An experimental teaching demonstration device and method for demonstrating wave-particle duality of light

Abstract

This invention discloses an experimental teaching demonstration device for demonstrating the wave-particle duality of light, comprising a laser, a polarization beam splitter, a λ / 2 waveplate, an electro-optic modulator, a mirror and detector, a photon counter, and a pulse counter. The polarization beam splitter and λ / 2 waveplate split and combine horizontally and vertically polarized light, while the electro-optic modulator alters the relative phase of the horizontally and vertically polarized light, forming a phase-stable common-path interference system. Stable interference fringes under strong light are obtained using the detector, while photon counting is performed using the photon counter and pulse counter. Based on this demonstration device, this invention also discloses an experimental teaching demonstration method for demonstrating the wave-particle duality of light. On one hand, interference fringes and photon counts are obtained using the detector and counter respectively, verifying the wave and particle properties of light; on the other hand, the statistical distribution of photons under different cumulative counts is recorded, verifying that light simultaneously possesses wave and particle properties.

Description

Technical Field

[0001] This invention relates to the fields of quantum physics and optical measurement technology, and in particular to an experimental teaching demonstration device and method for demonstrating the wave-particle duality of light. Background Technology

[0002] As one of the fundamental theories underpinning modern physics, quantum mechanics primarily studies the existence and laws of motion of the microscopic world, and is indispensable in research on cutting-edge physics issues. However, the abstract nature of quantum mechanics, its complex mathematical derivations, and the difficulty in directly observing related experimental phenomena in real life have resulted in undergraduate teaching of quantum mechanics remaining largely at the theoretical lecture stage, lacking vivid and illustrative experimental verification to help students understand the relevant theories. Therefore, supplementing undergraduate teaching with quantum experimental techniques is extremely urgent.

[0003] Wave-particle duality is a crucial concept in quantum mechanics and plays a vital role in its teaching. Light possesses both particle and wave properties, which are inseparable characteristics of light. However, the wave-particle duality of light is difficult to observe simultaneously in a single phenomenon, making it challenging for most students. Therefore, designing wave-particle duality experiments suitable for undergraduate students is essential. Summary of the Invention

[0004] To achieve the above objectives, this invention provides an experimental teaching demonstration method and device for demonstrating the wave-particle duality of light, aiming to demonstrate the fundamental principles of quantum mechanics through experiments, so that undergraduate students can understand and master the basic principles and methods of quantum mechanics.

[0005] The experimental teaching demonstration device for demonstrating the wave-particle duality of light according to the present invention includes: a coherent light source, an attenuator, a first polarizing beam splitter, a first λ / 2 waveplate, a phase modulator, a Glan prism, a second λ / 2 waveplate, a second polarizing beam splitter, a detector, and a pulse counter arranged sequentially along the optical path; a photon counter is also arranged on the beam splitter of the second polarizing beam splitter. Among these,

[0006] The coherent light source is used to generate a monochromatic, frequency-stable coherent light field of arbitrary wavelength.

[0007] The attenuator is used to change the light intensity of the coherent light source and reduce the light intensity to the pW level.

[0008] The first polarization beam splitter is used to output horizontally linearly polarized light from the aforementioned coherent optical field.

[0009] The first λ / 2 waveplate is used to adjust the polarization direction of horizontally linearly polarized light. When the angle between the polarization direction and the fast axis of the waveplate is 45°, the horizontally linearly polarized light can be regarded as the linearly polarized light in the horizontal polarization direction and the linearly polarized light in the vertical polarization direction being superimposed in a 1:1 ratio, thereby achieving beam splitting of the linearly polarized light in the horizontal polarization direction and the linearly polarized light in the vertical polarization direction.

[0010] The phase modulator is used to change the relative phase of horizontally polarized light and vertically polarized light.

[0011] The second λ / 2 waveplate is used to adjust the polarization direction of the output light of the phase modulator. When the angle between the polarization direction and the fast axis of the waveplate is 45°, both the horizontally polarized light and the vertically polarized light output by the phase modulator are rotated by 45°. At this time, both the original horizontally polarized light and the original vertically polarized light can be projected in the horizontal and vertical polarization directions, and both the horizontal and vertical polarization directions are composed of two light signals with a phase difference.

[0012] The second polarization beam splitter is used to combine two optical signals with a phase difference in the horizontal and vertical polarization directions in the second λ / 2 waveplate, respectively.

[0013] The Glan prism is used to filter out horizontally polarized light or vertically polarized light.

[0014] The detector is used to convert optical signals into electrical signals and observe stable interference fringes under strong light.

