A balanced timing detection device and method using a single photodetector

Abstract

This invention discloses a balanced timing detection device and method using a single photodetector. The method is as follows: a radio frequency offset frequency is introduced into the optical signal to be modulated, generating two independent optical signals with different frequency offsets; a timing error is introduced into the unmodulated optical signal and delayed, the processed optical signal consisting of two pulses with time delay in the time domain; the two modulated signals with different frequency offsets and the unmodulated signal with introduced error are transmitted to the same coupler for coupling; the output optical signal after coupling is converted into an electrical signal and divided into two identical electrical signals, each containing a radio frequency offset signal; the envelope signal of each radio frequency offset frequency signal is extracted and differentially calculated; the voltage value of the differential signal under different delays is recorded in real time to obtain the relationship curve between the timing information introduced by the timing device to be measured and the final output voltage of the detection device of this invention, thereby completing the timing calibration process.

Description

Technical Field

[0001] This invention relates to the field of ultrafast optics technology, and in particular to a high-precision timing device and method utilizing a single photodetector. Background Technology

[0002] High-precision timing detection technology plays a crucial role in various cutting-edge research fields, such as large-scale timing distribution systems, remote laser / microwave synchronization, and pump-probe experiments. Over the past 20 years, researchers have proposed timing detection methods based on balanced cross-correlation (BOC), optical heterodyne, optical delay lines, and acousto-optic modulators (AOM) to achieve ultra-high precision timing detection. Among these, the BOC timing detection method typically employs a balanced architecture with two photodetectors to eliminate laser amplitude noise and background ambient noise. However, since the electronic noise generated by the two independent photodetection processes is not strictly consistent, this electronic noise cannot be canceled out by the balanced architecture, which limits the resolution of the timing detector at high frequencies (greater than 10 kHz). Furthermore, BOC technology is based on the second sum-frequency effect of optics, and it usually cannot provide sufficient timing resolution when the average input optical power is less than 1 mW. Optical heterodyne timing detection schemes may work in low-power scenarios, but the implementation of this scheme requires complex optical filtering devices, which are costly. Therefore, in recent years, the optimization and design of timing detectors have gone far beyond accuracy as a single indicator, and have placed higher demands on the power consumption, layout and practical feasibility required for timing detection. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a device and method for achieving balanced timing detection using a single photodetector. This scheme combines the AOM timing detection method with a balanced architecture, and can achieve attosecond precision balanced detection in low-power scenarios using only one photodetector. By comparing the measurement results with those of a single-channel AOM timing detector, the invention proposed in this invention can greatly suppress the electronic noise generated during the photoelectric detection process.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A balanced timing detection device utilizing a single photodetector includes a laser source and beam splitting unit, an optical modulation unit, an optical coupling unit, a photodetector, and a differential operation unit arranged sequentially. The laser source and beam splitting unit includes a laser source and a beam splitting device; the optical modulation unit includes an optical isolator, an optical modulation device, and a beam splitting device arranged sequentially; the optical coupling unit includes a first coupling preprocessing device, a second coupling preprocessing device, and a multi-port coupler; the photodetector includes a photoelectric conversion unit, a filtering unit, and a detection unit; the photoelectric conversion unit includes a photodetector and a power divider; the filtering unit includes a first bandpass filter and a second bandpass filter; and the detection unit includes a first detection device and a second detection device.

[0006] The laser source and beam splitter output zero-order light and light to be modulated. The zero-order light will not be modulated, while the light to be modulated will be modulated subsequently by a modulator. The light to be modulated passes through an optical isolator and then enters an optical modulator. The carrier frequency of the first-order diffracted light output by the optical modulator obtains the frequency shift of the radio frequency signal. After passing through the beam splitter, the first-order diffracted light is split into reflected first-order diffracted light and transmitted first-order diffracted light. The transmitted first-order diffracted light is sequentially transmitted to the first coupling preprocessing device and the multi-port coupler. The reflected first-order diffracted light returns to the optical modulator. The carrier frequency of the second-order diffracted light output by the optical modulator again obtains the frequency shift of the radio frequency signal. The second-order diffracted light passes through an optical isolator and then enters the multi-port coupler.

