Single-shot imaging device and method based on grating coding and optical Kerr gate gating

Abstract

The invention provides a single-shot imaging device and method based on grating coding and optical Kerr gate gating, and the device comprises to-be-measured signal light, an optical beam splitter, a time delay adjustment module, a grating coding module, an optical beam combiner, an optical Kerr gate and an imaging module which are sequentially arranged in the laser transmission direction. The frequency domain identification and analysis module is connected with the imaging module; splitting the to-be-measured signal light passing through the optical beam splitter into a plurality of sub-beams; respectively setting time delay for each sub-beam by using a time delay adjusting module; performing modulation coding on each sub-beam by using a grating coding module; performing gating of different time slices on each sub-beam through an optical Kerr gate; recording the gated composite light field information on an imaging module; the composite light field information is processed through the frequency domain recognition and analysis module, light field information of different time slices is recovered, the system is suitable for research of non-repetitive and difficult-to-reproduce ultrafast phenomena, the imaging efficiency is greatly improved, and the ultrafast time resolution capability is achieved.

Description

Technical Field

[0001] The invention relates to the field of laser technology and devices, and in particular to a single-shot imaging device and method based on grating coding and optical Kerrgate gating. Background Art

[0002] Nanosecond shaped lasers play an irreplaceable role in many fields such as physics, chemistry and materials science. By precisely adjusting the shape of laser pulses, researchers can control the interaction with matter, promote in-depth exploration of material properties, and discover new physical phenomena under extreme conditions. However, the performance of these laser systems is severely hindered by nonlinear effects, especially small-scale self-focusing effects, which degrade beam quality and can cause catastrophic damage to optical components, thereby limiting the output power of laser systems.

[0003] The small-scale self-focusing effect exhibits temporal characteristics, and its evolution is a function of the time-dependent light field I(x,y,t). However, current measurement techniques fail to capture its three-dimensional spatiotemporal distribution. Current conventional parameter measurement techniques include the near-field F(x,y) of the time-domain integration of the laser pulse and the pulse waveform P(t) of the spatial domain integration. These two measurement techniques are not combined to describe the three-dimensional spatiotemporal information of the light beam. The spatiotemporal coupling distortion localized in the transverse (x,y) and longitudinal (t) directions of the light field I(x,y,t) will be submerged in the time integration of the near-field camera or the spatial integration of the power sensor.

[0004] In order to characterize the three-dimensional spatiotemporal distribution and dynamic evolution of the nanosecond shaped light field, the required ultrafast light field measurement technology should have a time resolution better than picoseconds, and should have high spatial resolution, wide spectral response and single-shot measurement capabilities. The local temporal shape of the shaped laser changes faster than 50ps. At this time scale, the polarization in the solid medium is mainly caused by two mechanisms: nuclear motion with a response time of picoseconds and electrostriction with a response time of nanoseconds. The spatiotemporal evolution behavior of the light field mainly depends on the polarization of the medium and the time domain change. Therefore, the time resolution of the ultrafast light field measurement technology should be in the picosecond level. Considering that harmonic conversion occurs during laser transmission and amplification, converting the fundamental frequency light into tripled frequency light, the ultrafast measurement technology should also have a wide spectral response capability. In addition, since each laser emission in the laser system is an independent random event, a single exposure measurement technology is required to capture the entire dynamic evolution process.

[0005] Based on the above analysis, there is an urgent need to develop single-shot ultrafast light field measurement technology to obtain the spatiotemporal evolution structure of the nanosecond shaped light field, providing new means and theoretical basis for suppressing small-scale self-focusing effects and improving the comprehensive performance of laser systems.

[0006] In the existing single-shot ultrafast light field imaging measurement technology, ultrashort pulse trains are usually used as probe primitives, actively encoded in dimensions such as space, angle, wavelength, polarization or spatial frequency, and then the transient event measurement is completed. This type of measurement method using ultrashort pulse trains as illumination probes detects transient events (such as laser-induced plasma), and it is difficult to measure the light field itself; another type of single-shot ultrafast light field imaging measurement technology does not require active illumination, and ultrafast time resolution is achieved by ultrafast photodetectors. Although it can measure the light field, it is difficult to take into account the measurement requirements of wide spectral range and high temporal and spatial resolution. Ultrafast light field detectors mainly include framing cameras based on fast electronics principles, in-situ storage electronic shutter cameras, and high-speed sampling cameras. Among them, the microchannel plate traveling wave gating framing camera is relatively mature. Its basic principle is to control the gating of extremely narrow pulse width electric pulses and amplify images at different times. The ultra-high-speed MCP framing camera currently developed can achieve a minimum gate width of 200ps. However, due to the problem of spectral response of photocathode in the infrared band, MCP framing cameras are difficult to cover the wide spectrum measurement requirements from ultraviolet to infrared.

[0007] Therefore, the prior art needs to be further developed. Summary of the invention

[0008] The purpose of the present invention is to overcome the above-mentioned technical deficiencies and provide a single-shot imaging device and method based on grating encoding and optical Kerrgate gating to solve the problems existing in the prior art and realize single-shot sub-high temporal and spatial resolution imaging measurement of nanosecond shaped laser pulses.

[0009] To achieve the above technical objectives, according to a first aspect of the present invention, the present invention provides a single-shot imaging device based on grating encoding and optical Kerrgate gating, comprising:

[0010] The signal light to be measured, the optical beam splitter, the time delay adjustment module, the grating encoding module, the optical beam combiner, the optical Kerr gate, the imaging module and the frequency domain identification and analysis module which are communicatively connected to the imaging module are arranged in sequence along the laser transmission direction.

