Ultra-short pulse synchronization testing device and method based on optical Kerr effect

Abstract

A kind of ultra-short pulse synchronization testing device and method based on optical Kerr effect. After the high-power density ultra-short pulse of multiple beams to be synchronized passes through optical Kerr medium, induced birefringence effect occurs, which instantaneously changes the polarization characteristics of the reference light beam, and the synchronization between multiple beams of ultra-short pulses is measured by the amplitude or phase change of the reference signal pulse. This method can realize the synchronization measurement of ultra-short pulses with large angle at the target point, and has the advantages of high measurement accuracy, good repeatability and high stability.

Description

Technical Field

[0001] This invention relates to the fields of ultrashort pulse synchronization, intensity measurement, phase imaging, and third-order nonlinearity, and particularly to a device and method for time synchronization measurement between multiple ultrashort pulses. Background Technology

[0002] With the development of high-power ultrashort pulse technology, the time synchronization problem between different ultrashort pulses has been extensively studied. For example, in the research of biconical collision laser fusion ignition, multiple short pulses from different angles are required to bombard the target simultaneously; for high-energy petawatt devices, coherent beam combining is used to further improve peak intensity, which also places high demands on the time synchronization between pulses; for pump-probe experiments that can realize various transient process measurements, high-precision time synchronization measurement and control are also particularly important. Currently, common methods for measuring ultrashort pulse synchronization include: phototube combined with oscilloscope method, spectral interferometry, optical cross-correlation method, and laser plasma method. The phototube combined with oscilloscope method is currently the most commonly used method, but due to the limitations of the response time and bandwidth of the phototube and oscilloscope, the current synchronization measurement accuracy is generally around 10 ps. The spectral interferometry method can only be used for the synchronous measurement of broadband ultrashort pulses, and considering the interference situation, it is not suitable for the synchronous measurement of focused pulses at an angle. Optical cross-correlation methods utilize the sum-frequency signal intensity of two pulses to obtain the relative delay. This method can achieve femtosecond-level accuracy; however, due to nonlinear effects, it is difficult to perform complex wavefront measurements. Laser-plasma methods are suitable for large-angle beam synchronization measurements (Qihua Zhu et al 2018 Laser Phys. Lett. 15 015301), but plasma generation requires a laser power density higher than 10. 15 W / cm 2 .

[0003] Therefore, the above-mentioned solutions cannot simultaneously achieve high-precision, large-angle synchronous measurement of ultrashort pulses at the target point using lower energy. Summary of the Invention

[0004] This invention addresses the limitations of the aforementioned ultrashort pulse synchronization techniques by proposing an ultrashort pulse synchronization testing device and method based on the optical Kerr effect. It utilizes the optical Kerr effect of the medium to determine the time delay of the synchronization pulse. Different time delays between multiple ultrashort pulses result in different changes in the amplitude and phase distribution of the signal pulses after passing through the optical Kerr medium, which can effectively improve the synchronization accuracy of ultrashort pulses. This method quantifies the synchronization accuracy and allows for repeated measurements in liquid optical Kerr media. It features high stability and high time synchronization accuracy.

[0005] The technical solution of the present invention is as follows:

[0006] On the one hand, the present invention provides an ultrashort pulse synchronization testing device based on the optical Kerr effect, characterized in that it includes:

[0007] An externally injected signal light, used as a reference light, is either a picosecond pulse or a femtosecond pulse.

[0008] A polarizer is used to adjust the polarization direction of the externally injected signal light;

[0009] A delay line is used to generate a spatial delay, adjust the time delay of the externally injected signal light, and incident it onto the optical Kerr medium;

[0010] An optical Kerr medium is used to generate an optical Kerr effect when two or more synchronous pulses are incident on it, thereby changing the polarization state of the externally injected signal light.

[0011] A polarizer, the optical axis of which is perpendicular to the optical axis of the polarizer, is used to detect the optical Kerr effect;

[0012] The detector is used to detect the pulse intensity and phase distribution after it has been transmitted or reflected by the analyzer;

[0013] The control and data processing module is used to control the detector and all delay lines, process the acquired data, obtain the delay information between different pulses to be synchronized and the externally injected signal light, and synchronize with multiple pulses to be synchronized.

