Teaching experiment device and method for measuring second-order coherence of light field based on classical light source

Abstract

The invention belongs to the field of photoelectric measurement teaching experiment devices, and provides a classical light source-based light field second-order coherence measurement teaching experiment device and a classical light source-based light field second-order coherence measurement teaching experiment method, the classical light source-based light field second-order coherence measurement teaching experiment device comprises a light source module, the light source module outputs chaotic light source light spots, and the chaotic light source light spots are irradiated on a fixed light detector and a movable light detector after passing through a beam splitter; the movable optical detector is fixed on a three-dimensional displacement table, and the positions of the first optical detector and the second optical detector are calibrated by utilizing the three-dimensional displacement table, so that the two optical detectors can detect the light intensity of the same beam of light at the same moment after light splitting; the light source module comprises a light source, a convex lens, a plano-convex lens, ground glass and a light shielding plate which are arranged in sequence; wherein the plano-convex lens is fixed on the one-dimensional displacement table, and the one-dimensional displacement table moves back and forth along the light beam direction; and the center of the ground glass is fixed on a rotating shaft of the rotating speed-adjustable motor so as to rotate to generate dynamic speckles. According to the invention, the cost is reduced, and the education suitability is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of light field measurement teaching experiment devices in quantum optics and quantum information technology, and specifically relates to a light field second-order coherence measurement teaching experiment device and method based on a classical light source. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The Hanbury Brown-Twiss (HBT) experiment is a core experiment in quantum optics for studying the second-order coherence properties of light fields. First proposed by Hanbury Brown and Twiss in 1956, it verifies the quantum nature of light fields by measuring the correlation function of light intensity. This experiment is of great significance for understanding quantum optics theory and subsequent technologies (such as quantum electromagnetic field classification, ghost imaging, and single-pixel imaging). However, traditional HBT experimental equipment relies on high-precision optical components (such as single-photon sources and ultra-sensitive detectors), resulting in high equipment costs, complex maintenance, cumbersome operation procedures, and high technical barriers. Currently, there is a general lack of experimental equipment dedicated to second-order coherence property measurements in undergraduate courses in China, making it difficult for students to intuitively understand the relevant theories through practical experience, which seriously restricts the popularization and in-depth study of quantum optics.

[0004] The closest existing implementation options include open-source, low-cost HBT experimental designs (such as the project by Sebastian Ritter's team) and commercial high-precision experimental systems. While the former reduces costs, the operational procedures are not optimized for teaching scenarios; the latter, due to its high price, hinders widespread use in teaching. Specifically, existing HBT experimental equipment relies on highly sensitive detectors and complex optical paths, making it sensitive to environmental perturbations and unstable. The experimental procedures are complex and lack a simplified user interface for undergraduates, making it difficult for students to get started. Core components such as single-photon sources and precision translation stages are expensive, and the overall equipment cost far exceeds the teaching budget. Maintenance costs are high, and optical components are fragile and expensive to replace. Setting up the experimental system is time-consuming and difficult to debug, making it difficult to achieve teaching objectives within the limited class time. Summary of the Invention

[0005] In order to solve the above problems, the present invention proposes a teaching experimental device and method for measuring the second-order coherence of light fields based on a classical light source. By optimizing the optical path structure, the present invention greatly reduces the cost of the light source and detector modules, while improving the anti-interference ability of the equipment and extending the equipment maintenance cycle.

[0006] According to some embodiments, a first solution of the present invention provides a teaching experimental device for measuring the second-order coherence of a light field based on a classical light source, which adopts the following technical solutions: The teaching experimental device for measuring the second-order coherence of a light field based on a classical light source includes a light source module, which outputs a chaotic light source spot, which is then irradiated onto a fixed light detector and a mobile light detector after passing through a beam splitter; The mobile light detector is fixed on a three-dimensional translation stage. The positions of the fixed light detector and the mobile light detector are calibrated using the three-dimensional translation stage based on the positions of the light spots displayed on the fixed light detector and the mobile light detector and the relative positions of the two light detectors from the center of the beam splitter, so that the two light detectors can detect the light intensity changes at the same position and time of the same beam after splitting; The light source module includes a light source, a convex lens, a plano-convex lens, a frosted glass, and a light shielding plate, which are arranged in sequence. The plano-convex lens is fixed on a one-dimensional translation stage, which moves back and forth along the direction of the light beam. The center of the frosted glass is fixed on the shaft of an adjustable speed motor so as to rotate to generate dynamic speckle.

