraviolet microscope objective lens, the second semi-reflective semi-transmissive lens, the first semi-reflective semi-transmissive lens, a first quartz convex lens, a filter, a second quartz convex lens, an adjustable pinhole, a third quartz convex lens, and an ultraviolet area array spectrometer. The present invention also provides a method for measuring the exciton-polariton interaction constant. The present invention can accurately measure the concentration of exciton-polaritons and the exciton-polariton interaction constant.

Description

Technical Field

[0001] The present invention belongs to the technical field of spectral measurement, and particularly relates to a momentum filtering system and a method for measuring the exciton-polariton interaction constant. Background Art

[0002] As the product of strong light-matter coupling, exciton-polaritons have been a strong candidate for next-generation optoelectronic devices since their discovery due to their excellent optoelectronic properties. Most traditional optoelectronic devices are based on the conversion between light and electricity. Due to the diffraction and quantum effects of light in small-sized devices, it is relatively difficult to fabricate pure optical devices with small sizes.

[0003] The manipulation of light has always been an unremitting pursuit of scientists. The inventions from optical fibers to optical tweezers are all great achievements of human beings in light manipulation. Limited by the quantum tunneling effect of electrons, Moore's Law will surely fail. To meet the strong computing power demand, people turn their attention to photons, but the manipulation of photons in small sizes is more difficult. Against this background, exciton-polaritons, which are semi-light and semi-matter, have great potential because their particle nature determines their easy manipulability, and their semi-light characteristics also enable them to retain easy propagation and high speed.

[0004] The exciton-polariton interaction constant is a fundamental parameter of exciton-polaritons, which affects the stability of exciton-polariton devices. Currently, there are two main difficulties in measuring the exciton-polariton interaction constant. The first is the inability to accurately measure the concentration of exciton-polaritons; the second is that exciton-polaritons and excitons are generated simultaneously and in the same place, and it is very difficult experimentally to distinguish the interaction between exciton-polaritons from the interaction of excitons on exciton-polaritons. Therefore, it is impossible to accurately obtain the exciton-polariton interaction constant. Summary of the Invention

[0005] The main objective of the present invention is to provide a momentum filtering system and a method for measuring the exciton-polariton interaction constant. This system and method can not only accurately measure the concentration of exciton-polaritons but also exclude the interference of excitons on the measurement, thereby obtaining an accurate exciton-polariton interaction constant.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A momentum filtering system includes a pulsed laser, a first semi-transmissive semi-reflective mirror, a first silver-coated plane mirror, a second silver-coated plane mirror, a light baffle, a light baffle control module, a second semi-transmissive semi-reflective mirror, an ultraviolet microscope objective, a zinc oxide single crystal micro-rods, a two-dimensional precision moving stage, a first quartz convex lens, a filter, a second quartz convex lens, an adjustable pinhole, a pinhole control module, a third quartz convex lens, an ultraviolet area array spectrometer, and a data processing system;

[0008] The laser of the pulsed laser passes through the first half-silvered half-mirror and is reflected by the first silver-plated plane mirror, the second silver-plated plane mirror, and the second half-silvered half-mirror, and then is focused on the surface of the zinc oxide single crystal micro-rod through the ultraviolet microscope objective lens. This beam of light is named the control light; a light-blocking plate is provided between the second silver-plated plane mirror and the second half-silvered half-mirror, and the light-blocking plate is controlled by a light-blocking plate control module to realize the passing and blocking of the laser.

[0009] The laser of the pulsed laser passes through the first half-silvered half-mirror and the second half-silvered half-mirror, and after being focused by the ultraviolet microscope objective lens, directly irradiates the zinc oxide single crystal micro-rod. This beam of light is named the pump light; the zinc oxide single crystal micro-rod is placed on a three-dimensional precision moving stage.

[0010] The exciton polariton signal emitted by the zinc oxide single crystal micro-rod and the partially reflected laser pass through the ultraviolet microscope objective lens and the second half-silvered half-mirror, and after being reflected by the first half-silvered half-mirror, sequentially pass through the first quartz convex lens, the filter, the second quartz convex lens, the adjustable pinhole, and the third quartz convex lens, and then are transmitted to the data processing system through the ultraviolet area array spectrometer; the adjustable pinhole is controlled by a pinhole control module to adjust the position and size of the pinhole.