[0014] The first and Nth pulses to be synchronized are the N pulses that need to be synchronized, which are picosecond or femtosecond pulses, where N≥2; the angle between the N pulses to be synchronized and the externally injected signal light is in the range of (0, π).

[0015] The first delay line and the Nth delay line are used to generate spatial delay, which are used to adjust the time delay of the first and Nth bundles of pulses to be synchronized, respectively.

[0016] The first half-wave plate and the Nth half-wave plate are used to control the polarization direction of the first and Nth pulses to be synchronized after passing through the first and Nth delay lines, respectively, and then incident into the optical Kerr medium to generate the optical Kerr effect.

[0017] The detector is a phototube, a spot intensity detector, or a phase measuring instrument module.

[0018] Furthermore, when the detector is a phase detector module, the phase detector module is characterized in that it includes a wavefront modulator module and a spot detector.

[0019] A wavefront modulator module is used to perform phase modulation on the externally injected signal light;

[0020] A light spot detector is used to record the intensity distribution of the externally injected signal light after being modulated by the wavefront modulator module.

[0021] The wavefront modulator module is a binary step phase wavefront modulator, a ternary step phase wavefront modulator, a deca-step phase wavefront modulator, a continuous phase modulator, a continuous amplitude phase modulator, or a pure amplitude wavefront modulator.

[0022] The polarization axes of the polarizer and the analyzer are perpendicular to each other; the polarizer and the analyzer can be polarizers, polarizing beam splitters or Nicol prisms.

[0023] The delay line, the first delay line, and the Nth delay line include four 45° reflectors mounted on an electric or manual displacement stage.

[0024] The photoker medium is carbon disulfide, fused silica, bismuthate glass, tellurate glass, nitrobenzene, chalcogenide glass, silicate glass, heavy flint glass, or neodymium glass.

[0025] On the other hand, the present invention also provides a method for synchronizing ultrashort pulses based on the optical Kerr effect, the method comprising the following steps:

[0026] ①The externally injected signal light passes through the polarizer and delay line in sequence and is then collimated and incident on the optical Kerr medium;

[0027] ② After the first pulse to be synchronized passes through the first delay line, it is incident on the first half-wave plate. After the first half-wave plate is rotated so that its polarization direction is 45° with that of the externally injected signal light, it is incident on the optical Kerr medium to generate the optical Kerr effect. When the externally injected signal light passes through the optical Kerr medium, its polarization state changes and then it is incident on the analyzer.

[0028] ③ Utilize a detector to perform real-time intensity and phase spatial distribution measurements on the output pulse signal after the analyzer, using any of the following methods;

[0029] Method 1:

[0030] When the detector is a phototube, the intensity of the transmitted or reflected pulses from the analyzer is measured in real time. The first pulse to be synchronized is represented as... The externally injected signal light output after reaching the analyzer is represented as First, the reference signal pulse is made by adjusting the delay line within the reference optical path. The polarization component is strongest at the phototube, meaning the amplitude displayed on the oscilloscope is the largest; this position is designated as position L1. At this point, the delay line in the reference optical path is locked into position.

[0031] Method 2:

[0032] When the detector is a spot detector, the spatial distribution of the intensity of the transmitted or reflected pulses from the analyzer is measured in real time. The first pulse to be synchronized is represented as... The externally injected signal light output after reaching the analyzer is represented as By adjusting the delay line within the reference optical path, the reference signal pulse is made more efficient. The polarization component of the light spot Q1 is strongest at the light spot detector. Due to the influence of the first synchronization pulse, fringes will be generated on the light spot detector. After adjustment, the fringe width is maximized, and this position is denoted as L1. At this time, the position of the delay line in the reference optical path is locked.

[0033] Method 3:

[0034] When the detector is a phase measurement module composed of a wavefront modulator module and a spot detector, it performs real-time intensity and phase spatial distribution measurements on the transmitted or reflected signal light after the analyzer; the first pulse to be synchronized is represented as... The externally injected signal light output after reaching the analyzer is represented as First, the reference signal pulse is made by adjusting the delay line within the reference optical path. The polarization component spot Q1 at the phase measurement module has the strongest intensity. Phase values ​​are measured near this location, and the beam is precisely adjusted to the position of the highest phase abrupt change. Due to the influence of the first synchronization pulse, stripes will be generated on the spot detector. After adjustment, the stripe width is maximized, and phase values ​​are measured near this location to find the position with the strongest stripe phase abrupt change, denoted as position L1. At this point, the delay line in the reference optical path is locked in position.