[0007] Furthermore, the fixed light detector and the mobile light detector transfer the collected light intensity signals to the data acquisition card via the coaxial cable to complete digital-to-analog conversion, obtain electrical signals and transmit them to the data processing and display module; The data processing and display module performs calculation processing on the electrical signal to obtain the experimental results.

[0008] Furthermore, it also includes a power supply module, which supplies power to the light source module, the fixed light detector, the mobile light detector and the data processing and display module of the teaching experiment device; The light source adopts a laser diode outputted by a single-mode optical fiber as the illumination light source.

[0009] Furthermore, the convex lens collimates the Gaussian beam emitted from the optical fiber of the light source into quasi-parallel light to obtain a collimated beam; The plano-convex lens converges the collimated light beam output by the convex lens onto the frosted glass.

[0010] Furthermore, an optical hole is provided in the middle of the light shielding plate, and the optical hole is aligned with the optical axis to limit the actual detection area.

[0011] Furthermore, the fixed light detector and the movable light detector both adopt photodiodes.

[0012] According to some embodiments, a second solution of the present invention provides a working method of a teaching experimental device for measuring second-order coherence of a light field based on a classical light source, which adopts the following technical solution: The working method of the teaching experimental device for measuring the second-order coherence of light fields based on classical light sources includes: Step 1: Power the device using the power supply module to ensure that all devices are operating normally. Adjust the positions of the convex lens, plano-convex lens, and light shield to achieve coaxiality until speckle generation is observed on the first and second light detectors. Step 2: By adjusting the one-dimensional translation stage to move the position of the plano-convex lens, the changes in the speckle distribution on the first and second light detectors are observed to determine the relationship between the speckle particle size and the position of the plano-convex lens, thus completing the speckle generation experiment; Step 3: Perform synchronous detection calibration by adjusting the positions of the one-dimensional translation stage and the three-dimensional translation stage to determine the readings of the three-dimensional translation stage in the calibration position in three directions; Step 4: Adjust the 3D translation stage laterally and record the second-order coherence value after each set distance until the second-order coherence value no longer changes. Plot a curve between the lateral displacement direction and the second-order coherence to complete the chaotic light spatial coherence experiment. Step 5: By adjusting the speed of the adjustable-speed motor and the position of the one-dimensional translation stage, the spatial coherence of the chaotic light is experimentally explored to determine the relationship between the actual spatial coherence length and the speed, as well as the relationship between the actual transverse coherence length and the speckle size. Step 6: Use the 3D translation stage to reset the mobile light detector to the calibration position. Adjust the 3D translation stage along the direction of the light beam and record the second-order coherence value at each set distance until the second-order coherence value stops changing. Plot a curve of time delay and second-order coherence to complete the chaotic light temporal coherence experiment. Step 7: By adjusting the speed of the adjustable-speed motor and the position of the one-dimensional translation stage, the temporal coherence of chaotic light is experimentally explored to determine the relationship between the actual temporal coherence length and the degree of chaos, as well as the relationship between the actual longitudinal coherence length and the speckle size. Step 8: Turn off the adjustable speed motor, remove the frosted glass, and repeat steps 2, 3, 4, and 6 above to observe the difference between the light and chaotic light, thus completing the coherent light space-time coherence experiment.

[0013] Furthermore, the step 3, synchronous detection calibration is specifically as follows: Adjust the one-dimensional translation stage to maximize the speckle particles on the fixed and mobile light detectors, and adjust the size of the light shield to limit the speckle area to the set size; Observe the detection position of the light spot on the fixed light detector, adjust the three-dimensional translation stage, roughly adjust the position of the mobile detector to the same position, start the adjustable speed motor, and adjust the control knob to the lowest speed; Use a three-dimensional translation stage to adjust the position of the mobile detector in three directions. While adjusting, observe the real-time coherence curve results on the data processing and display module until the maximum amplitude curve coherence value can be maintained on the axes of the three directions to obtain the calibration position. Based on the calibration position, the light detected by the two light detectors at this time is correlated light, that is, the light split by the beam splitter at the same time and space position; Record the calibration degrees of the precision translation stage in three directions at the calibration position for resetting in subsequent experiments.