[0011] According to the above scheme, the lateral distance between the control light and the pump light at the focus of the ultraviolet microscope objective lens is 40 micrometers.

[0012] According to the above scheme, the zinc oxide single crystal micro-rod is placed at the focus position of the ultraviolet microscope objective lens.

[0013] According to the above scheme, the zinc oxide single crystal micro-rod is a zinc oxide single crystal micro-rod with a gradually changing radius and a regular hexagon cross-section; a large number of excitons will be formed after the zinc oxide single crystal micro-rod is excited by the pump light, and strong coupling will occur between the excitons and the whispering gallery mode formed by the regular hexagon cross-section to form exciton polaritons.

[0014] According to the above scheme, the pulsed laser is a 355-nanometer nanosecond pulsed laser; the ultraviolet microscope objective lens is an 80-fold ultraviolet microscope objective lens.

[0015] According to the above scheme, the filter is placed at the focus position of the first quartz convex lens, and the filter will filter out the laser; the signal of the exciton polariton passing through the filter will form a Fourier plane at its focus position after being focused by the second quartz convex lens.

[0016] According to the above scheme, the adjustable pinhole is placed at the focus position of the second quartz convex lens to filter out the exciton polariton signal at large angles, so that the adjustable pinhole only passes the exciton polariton signal with an angle of 0.

[0017] According to the above scheme, the ultraviolet area array spectrometer is placed at the focal position of the third quartz convex lens to collect the exciton polariton signals vertically emitted from different positions on the zinc oxide single crystal micro-rods, that is, the signals with a momentum of 0.

[0018] The working process is as follows:

[0019] (1) Turn on the pulsed laser to generate laser light. The laser light is split into two beams after passing through the first half-reflecting and half-transmitting lens. One of the laser beams will converge on the surface of the zinc oxide single crystal micro-rods through the reflections of the first half-reflecting and half-transmitting lens, the first silver-coated plane mirror, the second silver-coated plane mirror, and the second half-reflecting and half-transmitting lens, and this beam of light is named the control light; the light baffle controls the passing and blocking of the control light.

[0020] (2) The other beam of laser light passes through the first half-reflecting and half-transmitting lens and the second half-reflecting and half-transmitting lens, and after being converged by the ultraviolet microscope objective lens, it directly irradiates the zinc oxide single crystal micro-rods, and this beam of light is named the pump light. By precisely adjusting the three-dimensional precision moving stage, the zinc oxide single crystal micro-rods are precisely placed at the focal position of the ultraviolet microscope objective lens. Adjust the lateral spacing between the control light and the pump light at the focal point of the ultraviolet microscope objective lens to make this spacing 40 microns.

[0021] (3) First, use the light baffle control module to control the light baffle to block the control light from incident on the zinc oxide single crystal micro-rods. After being excited by the pump light, a large number of excitons will be formed in the zinc oxide single crystal micro-rods. The excitons and the whispering gallery mode formed by the regular hexagonal cross-section of the zinc oxide single crystal micro-rods undergo strong coupling to form exciton polaritons. The lifetime of the exciton polaritons is very short (generally about 10 picoseconds). After the lifetime of the exciton polaritons ends, photons carrying their own energy and momentum will be released.

[0022] (4) The exciton polariton optical signals emitted by the entire zinc oxide single crystal micro-rods and the partially reflected laser light will pass through the ultraviolet microscope objective lens and the second half-reflecting and half-transmitting lens, and after being reflected by the first half-reflecting and half-transmitting lens, a real image of the zinc oxide single crystal micro-rods will be formed at the focal position of the first quartz convex lens. The focal point of the first quartz convex lens is the position of the filter. The filter will filter out the laser light. After being focused by the second quartz convex lens, the signal of the exciton polaritons will form a Fourier plane at its focal position. An adjustable pinhole is placed at the focal position of the second quartz convex lens.

[0023] (5) Different positions on the Fourier plane represent the angles between the signal light of the exciton polaritons and the normal of the zinc oxide single crystal micro-rods. The more deviated from the optical axis, the larger the angle and the greater the momentum. The function of the adjustable pinhole placed on the Fourier plane is to filter out the exciton polariton signals at large angles. By precisely adjusting the position and size of the adjustable pinhole through the pinhole control module, the adjustable pinhole only passes the exciton polariton signals with an angle of 0 (near the optical axis).