[0007] The zero-order light is transmitted to the delay introduction device after passing through the timing device to be measured. The zero-order light output by the delay introduction device contains two pulses with time delay in the time domain, and is transmitted sequentially to the second coupling preprocessing device and the multi-port coupler.

[0008] The optical signal output from the multi-port coupler is converted into an electrical signal by a photodetector and then split into two equal-power electrical signals by a power divider. One electrical signal passes sequentially through a first bandpass filter and a first detector, while the other electrical signal passes sequentially through a second bandpass filter and a second detector. Finally, the two electrical signals enter the two input ports of the differential operation unit, which outputs the detection result. After passing through the first and second bandpass filters, only the radio frequency offset signal with the radio frequency offset frequency component remains. The first and second detectors are used to detect the envelope of the radio frequency offset signal. A data acquisition device is connected to the output of the differential operation unit and uses it to acquire the voltage signal output by the differential operation unit in real time. This voltage signal contains all the timing information to be measured.

[0009] Furthermore, the delay introduction device consists of a polarizing beam splitter prism, a quarter-wave plate, a plane mirror, and a free-space polarizer. Zero-order light enters from face one of the polarizing beam splitter prisms and exits as two beams of zero-order light from face two and face three. After face two and face three of the polarizing beam splitter prisms, quarter-wave plates and plane mirrors are arranged sequentially. After each of the two beams of zero-order light passes through the plane mirror and quarter-wave plate twice, they are combined into one beam in the polarizing beam splitter prism and emitted from face four. The free-space polarizer is located after face four and before the second coupling preprocessing device.

[0010] Furthermore, the two zero-order beams have an optical path difference when they pass through two quarter-wave plates and a plane mirror arranged in sequence, thus introducing a time-domain delay difference into the two orthogonally polarized zero-order beams.

[0011] Furthermore, the free-space polarizer is used to adjust two orthogonally polarized zero-order lights to the same polarization direction, and to transmit the zero-order light to the multi-port coupler along the set polarization direction.

[0012] Furthermore, the timing device to be measured is one of the following: a delay line, a medium with birefringence, a piezoelectric device, a translation stage, or a light-transmitting medium that is disturbed by physical effects.

[0013] Furthermore, both the first coupling preprocessing device and the second coupling preprocessing device are used to adjust the polarization direction of the optical signal and to guide the optical signal to the input port of the corresponding multi-port coupler, and both are composed of a half-wave plate and an optical collimator arranged in sequence.

[0014] Furthermore, both the first and second detectors consist of a low-noise radio frequency amplifier and a Schottky diode arranged sequentially.

[0015] Furthermore, the optical modulation device is one of an acousto-optic modulator, electro-optic modulator, magneto-optic modulator, or integrated optoelectronic modulator that is coupled in optical fiber or free space, and is used to shift the carrier frequency of the incident light source.

[0016] A balanced timing detection method utilizing a single photodetector, based on the balanced timing detection device, includes the following steps:

[0017] Step 1: Introduce an radio frequency offset frequency to the optical signal to be modulated, and generate two independent optical signals with different frequency offsets;

[0018] Step 2: Introduce timing error into the zero-order optical signal and perform delay processing. The processed optical signal consists of two pulses with time delay in the time domain.

[0019] Step 3: Transmit the two modulated optical signals with different frequency offsets and the zero-order optical signal that introduces time delay error to the same coupler;

[0020] Step 4: The optical signal output after coupling is converted into an electrical signal and then split into two identical electrical signals by a power divider. Each electrical signal contains a radio frequency offset signal, and the radio frequency offset signal is extracted by a bandpass filter.

[0021] Step 5: Extract the envelope signal of each RF offset signal. The envelope signal contains the timing information to be measured. Perform differential operation on the two envelope signals. Record the voltage values ​​of the differential signals under different delays in real time to obtain the relationship curve between the timing information introduced by the timing device to be measured and the final output voltage, thereby completing the timing calibration process.