[0014] Furthermore, the step 5 is specifically as follows: The mobile light detector was reset to the calibration position using a three-dimensional translation stage. The speed of the adjustable-speed motor was then increased sequentially at set speed intervals to change the degree of chaos in the light field. The synchronous detection calibration and chaotic light spatial coherence experiment were repeated. The coherence curves were observed at different speeds, and the conclusion was reached that the actual spatial coherence length is independent of the speed. The one-dimensional translation stage was adjusted sequentially at set distance intervals to gradually reduce the size of the speckle particles. The synchronous detection calibration and chaotic light spatial coherence experiment process was repeated, and the changes in the coherence curves of light sources with different speckle sizes were observed. The conclusion was drawn that the actual lateral coherence length is negatively correlated with the speckle size.

[0015] Furthermore, the step 7 is specifically as follows: The mobile light detector was reset to the calibration position using a three-dimensional translation stage. The speed of the adjustable speed motor was then increased sequentially according to the set speed intervals to change the degree of chaos in the light field. The synchronous detection calibration and chaotic light temporal coherence experiment were repeated. The changes in the coherence curve at different speeds were observed, and it was concluded that the actual temporal coherence length was positively correlated with the degree of chaos. The one-dimensional translation stage was adjusted sequentially at set distance intervals to reduce the size of speckle particles. The synchronous detection calibration and chaotic light temporal coherence experiment processes were repeated, and the changes in the coherence curves of light sources with different speckle sizes were observed. The conclusion was drawn that the actual longitudinal coherence length is independent of the speckle size.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention reduces equipment costs by simplifying the optical elements of the experimental device and optimizing the selection of optical elements. It also designs a modular optical path structure and interactive interface to reduce the difficulty of experimental operation, assist students in understanding the second-order coherence characteristics, and improve educational adaptability. It also reduces environmental sensitivity through structural optimization and extends the service life of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0018] Figure 1 1 is a diagram showing the overall architecture of a light field second-order coherence measurement teaching experimental device based on a classical light source according to an embodiment of the present invention; Figure 21 is a diagram of the optical path structure of a teaching experimental device for measuring the second-order coherence of a light field based on a classical light source in an embodiment of the present invention; Figure 3 is an interface diagram of a data processing and display module in an embodiment of the present invention; In the figure, 1-light source; 2-convex lens; 3-plano-convex lens; 4-ground glass; 5-one-dimensional translation stage; 6-adjustable speed motor; 7-light shield; 8-movable light detector; 9-fixed light detector; 10-beam splitter; 11-three-dimensional translation platform. DETAILED DESCRIPTION

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0021] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0022] In the absence of conflict, the embodiments of the present invention and the features thereof may be combined with each other.

[0023] Example 1 like Figure 1 As shown, this embodiment provides a teaching experimental device for measuring the second-order coherence of a light field based on a classical light source. Specifically, this embodiment includes: Light source module, the light source module outputs chaotic light source spot, which is irradiated on the fixed light detector 9 and the mobile light detector 8 after passing through the beam splitter 10; Figure 2 As shown, the light source module includes a light source 1, a convex lens 2, a plano-convex lens 3, a frosted glass 4 and a light shielding plate 7 arranged in sequence; wherein, the plano-convex lens 3 is fixed on a one-dimensional translation stage 5, and the one-dimensional translation stage 5 moves back and forth along the direction of the light beam; the center of the frosted glass 4 is fixed on the rotating shaft of an adjustable speed motor 6 to rotate to generate dynamic speckle; the laser generated by the laser first passes through the convex lens 2 to become parallel light and then passes through the plano-convex lens 3 to generate a large light spot. The laser is scattered by the rotating frosted glass 4 to realize a low-cost chaotic light source; the chaotic light source can use a traditional quantum light source instead of the rotating frosted glass, but the cost of this light source is extremely high and is not suitable for large-scale teaching.