[0024] (6) The Fourier transform surface forms a real image at its focal position after passing through the third quartz convex lens. The ultraviolet area array spectrometer is placed at the focal position of the third quartz convex lens. At this time, the signal collected by the ultraviolet area array spectrometer is the exciton-polariton signal vertically emitted from different positions on the zinc oxide single crystal micro-rods, that is, the signal with a momentum of 0. After being split by the ultraviolet area array spectrometer, the wavelengths (i.e., energies) of the exciton-polaritons with a momentum of 0 at different positions on the zinc oxide single crystal micro-rods can be obtained, denoted as signal A, and the data is transmitted to the data processing system.

[0025] (7) Under the condition that other conditions remain unchanged, the light shielding plate control module controls the light shielding plate to release the control light to pass through. At this time, the collected signal is denoted as signal B, and the data is transmitted to the data processing system. The data processing system subtracts the energies of the exciton-polaritons at the same position of signal B and signal A. This increased energy is caused by the exciton-polariton interaction generated by the control light, denoted as energy E.

[0026] The present invention also provides a method for measuring the exciton-polariton interaction constant. This method uses the above-mentioned momentum filtering system; the method includes the following steps:

[0027] 1) Block the control light through the light shielding plate, increase the pump laser power, so that the exciton-polaritons generated by the pump laser pumping undergo Bose-Einstein condensation, and record the light intensity I0 when Bose-Einstein condensation occurs;

[0028] 2) Calculate the concentration of exciton-polaritons when the exciton-polaritons just undergo Bose-Einstein condensation:

[0029]

[0030] In the formula, m is the concentration of exciton-polaritons, k B is the Boltzmann constant, T is the temperature, is the reduced Planck constant;

[0031] 3) According to the light intensity I0 when the exciton-polaritons just condense measured in step 1) and the concentration n0 of the exciton-polaritons obtained in step 2), obtain the relationship between the concentration and the light intensity of the exciton-polaritons k = n0 / I0;

[0032] 4) When only the pump light irradiates on the zinc oxide single crystal micro-rods, the light intensity I of the exciton-polaritons generated by the control light can be obtained through the above-mentioned momentum filtering system. The concentration n of the corresponding exciton-polaritons can be calculated by k obtained in step 3), n = k × I;

[0033] 5) When the pump light and the control light irradiate on the zinc oxide single crystal micro-rods at the same time, according to the above-mentioned momentum filtering system, the energy blue shift E caused by the exciton-polariton interaction can be obtained;

[0034] 6) Calculate the exciton-polariton interaction constant according to the mean-field approximation based on the exciton-polariton concentration n obtained in step 4) and the blue shift amount E obtained in step 5):

[0035]

[0036] The beneficial effects of the present invention are as follows:

[0037] According to the Bose-Einstein condensation characteristics of exciton-polaritons, the absolute concentration of exciton-polaritons can be accurately measured;

[0038] By setting up a light-blocking plate, a filter, an adjustable pinhole, and a UV area array spectrometer, the influence of other carriers such as excitons can be excluded, the measurement accuracy is improved, and the influence of dark noise is reduced;

[0039] Since the propagation distance of excitons is very short (about 2 microns), in order to exclude the interference of excitons on the measurement, the two beams of light are separated, that is: the lateral distance between the control light and the pump light at the focus of the UV microscope objective is 40 microns. Description of the Drawings

[0040] The present invention will be further described below in conjunction with the drawings and embodiments. In the drawings:

[0041] Figure 1 is a schematic structural diagram of the momentum filtering system;

[0042] In the figure: 1. 355-nanometer nanosecond pulsed laser, 2. First semi-reflective semi-transmissive lens, 3. First silver-plated plane mirror, 4. Second silver-plated plane mirror, 5. Light-blocking plate, 6. Light-blocking plate control module, 7. Second semi-reflective semi-transmissive lens, 8. 80x UV microscope objective, 9. Zinc oxide single-crystal micro-rods, 10. Precision moving stage, 11. First quartz convex lens, 12. Filter, 13. Second quartz convex lens, 14. Adjustable pinhole, 15. Pinhole control module, 16. Third quartz convex lens, 17. UV area array spectrometer, 18. Data processing system. Detailed Embodiments