[0035] ④ After the Nth pulse to be synchronized passes through the Nth delay line, it is incident on the Nth half-wave plate. After the Nth half-wave plate is rotated so that its polarization direction is 45° with that of the externally injected signal light, it is incident on the optical Kerr medium to generate the optical Kerr effect. When the externally injected signal light passes through the optical Kerr medium, its polarization state changes and then it is incident on the analyzer.

[0036] ⑤ Use a detector to measure the intensity and phase spatial distribution of the output pulse signal after the analyzer in real time. Based on the method selected in step ③, select the corresponding method as follows;

[0037] Method 1:

[0038] When the detector is a phototube, the intensity of the transmitted or reflected pulses from the analyzer is measured in real time. The Nth pulse to be synchronized is represented as... The externally injected signal light output after reaching the analyzer is represented as The reference signal pulse is made through the Nth delay line. The polarization component intensity is strongest at the phototube, meaning the amplitude displayed on the oscilloscope is the largest; this location is denoted as position L. N At this point, the first and Nth pulses to be synchronized can achieve time synchronization.

[0039] Method 2:

[0040] When the detector is a spot detector, the spatial distribution of the intensity of the transmitted or reflected pulses from the analyzer is measured in real time. The Nth pulse to be synchronized is represented as... The externally injected signal light output after reaching the analyzer is represented as The reference signal pulse is made through the Nth delay line. The polarization component of the light spot Q at the light spot detector N The intensity is strongest. Due to the influence of the Nth synchronization pulse, stripes will be generated on the spot detector. After adjustment, the stripe width is maximized, and this position is denoted as L. N At this point, the first and Nth pulses to be synchronized can not only achieve time synchronization, but also precisely control their positions in the optical Kerr medium.

[0041] Method 3:

[0042] When the detector is a phase measurement module composed of a wavefront modulator module and a spot detector, it performs real-time intensity and phase spatial distribution measurements on the transmitted or reflected signal light after the analyzer; the Nth pulse to be synchronized is represented as... The externally injected signal light output after reaching the analyzer is represented as First, adjust the Nth delay line to make the reference signal pulse... The polarization component spot Q at the phase measurement module N The intensity is strongest at this location. The phase value is measured near this position, and the system is precisely adjusted to the position of the highest phase change. Due to the influence of the Nth pulse to be synchronized, stripes will be generated on the spot detector. After adjustment, the stripe width is maximized, and the phase value is measured near this position to find the location with the strongest stripe phase change, denoted as position L. N At this point, the first and Nth pulses to be synchronized can not only achieve high-precision time synchronization, but also precisely control their positions in the optical Kerr medium.

[0043] The phase measurement method of the phase measuring instrument module in steps ③ and ⑤ is as follows:

[0044] Step 3-3-1. The transmittance distribution of the wavefront modulator module (14) is calibrated as T(x,y), the wavefront distribution in front of the wavefront modulator module is represented as Em(x,y), and the wavefront after passing through the wavefront modulator is represented as Ev(x,y)=Em(x,y)·T(x,y). This wavefront is propagated to the spot detector to obtain the wavefront: Where Ld is the distance between the wavefront modulator module and the spot detector. This indicates that the wavefront will propagate a distance L in free space.

[0045] Step 3-3-2. The intensity of the light spot recorded by the light spot detector is represented as I(x,y). The amplitude update of Ed(x,y) is represented as Ed'(x,y)=sqrt(I(x,y))·exp(i·angle(Ed'(x,y))), where sqrt() represents the square root operation and angle() represents the phase operation. Then, it is backpropagated to the wavefront modulator module to obtain the wavefront. in This represents the reverse propagation distance L in the free space of the wavefront. Using the following update formula, the wavefront distribution before the wavefront modulator module is obtained as: Em'=Em+conj(T) / max(conj(T)·T)·(Ev'-Ev)

[0046] Propagating the wavefront to the focal plane and constraining it yields:

[0047] Where Lf is the distance between the wavefront modulator module and the focal plane, and H is the pinhole confinement operation. Then, the data is fed back to the wavefront modulation module to obtain the wavefront.