[0024] The mobile light detector 8 is fixed on a three-dimensional translation stage 11. The positions of the fixed light detector and the mobile light detector are calibrated using the three-dimensional translation stage based on the positions of the light spots displayed on the fixed light detector and the mobile light detector and the relative positions of the two light detectors from the center of the beam splitter, so that the two light detectors can detect the light intensity changes at the same position and time of the same beam after splitting; The fixed and mobile photodetectors transfer the collected photocurrents via a coaxial cable to a data acquisition card for digital-to-analog conversion, obtaining digital electrical signals that are then transmitted to a data processing and display module. The photodetectors collect light intensity data and convert them into electrical signals that are then transmitted to the data processing and display module. The electrical signals are collected using the data acquisition card and input into a program as data, ultimately obtaining and plotting the experimental results. The program utilizes a normalized auto-coherence function, and the normalized mutual coherence function algorithm can replace quantum coherence operations, but requires adjustments to the data processing flow. The data processing and display module performs calculation processing on the electrical signal to obtain the experimental results.

[0025] The power supply module supplies power to the light source module, fixed light detector, mobile light detector and data processing and display module of the teaching experiment device, and converts the 220V standard voltage into the standard DC voltage required by each device.

[0026] Light source 1 uses a laser diode outputted by a single-mode optical fiber as the illumination light source, which has low cost, compact structure, omits the beam expansion device, and is conducive to integrated construction.

[0027] Convex lens 2 (f=100mm) collimates the Gaussian beam emitted from the optical fiber of the light source into quasi-parallel light, obtaining a collimated beam; The plano-convex lens 3 (f=50 mm) converges the collimated light beam output by the convex lens onto the frosted glass 4 to generate optical speckles through the phase modulation effect of the frosted glass; and the focal length of the convex lens 2 is greater than the focal length of the plano-convex lens 3.

[0028] It should be noted that the focal lengths of convex lens 2 and plano-convex lens 3 are shown here as two values, but they can be adjusted as needed in actual applications. It is only necessary to ensure that the focal length of convex lens 2 and the position of convex lens 2 relative to the light source correspond to refract parallel light, and the focal length of plano-convex lens 3 and the position of plano-convex lens 3 relative to the frosted glass to produce a large light spot.

[0029] An optical hole is provided in the middle of the light shielding plate 7 , and the optical hole is aligned with the optical axis to limit the actual detection area and facilitate alignment.

[0030] Both the fixed and mobile light detectors 9 and 8 utilize photodiodes. After passing through a beam splitter, the two beams of light strike the fixed and mobile light detectors, respectively, where they are collected and detected by the fiber-coupled photodiodes. The fiber core size limits the detection area. The photoelectric signals collected by the detectors are transferred via coaxial cables to a data acquisition card for digital-to-analog conversion, and the collected voltage is then acquired by a host computer.

[0031] The data processing and display module integrates a touch screen to display the experimental process, parameter settings and real-time data charts (such as autocorrelation curves), supporting one-button operation and data export. Figure 3 As shown, the raw data set is the voltage detection value of the two detectors; the processed data set is the detector voltage value after DC removal; the second-order coherence is obtained after processing; and the second-order coherence curve is obtained by real-time data update. PC-based software control can replace the embedded touch screen, but it reduces portability.

[0032] Example 2 This embodiment provides a method for a teaching experiment device for measuring second-order coherence of a light field based on a classical light source, including: Step 1: Power the device using the power supply module to ensure that all devices are operating normally. Adjust the positions of the convex lens, plano-convex lens, and light shield to achieve coaxiality until speckle generation is observed on the first and second light detectors. Specifically, pre-experiment equipment inspection: Turn on the power and ensure that all components, including the laser diode, photodetector, and low-speed motor, are functioning properly. Connect the detector's signal and ground ports to the data acquisition card. Open the host computer software and confirm that the data acquisition card is functioning properly. Set the data acquisition rate to the highest possible (no less than 300kHz). Adjust the position of the fiber port. You will see that the collected voltage fluctuates with position. Try blocking the light path. The voltage will return to its lowest value (this value depends on the detector noise level, generally around 0.1V). Adjust the position of convex lens 2, plano-convex lens 3, and the optical aperture so that all optical components are coaxial. At this point, speckle formation will be visible at the photodetector end. This step allows students to learn how to align and align optical components and ensure stable operation.