[0043] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0044] Example 1

[0045] A momentum filtering system, which includes a 355-nanometer nanosecond pulsed laser 1, a first semi-reflective semi-transmissive lens 2, a first silver-plated plane mirror 3, a second silver-plated plane mirror 4, a light baffle 5, a light baffle control module 6, a second semi-reflective semi-transmissive lens 7, an ultraviolet microscope objective lens 8, a zinc oxide single crystal micro-rod 9, a precision moving stage 10, a first quartz convex lens 11, a filter 12, a second quartz convex lens 13, an adjustable pinhole 14 (adjustable aperture), a pinhole control module 15, a third quartz convex lens 16, an ultraviolet area array spectrometer 17, and a data processing system 18.

[0046] The laser of the 355-nanometer nanosecond pulsed laser 1 is reflected by the first semi-reflective semi-transmissive lens 2 and then passes through the first silver-plated plane mirror 3, the second silver-plated plane mirror 4, and the second semi-reflective semi-transmissive lens 7, and then is focused on the surface of the zinc oxide single crystal micro-rod 9 by the 80-fold ultraviolet microscope objective lens 8. This beam of light is named the control light; a light baffle 5 is provided between the second silver-plated plane mirror 4 and the second semi-reflective semi-transmissive lens 7, and the light baffle 5 is controlled by the light baffle control module 6 to achieve the passing and blocking of the laser.

[0047] The laser of the 355-nanometer nanosecond pulsed laser 1 passes through the first semi-reflective semi-transmissive lens 2 and the second semi-reflective semi-transmissive lens 7, and then is focused by the 80-fold ultraviolet microscope objective lens 8 and directly irradiates the zinc oxide single crystal micro-rod 9. This beam of light is named the pump light; the zinc oxide single crystal micro-rod 9 is placed on the precision moving stage 10.

[0048] The exciton-polariton signal emitted by the zinc oxide single crystal micro-rod 9 and the partially reflected laser pass through the 80-fold ultraviolet microscope objective lens 8 and the second semi-reflective semi-transmissive lens 7, and then after being reflected by the first semi-reflective semi-transmissive lens 2, they pass through the first quartz convex lens 11, the filter 12, the second quartz convex lens 13, the adjustable pinhole 14, and the third quartz convex lens 16 in sequence, and then are transmitted to the data processing system 18 through the ultraviolet area array spectrometer 17; the adjustable pinhole 14 is controlled by the pinhole control module 15 to adjust the position and size of the pinhole 14.

[0049] In this embodiment, the lateral spacing between the control light and the pump light at the focus of the 80x ultraviolet microscope objective 8 is 40 micrometers. The zinc oxide single-crystal micro-rods 9 are placed at the focal position of the 80x ultraviolet microscope objective 8. The zinc oxide single-crystal micro-rods 9 are zinc oxide single-crystal micro-rods with a gradually changing radius and a regular hexagonal cross-section; after being excited by the pump light, a large number of excitons will be formed in the zinc oxide single-crystal micro-rods 9, and strong coupling will occur between the excitons and the whispering gallery mode formed by the regular hexagonal cross-section to form exciton polaritons. The filter 12 is placed at the focal position of the first quartz convex lens 11, and the filter 12 will filter out the laser; the signal of the exciton polaritons passing through the filter 12 will form a Fourier plane at its focal position after being focused by the second quartz convex lens 13. The adjustable pinhole 14 is placed at the focal position of the second quartz convex lens 13 to filter out the exciton polariton signals at large angles, so that the adjustable pinhole 14 only passes the exciton polariton signals at an angle of 0. The ultraviolet area array spectrometer 17 is placed at the focal position of the third quartz convex lens 16 to collect the exciton polariton signals vertically emitted from different positions on the zinc oxide single-crystal micro-rods 9, that is, the signals with a momentum of 0.

[0050] The working process is as follows:

[0051] (1) Turn on the 355-nanometer nanosecond pulsed laser 1 to generate laser light. After passing through the first half-reflective and half-transmissive mirror 2, the laser light is divided into two beams. One of the laser beams will converge on the surface of the zinc oxide single-crystal micro-rods 9 through the reflections of the first half-reflective and half-transmissive mirror 2, the first silver-plated plane mirror 3, the second silver-plated plane mirror 4, and the second half-reflective and half-transmissive mirror 7 and then converge at the 80x ultraviolet microscope objective 8. This beam of light is named the control light; the light-blocking plate 5 controls the passing and blocking of the control light.