[0048] Calculate the error value: The abs() function represents the absolute value operation.

[0049] Assign Ef'(x,y) to Em(x,y), and repeat steps 3-3-1 and 3-3-2 until the error value ERR is less than the expected value, thus obtaining Em(x,y) as the complex amplitude distribution of the wavefront to be measured.

[0050] Compared with the prior art, the beneficial effects of the present invention are as follows: it provides a device and method for achieving high-precision, large-angle synchronous measurement of multiple ultrashort pulses using low energy. Furthermore, because the optical Kerr medium can be placed at the center of the target range, synchronous measurement at the target point of a large laser device can be achieved, resulting in advantages such as high measurement accuracy, good repeatability, and high stability. Attached Figure Description

[0051] Figure 1 This is an optical path diagram of an embodiment of the optical Kerr effect-based ultrashort pulse synchronization device of the present invention.

[0052] Figure 2 Schematic diagram of a space wavefront phase measurement device

[0053] Figure 3 This is a graph showing the signal pulse amplitude measurement results at times T1-T5 in Example 1.

[0054] Figure 4 This is a one-dimensional curve of the signal pulse amplitude at times T1-T5 in Example 1.

[0055] Figure 5 This is a graph showing the signal pulse phase measurement results at times T1-T5 in Example 1.

[0056] Figure 6 This is a one-dimensional curve of the signal pulse phase at times T1-T5 in Example 1.

[0057] Figure 7 Schematic diagram of an ultrashort pulse synchronous measurement device based on the optical Kerr effect for the ICF high-power laser facility. Detailed Implementation

[0058] The present invention will be further described below with reference to different types of measurement requirements, embodiments and accompanying drawings, but the scope of protection of the present invention should not be limited by these embodiments.

[0059] Please see Figure 1 , Figure 1 The optical path of an embodiment of the ultrashort pulse synchronization device based on the optical Kerr effect of the present invention is shown in the figure. An ultrashort pulse synchronization test device based on the optical Kerr effect includes: a reference optical path consisting of an externally injected signal light 1 passing sequentially through a polarizer 2, a delay line 3, an optical Kerr medium 4, an analyzer 5, and a detector 6; the detector 6 is externally connected to a control and data processing module 7. In the test optical path 1, the first beam of pulse 8 to be synchronized passes through the first delay line 9 and is incident on the first half-wave plate 10. After rotating the first half-wave plate 10 to make its polarization direction 45° with that of the externally injected signal light 1, it is incident into the optical Kerr medium 4 to generate the optical Kerr effect. In the test optical path 2, the second beam of pulse 11 to be synchronized passes through the first delay line 12 and is incident on the second half-wave plate 13. After rotating the first half-wave plate 13 to make its polarization direction 45° with that of the externally injected signal light 1, it is incident into the optical Kerr medium 4 to generate the optical Kerr effect.

[0060] In this embodiment, the externally injected signal light 1 is a picosecond pulse light, which serves as a reference light; the polarizer 2 and analyzer 5 are polarizing beam splitters; the optical Kerr medium 4 is carbon disulfide liquid contained in a quartz cuvette; the delay line 3, the first delay line 9, and the second delay line 12 are all four 45° reflectors mounted on an electric displacement stage; the detector 6 is a phase measurement module composed of a wavefront modulator module 14 and a spot detector 15; the wavefront modulator module 14 is a binary step phase wavefront modulator with a phase gradient distributed between 0 and π; the spot detector 15 is a CCD; and the control and data processing module 7 is a computer.