[0033] Step 2: By adjusting the one-dimensional translation stage to move the position of the plano-convex lens, observe the changes in the speckle distribution on the first and second light detectors, and determine the relationship between speckle particle size and the position of the plano-convex lens, thus completing the speckle generation experiment. This step allows students to summarize the relationship between speckle particle size and lens position. The relationship between speckle statistical characteristics and optical diffraction can be linked to provide targeted teaching on the speckle generation mechanism and optical filtering.

[0034] Step 3: Perform synchronous detection calibration by adjusting the positions of the one-dimensional translation stage and the three-dimensional translation stage to determine the readings of the three-dimensional translation stage in the calibration position in three directions; The step 3, synchronous detection calibration is specifically as follows: Adjust the one-dimensional translation stage to maximize the speckle particles on the fixed and mobile light detectors (generally at a distance of about 50 mm from the ground glass 4, i.e., the focal length of the convex lens 3). Adjust the size of the light shield to limit the speckle area to the set size. Observe the detection position of the light spot on the fixed light detector, adjust the three-dimensional translation stage, and roughly adjust the position of the mobile detector to the same position (the same position here means that the relative positions of the detection centers of the two detectors are the same with the spectral center of the spectroscope as the spatial origin). Start the adjustable speed motor and adjust the control knob to the lowest speed; Use a three-dimensional translation stage to adjust the position of the mobile detector in three directions, observing the real-time coherence curve results on the data processing and display module while adjusting, until the maximum amplitude curve coherence value is maintained on the axes of the three directions, and the calibration position is obtained. It is worth mentioning that within the detectable spatial range, the obtained curve should be an irregular fluctuation curve jumping between 1.5 and 1.00. If the relative position of light detectors 8 and 9 is too large, the result obtained will be a straight line with a very small amplitude fluctuation of 1. Based on the calibration position, the light detected by the two light detectors at this time is correlated light, that is, the light split by the beam splitter at the same time and space position; Record the calibration degrees of the precision translation stage in three directions at the calibration position for resetting in subsequent experiments; This step can accurately find the most suitable coherence position, that is, the light detected by the two detectors at this time is the same light split by the spectrometer at the same time. The degrees of the precision translation stage in the three directions at this time are recorded for resetting in subsequent experiments.

[0035] Step 4: Adjust the 3D translation stage laterally and record the second-order coherence value after each set distance (0.01 mm) until the second-order coherence value stops changing. Plot a curve between the lateral displacement direction and the second-order coherence to complete the chaotic light spatial coherence experiment. Step 5: By adjusting the speed of the adjustable-speed motor and the position of the one-dimensional translation stage, the spatial coherence of the chaotic light is experimentally explored to determine the relationship between the actual spatial coherence length and the speed, as well as the relationship between the actual transverse coherence length and the speckle size. The step 5 is specifically as follows: The mobile light detector was reset to the calibration position using a three-dimensional translation stage. The speed of the adjustable-speed motor was then increased sequentially at set speed intervals (in increments of 1 r / min) to change the degree of chaos in the light field. The synchronous detection calibration and chaotic light spatial coherence experiment were repeated, and the changes in the coherence curve at different speeds were observed. The conclusion was reached that the actual spatial coherence length is independent of the speed. The one-dimensional translation stage was adjusted sequentially at set distance intervals (0.1 mm) to gradually reduce the size of the speckle particles. The synchronous detection calibration and chaotic light spatial coherence experiment were repeated. The coherence curves of light sources with different speckle sizes were observed, and it was concluded that the actual lateral coherence length is negatively correlated with the speckle size. Step 6: Use the 3D translation stage to reset the moving light detector to the calibration position. Adjust the 3D translation stage along the direction of the light beam and record the second-order coherence value at every set interval (0.01 mm) until the second-order coherence value stops changing. Plot a curve of time delay and second-order coherence to complete the chaotic light temporal coherence experiment. The time delay here refers to the detection time delay caused by the movement of the light beam direction. Step 7: By adjusting the speed of the adjustable-speed motor and the position of the one-dimensional translation stage, the temporal coherence of chaotic light is experimentally explored to determine the relationship between the actual temporal coherence length and the degree of chaos, as well as the relationship between the actual longitudinal coherence length and the speckle size. The step 7 is specifically as follows: The mobile light detector was reset to the calibration position using a three-dimensional translation stage. The speed of the adjustable speed motor was then increased in steps of 1 r / min at set speed intervals to change the degree of chaos in the light field. The synchronous detection calibration (step 3) and chaotic light temporal coherence experiment (step 6) were repeated. The coherence curves at different speeds were observed, and it was concluded that the actual temporal coherence length was positively correlated with the degree of chaos. The one-dimensional translation stage was adjusted sequentially at set distance intervals (0.1 mm) to reduce the size of the speckle particles. The synchronous detection calibration and chaotic light temporal coherence experiment were repeated. The coherence curves of light sources with different speckle sizes were observed, and the conclusion was drawn that the actual longitudinal coherence length is independent of the speckle size. It is understood that the repetition of step 3 in steps 5, 6, and 7 refers to directly resetting the calibration position recorded in step 3. Before the positions of the beam splitter and the fixed light detector 9 are moved, the mobile light detector 8 in the calibration position can detect the light at the same position at the same time as the fixed light detector 9 (after splitting).