[0015] The photon counter is used to convert weak light signals into electrical pulse signals;

[0016] The pulse counter is used to count voltage pulse signals and observe the distribution of photons.

[0017] The first polarization beam splitter, the first λ / 2 waveplate, the phase modulator, the second polarization beam splitter, and the second λ / 2 waveplate can constitute a common-path interference system, that is, the two interfering beams spatially coincide and the phase is stable, without the need for additional phase-locking control.

[0018] Based on the above apparatus, this invention also proposes an experimental teaching demonstration method for demonstrating the wave-particle duality of light. On one hand, interference fringes and photon counts are obtained using a detector and a counter, respectively, to verify the wave and particle properties of light. On the other hand, the statistical distribution of photons under different cumulative counts is recorded to verify that light simultaneously possesses both wave and particle properties. Specifically, the method includes the following steps:

[0019] Step 1: Construct a common-path interferometer using a first polarization beam splitter, a first λ / 2 waveplate, a phase modulator, a second λ / 2 waveplate, and a second polarization beam splitter.

[0020] Step 2: Using a light-blocking plate, block the light path in front of the first λ / 2 waveplate, and record the dark count generated by the photon counter within 2 seconds multiple times, calculating the average value. Due to environmental noise and electronic noise, the photon counter can still record pulse signals even without actual light signal input; these are called dark counts. This step is used to measure the dark count value per unit time. Subsequent data acquisitions should all be subtracted from the dark count generated within the corresponding time period.

[0021] Step 3: Apply voltage to the phase modulator to change the relative phase of the horizontally polarized light in the common-path interferometer, and record the changes in light intensity detected by the photodetector.

[0022] Step 4: Adjust the attenuator and use a pulse counter to record the photon counter's count. Obtain the voltage values ​​output by the photodetector at each point within two seconds, as well as the number of photons detected by the photon counter at each point (i.e., the number of pulses). Note that the dark count within the corresponding time period needs to be removed from the photon counter.

[0023] Step 5: Then change the duration of the statistics (starting from two seconds and decreasing sequentially), and repeat Step 3.

[0024] Step Six: Insert a Glan prism between the second λ / 2 waveplate and the phase modulator. Rotate the prism so that the voltage output of the photodetector is halved, filtering out horizontally or vertically polarized light. Obtain the voltage output of the photodetector at each point within two seconds, as well as the number of photons detected by the photon counter at each point (i.e., the number of pulses). Then, rotate the Glan prism 90° and repeat the above steps.

[0025] The experimental teaching demonstration device and method for demonstrating the wave-particle duality of light provided by this invention can, on the one hand, deepen students' understanding of basic quantum physics concepts such as wave-particle duality, and on the other hand, help students understand the development of cutting-edge science and technology, laying the foundation for the cultivation of innovative talents. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of an undergraduate experimental teaching demonstration device for demonstrating the wave-particle duality of light, as proposed in this invention.

[0028] Figure 2 This is a flowchart of an undergraduate experimental teaching demonstration method for demonstrating the wave-particle duality of light, as proposed in this invention.

[0029] Figure 1 In the diagram, 1-coherent light source, 2-attenuator; 3-first polarization beam splitter, 4-first λ / 2 waveplate, 5-phase modulator, 6-Glan prism, 7-second λ / 2 waveplate, 8-second polarization beam splitter, 9-detector, 10-photon counter, 11-pulse counter. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the specific embodiments and accompanying drawings. Except for the contents specifically mentioned below, the processes, conditions, and experimental methods for implementing the present invention are all common knowledge and general knowledge in the art, and the present invention does not have any particular limitations.

[0031] This embodiment provides an experimental teaching demonstration device for demonstrating the wave-particle duality of light. The device consists of a coherent light source, an attenuator, a first polarization beam splitter, a first λ / 2 waveplate, a phase modulator, a Glan prism, a second λ / 2 waveplate, a second polarization beam splitter, a detector, and a pulse counter arranged sequentially along the optical path. A photon counter is also provided on the beam splitter of the second polarization beam splitter.

[0032] The coherent light source 1 is used to generate a monochromatic frequency-stabilized coherent light field of arbitrary wavelength.

[0033] The attenuator 2 is used to change the light intensity of the coherent light source and reduce the light intensity to the pW level.

[0034] The first polarization beam splitter 3 is used to output horizontally linearly polarized light from the aforementioned coherent optical field;

[0035] The first λ / 2 waveplate 4 is used to adjust the polarization direction of horizontally linearly polarized light. When the angle between the polarization direction and the fast axis of the waveplate is 45°, the horizontally linearly polarized light output by the first polarization beam splitter 3 will rotate by 45°. At this time, the horizontally linearly polarized light can be regarded as the linearly polarized light in the horizontal polarization direction and the linearly polarized light in the vertical polarization direction being superimposed in a 1:1 ratio, thereby realizing the beam splitting of the linearly polarized light in the horizontal polarization direction and the linearly polarized light in the vertical polarization direction.