[0022] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0023] (1) Compared with timing detection methods based on the same balanced architecture (such as BOC method and AOM balanced detection method), the timing detection method proposed in this invention only requires one photodetector to achieve balanced detection, and the layout is further simplified.

[0024] (2) BOC timing detectors based on optical quadratic sum-frequency effect often require hundreds of milliwatts of input power to compensate for the low optical nonlinear efficiency. However, the timing detection method proposed in this invention can achieve timing detection performance comparable to that of a BOC detector with an input power of 100 milliwatts at a low input power (less than 2 milliwatts), which is very suitable for low-power applications that are sensitive to nonlinear effects.

[0025] (3) Compared with superheterodyne timing detectors, optical delay line timing detectors and traditional balanced timing detectors, the timing method provided by the present invention has the advantages of simple layout and low cost. It only requires an optical modulator, a photodetector and several commonly used optical components to complete the timing detection function with attosecond precision, and it is easier to integrate later.

[0026] (4) The present invention adopts a balanced detection architecture: By combining the balanced architecture with the method proposed in this invention, it has been experimentally proven that it can not only effectively suppress interference such as environmental noise and laser amplitude noise, and obtain a lower measurement noise floor, but also suppress electronic noise generated during photoelectric detection, and provide higher timing resolution at high frequencies. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the balancing timing detection device of the present invention.

[0028] Figure 2 This is a schematic diagram of the structure of the balance timing detection device in a specific embodiment of the present invention.

[0029] Figure 3 This is the timing characteristic curve obtained during the specific implementation process. The horizontal axis represents the timing error Δt, and the vertical axis represents the differential output voltage V, where V = G is the magnification factor of the differential operation unit.

[0030] Figure 4 The timing jitter power spectral density and timing jitter integral curve are measured during the specific implementation process. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0032] like Figure 1 As shown, the attosecond precision timing detection device using a single photodetector provided in this embodiment includes a laser source and beam splitting unit, an optical modulation unit, an optical coupling unit, a photodetector, and a differential operation unit arranged sequentially. The laser source and beam splitting unit includes a laser source 1 and a beam splitting device 2; the optical modulation unit includes an optical isolator 5, an optical modulation device 6, and a beam splitting device 7; the optical coupling unit includes a first coupling preprocessing device 8, a second coupling preprocessing device 9, and a multi-port coupler 10; the photodetector includes a photoelectric conversion unit, a filtering unit, and a detection unit; the photoelectric conversion unit includes a photodetector 11 and a power distribution device 12; the filtering unit includes a first bandpass filter 13 and a second bandpass filter 14; and the detection unit includes a first detection device 15 and a second detection device 16.

[0033] The laser source and beam splitting unit output zero-order light and light to be modulated. The light to be modulated passes through optical isolator 5 and then enters optical modulator 6. The carrier frequency of the output first-order diffracted light obtains the frequency shift of the radio frequency signal. The first-order diffracted light passes through beam splitter 7 and is divided into reflected first-order diffracted light and transmitted first-order diffracted light. The transmitted first-order diffracted light is transmitted sequentially to the first coupling preprocessing device 8 and the multi-port coupler 10. The reflected first-order diffracted light returns to optical modulator 6. The carrier frequency of the second-order diffracted light output by optical modulator 6 again obtains the frequency shift of the radio frequency signal. The second-order diffracted light passes through optical isolator 5 and then enters multi-port coupler 10.

[0034] The zero-order light is transmitted to the delay introduction device 4 after passing through the timing device 3, and the output zero-order light contains two light particles with a time delay T in the time domain. D The pulses are transmitted sequentially to the second coupling preprocessing device 9 and the multi-port coupler 10;

[0035] The optical signal output from the multi-port coupler 10 is converted into an electrical signal by the photodetector 11, and then split into two equal-power electrical signals by the power divider 12. One electrical signal passes sequentially through the first bandpass filter 13 and the first detector 15, while the other electrical signal passes sequentially through the second bandpass filter 14 and the second detector 16. Both electrical signals enter the two input ports of the differential operation unit 17, which ultimately outputs the detection result. After passing through the bandpass filter, only the radio frequency offset signal remains, which is detected by the detector to detect its envelope. A separate data acquisition device is connected to the output of the final differential operation unit 17 to acquire the output voltage signal under different delays in real time. The voltage signal contains all the timing information of the measurement.