[0061] The specific implementation steps of this embodiment are as follows:

[0062] The first pulse to be synchronized, 8, passes through the first delay line, 9, and is incident on the first half-wave plate, 10. After rotating the first half-wave plate, 10 is aligned 45° with the polarization direction of the externally injected signal light, 1, it is incident on the optical Kerr medium, 4, generating the optical Kerr effect. Meanwhile, the externally injected signal light 1 in the reference path passes sequentially through the polarizer, 2, and delay line, 3, and is collimated into the optical Kerr medium 4, where its polarization state changes. It then enters the analyzer, 5. The detector, 6 (phase measurement module), measures the intensity and phase spatial distribution of the output pulse signal after the analyzer, and the first pulse to be synchronized, 8, is represented as... The externally injected signal light 1 output after reaching the analyzer is represented as By adjusting the delay line 3 in the reference optical path, the reference signal pulse is made more efficient. The polarization component spot Q1 at the phase measuring module has the strongest intensity. Phase values ​​are measured near this location to find the position with the strongest fringe phase abrupt change, denoted as position L1. At this point, the delay line 3 in the reference optical path is locked. Subsequently, the second pulse to be synchronized 11 passes through the second delay line 12 and is incident on the second half-wave plate 13. The first half-wave plate 13 is rotated so that its polarization direction is 45° to that of the externally injected signal light 1, and then incident into the optical Kerr medium 4 to generate the optical Kerr effect. The reference optical path follows the same steps as above. The phase measuring module continues to measure the real-time intensity and phase spatial distribution of the output pulse signal after the analyzer 5. By adjusting the second delay line 12, the polarization component spot Q2 of the reference signal pulse at the phase measuring module has the strongest intensity. Phase values ​​are measured near this location to find the position with the strongest fringe phase abrupt change, denoted as position L2.

[0063] The phase measurement method used by the phase measuring instrument module in the above steps is as follows:

[0064] 1) The transmittance distribution of the calibrated wavefront modulator module (14) is T(x,y), the wavefront distribution in front of the wavefront modulator module 14 is represented as Em(x,y), and the wavefront after passing through the wavefront modulator is represented as Ev(x,y)=Em(x,y)·T(x,y). This wavefront is propagated to the spot detector 15 to obtain the wavefront: Where Ld is the distance between the wavefront modulator module 14 and the spot detector 15. This indicates that the wavefront will propagate a distance L in free space.

[0065] 2) The intensity of the light spot recorded by the light spot detector 15 is represented as I(x,y). The amplitude update of Ed(x,y) is represented as Ed'(x,y)=sqrt(I(x,y))·exp(i·angle(Ed'(x,y))), where sqrt() represents the square root operation and angle() represents the phase operation. Then, it is backpropagated to the wavefront modulator module 14 to obtain the wavefront. in This represents the reverse propagation distance L in the free space of the wavefront. Using the following update formula, the wavefront distribution before the wavefront modulator module 14 is obtained as: Em'=Em+conj(T) / max(conj(T)·T)·(Ev'-Ev)

[0066] Propagating the wavefront to the focal plane and constraining it yields:

[0067] Where Lf is the distance between the wavefront modulator module 14 and the focal plane, and H is the pinhole confinement operation. Then, the data is transmitted back to the wavefront modulation module to obtain the wavefront.

[0068] Calculate the error value: The abs() function represents the absolute value operation.

[0069] Assign Ef'(x,y) to Em(x,y), and repeat steps 1) and 2) until the error value ERR is less than the expected value, thus obtaining Em(x,y) as the complex amplitude distribution of the wavefront to be measured.

[0070] Figure 3 The following graph shows the signal pulse amplitude measurement results obtained from the example at times T1-T5. Figure 4 This is a one-dimensional curve of the signal pulse amplitude at times T1-T5 in the example, where the time interval between different times T1-T5 is approximately 0.83 ps. Figure 4 It can be seen that the amplitudes of T3 and T4 are close, and the time synchronization accuracy of these two moments is similar. Figure 5 This is a graph showing the signal pulse phase measurement results at times T1-T5 in the example. Figure 6This is a one-dimensional curve of the signal pulse phase at times T1-T5 in the example. Figure 6 The phase amplitude at T3 is higher than that at T4, so the more accurate time synchronization position is at time T3. This shows that the phase synchronization measurement accuracy is higher, and its time measurement accuracy is better than ±0.42ps.

[0071] The specific parameters of the embodiments of the present invention are as follows:

[0072] 1. The laser used in this embodiment has a wavelength of 1053nm, a pulse width of 10ps, a frequency of 1Hz, an energy of 0.3mJ, and an energy fluctuation of approximately 7.7%.