[0036] The phase modulator 5 is used to change the relative phase of horizontally polarized light and vertically polarized light.

[0037] The second λ / 2 waveplate 7 is used to adjust the polarization direction of the output light of the phase modulator. When the angle between the polarization direction and the fast axis of the waveplate is 45°, both the horizontally polarized light and the vertically polarized light output by the phase modulator 5 are rotated by 45°. At this time, both the original horizontally polarized light and the original vertically polarized light can be projected in the horizontal and vertical polarization directions, and both the horizontal and vertical polarization directions are composed of two light signals with a phase difference.

[0038] The second polarization beam splitter 8 is used to combine two optical signals with a phase difference in the horizontal polarization direction and the vertical polarization direction in the second λ / 2 waveplate 7, respectively.

[0039] The Glan prism 6 is used to filter out horizontally polarized light or vertically polarized light.

[0040] The detector 9 is used to convert optical signals into electrical signals and observe stable interference fringes under strong light.

[0041] The photon counter 10 is used to convert weak light signals into electrical pulse signals;

[0042] The pulse counter 11 is used to count voltage pulse signals and observe the distribution of photons.

[0043] The first polarization beam splitter 3, the first λ / 2 waveplate 4, the phase modulator 5, the second λ / 2 waveplate 7, and the second polarization beam splitter 8 can form a common-path interference system, that is, the two beams of light interfering with each other spatially coincide, the phase is stable, and no additional phase-locking control is required.

[0044] The second aspect of this invention provides an undergraduate experimental teaching demonstration method for demonstrating the wave-particle duality of light. Its characteristics include: firstly, obtaining interference fringes and photon counts using a detector and a counter respectively to verify the wave and particle properties of light; and secondly, recording the statistical distribution of photons at different accumulation times to verify that light simultaneously possesses both wave and particle properties. The specific steps are as follows:

[0045] Step 1: Construct a common-path interferometer using a first polarization beam splitter, a first λ / 2 waveplate, a phase modulator, a second λ / 2 waveplate, and a second polarization beam splitter.

[0046] Step 2: Using a light-blocking plate, block the light path in front of the first λ / 2 waveplate, and record the dark count generated by the photon counter within 2 seconds multiple times, calculating the average value. Due to environmental noise and electronic noise, the photon counter can still record pulse signals even without actual light signal input; these are called dark counts. This step is used to measure the dark count value per unit time. Subsequent data acquisitions should all be subtracted from the dark count generated within the corresponding time period.

[0047] Step 3: Apply voltage to the phase modulator to change the relative phase of the horizontally polarized light in the common-path interferometer, and record the changes in light intensity detected by the photodetector.

[0048] Step 4: Adjust the attenuator and use a pulse counter to record the photon counter's count. Obtain the voltage values ​​output by the photodetector at each point within two seconds, as well as the number of photons detected by the photon counter at each point (i.e., the number of pulses). Note that the dark count within the corresponding time period needs to be removed from the photon counter.

[0049] Step 5: Then change the duration of the statistics (starting from two seconds and decreasing sequentially), and repeat Step 3.

[0050] Step Six: Insert a Glan prism between the second λ / 2 waveplate and the phase modulator. Rotate the prism so that the voltage output of the photodetector is halved, filtering out horizontally or vertically polarized light. Obtain the voltage output of the photodetector at each point within two seconds, as well as the number of photons detected by the photon counter at each point (i.e., the number of pulses). Then, rotate the Glan prism 90° and repeat the above steps.

[0051] This invention demonstrates both the wave and particle properties of light through a common-path interference experiment, allowing students to perceive the microscopic world. The device is simple and easy to operate, which helps students deepen their understanding of quantum physics through experiments.

[0052] The specific embodiments of the present invention have been described in detail above, but they are merely examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of the present invention should be covered within the scope of the present invention.

[0053] The scope of protection of this invention is not limited to the above embodiments. Any variations and advantages that can be conceived by those skilled in the art without departing from the spirit and scope of the inventive concept are included in this invention and are protected by the appended claims.

