Single-shot laser pulse spatiotemporal complex amplitude measurement device and method

Abstract

The application discloses a laser pulse space-time complex amplitude measuring device and method based on single exposure, and belongs to the technical field of optical detection. The method comprises the following steps: time modulation of a laser pulse is carried out by using an electro-optic deflector, the deflected optical field is spatially modulated by using an encoding plate, the intensity of the time-space modulated optical field is recorded by using a photoelectric detector through single exposure, and the space-time complex amplitude distribution of the pulse is reconstructed from the recorded intensity image by using a multi-modal iterative phase recovery algorithm. Through the space-time modulation of the laser pulse and the phase recovery mode, the problem that the time and space, intensity and phase distribution of the laser pulse cannot be simultaneously measured by using the single exposure method is solved, and the effect of complete measurement of the space-time complex amplitude distribution of the laser pulse is achieved.

Description

Technical Field

[0001] This invention relates to a device and method for measuring the spatiotemporal complex amplitude of laser pulses based on a single exposure, belonging to the field of optical detection technology. Background Technology

[0002] Ultrashort, ultra-intense laser pulses can create extreme physical conditions in the laboratory, such as high temperature, high pressure, and high density, conditions only found inside stars. This provides a crucial platform for cutting-edge scientific research in fusion physics, new energy sources, high-density physics, astrophysics, and condensed matter physics. The characteristics of a laser pulse can be described by a complex amplitude function. To describe this precisely, laser physics experiments place stringent requirements on the distribution of this complex amplitude function. The rapid increase in the output energy and power of laser devices presents new challenges to the measurement and control of pulse complex amplitude. To ensure the success rate and accuracy of physics experiments, it is necessary to precisely measure the laser pulse complex amplitude. Precise online measurement of the spatiotemporal distribution.

[0003] Traditional methods use streak cameras to measure the temporal waveform of pulses and ordinary imaging to observe their spatial intensity. However, the former loses spatial information, and the latter loses temporal information. Furthermore, neither method can measure the phase distribution of the beam. With the steady improvement of device performance and the rapid increase in the demand for beam precision in physical experiments, existing measurement methods can no longer meet the actual needs of scientific research. Autocorrelation and cross-correlation methods measure estimated pulse lengths, not precise intensity changes over time, and cannot obtain phase information. Frequency-resolved optical switching (FROG) and spectral phase interferometry (SPIDER) can be used for ultrashort pulse measurements, but they obtain spatial average values ​​of the pulses, still failing to provide complete spatial information. While delayed-scan-based pulse spatiotemporal measurement techniques can measure the complex amplitude distribution of pulses, they are not single-exposure methods and therefore cannot be used to measure ultrashort, ultra-intense laser pulses (each ultrashort, ultra-intense laser pulse has a different distribution). Holographic pulse complex amplitude spatiotemporal measurement techniques (STRIPED FISH) can measure femtosecond pulses in a single exposure, but this technique cannot measure the spatiotemporal distribution of nanosecond or picosecond laser pulses in a single exposure. Compressed sensing ultrafast imaging measurement techniques can measure the time-resolved intensity of laser pulses, but cannot obtain pulse phase distribution information.

[0004] Therefore, there is an urgent need for a measuring device and method that can measure the spatiotemporal complex amplitude of laser pulses using a single exposure method. Summary of the Invention

[0005] To measure ultrashort, ultra-intense laser pulses and simultaneously acquire their temporal and spatial information, this invention provides a device and method for measuring the spatiotemporal complex amplitude of laser pulses based on a single exposure. The technical solution is as follows:

[0006] The first objective of this invention is to provide a laser pulse spatiotemporal complex amplitude measurement device based on a single exposure, comprising: an electro-optic deflector, an encoding plate, and a photodetector arranged sequentially along the propagation direction of the laser to be measured, wherein the photodetector and the electro-optic deflector are respectively connected to a computer;

[0007] The electro-optic deflector is used to modulate the time signal of the light field, causing the light field of the laser pulse under test to deflect at different angles at different times; the encoding board is used to modulate the spatial distribution of the light field; the photodetector is used to record the intensity image of the two-dimensional light field; the electro-optic deflector, encoding board and photodetector are controlled by the computer, and the computer uses an iterative phase reconstruction method to recover the complex amplitude distribution of the laser pulse from the light field intensity image acquired by the photodetector.

[0008] Optionally, the iterative phase reconstruction method includes:

[0009] Step 1: Randomly guess the complex amplitude distribution of the laser pulse to be tested at the nth discrete time as E g (x,y,nΔt), the guessed pulse distribution is propagated to the detector plane through equations (1) and (2) to obtain the complex amplitude distribution U of the corresponding diffracted light field. g (x2,y2,nΔt);

[0010] S(x1,y1,nΔt)=Π{E g (x,y,nΔt)exp(ikθ n ),z1} (11)

[0011] Where (x, y) represents the beam plane coordinates of the laser pulse to be measured, (x1, y1) represents the plane coordinates of the encoder plate, Π represents the Fresnel propagation operator, z1 is the distance between the electro-optic deflector and the encoder plate, and θ n The deflection angle of the laser pulse under test after passing through the electro-optic deflector, where k represents the wave number and i represents the imaginary unit;

[0012] After modulation by the encoding plate, the light field distribution of the photodetector plane is as follows:

[0013] U g (x2,y2,nΔt)=Π{S(x1,y1,nΔt)M(x1,y1),z2}, (12)

[0014] Where (x2,y2) represents the planar coordinates of the photodetector, M(x1,y1) is the transmittance function of the encoding plate, and z2 is the distance between the encoding plate and the photodetector;

[0015] Since the exposure time of the photodetector is greater than the duration of the laser pulse, the intensity image acquired by the photodetector is equal to the sum of the light field intensities at all moments when the light reaches the detector plane, that is:

[0016]

[0017] Step 2: Update the complex amplitude distribution of the diffracted light field at each time step using the following formula:

[0018]

[0019] Step 3: Update the light field U g The light propagates backwards from (x2, y2, nΔt) to the plane of the encoding plate, resulting in the transmitted light field distribution p of that plane. g '(x1,y1,nΔt), update the light field distribution on the front surface of the encoder board:

[0020]

[0021] Where p g (x1,y1,nΔt) represents the light field distribution propagating forward to the rear surface of the encoder plate, and M represents the transmittance function of the encoder plate. S'(x1,y1,nΔt) is back-propagated to the plane under test, and exp(ikθ) is removed. n The improved complex amplitude E of the laser pulse was obtained. g (x,y,nΔt);

[0022] Step 4: Repeat steps 1-3 until E g (x,y,nΔt) converges.

[0023] Optionally, the encoding board is an amplitude-type encoding board.

[0024] Optionally, the encoding board is a phase-type encoding board.

[0025] Optionally, the encoding board is a spatial light modulator type encoding board.

[0026] Optionally, the encoding board is a cascaded encoding board.

[0027] Optionally, the photodetector is an area array photodetector.

[0028] The second objective of this invention is to provide a method for measuring the spatiotemporal complex amplitude of a laser pulse based on a single exposure, implemented using the laser pulse spatiotemporal complex amplitude measuring device described in any of the preceding claims, comprising:

[0029] Step 1: Device calibration;

[0030] Illuminate the center of the aperture of the electro-optic deflector without applied voltage using a fine collimated laser beam, observe the laser exit position of the electro-optic deflector, and ensure that it is in the center of the exit port; adjust the position of the encoder board so that the laser emitted from the electro-optic deflector is perpendicularly incident on the center of the encoder board; adjust the position of the photodetector so that the beam is perpendicularly incident on the center of the photodetector.

[0031] Apply a DC voltage in the vertical direction of the electro-optic deflector, observe the direction of the beam's movement on the photodetector, and adjust the relative positions of the electro-optic deflector and the photodetector to ensure that the beam moves in the vertical direction of the photodetector after the voltage is applied.

[0032] Step Two: Data Collection;

[0033] The laser pulse to be tested is perpendicularly incident on the center position of the electro-optic deflector. When the laser pulse to be tested reaches the incident aperture position of the electro-optic deflector, a voltage that varies with time is applied to the electro-optic deflector. At the same time, the photodetector turns on the exposure mode. The exposure time is greater than or equal to the duration of the pulse. The computer saves the intensity image recorded by the photodetector in a single exposure.

[0034] Step 3: Iterative Reconstruction;

[0035] A continuously distributed laser pulse is decomposed in time into a series of discrete optical fields with time intervals Δt. Assuming the complex amplitude distribution of the laser pulse under test at the nth discrete moment is E(x,y,nΔt), and the deflection angle θ after passing through the electro-optic deflector... n After propagating to the front surface of the encoder board, its light field distribution is as follows:

[0036] S(x1,y1,nΔt)=Π{E(x,y,nΔt)exp(ikθ n ),z1} (16)

[0037] Where (x,y) represents the plane coordinates of the pulse beam to be measured, (x1,y1) represents the plane coordinates of the encoder board, k represents the wave number, i represents the imaginary unit, Π represents the Fresnel propagation operator, and z1 is the distance between the electro-optic deflector and the encoder board.

[0038] After modulation by the encoding plate, the light field distribution of the photodetector plane is as follows:

[0039] U(x2,y2,nΔt)=Π{S(x1,y1,nΔt)M(x1,y1),z2}, (17)

[0040] Where (x2,y2) represents the plane coordinates of the photodetector, M(x1,y1) is the transmittance function of the encoder plate, and z2 is the distance between the encoder plate and the photodetector;

[0041] The intensity image acquired by the photodetector is equal to the sum of the light field intensities at all moments when the light reaches the detector plane, that is:

[0042]

[0043] The intensity of the overlapping portion recorded by the photodetector is equal to the incoherent superposition of the overlapping portions of the light field at each moment. During the reconstruction process, a multi-mode reconstruction method is used to separate the complex amplitude distribution of the light field at each moment.

[0044] Optionally, the multimodal reconstruction method includes:

[0045] Step 1: Randomly guess the complex amplitude distribution of the laser pulse to be tested at the nth discrete time as E g (x,y,nΔt), the guessed pulse distribution is propagated to the detector plane through equations (1) and (2) to obtain the complex amplitude distribution U of the corresponding diffracted light field. g (x2,y2,nΔt);

[0046] Step 2: Update the complex amplitude distribution of the diffracted light field at each time step using the following formula:

[0047]

[0048] Step 3: Update the light field U g The transmitted light field distribution p of (x2, y2, nΔt) propagates backward to the plane of the encoding plate, yielding the transmitted light field distribution p of that plane. g '(x1,y1,nΔt), update the light field distribution on the front surface of the encoder board:

[0049]

[0050] Where p g (x1,y1,nΔt) represents the light field distribution propagating forward to the rear surface of the encoder plate, and M represents the transmittance function of the encoder plate. Let S'(x1,y1,nΔt) be the light field distribution propagating forward to the rear surface of the encoder plate. t Reverse propagation to the plane under test and removal of exp(ikθ) n The improved complex amplitude E of the laser pulse was obtained. g (x,y,nΔt);

[0051] Step 4: Repeat steps 1-3 until Eg (x,y,nΔt) converges.

[0052] The beneficial effects of this invention are:

[0053] The present invention relates to a laser pulse spatiotemporal complex amplitude measurement device and method based on single exposure. By using an electro-optic deflector to time-modulate the laser pulse and an encoder to spatially modulate the pulse, the spatiotemporal complex amplitude distribution of the pulse is reconstructed using a multimodal phase retrieval algorithm. This solves the shortcomings of existing technologies that cannot simultaneously measure the time, space, amplitude, and phase distribution of high-power laser pulses, and achieves the goal of complete measurement of the spatiotemporal complex amplitude of high-power laser pulses. At the same time, the measurement device and method also have the advantages of simple structure and high measurement accuracy. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 This is a schematic diagram of the structure of the laser pulse spatiotemporal complex amplitude measurement device based on a single exposure according to the present invention.

[0056] Figure 2 This is a schematic diagram of the amplitude-type encoder plate according to Embodiment 3 of the present invention.

[0057] Figure 3 This is a schematic diagram of the phase-type encoder board according to Embodiment 4 of the present invention.

[0058] Figure 4 This is a schematic diagram of the measuring device using a spatial light modulator type encoder board in Embodiment 5 of the present invention.

[0059] Figure 5 This is a schematic diagram of a measuring device using a cascaded encoder board in Embodiment Six of the present invention.

[0060] In the diagram: 1—Electro-optic deflector, 2—Encoding board, 3—Area array photodetector, 4—Computer, 5—Spatial light modulator, 6—Cascaded encoding board Detailed Implementation

[0061] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0062] Example 1:

[0063] This embodiment provides a laser pulse spatiotemporal complex amplitude measurement device based on a single exposure, such as... Figure 1 As shown, along the propagation direction of the laser to be tested, the optical path consists of: 1. Electro-optic deflector, 2. Encoding board, and 3. Area array photodetector.

[0064] The characteristics of an electro-optic deflector are as follows: its core part is an electro-optic crystal, the refractive index of which is related to the voltage applied to the crystal. Changing the voltage can achieve the deflection of light. A voltage that changes with time is applied to the electro-optic deflector. The correspondence between the voltage value and time is controlled by a computer. Its function is to modulate the time signal of the light field, so that the light field of the laser pulse at different times will be deflected at different angles.

[0065] The function of the encoding plate is to modulate the spatial distribution of the light field. The encoding plate can be an amplitude-type encoding plate or a phase-type encoding plate. The amplitude-type encoding plate is characterized by being composed of rectangular or circular light-transmitting apertures with random positions. The phase-type encoding plate is characterized by: 1. high light transmittance, 2. its surface shape has slight random undulations.

[0066] A planar photodetector is used to record intensity images of a two-dimensional light field.

[0067] The electro-optic deflector, encoder board, and area array photodetector are controlled by computer 4, which has hardware and software systems for data acquisition and signal processing. The light field intensity image acquired by the area array photodetector is stored in the computer, and the computer uses an iterative phase reconstruction algorithm to recover the complex amplitude distribution of the laser pulse from the stored intensity image.

[0068] The laser pulse spatiotemporal complex amplitude measurement device based on single exposure in this embodiment modulates the laser pulse temporally using an electro-optic deflector and spatially modulates the pulse using an encoder board. It then reconstructs the spatiotemporal complex amplitude distribution of the pulse using a multimodal phase recovery algorithm. This solves the shortcomings of existing technologies that cannot simultaneously measure the temporal, spatial, amplitude, and phase distributions of high-power laser pulses, achieving the goal of complete measurement of the spatiotemporal complex amplitude of high-power laser pulses. In addition, the measurement device and method also have the advantages of simple structure and high measurement accuracy.

[0069] Example 2:

[0070] This embodiment provides a method for measuring the spatiotemporal complex amplitude of a laser pulse based on a single exposure, implemented using the apparatus described in Embodiment 1. The method includes the following steps:

[0071] A. Device Calibration: Illuminate the center of the aperture of the electro-optic deflector (without applied voltage) using a fine collimated laser beam, and observe the laser exit position at the deflector's output port, ensuring it is centered. Adjust the position of the encoder board so that the laser emitted from the electro-optic deflector is perpendicularly incident on the center of the encoder board. Adjust the position of the area array detector so that the beam is perpendicularly incident on the center of the detector. Apply a DC voltage vertically to the electro-optic deflector, observe the direction of the beam's movement on the detector, and adjust the relative positions of the electro-optic deflector and the photodetector to ensure that the beam moves vertically in the photodetector after the voltage is applied.

[0072] B. Data Acquisition: The laser pulse to be tested is incident perpendicularly onto the center of the electro-optic deflector. When the pulse reaches the incident aperture of the electro-optic deflector, a voltage that varies with time is applied to the electro-optic deflector. At the same time, the photodetector is activated in exposure mode. The exposure time is greater than or equal to the duration of the pulse. The computer saves the intensity image recorded by the photodetector in a single exposure.

[0073] C. Iterative Reconstruction: A continuously distributed laser pulse can be decomposed in time into a series of discrete optical fields with time intervals of Δt. Assume the complex amplitude distribution of the pulse beam at the nth discrete moment is E(x,y,nΔt), and the deflection angle θ after passing through the electro-optic deflector... n After propagating to the front surface of the encoder board, its light field distribution is as follows:

[0074] S(x1,y1,nΔt)=Π{E(x,y,nΔt)exp(ikθ n ),z1} (21)

[0075] Where Π represents the Fresnel propagation operator, z1 is the distance between the electro-optic deflector and the encoder, (x,y) represents the plane coordinates of the pulse beam to be measured, i represents the imaginary unit, k represents the wave number, and (x1,y1) represents the plane coordinates of the encoder.

[0076] After modulation by the encoder, the light field distribution on the photodetector plane is as follows:

[0077] U(x2,y2,nΔt)=Π{S(x1,y1,nΔt)M(x1,y1),z2}, (22)

[0078] Where (x2,y2) represents the plane coordinates of the photodetector, M(x1,y1) represents the transmittance function of the encoder plate, and z2 represents the distance between the encoder plate and the photodetector.

[0079] Since the detector's exposure time is longer than the duration of the laser pulse, the intensity image acquired by the detector is equal to the sum of the light field intensities at all moments when the light reaches the detector plane, that is:

[0080]

[0081] Due to limitations in detector chip size, the deflection angle of the streak camera on the light field cannot be too large. Therefore, in the image acquired by the detector in a single exposure, the intensity of the diffracted light field at different times partially overlaps. The intensity of the overlapping portion recorded by the detector is equal to the incoherent superposition of the overlapping portions of the light field at each time moment. During the reconstruction process, this project uses a multimodal reconstruction algorithm to separate the complex amplitude distribution of the light field corresponding to each time moment. The reconstruction algorithm of this invention is as follows:

[0082] Step 1: Randomly guess the complex amplitude distribution of the pulse at n different times as E g (x,y,nΔt), the guessed pulse distribution is propagated to the detector plane through equations (1)–(2) to obtain the complex amplitude distribution U of the corresponding diffracted light field. g (x2,y2,nΔt);

[0083] Step 2: Update the complex amplitude distribution of the diffracted light field at each time step using the following formula:

[0084]

[0085] Where i represents the imaginary unit.

[0086] Step 3: Update the light field U g The transmitted light field distribution p of (x2, y2, nΔt) propagates backward to the plane of the encoding plate, yielding the transmitted light field distribution p of that plane. g '(x1,y1,nΔt), update the light field distribution on the front surface of the encoder board:

[0087]

[0088] Where p g (x1, y1, nΔt) represents the light field distribution propagating forward to the rear surface of the encoder plate, M represents the transmittance function of the encoder plate, and p g S'(x1,y1,nΔt) represents the updated optical field distribution on the front surface of the encoder board. S'(x1,y1,nΔt) is backpropagated to the plane under test and exp(ikθ) is removed. n The improved complex amplitude E of the laser pulse was obtained. g (x,y,nΔt).

[0089] Repeat steps 1–3 until E g (x,y,nΔt) converges.

[0090] This embodiment of the laser pulse spatiotemporal complex amplitude measurement method based on single exposure modulates the laser pulse temporally using an electro-optic deflector, spatially modulates the pulse using an encoder, and reconstructs the spatiotemporal complex amplitude distribution of the pulse using a multimodal phase retrieval algorithm. This solves the shortcomings of existing technologies that cannot simultaneously measure the temporal and spatial, amplitude and phase distributions of high-power laser pulses, achieving the goal of complete measurement of the spatiotemporal complex amplitude of high-power laser pulses. At the same time, the measurement device and method also have the advantages of simple structure and high measurement accuracy.

[0091] Example 3:

[0092] This embodiment provides a laser pulse spatiotemporal complex amplitude measurement device based on a single exposure. Based on Embodiment 1, the encoding board used in this embodiment is an amplitude-type encoding board.

[0093] Amplitude-type encoder board, such as Figure 2 As shown, the entire encoding board is divided into N×N square sub-regions of equal size. The side length of the sub-region can be any value within [0-100um]. The intensity transmittance corresponding to each region is randomly selected as 0 or 1, where 0 represents that light cannot pass through the region at all, and 1 represents that light can pass through the region at all.

[0094] Example 4:

[0095] This embodiment provides a laser pulse spatiotemporal complex amplitude measurement device based on a single exposure. Based on Embodiment 1, this embodiment uses a phase-type encoding board.

[0096] The binary phase type encoder board uses, for example, Figure 3 The structure shown divides the entire encoding board into N×N equally sized square sub-regions. The side length of each sub-region can be any value within the range of [0-100um]. The intensity transmittance of each sub-region is 1, and the phase value of each sub-region is randomly selected as 0 or pi. The continuous phase encoding board is made of frosted glass or a holographic scattering sheet with high transmittance.

[0097] Example 5:

[0098] This embodiment provides a laser pulse spatiotemporal complex amplitude measurement device based on a single exposure. Building upon Embodiment 1, this embodiment uses a spatial light modulator type encoder board 5. A schematic diagram of the measurement optical path is shown below. Figure 4 As shown, a spatial light modulator is used as the encoding board of the measurement device.

[0099] Example 6:

[0100] This embodiment provides a laser pulse spatiotemporal complex amplitude measurement device based on a single exposure. Building upon Embodiment 1, this embodiment uses a cascaded encoder board 6. A schematic diagram of the measurement device is shown below. Figure 5 As shown, the cascaded encoder 6 is constructed by stacking multiple encoders together closely along the direction of light propagation or by staggering them slightly.

[0101] Some steps in the embodiments of the present invention can be implemented using software, and the corresponding software program can be stored in a readable storage medium, such as an optical disc or a hard disk.

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A laser pulse spatiotemporal complex amplitude measurement device based on a single exposure, characterized in that, The device includes: an electro-optic deflector, an encoding plate, and a photodetector arranged sequentially along the propagation direction of the laser to be tested, wherein the photodetector and the electro-optic deflector are respectively connected to a computer; The electro-optic deflector is used to modulate the time signal of the light field, causing the light field of the laser pulse under test to deflect at different angles at different times; the encoding board is used to modulate the spatial distribution of the light field; the photodetector is used to record the intensity image of the two-dimensional light field; the electro-optic deflector, encoding board and photodetector are controlled by the computer, and the computer uses an iterative phase reconstruction method to recover the complex amplitude distribution of the laser pulse from the light field intensity image acquired by the photodetector.

2. The laser pulse spatiotemporal complex amplitude measurement device based on a single exposure according to claim 1, characterized in that, The iterative phase reconstruction method includes: Step 1: Randomly guess the complex amplitude distribution of the laser pulse to be tested at the nth discrete time as E g (x,y,nΔt), the guessed pulse distribution is propagated to the detector plane through equations (1) and (2) to obtain the complex amplitude distribution U of the corresponding diffracted light field. g (x2,y2,nΔt); S(x1,y1,nΔt)=Π{E g (x,y,nΔt)exp(ikθ n ),z1} (1) Where (x, y) represents the beam plane coordinates of the laser pulse to be measured, (x1, y1) represents the plane coordinates of the encoder plate, Π represents the Fresnel propagation operator, z1 is the distance between the electro-optic deflector and the encoder plate, and θ n The deflection angle of the laser pulse under test after passing through the electro-optic deflector, where k represents the wave number and i represents the imaginary unit; After modulation by the encoding plate, the light field distribution of the photodetector plane is as follows: U g (x2,y2,nΔt)=Π{S(x1,y1,nΔt)M(x1,y1),z2}, (2) Where (x2,y2) represents the planar coordinates of the photodetector, M(x1,y1) is the transmittance function of the encoding plate, and z2 is the distance between the encoding plate and the photodetector; Since the exposure time of the photodetector is greater than the duration of the laser pulse, the intensity image acquired by the photodetector is equal to the sum of the light field intensities at all moments when the light reaches the detector plane, that is: Step 2: Update the complex amplitude distribution of the diffracted light field at each time step using the following formula: Step 3: Update the light field U g The light propagates backwards from (x2, y2, nΔt) to the plane of the encoding plate, resulting in the transmitted light field distribution p of that plane. g '(x1,y1,nΔt), update the light field distribution on the front surface of the encoder board: Where p g (x1, y1, nΔt) represents the light field distribution propagating forward to the rear surface of the encoder plate, and M represents the transmittance function of the encoder plate. S'(x1, y1, nΔt) is back-propagated to the plane under test, and exp(ikθ) is removed. n The improved complex amplitude E of the laser pulse was obtained. g (x,y,nΔt); Step 4: Repeat steps 1-3 until E g (x,y,nΔt) converges.

3. The laser pulse spatiotemporal complex amplitude measurement device based on a single exposure according to claim 1, characterized in that, The encoding board is an amplitude-type encoding board.

4. The laser pulse spatiotemporal complex amplitude measurement device based on a single exposure according to claim 1, characterized in that, The encoder board is a phase-type encoder board.

5. The laser pulse spatiotemporal complex amplitude measurement device based on a single exposure according to claim 1, characterized in that, The encoding board is a spatial light modulator type encoding board.

6. The laser pulse spatiotemporal complex amplitude measurement device based on a single exposure according to claim 1, characterized in that, The encoding board is a cascaded encoding board.

7. The laser pulse spatiotemporal complex amplitude measurement device based on a single exposure according to claim 1, characterized in that, The photodetector is a planar array photodetector.

8. A method for measuring the spatiotemporal complex amplitude of a laser pulse based on a single exposure, characterized in that, The method is implemented based on the laser pulse spatiotemporal complex amplitude measurement device according to any one of claims 1-7, and includes: Step 1: Device calibration; Illuminate the center of the aperture of the electro-optic deflector without applied voltage using a fine collimated laser beam, observe the laser exit position of the electro-optic deflector, and ensure that it is in the center of the exit port; adjust the position of the encoder board so that the laser emitted from the electro-optic deflector is perpendicularly incident on the center of the encoder board; adjust the position of the photodetector so that the beam is perpendicularly incident on the center of the photodetector. Apply a DC voltage in the vertical direction of the electro-optic deflector, observe the direction of the beam's movement on the photodetector, and adjust the relative positions of the electro-optic deflector and the photodetector to ensure that the beam moves in the vertical direction of the photodetector after the voltage is applied. Step Two: Data Collection; The laser pulse to be tested is perpendicularly incident on the center position of the electro-optic deflector. When the laser pulse to be tested reaches the incident aperture position of the electro-optic deflector, a voltage that varies with time is applied to the electro-optic deflector. At the same time, the photodetector turns on the exposure mode. The exposure time is greater than or equal to the duration of the pulse. The computer saves the intensity image recorded by the photodetector in a single exposure. Step 3: Iterative Reconstruction; A continuously distributed laser pulse is decomposed in time into a series of discrete optical fields with time intervals Δt. Assuming the complex amplitude distribution of the laser pulse under test at the nth discrete moment is E(x,y,nΔt), and the deflection angle θ after passing through the electro-optic deflector... n After propagating to the front surface of the encoder board, its light field distribution is as follows: S(x1,y1,nΔt)=Π{E(x,y,nΔt)exp(ikθ n ),z1} (6) Where (x,y) represents the plane coordinates of the pulse beam to be measured, (x1,y1) represents the plane coordinates of the encoder, i represents the imaginary unit, k represents the wave number, Π represents the Fresnel propagation operator, and z1 is the distance between the electro-optic deflector and the encoder. After modulation by the encoding plate, the light field distribution of the photodetector plane is as follows: U(x2,y2,nΔt)=Π{S(x1,y1,nΔt)M(x1,y1),z2}, (7) Where (x2,y2) represents the planar coordinates of the photodetector, M(x1,y1) is the transmittance function of the encoding plate, and z2 is the distance between the encoding plate and the photodetector; The intensity image acquired by the photodetector is equal to the sum of the light field intensities at all moments when the light reaches the detector plane, that is: The intensity of the overlapping portion recorded by the photodetector is equal to the incoherent superposition of the overlapping portions of the light field at each moment. During the reconstruction process, a multi-mode reconstruction method is used to separate the complex amplitude distribution of the light field at each moment.

9. The method for measuring the spatiotemporal complex amplitude of a laser pulse based on a single exposure according to claim 8, characterized in that, The multimodal reconstruction method includes: Step 1: Randomly guess the complex amplitude distribution of the laser pulse to be tested at the nth discrete time as E g (x,y,nΔt), the guessed pulse distribution is propagated to the detector plane through equations (1) and (2) to obtain the complex amplitude distribution U of the corresponding diffracted light field. g (x2,y2,nΔt); Step 2: Update the complex amplitude distribution of the diffracted light field at each time step using the following formula: Step 3: Update the light field U g The light propagates backwards from (x2, y2, nΔt) to the plane of the encoding plate, resulting in the transmitted light field distribution p of that plane. g '(x1,y1,nΔt), update the light field distribution on the front surface of the encoder board: Where p g (x1, y1, nΔt) represents the light field distribution propagating forward to the rear surface of the encoder plate, and M represents the transmittance function of the encoder plate. S'(x1, y1, nΔt) is back-propagated to the plane under test, and exp(ikθ) is removed. n The improved complex amplitude E of the laser pulse was obtained. g (x,y,nΔt); Step 4: Repeat steps 1-3 until E g (x,y,nΔt) converges.

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