[0036] Laser source 1 is used to generate laser signals as the incident light source for the entire device; beam splitter 2 is used to split the incident laser source into modulated light and zero-order light.

[0037] Optical isolator 5 is used for unidirectional transmission of optical signals with different carrier frequencies, which can be achieved through a circulator; optical modulation device 6 is used to introduce radio frequency offset frequency into the optical signal, which can be achieved through the modulation effect of modulation devices such as optical fiber coupled or free space coupled acousto-optic modulator, electro-optic modulator, magneto-optic modulator, integrated optoelectronic modulator, etc.

[0038] The differential operation unit 17 embodies the main features of the architecture. In the experiment, two timing links are symmetrically set. Since the two signals are subjected to the same environmental noise and laser amplitude noise during transmission, theoretically, these noises can be greatly suppressed after differential operation, and some noise components can even be completely suppressed. In this embodiment, only a single photodetector is used, and the electronic noise introduced by the photodetector 11 at high frequencies can be further canceled. To achieve a balanced architecture, the electrical signal output by the photodetector 11 is divided into two completely equal paths by a high-isolation power divider. Each electrical signal is processed symmetrically, passing through a filtering unit and a detection unit in sequence, and then the differential operation unit performs differential operation on the two voltage signals.

[0039] The attosecond precision timing detection method for a single photodetector based on the above-mentioned timing detection device includes the following steps:

[0040] Step 1: Introduce an radio frequency offset frequency to the optical signal to be modulated, generating two independent optical signals with different frequency offsets;

[0041] Step 2: Introduce timing error into the zero-order light and perform delay processing. The processed optical signal consists of two pulses with a timing delay in the time domain.

[0042] Step 3: Transmit the two modulated signals with different frequency offsets and the unmodulated signal with introduced error to the same multiport coupler;

[0043] Step 4: The optical signal output after coupling is converted into an electrical signal and then split into two identical electrical signals by a power divider. Each electrical signal contains a radio frequency offset signal, and the radio frequency offset signal is extracted by a bandpass filter.

[0044] Step 5: Extract the envelope signal of each RF offset signal. The envelope signal contains the timing information to be measured. Perform differential operation on the two envelope signals. Record the voltage value of the differential signal under different delays in real time to obtain the relationship curve between the timing information introduced by the timing device to be measured and the final output voltage, thereby completing the timing calibration process.

[0045] More specifically, this embodiment also provides a diagram of a balanced timing detection device with attosecond precision based on a single photodetector, as shown in the experiment. Figure 2 As shown, the experimental setup includes the following instruments and devices: a laser source 1; a beam splitter 2 consisting of a polarizing beam splitter prism 19, a half-wave plate 20, and an optical collimator 21; a timing device for the measurement consisting of an electric translation stage 22 and a retroreflector 23; a delay introduction device 4 consisting of quarter-wave plates 26 and 28, plane mirrors 27 and 29, a polarizing beam splitter prism 30, and a free-space polarizer 31; an optical isolation device 5; an optical modulation device 6 consisting of an optical fiber coupled acousto-optic frequency shifter 34, an amplifier 35, and an arbitrary signal generator 36; and a beam splitter consisting of a plane beam splitter 38 and a manual translation stage 39. Device 7, a first coupling preprocessing device 8 consisting of a half-wave plate 40 and an optical collimator 41, a second coupling preprocessing device 9 consisting of a half-wave plate 32 and an optical collimator 33, a 3×1 multi-port coupler 10, an avalanche photodiode 11, a power divider 12, a first bandpass filter 13, a second bandpass filter 14, a first detection device 15 consisting of a low-noise amplifier 42 and a Schottky diode 43, a second detection device 16 consisting of a low-noise amplifier 44 and a Schottky diode 45, a differential operation unit 17, a half-wave plate 18, plane mirrors 24 and 25, and an optical collimator 37.