Claims

1. An experimental teaching demonstration device for demonstrating the wave-particle duality of light, characterized in that, include: The optical path is sequentially arranged with a coherent light source, an attenuator, a first polarization beam splitter, a first λ / 2 waveplate, a phase modulator, a Glan prism, a second λ / 2 waveplate, a second polarization beam splitter, a detector, and a pulse counter; a photon counter is also disposed on the beam splitter of the second polarization beam splitter; wherein, The coherent light source is used to generate a monochromatic, frequency-stable coherent light field of arbitrary wavelength. The attenuator is used to change the light intensity of the coherent light source and reduce the light intensity to the pW level. The first polarization beam splitter is used to output horizontally linearly polarized light from the aforementioned coherent optical field. The first λ / 2 waveplate is used to adjust the polarization direction of the horizontally linearly polarized light. When the angle between the polarization direction and the fast axis of the waveplate is 45°, the horizontally linearly polarized light is regarded as the linearly polarized light in the horizontal polarization direction and the linearly polarized light in the vertical polarization direction are superimposed in a 1:1 ratio, thereby realizing the beam splitting of the linearly polarized light in the horizontal polarization direction and the linearly polarized light in the vertical polarization direction. The phase modulator is used to change the relative phase of horizontally polarized light and vertically polarized light. The second λ / 2 waveplate is used to adjust the polarization direction of the output light of the phase modulator. When the angle between the polarization direction and the fast axis of the waveplate is 45°, the horizontally polarized light and the vertically polarized light output by the phase modulator are both rotated by 45°. At this time, the original horizontally polarized light and the original vertically polarized light are projected in the horizontal polarization direction and the vertical polarization direction, and both the horizontal polarization direction and the vertical polarization direction are composed of two light signals with a phase difference. The second polarization beam splitter is used to combine two optical signals with a phase difference in the horizontal and vertical polarization directions in the second λ / 2 waveplate, respectively. The Glan prism is used to filter out horizontally polarized light or vertically polarized light. The detector is used to convert optical signals into electrical signals and observe stable interference fringes under strong light. The photon counter is used to convert weak light signals into electrical pulse signals; The pulse counter is used to count voltage pulse signals and observe the distribution of photons.

2. The experimental teaching demonstration device as described in claim 1, characterized in that, The first polarization beam splitter, the first λ / 2 waveplate, the phase modulator, the second polarization beam splitter, and the second λ / 2 waveplate constitute a common-path interference system, that is, the two beams of light that interfere with each other spatially coincide and are perpendicularly polarized.

3. The experimental teaching demonstration device as described in claim 2, characterized in that, In the common-path interference system, the two interfering beams spatially overlap and their phases are stable, requiring no additional phase-locking control.

4. An experimental teaching demonstration method for demonstrating the wave-particle duality of light, characterized in that, The method employs the experimental teaching demonstration device as described in any one of claims 1-3, and the method includes: Interference fringes and photon counts were obtained using detectors and counters, respectively, to verify the wave and particle properties of light. The statistical distribution of photons under different cumulative counts was recorded to verify that light has both wave and particle properties.

5. The experimental teaching demonstration method as described in claim 4, characterized in that, The method specifically includes the following steps: Step 1: Construct a common-path interferometer using the first polarization beam splitter, the first λ / 2 waveplate, the phase modulator, the second λ / 2 waveplate, and the second polarization beam splitter; Step 2: Using a light-blocking plate, the light path is blocked in front of the first λ / 2 waveplate. The dark count generated by the photon counter within 2 seconds is recorded multiple times and the average value is calculated. The dark count is the pulse signal recorded by the photon counter even when there is no actual light signal input due to environmental noise and electronic noise. Step 2 is used to measure the dark count value per unit time. Subsequent data acquisitions are all subtracted from the dark count generated in the corresponding time period. Step 3: Apply voltage to the phase modulator to change the relative phase of the horizontally polarized light in the common-path interferometer, and record the changes in light intensity detected by the photodetector; Step 4: Adjust the attenuator and use the pulse counter to record the count of the photon counter. Obtain the voltage value output by the photodetector at each point within two seconds and the number of photons detected by the single photon counter at each point. The number of photons is the number of pulses. The photon counter should exclude the dark count within the corresponding time period. Step 5: Change the duration of the statistics and repeat step 3; Step Six: Add a Glan prism between the second λ / 2 waveplate and the phase modulator. Rotate the Glan prism so that the voltage output of the photodetector is halved. Filter out horizontally polarized light or vertically polarized light. Obtain the voltage output of the photodetector at each point within two seconds and the number of photons detected by the photon counter at each point. The number of photons is the number of pulses. Then, rotate the Glan prism 90° and repeat the above steps.

6. The experimental teaching demonstration method as described in claim 5, characterized in that, In step five, the duration of the statistics is changed to decrease sequentially starting from two seconds.

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