[0052] (2) The other beam of laser light passes through the first half-reflective and half-transmissive mirror 2 and the second half-reflective and half-transmissive mirror 7, and after being converged by the 80x ultraviolet microscope objective 8, it directly irradiates the zinc oxide single-crystal micro-rods 9. This beam of light is named the pump light. By precisely adjusting the three-dimensional precision moving stage 10, the zinc oxide single-crystal micro-rods 9 are precisely placed at the focal position of the 80x ultraviolet microscope objective 8. Adjust the lateral spacing between the control light and the pump light at the focal point of the 80x ultraviolet microscope objective 8 so that the spacing is 40 micrometers.

[0053] (3) First, use the light-blocking plate control module 6 to control the light-blocking plate 5 so that the light-blocking plate 5 blocks the control light from entering the zinc oxide single-crystal micro-rods 9. After being excited by the pump light, a large number of excitons will be formed in the zinc oxide single-crystal micro-rods 9, and strong coupling will occur between the excitons and the whispering gallery mode formed by the regular hexagonal cross-section of the zinc oxide single-crystal micro-rods 9 to form exciton polaritons. The lifetime of the exciton polaritons is very short (generally about 10 picoseconds). After the lifetime of the exciton polaritons ends, photons carrying their own energy and momentum will be released.

[0054] (4) The exciton-polariton optical signal emitted by the entire zinc oxide single-crystal micro-rod 9 and the partially reflected laser will pass through the 80x ultraviolet microscope objective 8 and the second half-reflecting and half-transmitting lens 7. After being reflected by the first half-reflecting and half-transmitting lens 2, a real image of the zinc oxide single-crystal micro-rod 9 is formed at the focal position of the first quartz convex lens 11. The focal point of the first quartz convex lens 11 is the position of the filter 12. The filter 12 will filter out the laser, and the signal of the exciton-polariton will form a Fourier plane at its focal position after being focused by the second quartz convex lens 13. The adjustable pinhole 14 is placed at the focal position of the second quartz convex lens 13.

[0055] (5) Different positions on the Fourier plane represent the angles between the signal light of the exciton-polariton and the normal of the zinc oxide single-crystal micro-rod 9. The greater the deviation from the optical axis, the larger the angle and the greater the momentum. The function of the adjustable pinhole 14 placed on the Fourier plane is to filter out the exciton-polariton signals at large angles. By precisely adjusting the position and size of the adjustable pinhole 14 through the pinhole control module 15, the adjustable pinhole 14 only passes the exciton-polariton signals with an angle of 0 (near the optical axis).

[0056] (6) After passing through the third quartz convex lens 16, a real image is formed at its focal position on the Fourier plane. The ultraviolet area array spectrometer 17 is placed at the focal position of the third quartz convex lens 16. At this time, the signal collected by the ultraviolet area array spectrometer 17 is the exciton-polariton signal vertically emitted from different positions on the zinc oxide single-crystal micro-rod 9, that is, the signal with zero momentum. After being split by the ultraviolet area array spectrometer 17, the wavelengths (i.e., energies) of the exciton-polaritons with zero momentum at different positions on the zinc oxide single-crystal micro-rod 9 can be obtained, denoted as signal A, and the data is transmitted to the data processing system 18.

[0057] (7) Under the condition that other conditions remain unchanged, the shutter control module 6 controls the shutter 5 to release the control light to pass through. At this time, the collected signal is denoted as signal B, and the data is transmitted to the data processing system. The data processing system subtracts the energies of the exciton-polaritons at the same positions of signal B and signal A. This increased energy is caused by the exciton-polariton interaction generated by the control light, denoted as energy E.