[0036] Step 8: Turn off the adjustable speed motor, remove the frosted glass, and repeat steps 2, 3, 4, and 6 above to observe the difference between the coherent light and the chaotic light, completing the spatial and temporal coherence experiment of coherent light. The spatial and temporal coherence of coherent light is much greater than that of chaotic light, and the spatial and temporal coherence curve is basically a straight line.

[0037] This embodiment can simultaneously perform speckle generation experiments, chaotic light field spatiotemporal coherence experiments, and coherent light field spatiotemporal coherence experiments. The use of low-cost fiber-coupled photodiode detectors significantly reduces costs. By reducing the rotational speed and data processing, the data obtained from the low-cost detectors can still produce valid experimental results. Furthermore, the high requirements of the single-photon light source for experimental and maintenance environments (such as no light or weak light sources) are reduced, and the experimental device can detect results in normal environments. This facilitates wide-scale promotion, storage, and use.

[0038] It is understandable that the specific numerical values ​​of the various intervals used in the above steps are only one option of the method of this embodiment, and the specific numerical values ​​are modified according to actual needs, experimental accuracy requirements and relevant parameters of the equipment.

[0039] In steps 4 to 8, during the experiment, the first photocurrent and the second photocurrent are obtained using the mobile photodetector and the fixed photodetector. Based on the first photocurrent and the second photocurrent and the first light intensity corresponding to the first photocurrent and the second light intensity corresponding to the second photocurrent, the second-order coherence of the chaotic light is determined. As shown in formula (6), the first photocurrent is proportional to the first light intensity corresponding to the first photocurrent, and the second photocurrent is proportional to the second light intensity corresponding to the second photocurrent.

[0040] Specifically, in this embodiment, the coherence curve is generated by using the auto-coherence algorithm, and the specific principle is as follows: The core principle formula is: (1); in, The light detector 、 The second-order coherence of light is measured at two points in space and time.

[0041] In this embodiment, the photocurrent is obtained by using a photodetector, so the following can be obtained: (2); (3); in, , is the first photocurrent, the second photocurrent, is the light intensity, i.e. 、 is the first light intensity and the second light intensity, so the photocurrent value can be used to replace the above formula In quantum experiments, single-photon technology is used. However, in classical simulations, there is background light and background noise, so the signal needs to be preprocessed. This embodiment proposes a second-order coherence calculation method based on simulation to remove the background light.

[0042] This embodiment first uses the value of the following formula to measure the second-order coherence of light: (4); It is worth noting that this embodiment uses a non-quantum light source for the experiment. Therefore, part of the light intensity obtained in this embodiment is the DC component of the non-quantum light source. The formula in the calculation process of this embodiment will be as follows: (5); in, ; ; is the actual chaotic light intensity, including the first actual chaotic light intensity and the second actual chaotic light intensity ; is the background light component (DC light), including the first background light component and the second background light component ,have ; In order to obtain better results, this embodiment only needs to perform DC removal processing on the obtained data, that is: (6); By using this formula, the present embodiment can remove the background light component and obtain the second-order coherence of the chaotic light; In actual operation, this embodiment uses the property that the intensity of chaotic light is always greater than 0 and uses the following formula to obtain the background light component, specifically: (7); in, A constant term set to prevent negative values.