[0073] 2. In the embodiment, the displacement stage used to adjust the pulse light delay has a range of 25mm, a single adjustment displacement of 125um, a corresponding optical path change of 250um, and a time delay change of approximately 0.83ps.

[0074] Application Examples:

[0075] like Figure 7 As shown, the above-mentioned ultrashort pulse synchronization measurement method based on the optical Kerr effect is applied to the ICF high-power laser device. The ICF high-power laser device needs to simultaneously incident multiple ultrashort pulses onto a target located at the center of the target range. Therefore, it is necessary to achieve synchronization of multiple ultrashort pulses at the target point. Two opposing target mirror windows of the target sphere are selected or a reference optical path is built inside the target sphere. An externally injected signal light 1 is introduced from elsewhere. Then, a polarizer 2 and a delay line 3 are placed. The optical Kerr medium 4 is placed at the exact center of the target range using the target range holder and target positioning system. An analyzer 5, a wavefront modulator module 14, and a spot detector 15 are placed along the transmission direction of the externally injected signal light 1, and an external control and data processing module 7 is connected. The ICF high-power device generates multiple pulses. For example, each optical path of the pulses to be synchronized, 8 and 11, has its own delay line, and a half-wave plate is placed in each optical path. Therefore, Figure 7 These two parts are not labeled. In this application embodiment, the externally injected signal light 1 is a picosecond pulse light, which serves as the reference light; the polarizer 2 and analyzer 5 are polarizing beam splitters; the optical Kerr medium 4 is carbon disulfide liquid placed in a quartz cuvette; the delay line 3 consists of four 45° mirrors mounted on an electric displacement stage; the wavefront modulator module 14 is a binary stepped phase wavefront modulator with a phase gradient distributed between 0 and π; the spot detector 15 is a CCD; and the control and data processing module 7 is a computer.

[0076] The specific measurement steps and phase measurement methods are the same as those in the above embodiments. For the case of multi-pulse, the specific implementation steps of the above embodiments can be repeated multiple times.

Claims

1. A device for testing synchronization of ultrashort pulses based on the optical Kerr effect, characterized in that it comprises: include: Externally injected signal light (1) serves as a reference light, and can be either a picosecond pulse or a femtosecond pulse. A polarizer (2) is used to adjust the polarization direction of the externally injected signal light (1); Delay line (3) is used to generate spatial delay, adjust the time delay of the externally injected signal light (1), and incident on the photoker medium (4). The optical Kerr medium (4) is used to generate the optical Kerr effect when two or more synchronous pulses are incident on it, thereby changing the polarization state of the externally injected signal light (1). Analyzer (5), the optical axis of which is perpendicular to the optical axis of the polarizer (2), is used to detect the optical Kerr effect; Detector (6) is used to detect the pulse intensity and phase distribution after transmission or reflection by analyzer (5); The control and data processing module (7) is used to control the detector (6) and all delay lines, and to process the acquired data to obtain the delay information between different pulses to be synchronized and the externally injected signal light (1), and to synchronize with the multiple pulses to be synchronized. The first pulse to be synchronized (8), the Nth pulse to be synchronized (11) are the N pulses that need to be synchronized, which are picosecond or femtosecond pulses, where N≥2; the angle between the N pulses to be synchronized and the externally injected signal light (1) is in the range of (0, π); The first delay line (9) and the Nth delay line (12) are used to generate spatial delay, and are used to adjust the time delay of the first bundle of pulses to be synchronized (8) and the Nth bundle of pulses to be synchronized (11), respectively. The first half-wave plate (10) and the Nth half-wave plate (13) are used to control the polarization direction of the first pulse to be synchronized (8) and the Nth pulse to be synchronized (11) after passing through the first delay line (9) and the Nth delay line (12), respectively, and then incident into the optical Kerr medium (4) to generate the optical Kerr effect.

2. The optical Kerr effect based ultrashort pulse synchronization test apparatus according to claim 1, wherein The detector (6) is a phototube, a spot intensity detector, or a phase measuring instrument module.