[0046] Laser source 1 outputs a laser pulse sequence with a center wavelength of 1555 nm, a repetition frequency of 216.667 MHz, and a pulse width of 170 fs.

[0047] The arbitrary signal generator 36 outputs a sinusoidal signal with a frequency of 80 MHz and an effective voltage of 200 mV, which is then amplified to 3 W by the amplifier 35 and used to drive the fiber-coupled acousto-optic frequency shifter 34.

[0048] The photodetector in this embodiment uses an avalanche photodiode (APD), which has the following parameters: equivalent noise power of 2 pW / √Hz, responsivity of 0.9 A / W, transconductance gain of 50 V / A, and a 3 dB bandwidth of 100 MHz. The center frequency of the first bandpass filter is 80 MHz, and the center frequency of the second bandpass filter is 160 MHz. The differential operation unit has an amplification gain of 40 dB and a bandwidth of 1 MHz.

[0049] The specific timing calibration process is as follows: The laser pulse output from the mode-locked laser, which serves as the laser source, is split into two paths by a polarizing beam splitter, denoted as the modulated light and the zero-order light. The modulated light enters the optical collimator through a half-wave plate. The optical collimator couples the light in free space into the optical fiber and continues to transmit it to port 1 of the optical isolator. The radio frequency signal output from the arbitrary signal generator is amplified to 3W and then used to drive the fiber-coupled acousto-optic frequency shifter. The modulated light is output from port 2 of the optical isolator and enters the acousto-optic modulator. Its optical carrier frequency obtains the frequency shift of the radio frequency signal, denoted as the first-order diffracted light A. Subsequently, the first-order diffracted light A is transmitted to free space through the optical collimator and splits into the first-order transmitted light B and the first-order reflected light C by a plane beam splitter fixed on a manual translation stage. The first-order reflected light C passes through the optical collimator and the fiber-coupled acousto-optic frequency shifter in sequence, outputting the second-order diffracted light D, which again obtains the frequency shift of the radio frequency signal. It is then transmitted from port 2 of the optical isolator to port 3, and finally... The first-order transmitted light B enters the 1 input port of the 3×1 multiport coupler; after passing through a half-wave plate and being collimated by an optical collimator, it enters the optical fiber and is transmitted to the 2 input port of the 3×1 multiport coupler; the zero-order light, after being reflected by a retroreflector fixed on an electric translation stage, is introduced with a timing error Δt compared to the light to be modulated; the zero-order light with the introduced timing error is split into two beams of equal power by a polarization beam splitter. Each beam passes through a quarter-wave plate and a mirror, and then returns to the polarization beam splitter and is combined into a beam E. By adjusting the distance between the two mirrors and the polarization beam splitter, the beam E is composed of two orthogonally polarized pulse sequences E0 and E1 with a time delay interval in the time domain. After passing through a quarter-wave plate and a free-space polarizer, E0 and E1 are adjusted to the same polarization direction. Finally, the E beam is coupled into the optical fiber by an optical collimator and transmitted to the 3 input port of the 3×1 coupler. The output optical signal of a 3×1 multiport coupler is input to an avalanche photodiode, where it is converted into an electrical signal. In the avalanche photodiode, the zero-order E0 light beats the first-order transmitted light (B), and the zero-order E1 light beats the second-order diffracted light (D). The electrical signal is strictly split into two equal paths by a high-isolation power divider. To achieve a balanced architecture, the two electrical signals require completely symmetrical processing. After passing through a bandpass filter and a differential operation unit, the two signals enter a Schottky diode. The two signals, after detection by the Schottky diode, serve as the two inputs to the differential operation unit. In the experiment, the incident light power of the avalanche photodiode was selected as 1.4 milliwatts, meaning the average optical power of each light pulse sequence was 0.35 milliwatts.

[0050] During the timing calibration, the electric translation stage 22 is controlled by a computer to make minute displacements, and the voltage signal output by the differential operation unit is collected in real time by the data acquisition device and stored in the computer for subsequent data processing.