[0043] In summary, the specific algorithm principle for using non-quantum light sources to perform second-order space-time coherence of light.

[0044] By controlling the frosted glass and thus the properties of coherent light, the change in coherence can be observed by adjusting the rotational speed (0 speed is coherent light, and the higher the speed, the worse the temporal coherence of chaotic light). A one-dimensional translation stage can be used to adjust the distance between the rotating motor and the lens to observe the change in coherence (speckle particle size).

[0045] The mobile light detector uses a longitudinal displacement device (three-dimensional displacement platform 11), so that the light field second-order coherence measurement teaching experiment device based on the classical light source can detect the second-order coherence of light at each point in space and the second-order temporal coherence under different delays.

[0046] This experimental setup provides a variety of operational options for changing the properties of chaotic light sources (changing the rotation speed and lens position) and multi-dimensional second-order coherence measurements (spatial and temporal). It also presents all raw data and data processing processes through an interactive interface, which is extremely advantageous for the target users (university quantum-related undergraduate students) to understand the second-order coherence properties of light.

[0047] Although the above describes the specific embodiments of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without any creative work are still within the scope of protection of the present invention.

Claims

1. The teaching experimental device for measuring the second-order coherence of light fields based on classical light sources is characterized by: It includes a light source module, which outputs a chaotic light source spot, which is irradiated on a fixed light detector and a mobile light detector after passing through a beam splitter; The mobile light detector is fixed on a three-dimensional translation stage. The positions of the fixed light detector and the mobile light detector are calibrated using the three-dimensional translation stage based on the positions of the light spots displayed on the fixed light detector and the mobile light detector and the relative positions of the two light detectors from the center of the beam splitter, so that the two light detectors can detect the light intensity changes at the same position and time of the same beam after splitting; The light source module includes a light source, a convex lens, a plano-convex lens, a frosted glass, and a light shielding plate, which are arranged in sequence. The plano-convex lens is fixed on a one-dimensional translation stage, which moves back and forth along the direction of the light beam. The center of the frosted glass is fixed on the shaft of an adjustable speed motor so as to rotate to generate dynamic speckle.

2. The light field second-order coherence measurement teaching experimental device based on a classical light source according to claim 1 is characterized in that: The fixed light detector and the mobile light detector transfer the collected light intensity signals to the data acquisition card through the coaxial cable to complete the digital-to-analog conversion, obtain the electrical signals and transmit them to the data processing and display module; The data processing and display module performs calculation processing on the electrical signal to obtain the experimental results.

3. The light field second-order coherence measurement teaching experimental device based on a classical light source according to claim 1 is characterized in that: It also includes a power supply module, which supplies power to the light source module, the fixed light detector, the mobile light detector, and the data processing and display module of the teaching experiment device; The light source adopts a laser diode outputted by a single-mode optical fiber as the illumination light source.

4. The light field second-order coherence measurement teaching experimental device based on a classical light source according to claim 1 is characterized in that: The convex lens collimates the Gaussian beam emitted from the optical fiber of the light source into quasi-parallel light to obtain a collimated beam; The plano-convex lens converges the collimated light beam output by the convex lens onto the frosted glass.

5. The light field second-order coherence measurement teaching experimental device based on a classical light source according to claim 1 is characterized in that: An optical hole is provided in the middle of the light shielding plate, and the optical hole is aligned with the optical axis to limit the actual detection area.

6. The light field second-order coherence measurement teaching experimental device based on a classical light source according to claim 1 is characterized in that: The fixed light detector and the movable light detector both adopt photodiodes.