3. The optical Kerr effect based ultrashort pulse synchronization test apparatus according to claim 2, wherein When the detector (6) is a phase detector module, the phase detector module includes a wavefront modulator module (14) and a spot detector (15). A wavefront modulator module (14) is used to perform phase modulation on the externally injected signal light (1); A spot detector (15) is used to record the intensity distribution of the externally injected signal light (1) modulated by the wavefront modulator module (14).

4. The optical Kerr effect based ultrashort pulse synchronization test apparatus according to claim 3, wherein The wavefront modulator module (14) is a binary step phase wavefront modulator, a ternary step phase wavefront modulator, a deca-step phase wavefront modulator, a continuous phase modulator, a continuous amplitude phase modulator, or a pure amplitude wavefront modulator.

5. The optical Kerr effect based ultrashort pulse synchronization test apparatus according to claim 1, wherein The polarization axes of the polarizer (2) and the analyzer (5) are perpendicular to each other; the polarizer (2) and the analyzer (5) are polarizers, polarizing beam splitters or Nicol prisms.

6. The optical Kerr effect based ultrashort pulse synchronization test apparatus according to claim 1, wherein The delay line (3), the first delay line (9) and the Nth delay line (12) include four 45° reflectors mounted on an electric or manual displacement stage.

7. The optical Kerr effect based ultrashort pulse synchronization test apparatus according to claim 1, wherein The photoker medium is carbon disulfide, fused silica, bismuthate glass, tellurate glass, nitrobenzene, chalcogenide glass, silicate glass, heavy flint glass, and neodymium glass.

8. A method for testing synchronization of ultrashort pulses based on the optical Kerr effect, characterized in that, The method includes the following steps: The external injection signal light (1) is collimated to be incident to the optical Kerr medium (4) after passing through the polarizer (2) and the delay line (3) in this order. The first beam of the to-be-synchronized pulses (8) passes through the first delay line (9), is incident to the first half-wave plate (10), the first half-wave plate (10) is rotated to be 45° with the polarization direction of the external injection signal light (1), is incident to the optical Kerr medium (4) to generate the optical Kerr effect, the polarization state of the external injection signal light (1) is changed when passing through the optical Kerr medium (4), and then is incident to the polariscope (5). The output pulse signal after the polarizer (5) is measured in real time for intensity and phase spatial distribution by the detector (6) using any one of the following methods: Method 1: When the detector (6) is a photoelectric cell, the transmitted or reflected pulse of the polarizer (5) is measured in real time, and the first beam of the pulse to be synchronized (8) is represented as The external injection signal light (1) output after the polarizer is represented as The polarization component intensity of the reference signal pulse is the strongest at the photoelectric cell, that is, the amplitude displayed by the oscilloscope is the largest, and this position is represented as position L1. At this time, the delay line (3) in the reference light path is locked. Method 2: When the probe (6) is a spot detector, the transmitted or reflected pulse of the polarizer (5) is measured in real time for the intensity spatial distribution, and the first beam of the pulse to be synchronized (8) is represented as The external injection signal light (1) output after the polarizer is represented as The reference signal pulse The polarization component spot Q1 intensity at the spot detector is the strongest; due to the influence of the first beam of the pulse to be synchronized (8), a stripe will be generated on the spot detector, and the stripe width is adjusted to be the largest, and this position is represented as L1, and the delay line (3) in the reference light path is locked at this position. Method 3: When the detector (6) is a phase measurement module composed of a wavefront modulator module (14) and a spot detector (15), it performs real-time intensity and phase spatial distribution measurements on the transmitted or reflected signal light after the analyzer (5); the first beam of pulses to be synchronized (8) is represented as The externally injected signal light (1) output after reaching the analyzer is represented as First, the reference signal pulse is made by adjusting the delay line (3) in the reference optical path. The polarization component spot Q1 at the phase measuring instrument module has the strongest intensity. The phase value is measured near this position and precisely adjusted to the position of the highest phase change. Due to the influence of the first synchronization pulse (8), stripes will be generated on the spot detector. After adjustment, the stripe width is maximized, and the phase value is measured near this position to find the position of the strongest stripe phase change, which is represented as position L1. At this time, the position of the delay line (3) in the reference optical path is locked. After the Nth pulse to be synchronized (11) passes through the Nth delay line (12), it is incident on the Nth half-wave plate (13). After the Nth half-wave plate (13) is rotated so that its polarization direction is 45° with that of the externally injected signal light (1), it is incident on the optical Kerr medium (4) to generate the optical Kerr effect. When the externally injected signal light (1) passes through the optical Kerr medium (4), its polarization state changes and then it is incident on the analyzer (5). The detector (6) is used to measure the intensity and phase spatial distribution of the output pulse signal after the analyzer (5) in real time, according to the steps. The selected method should be one of the following: Method 1: When the detector (6) is a phototube, the intensity of the transmitted or reflected pulse of the analyzer (5) is measured in real time, and the Nth pulse to be synchronized (11) is represented as The externally injected signal light (1) output after reaching the analyzer is represented as The reference signal pulse is made possible by the Nth delay line (12). The polarization component intensity is strongest at the phototube, meaning the amplitude displayed on the oscilloscope is the largest; this location is denoted as position L. N At this time, the first pulse to be synchronized (8) and the Nth pulse to be synchronized (11) can achieve time synchronization; Method 2: When the detector (6) is a spot detector, the real-time spatial distribution of the transmitted or reflected pulses of the analyzer (5) can be measured. The Nth pulse to be synchronized (11) is represented as... The externally injected signal light (1) output after reaching the analyzer is represented as The reference signal pulse is made possible by the Nth delay line (12). The polarization component of the light spot Q at the light spot detector N The intensity is strongest; due to the influence of the Nth pulse to be synchronized (11), stripes will be generated on the spot detector. After adjustment, the stripe width is maximized. This position is denoted as L. N At this time, the first pulse to be synchronized (8) and the Nth pulse to be synchronized (11) can not only achieve time synchronization, but also precisely control their position in the optical Kerr medium to be consistent. Method 3: When the detector (6) is a phase measurement module composed of a wavefront modulator module (14) and a spot detector (15), it can perform real-time intensity and phase spatial distribution measurement on the transmitted or reflected signal light after the analyzer (5); the Nth pulse to be synchronized (11) is represented as The externally injected signal light (1) output after reaching the analyzer is represented as First, the reference signal pulse is adjusted by adjusting the Nth delay line (12). The polarization component spot Q at the phase measurement module N The intensity is strongest at this location. Measure the phase value near this location and precisely adjust it to the position of the highest phase change. Due to the influence of the Nth pulse to be synchronized (11), stripes will be generated on the spot detector. After adjustment, the stripe width is maximized, and the phase value is measured near this location to find the position with the strongest stripe phase change, denoted as position L. N At this time, the first pulse to be synchronized (8) and the Nth pulse to be synchronized (11) can not only achieve high-precision time synchronization, but also precisely control their position in the optical Kerr medium.