[0011] Specifically, the optical beam splitter is used to split the signal light to be measured into multiple sub-beams;

[0012] The grating encoding module includes a plurality of gratings arranged in different spatial orientations, and the gratings are used to modulate and encode each sub-beam;

[0013] The optical beam combiner is used to combine the modulated and coded sub-beams.

[0014] Specifically, the time delay adjustment module includes at least any one of the following:

[0015] A combination of an electric displacement platform and a reflector group, and an adjustable optical path element;

[0016] The time delay adjustment module is used to set different time delays for each sub-beam.

[0017] Specifically, the optical Kerr gate includes a Kerr medium and two polarizers whose polarization directions are perpendicular to each other. The optical Kerr gate is used to perform gating on each sub-beam at different time slices.

[0018] Specifically, the Kerr medium is located between two polarizers whose polarization directions are perpendicular to each other.

[0019] Specifically, the imaging module is used to record the composite light field information after the optical Kerrgate gating;

[0020] The frequency domain identification and analysis module is used to perform frequency domain identification and analysis on the composite light field information recorded by the imaging module to restore the light field information of different time slices.

[0021] Specifically, the device further includes a transient event device to be detected, and the transient event device to be detected is arranged on the optical path of laser transmission.

[0022] According to a second aspect of the present invention, there is provided a single-shot imaging method based on grating coding and optical Kerrgate gating, comprising:

[0023] S100, splitting the signal light to be measured through the optical beam splitter into a plurality of sub-beams;

[0024] S200, using a time delay adjustment module to set different time delays for each beamlet;

[0025] S300, modulating and encoding each sub-beam using gratings at different spatial orientations in a grating encoding module to form coded sub-beams;

[0026] S400, combining the encoded sub-beams through an optical beam combiner to form a first combined beam;

[0027] S500, passing the first combined beam through an optical Kerr gate, and gating each sub-beam at different time slices;

[0028] S600, overlapping and imaging the gated composite light field information on an imaging module;

[0029] S700 , processing the composite light field information recorded by the imaging module through the frequency domain recognition and analysis module to restore the light field information of different time slices.

[0030] Specifically, the composite light field information recorded by the imaging module is processed by the frequency domain recognition and analysis module to restore the light field information of different time slices, including:

[0031] The overlapping composite light field information in the spatial domain is analyzed and reconstructed into light field information of different time slices through frequency domain calculation.

[0032] Specifically, the frequency domain calculation includes:

[0033] Fourier transform, spatial frequency shift, low-pass filtering, inverse Fourier transform.

[0034] Beneficial effects:

[0035] 1. The present invention provides a single-shot optical imaging method based on grating encoding and optical Kerrgate gating. The frequency domain recognition and analysis module can capture multiple spatiotemporal resolved images of the entire light field evolution in a single exposure, and restore the light field information of different time slices. It is suitable for the study of non-repetitive and difficult-to-reproduce ultrafast phenomena, greatly improves the imaging efficiency, and realizes the ability of ultrafast time resolution.

[0036] 2. The use of grating coded multiplexing further increases the number of image frames, and ultrafast optical Kerrgate gating can achieve ultrafast time-resolved measurement. Based on the imaging principle of the single-shot imaging device in the present invention, a wide spectral response can be achieved, which is not limited to a specific wavelength range and is suitable for a variety of spectral measurement needs, providing a powerful tool for laser performance optimization and ultrafast phenomenon research.

[0037] 3. The single-shot imaging device of the present invention is simple in composition and does not require precise optical and mechanical instruments, which greatly reduces the cost and improves the usability and reliability of the present invention to a great extent.

[0038] 4. Based on the single-shot imaging device provided by the present invention, a transient event device to be measured is set on the laser transmission optical path, and a uniform illumination light source is used to measure the transient event, which can achieve ultra-fast time-resolved imaging of the transient event. Therefore, this device can not only image the light field itself, but also characterize transient events in research fields such as physical chemistry. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the overall structure of a single-shot imaging device based on grating encoding and optical Kerrgate gating provided in a specific embodiment of the present invention;

[0040] Figure 2 It is a schematic diagram of the optical path structure of a single-shot imaging device based on grating encoding and optical Kerrgate gating provided in a specific embodiment of the present invention;

[0041] Figure 3 The specific implementation mode of the present invention provides the use of CS 2 Schematic diagram of the time resolution of the system when used as an optical Kerr medium 22;

[0042] Figure 4is an original image captured by a camera provided in a specific embodiment of the present invention;

[0043] Figure 5 is the spatial frequency domain image corresponding to the original image provided in the specific implementation mode of the present invention

[0044] Figure 6 is a spatial frequency domain frequency shift diagram of an original image at a first moment provided in a specific embodiment of the present invention;

[0045] Figure 7 is a restored image corresponding to the spatial frequency domain frequency shift image at the first moment provided in a specific embodiment of the present invention;

[0046] Figure 8 is a spatial frequency domain frequency shift diagram of the original image at the second moment provided in a specific embodiment of the present invention;

[0047] Fig. 9 is a restored image corresponding to the spatial frequency domain frequency shift image at the second moment provided in a specific embodiment of the present invention;

[0048] Fig.10 is a spatial frequency domain frequency shift diagram of the original image at the third moment provided in a specific embodiment of the present invention;

[0049] Fig.11 is a restored image corresponding to the spatial frequency domain frequency shift image at the third moment provided in a specific embodiment of the present invention;

[0050] Fig.12 It is a schematic diagram of a time-resolved light beam far-field experimental result obtained by a single shot provided in a specific embodiment of the present invention;

[0051] