Phase locking device and system based on unequal-arm interferometer
By setting a frequency regulator and phase locking unit in an unequal arm interferometer, adjusting the frequency of the initial beam and detecting the light intensity of the interference beam, the problem of phase locking at any phase in the prior art is solved, and phase locking at any position is achieved and measurement sensitivity is improved.
Patent Information
- Application Number
- CN202421724551.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-19
- Publication Date
- 2025-04-25
- Estimated Expiration
- 2034-07-19
AI Technical Summary
Existing unequal arm interferometers cannot perform phase locking at any phase, especially when sufficient phase locking is not possible near the extreme point of light intensity, affecting energy-time entanglement measurements in quantum optics.
By setting a frequency regulator before the initial beam is shot into the unequal arm interferometer, the frequency of the initial beam is adjusted to change the phase difference of the interference beam, and the phase locking unit is used to detect the light intensity of the interference beam, determine the phase lock point, and balance the phase difference through the phase regulator.
Phase locking at any position is achieved, which improves the adjustability and measurement sensitivity of the interferometer, ensuring stable phase locking can be achieved near extreme points.
Smart Images
Figure CN222799919U_ABST
Abstract
Description
Technical Field
[0001] The present application belongs to the field of optical measurement technology, and in particular, relates to a phase-locking device and system based on an unequal-arm interferometer. Background Art
[0002] The unequal-arm interferometer is a precision measuring instrument based on the principle of optical interference. Its core feature is that the lengths of the two interference arms are unequal, and the light signal is transmitted through two optical fiber arms of unequal lengths, which are called the reference arm and the measurement arm. When the light signal is transmitted in these two arms, due to the difference in path length, an optical path difference will be generated, and then interference will occur at the junction. By changing the optical path difference, the light field can be controlled to be manipulated based on interference, including beam splitting with a controllable splitting ratio and measuring the input photon in the superposition state basis vector.
[0003] However, the unequal-arm interferometer does not have sufficient stability. Environmental factors will randomly cause the relative phase of the two optical signals to drift. For example, temperature will affect the change of the refractive index of the optical fiber, and vibration will cause the change of the optical fiber length, thereby interfering with the interference result. Therefore, an active feedback system needs to be established to balance the disturbance.
[0004] The common active feedback system currently adds a phase adjuster to the interferometer and uses the light intensity at one of the exits as the reference phase-locking point to establish a feedback circuit. However, the phase at the extreme points of light intensity, i.e., the maximum and minimum light intensity, does not have enough slope change and cannot be phase-locked through the active feedback system. Therefore, achieving phase locking of any phase, especially at the extreme points, is crucial for energy-time entanglement measurement in quantum optics. Utility Model Content
[0005] The present application provides a phase-locking device and system based on an unequal-arm interferometer, aiming to solve the problem that the existing unequal-arm interferometer cannot perform phase locking at any phase.
[0006] In a first aspect, the present application provides a phase-locking device based on an unequal-arm interferometer, wherein the unequal-arm interferometer is used to perform unequal-arm interference on an initial light beam emitted by a light source to output an interference light beam with a phase difference; the device comprises:
[0007] A phase locking unit, used to detect the light intensity of the interference light beam to determine a phase locking point, and adjust the unequal-arm interferometer according to the change of the light intensity to balance the phase difference of the interference light beam according to the phase locking point;
[0008] The frequency adjustment unit is used to adjust the frequency of the initial light beam to change the phase difference of the interference light beam.
[0009] Furthermore, the frequency adjustment unit includes an acousto-optic modulator and an adjustable attenuator, the input end of the acousto-optic modulator is used to receive the initial light beam, and the adjustable attenuator is connected to the output end of the acousto-optic modulator.
[0010] Furthermore, the phase-locked unit includes a photodetector, a feedback circuit and a phase adjuster, the input end of the photodetector is used to receive the interference light beam, the feedback circuit is connected between the output end of the photodetector and the input end of the phase adjuster, and the output end of the phase adjuster is connected to the unequal-arm interferometer.