9. The method for synchronous testing of ultrashort pulses based on the optical Kerr effect according to claim 8, characterized in that, The steps The phase measurement method used in the phase measurement instrument module of Method 3 is as follows: Step 3-3-1. Calibrate the transmittance distribution of the wavefront modulator module (14) as follows: The wavefront distribution in front of the wavefront modulator module (14) is represented as follows: Its wavefront representation after passing through the wavefront modulator is as follows The wavefront is propagated to the spot detector (15) to obtain the wavefront: ,in The distance between the wavefront modulator module (14) and the spot detector (15) is... This indicates that the wavefront will propagate a distance L in free space; Step 3-3-2. The intensity of the light spot recorded by the light spot detector (15) is expressed as follows: ,Will The amplitude update is represented as ,in This represents the square root operation. This indicates a phase-taking operation; then it is backpropagated to the wavefront modulator module (14) to obtain the wavefront. ,in This indicates that the wavefront free space is propagated backward by a distance L; the wavefront distribution is obtained before the wavefront modulator module (14) using the following update formula: Propagating the wavefront to the focal plane and constraining it yields: ,in The distance between the wavefront modulator module (14) and the focal plane. The pinhole is limited; then the data is sent back to the wavefront modulation module to obtain the wavefront. ; Calculate the error value: ,in This indicates the absolute value operation; Will Assigned to Repeat steps 3-3-1 and 3-3-2 until the error value is reached. Less than expected value thus obtained This represents the complex amplitude distribution of the wavefront to be measured.

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