7. The working method of the teaching experimental device for measuring the second-order coherence of light fields based on classical light sources is characterized by: include: Step 1: Power the device using the power supply module to ensure that all devices are operating normally. Adjust the positions of the convex lens, plano-convex lens, and light shield to achieve coaxiality until speckle generation is observed on the first and second light detectors. Step 2: By adjusting the one-dimensional translation stage to move the position of the plano-convex lens, the changes in the speckle distribution on the first and second light detectors are observed to determine the relationship between the speckle particle size and the position of the plano-convex lens, thus completing the speckle generation experiment; Step 3: Perform synchronous detection calibration by adjusting the positions of the one-dimensional translation stage and the three-dimensional translation stage to determine the readings of the three-dimensional translation stage in the calibration position in three directions; Step 4: Adjust the 3D translation stage laterally and record the second-order coherence value after each set distance until the second-order coherence value no longer changes. Plot a curve between the lateral displacement direction and the second-order coherence to complete the chaotic light spatial coherence experiment. Step 5: By adjusting the speed of the adjustable-speed motor and the position of the one-dimensional translation stage, the spatial coherence of the chaotic light is experimentally explored to determine the relationship between the actual spatial coherence length and the speed, as well as the relationship between the actual transverse coherence length and the speckle size. Step 6: Use the 3D translation stage to reset the mobile light detector to the calibration position. Adjust the 3D translation stage along the direction of the light beam and record the second-order coherence value at each set distance until the second-order coherence value stops changing. Plot a curve of time delay and second-order coherence to complete the chaotic light temporal coherence experiment. Step 7: By adjusting the speed of the adjustable-speed motor and the position of the one-dimensional translation stage, the temporal coherence of chaotic light is experimentally explored to determine the relationship between the actual temporal coherence length and the degree of chaos, as well as the relationship between the actual longitudinal coherence length and the speckle size. Step 8: Turn off the adjustable speed motor, remove the frosted glass, and repeat steps 2, 3, 4, and 6 above to observe the difference between the light and chaotic light, thus completing the coherent light space-time coherence experiment.

8. The operating method of the light field second-order coherence measurement teaching experimental device based on a classical light source according to claim 7 is characterized in that: The step 3, synchronous detection calibration is specifically as follows: Adjust the one-dimensional translation stage to maximize the speckle particles on the fixed and mobile light detectors, and adjust the size of the light shield to limit the speckle area to the set size; Observe the detection position of the light spot on the fixed light detector, adjust the three-dimensional translation stage, roughly adjust the position of the mobile detector to the same position, start the adjustable speed motor, and adjust the control knob to the lowest speed; Use a three-dimensional translation stage to adjust the position of the mobile detector in three directions. While adjusting, observe the real-time coherence curve results on the data processing and display module until the maximum amplitude curve coherence value can be maintained on the axes of the three directions to obtain the calibration position. Based on the calibration position, the light detected by the two light detectors at this time is correlated light, that is, the light split by the beam splitter at the same time and space position; Record the calibration degrees of the precision translation stage in three directions at the calibration position for resetting in subsequent experiments.

9. The operating method of the light field second-order coherence measurement teaching experimental device based on a classical light source according to claim 7 is characterized in that: The step 5 is specifically as follows: The mobile light detector was reset to the calibration position using a three-dimensional translation stage. The speed of the adjustable-speed motor was then increased sequentially at set speed intervals to change the degree of chaos in the light field. The synchronous detection calibration and chaotic light spatial coherence experiment were repeated. The coherence curves were observed at different speeds, and the conclusion was reached that the actual spatial coherence length is independent of the speed. The one-dimensional translation stage was adjusted sequentially at set distance intervals to gradually reduce the size of the speckle particles. The synchronous detection calibration and chaotic light spatial coherence experiment process was repeated, and the changes in the coherence curves of light sources with different speckle sizes were observed. It was concluded that the actual lateral coherence length is negatively correlated with the speckle size.

10. The operating method of the teaching experimental device for measuring the second-order coherence of a light field based on a classical light source according to claim 7, characterized in that: The step 7 is specifically as follows: The mobile light detector was reset to the calibration position using a three-dimensional translation stage. The speed of the adjustable speed motor was then increased in sequence according to the set speed intervals to change the degree of chaos in the light field. The synchronous detection calibration and chaotic light temporal coherence experiment were repeated. The coherence curve changes at different speeds were observed, and it was concluded that the actual temporal coherence length was positively correlated with the degree of chaos. The one-dimensional translation stage was adjusted sequentially at set distance intervals to reduce the size of speckle particles. The synchronous detection calibration and chaotic light temporal coherence experiment processes were repeated, and the changes in the coherence curves of light sources with different speckle sizes were observed. The conclusion was drawn that the actual longitudinal coherence length is independent of the speckle size.

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