[0058] Embodiment 2

[0059] The present invention also provides a method for measuring the exciton-polariton interaction constant. This method uses the above-mentioned momentum filtering system; the method includes the following steps:

[0060] 1) Block the control light through the shutter, increase the pump laser power, so that the exciton-polaritons generated by the pump laser pumping undergo Bose-Einstein condensation, and record the light intensity I0 when Bose-Einstein condensation occurs;

[0061] 2) Calculate the concentration of exciton-polaritons when Bose-Einstein condensation of exciton-polaritons just occurs:

[0062]

[0063] In the formula, m is the concentration of exciton-polaritons, k B is the Boltzmann constant, T is the temperature, is the reduced Planck constant;

[0064] 3) According to the light intensity I0 of exciton-polaritons when condensation just occurs measured in step 1) and the concentration n0 of exciton-polaritons obtained in step 2), obtain the relationship between the concentration and light intensity of exciton-polaritons k = n0 / I0;

[0065] 4) When only the pump light irradiates on the zinc oxide single crystal micro-rods, the exciton-polariton light intensity I generated by the control light can be obtained through the momentum filtering system in Example 1, and the corresponding concentration of exciton-polaritons n = k×I can be calculated by k obtained in step 3);

[0066] 5) When the pump light and the control light irradiate on the zinc oxide single crystal micro-rods simultaneously, the energy blue shift E caused by the interaction of exciton-polaritons can be obtained according to the momentum filtering system in Example 1;

[0067] 6) From the exciton-polariton concentration n obtained in step 4) and the blue shift amount E obtained in step 5), according to the mean field approximation, calculate the exciton-polariton interaction constant:

[0068]

[0069] In the present invention, the functions of each device are as follows:

[0070] 355 nm nanosecond pulsed laser 1: Generate pulsed laser;

[0071] First half-reflective and half-transmissive lens 2: Divide the laser into two beams, the control light is reflected, and the pump light passes through;

[0072] First silver-plated plane mirror 3, second silver-plated plane mirror 4: Reflect the laser;

[0073] Light baffle 5: Control the passing and blocking of the laser;

[0074] Light baffle control module 6: Control the opening and closing of the light baffle;

[0075] Second half-reflective and half-transmissive lens 7: Reflect the control laser and at the same time transmit the pump laser;

[0076] 80-fold ultraviolet objective lens 8: Focus the laser and collect the optical signal;

[0077] The zinc oxide single crystal micro-rods 9 with a gradually changing radius and a regular hexagonal cross-section: generate exciton polaritons;

[0078] The three-dimensional precision moving stage 10: positions the zinc oxide single crystal micro-rods 9 and controls the zinc oxide single crystal micro-rods 9 at the focal position of the objective lens;

[0079] The first quartz convex lens 11: images the zinc oxide single crystal micro-rods 9 to its focal point;

[0080] The filter 12: filters out the laser;

[0081] The second quartz convex lens 13: forms a Fourier plane at the focal position;

[0082] The adjustable pinhole 14: filters out signals with large angles (large momenta);

[0083] The pinhole control module 15: controls the size and position of the adjustable pinhole 14;

[0084] The third quartz convex lens 16: magnifies the image of the zinc oxide single crystal micro-rods 9 and enters the ultraviolet area array spectrometer 17;

[0085] The ultraviolet area array spectrometer 17: resolves the signal by wavelength (energy);

[0086] The data processing system 18: processes the data measured by the spectrometer.

[0087] It should be understood that for those of ordinary skill in the art, improvements or transformations can be made according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A momentum filtering system, characterized in that: Including a pulsed laser, a first semi-reflective semi-transmissive lens, a first silver-plated plane mirror, a second silver-plated plane mirror, a light baffle, a light baffle control module, a second semi-reflective semi-transmissive lens, an ultraviolet microscope objective lens, zinc oxide single-crystal micro-rods, a three-dimensional precision moving stage, a first quartz convex lens, a filter, a second quartz convex lens, an adjustable pinhole, a pinhole control module, a third quartz convex lens, an ultraviolet area array spectrometer, and a data processing system; The laser of the pulsed laser is reflected by the first semi-reflective semi-transmissive lens and then reflected by the first silver-plated plane mirror, the second silver-plated plane mirror, and the second semi-reflective semi-transmissive lens, and then converged onto the surface of the zinc oxide single-crystal micro-rods by the ultraviolet microscope objective lens. This beam of light is named the control light; A light baffle is provided between the second silver-plated plane mirror and the second semi-reflective semi-transmissive lens, and the light baffle is controlled by the light baffle control module to achieve the passing and blocking of the laser; The laser of the pulsed laser passes through the first semi-reflective semi-transmissive lens and the second semi-reflective semi-transmissive lens, and then directly irradiates the zinc oxide single-crystal micro-rods after being converged by the ultraviolet microscope objective lens. This beam of light is named the pump light; The zinc oxide single-crystal micro-rods are placed on the three-dimensional precision moving stage; The exciton-polariton signals emitted by the zinc oxide single-crystal micro-rods and the partially reflected laser pass through the ultraviolet microscope objective lens and the second semi-reflective semi-transmissive lens, and after being reflected by the first semi-reflective semi-transmissive lens, they sequentially pass through the first quartz convex lens, the filter, the second quartz convex lens, the adjustable pinhole, and the third quartz convex lens, and then are transmitted to the data processing system through the ultraviolet area array spectrometer; The adjustable pinhole controls the position and size of the pinhole through the pinhole control module.