[0011] In a second aspect, the present application provides a measurement system based on an unequal-arm interferometer, the system comprising a light source, an unequal-arm interferometer, and a phase-locking device based on the unequal-arm interferometer as described above.
[0012] Compared with the prior art, the present application sets a frequency regulator before the initial light beam enters the unequal-arm interferometer. Without changing the intensity of the phase-locking light, the frequency regulator is used to change the frequency of the initial light beam to achieve the translation of the interference curve, so that the phase originally located near the extreme point can also be converted into a position that is easy to lock, thereby achieving phase locking at any position, thereby ensuring stability while improving the adjustability of the interferometer. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.
[0014] Figure 1 A structural block diagram of a phase-locking device based on an unequal-arm interferometer provided in an embodiment of the present application.
[0015] Figure 2 for Figure 1 A schematic diagram of an implementation of the illustrated embodiment;
[0016] Figure 3 for Figure 1 A schematic diagram of an experimental scenario of the illustrated embodiment;
[0017] Figure 4 for Figure 1 A schematic diagram showing the relationship between the intensity of the interference light beam and the phase difference in the illustrated embodiment. DETAILED DESCRIPTION
[0018] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0019] Directional terms mentioned in this application, such as "upper", "lower", "front", "back", "left", "right", etc., are only used to refer to the directions of the attached drawings. Therefore, the directional terms used are used to illustrate and understand this application, but not to limit this application. In addition, in the drawings, structures with similar or identical structures are represented by the same reference numerals.
[0020] The present application provides a phase-locking device based on an unequal-arm interferometer, which can be applied to time-path entanglement measurement in quantum optics. Figure 1 As shown, in the phase-locking device based on the unequal-arm interferometer shown in the embodiment of the present application, the unequal-arm interferometer is used to perform unequal-arm interference on the initial light beam emitted by the light source to output an interference light beam with a phase difference; the phase-locking device includes a phase-locking unit and a frequency adjustment unit, wherein the phase-locking unit is used to detect the light intensity of the interference light beam to determine the phase-locking point, and adjust the unequal-arm interferometer according to the change in light intensity to balance the phase difference of the interference light beam according to the phase-locking point; the frequency adjustment unit is used to adjust the frequency of the initial light beam to change the phase difference of the interference light beam.
[0021] It can be known that the unequal arm interferometer is a kind of instrument mainly composed of a light source, a beam splitter, arms of unequal lengths, and a receiver and other auxiliary equipment. Its working principle is based on the interference phenomenon of light. By comparing the light signals in the reference light path formed by the arms of unequal lengths and the light path of the object to be measured, information about the object to be measured is obtained. Specifically, during the measurement process, an initial light beam is emitted by a continuous light or pulsed light laser, and the initial light beam is divided into two light beams by a beam splitter. The two light beams enter the arms of the unequal arm interferometer and travel two different light paths. One of them is a reference light path as a reference, and its length is fixed. The other is a measuring light beam passing through the object to be measured, and its length is not equal to the reference light path, so it has different phases. The properties and shape of the object to be measured will affect the light signal in this light path. Finally, the light signals in the two light paths are received by the receiver, and the interference light beam formed after their interference is observed. By analyzing the intensity of the interference light beam, the interference result at the output end of the interferometer can be obtained.