[0051] Figure 3 The S-shaped curve is the timing characteristic curve required for timing calibration. The horizontal axis represents the timing error Δt introduced by the electric translation stage, and the vertical axis represents the differential output voltage V, where V = G is the amplification factor of the differential operation unit. The curve shows that when the input optical power is 1.4 mW, the maximum sensitivity of the photodetector designed in this embodiment is 34.6 mV / fs. At the position of maximum sensitivity, the signal output from the differential operation unit is connected to a signal source analyzer. By measuring the output voltage of the differential operation unit using the baseband measurement function of the signal source analyzer, the noise floor of this measurement can be obtained, and the timing jitter power spectral density and timing jitter integral curve can be plotted. Figure 4 As shown in Figure (ii), compared to the timing jitter power spectral density (i) measured by a single-channel method, the balanced detector architecture effectively suppresses ambient noise and laser amplitude noise. Furthermore, electronic noise generated during photoelectric conversion (e.g., 20 kHz–100 kHz and 300 kHz–1 MHz) is clearly observed at high frequencies in curve (i). Since only a single photodetector is used, these high-frequency electronic noises are highly correlated and theoretically can be canceled out by differential operation. Experiments confirm that these electronic noises are well suppressed in curve (ii). In this embodiment, the minimum timing jitter substrate obtained by measurement is approximately 5 × 10⁻⁶. -10 fs 2 / Hz, the timing jitter after integration from 1 Hz to 1 MHz is only 43.73 as, and the timing measurement range in the timing characteristic curve is about 750 fs, which is equivalent to a detection dynamic range of 84.69 dB.

[0052] This invention is not limited to the embodiments described above. The above description of specific embodiments is intended to illustrate and explain the technical solutions of this invention. The specific embodiments described above are merely illustrative and not restrictive. Without departing from the spirit and scope of the claims, those skilled in the art can make many specific modifications based on the teachings of this invention, and these modifications all fall within the scope of protection of this invention.

Claims

1. A balanced timing detection device utilizing a single photodetector, characterized in that, The system includes a laser source and beam splitting unit, an optical modulation unit, an optical coupling unit, a photoelectric detection device, and a differential operation unit arranged sequentially. The laser source and beam splitting unit includes a laser source (1) and a beam splitting device (2). The optical modulation unit includes an optical isolation device (5), an optical modulation device (6), and a beam splitting device (7) arranged sequentially. The optical coupling unit includes a first coupling preprocessing device (8), a second coupling preprocessing device (9), and a multi-port coupler (10). The photoelectric detection device includes a photoelectric conversion unit, a filtering unit, and a detection unit. The photoelectric conversion unit includes a photodetector (11) and a power divider (12). The filtering unit includes a first bandpass filter (13) and a second bandpass filter (14). The detection unit includes a first detection device (15) and a second detection device (16). The laser source and the beam splitting unit output zero-order light and light to be modulated. The zero-order light will not be modulated, and the light to be modulated will be modulated by the optical modulator (6) in the future. The light to be modulated enters the optical modulator (6) after passing through the optical isolator (5). The carrier frequency of the first-order diffracted light output by the optical modulator (6) obtains the frequency shift of the radio frequency signal. The first-order diffracted light is split into reflected first-order diffracted light and transmitted first-order diffracted light after passing through the beam splitter (7). The transmitted first-order diffracted light is transmitted to the first coupling preprocessing device (8) and the multi-port coupler (10) in sequence. The reflected first-order diffracted light returns to the optical modulator (6). The carrier frequency of the second-order diffracted light output by the optical modulator (6) obtains the frequency shift of the radio frequency signal again. The second-order diffracted light enters the multi-port coupler (10) after passing through the optical isolator (5). The zero-order light is transmitted to the delay introduction device (4) after passing through the timing device (3) to be measured. The zero-order light output by the delay introduction device (4) contains two pulses with time delay in the time domain, and is transmitted to the second coupling preprocessing device (9) and the multi-port coupler (10) in sequence. The optical signal output by the multi-port coupler (10) is converted into an electrical signal by the photodetector (11) and then divided into two electrical signals with the same power by the power divider (12). One electrical signal passes through the first bandpass filter (13) and the first detector (15) in sequence, and the other electrical signal passes through the second bandpass filter (14) and the second detector (16) in sequence. Finally, the two electrical signals enter the two input ports of the differential operation unit (17), and the differential operation unit (17) outputs the detection result. After the electrical signal passes through the first bandpass filter (13) and the second bandpass filter (14), only the radio frequency offset signal with the radio frequency offset frequency component remains. The first detector (15) and the second detector (16) are used to detect the envelope of the radio frequency offset signal. The data acquisition device is connected to the output terminal of the differential operation unit (17) and uses the data acquisition device to acquire the voltage signal output by the differential operation unit (17) in real time. The voltage signal contains all the timing information to be measured.