2. The momentum filtering system according to claim 1, characterized in that: The lateral spacing between the control light and the pump light at the focal point of the ultraviolet microscope objective lens is 40 micrometers.

3. The momentum filtering system according to claim 1, wherein: The zinc oxide single-crystal micro-rods are placed at the focal position of the ultraviolet microscope objective lens.

4. The momentum filtering system according to claim 1 or 3, characterized in that: The zinc oxide single-crystal micro-rods are zinc oxide single-crystal micro-rods with a gradually changing radius and a regular hexagon cross-section; A large number of excitons will be formed after the zinc oxide single-crystal micro-rods are excited by the pump light, and strong coupling will occur between the excitons and the whispering gallery mode formed by the regular hexagon cross-section to form exciton-polaritons.

5. The momentum filtering system according to claim 1, characterized in that: The pulsed laser is a 355-nanometer nanosecond pulsed laser; The ultraviolet microscope objective lens is an 80-fold ultraviolet microscope objective lens.

6. The momentum filtering system according to claim 1, wherein: The filter is placed at the focal point of the first quartz convex lens, and the filter will filter out the laser; The signal of the exciton-polaritons passing through the filter will form a Fourier plane at its focal position after being focused by the second quartz convex lens.

7. The momentum filtering system according to claim 1, wherein: The adjustable pinhole is placed at the focal point of the second quartz convex lens to filter out the exciton-polariton signals at large angles, so that the adjustable pinhole only passes the exciton-polariton signals at an angle of 0.

8. The momentum filtering system according to claim 1, wherein: The ultraviolet area array spectrometer is placed at the focal point of the third quartz convex lens to collect the exciton-polariton signals vertically emitted from different positions on the zinc oxide single-crystal micro-rods, that is, the signals with a momentum of 0.

9. A method for measuring the exciton-polariton interaction constant, characterized in that: The method uses the momentum filtering system described in any one of claims 1-8; The method includes the following steps: 1) Block the control light through a light baffle, increase the pump laser power, so that the exciton-polaritons generated by the pump laser pumping undergo Bose-Einstein condensation, and record the light intensity I0 when Bose-Einstein condensation occurs; 2) Calculate the exciton-polariton concentration when the exciton-polaritons just undergo Bose-Einstein condensation: where m is the concentration of exciton-polaritons, k B is the Boltzmann constant, T is the temperature, is the reduced Planck constant; 3) According to the light intensity I0 when the exciton-polaritons just condense measured in step 1) and the concentration n0 of the exciton-polaritons obtained in step 2), obtain the relationship between the concentration and the light intensity of the exciton-polaritons k = n0 / I0; 4) Only when the pump light irradiates on the zinc oxide single crystal micro-rods, obtain the exciton-polariton light intensity I generated by the control light through the momentum filtering system described in any one of claims 1-8, and calculate the corresponding exciton-polariton concentration n = k × I through k obtained in step 3); 5) When the pump light and the control light irradiate on the zinc oxide single crystal micro-rods at the same time, obtain the energy blue shift E caused by the interaction of the exciton-polaritons according to the momentum filtering system described in any one of claims 1-8; 6) From the exciton-polariton concentration n obtained in step 4) and the blue shift amount E obtained in step 5), calculate the exciton-polariton interaction constant according to the mean field approximation: In the formula, E is the energy blue shift caused by the exciton-polariton interaction.

Images