[0022] Understandably, since the unequal-arm interferometer does not have sufficient stability, changes in the environment will randomly cause the relative phase of the two optical signals to drift. For example, temperature will affect the change in the refractive index of the optical fiber, and vibration will cause the change in the length of the optical fiber, thereby interfering with the interference result. Therefore, it is necessary to establish an active feedback system to balance the disturbance. The phase-locking unit is used to detect the light intensity of the interference light beam to determine the phase-locking point, and adjust the unequal-arm interferometer according to the change in light intensity to balance the phase difference of the interference light beam according to the phase-locking point; however, in the area near the extreme point of light intensity, since the light intensity does not have enough slope change relative to the phase, it is impossible to perform phase locking through the active feedback system. By setting a frequency adjustment unit before the initial light beam is emitted and enters the unequal-arm interferometer, the frequency of the initial light beam is adjusted to change the phase difference of the interference light beam. Without changing the magnitude of the phase-locking light intensity, the frequency of the initial light beam is changed by using a frequency regulator to achieve translation of the interference curve, so that the phase originally located near the extreme point can also be converted into a position that is easy to lock, thereby achieving phase locking at any position.
[0023] In an exemplary embodiment, the frequency adjustment unit includes an acousto-optic modulator and an adjustable attenuator, the input end of the acousto-optic modulator is used to receive the initial light beam, and the adjustable attenuator is connected to the output end of the acousto-optic modulator.
[0024] For the AOM, set the corresponding carrier frequency or operating frequency according to the laser frequency range to be adjusted. For the adjustable attenuator, set the attenuation to an appropriate initial value, which can be selected according to actual needs and the initial intensity of the laser signal. Adjust the carrier frequency or operating frequency of the laser to achieve the desired laser frequency through the control knob, switch or digital interface on the AOM. During the adjustment process, a spectrum analyzer or other test equipment can be used to monitor the frequency change of the laser to ensure the accuracy of the adjustment. Use the adjustable attenuator to adjust the attenuation of the laser signal as needed. Use the knob, switch or digital control on the adjustable attenuator, according to the specific model and operation method, and follow the instructions or markings. In the process of adjusting the attenuation, a signal analyzer or other test equipment can be used to monitor the intensity and quality of the laser signal, and the attenuation can be adjusted according to the monitoring results to achieve the desired laser power level.
[0025] In some embodiments, Figure 2 As shown, the phase-locked unit includes a photodetector, a feedback circuit and a phase adjuster. The input end of the photodetector is used to receive the interference light beam, the feedback circuit is connected between the output end of the photodetector and the input end of the phase adjuster, and the output end of the phase adjuster is connected to the unequal-arm interferometer.
[0026] The photodetector is used to detect the intensity of the interference beam. By converting the optical signal of the interference beam into an electrical signal, the feedback circuit performs PID analysis on the electrical signal generated by the photodetector, performs conversion and necessary amplification, obtains a high-voltage electrical signal, and sends it to the phase regulator. The phase regulator receives the high-voltage signal from the feedback circuit in real time, and physically adjusts the unequal-arm interferometer to change the phase of the second arm relative to the first arm in the optical path, balance the phase disturbance caused by the environment, and complete the real-time closed-loop optical phase locking.
[0027] When the phase to be locked needs to be changed, the frequency regulator is used to change the frequency of the phase-locked laser incident, which is equivalent to translating the interference curve; Figure 4 As shown in the figure, without changing the intensity of the phase-locked light, the frequency of the phase-locked laser is changed by the frequency regulator to achieve the translation of the interference curve from the solid line to the dotted line, and the phase originally located near the extreme point (the point where the normalized light intensity is 0 or 1) can also be converted into a position that is easy to lock. And because the slope of the phase-locked point has not changed, the PID parameters of the feedback circuit can be used at any phase after being adjusted once. Since the phase-locked point remains unchanged, the feedback circuit will drive the phase regulator to reach a new phase to reach the phase-locked point and maintain the phase balance of the interference beam.