2. The balanced timing detection device using a single photodetector according to claim 1, characterized in that, The delay introduction device (4) consists of a polarizing beam splitter (30), a quarter-wave plate, a plane mirror, and a free-space polarizer (31). Zero-order light enters from surface one of the polarizing beam splitter (30) and exits as two beams of zero-order light from surface two and surface three. After surface two and surface three of the polarizing beam splitter (30), there are quarter-wave plates and plane mirrors arranged in sequence. After each of the two beams of zero-order light passes through the plane mirror and quarter-wave plate twice, they are combined into one beam in the polarizing beam splitter (30) and emitted from surface four. The free-space polarizer (31) is set after surface four and before the second coupling preprocessing device (9).

3. The balanced timing detection device using a single photodetector according to claim 2, characterized in that, When two zero-order beams pass through two quarter-wave plates and a plane mirror arranged in sequence, they have an optical path difference, thus introducing a time-domain delay difference into the two orthogonally polarized zero-order beams.

4. The balanced timing detection device using a single photodetector according to claim 2, characterized in that, The free-space polarizer is used to adjust two orthogonally polarized zero-order lights to the same polarization direction and to transmit the zero-order light to the multi-port coupler (10) along the set polarization direction.

5. The balanced timing detection device using a single photodetector according to claim 1, characterized in that, The timing device to be measured (3) is one of the following: a delay line, a medium with birefringence, a piezoelectric device, a translation stage, or a light-transmitting medium that is disturbed by physical effects.

6. The balanced timing detection device using a single photodetector according to claim 1, characterized in that, The first coupling preprocessing device (8) and the second coupling preprocessing device (9) are both used to adjust the polarization direction of the optical signal and to guide the optical signal to the input port of the corresponding multi-port coupler (10). They are both composed of a half-wave plate and an optical collimator arranged in sequence.

7. The balanced timing detection device using a single photodetector according to claim 1, characterized in that, The first detector (15) and the second detector (16) are both composed of a low-noise radio frequency amplifier and a Schottky diode arranged in sequence.

8. The balanced timing detection device using a single photodetector according to claim 1, characterized in that, The optical modulation device (6) is one of an optical fiber coupled or free space coupled acousto-optic modulator, electro-optic modulator, magneto-optic modulator, or integrated optoelectronic modulator, used to shift the carrier frequency of the incident light source.

9. A balanced timing detection method using a single photodetector, based on the balanced timing detection device according to any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Introduce an radio frequency offset frequency to the optical signal to be modulated, and generate two independent optical signals with different frequency offsets; Step 2: Introduce timing error into the zero-order optical signal and perform delay processing. The processed optical signal consists of two pulses with time delay in the time domain. Step 3: Transmit the two modulated optical signals with different frequency offsets and the zero-order optical signal that introduces time delay error to the same coupler; Step 4: The optical signal output after coupling is converted into an electrical signal and then split into two identical electrical signals by a power divider. Each electrical signal contains a radio frequency offset signal, and the radio frequency offset signal is extracted by a bandpass filter. Step 5: Extract the envelope signal of each RF offset signal. The envelope signal of the RF offset signal contains the timing information to be measured. Perform differential operation on the two envelope signals. Record the voltage value of the differential signal under different delays in real time to obtain the relationship curve between the timing information introduced by the timing device to be measured and the final output voltage, thereby completing the timing calibration process.

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