[0028] In an experimental scenario, Figure 3 As shown, two light beams with different polarizations (detection beam H and phase-locked laser V) are used for phase locking and detection respectively. The light of the two light beams is transmitted independently in the interferometer and separated by the polarization beam splitter at the exit. The phase-locking point of the feedback circuit is set according to the intensity of the phase-locked laser, and the PID parameters are adjusted so that the feedback circuit can keep the light intensity at the photodetector 2 unchanged. At this time, in the unequal-arm interferometer, the phase difference between the two arms is fixed. If the phase-locking device functions normally, when the phase-locking point remains unchanged, as the frequency shift amount of the frequency regulator increases, the feedback circuit controls the phase regulator to gradually change the phase in the interferometer, and the phase difference felt by the detection laser will gradually change, so that the light intensity value at the photodetector 1 gradually changes. In the experiment, the arm length difference of the unequal-arm interferometer is about 15m, the free spectrum range is about 13MHz, and the adjustment range of the frequency regulator is 72MHz to 94MHz, which can completely cover one cycle.
[0029] The present application also provides a phase locking method based on an unequal-arm interferometer, the method comprising:
[0030] Step 1: Perform unequal-arm interference on the initial light beam through an unequal-arm interferometer to output an interference light beam with a phase difference;
[0031] Step 2: detecting the light intensity of the interference light beam to determine the phase-locking point, and adjusting the unequal-arm interferometer according to the change of the light intensity to balance the phase difference of the interference light beam according to the phase-locking point;
[0032] Step three: adjusting the frequency of the initial light beam to change the phase difference of the interference light beam.
[0033] In one embodiment, an initial light beam is subjected to unequal-arm interference by an unequal-arm interferometer to output an interference light beam with a phase difference; the light intensity of the interference light beam is detected by a phase-locking unit to determine a phase-locking point, and the unequal-arm interferometer is adjusted according to the change in light intensity to balance the phase difference of the interference light beam according to the phase-locking point; the frequency of the initial light beam is adjusted by setting a frequency regulator to change the phase difference of the interference light beam.
[0034] The present application also provides a measurement system based on an unequal-arm interferometer, the system comprising a light source, an unequal-arm interferometer, and a phase-locking device based on the unequal-arm interferometer as described above.
[0035] Compared with the related art, the present application sets a frequency regulator before the initial light beam enters the unequal-arm interferometer. Without changing the intensity of the phase-locking light, the frequency regulator is used to change the frequency of the initial light beam to achieve translation of the interference curve, so that the phase originally located near the extreme point can also be converted into a position that is easy to lock. Phase locking at any position is thus achieved, thereby further improving the sensitivity of the measurement system. And because the slope of the phase-locking point has not changed, the PID parameters of the feedback circuit can be adjusted once and can be used at any phase.
[0036] It is to be understood that the present application is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present application. In addition, under the guidance of the present application, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present application. Therefore, the present application is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present application are within the scope protected by the present application.
Claims
1. A phase-locking device based on an unequal-arm interferometer, characterized in that: The unequal-arm interferometer is used to perform unequal-arm interference on an initial light beam emitted by a light source to output an interference light beam with a phase difference; the device comprises: A phase locking unit, used to detect the light intensity of the interference light beam to determine a phase locking point, and adjust the unequal-arm interferometer according to the change of the light intensity to balance the phase difference of the interference light beam according to the phase locking point; The frequency adjustment unit is used to adjust the frequency of the initial light beam to change the phase difference of the interference light beam.
2. The device according to claim 1, characterized in that The frequency adjustment unit includes an acousto-optic modulator and an adjustable attenuator. The input end of the acousto-optic modulator is used to receive the initial light beam, and the adjustable attenuator is connected to the output end of the acousto-optic modulator.
3. The device according to claim 1 or 2, characterized in that: The phase-locked unit includes a photodetector, a feedback circuit and a phase adjuster. The input end of the photodetector is used to receive the interference light beam. The feedback circuit is connected between the output end of the photodetector and the input end of the phase adjuster. The output end of the phase adjuster is connected to the unequal-arm interferometer.
4. A measurement system based on unequal-arm interferometer, characterized in that: The system comprises a light source, an unequal-arm interferometer and a phase-locking device based on the unequal-arm interferometer according to any one of claims 1 to 3.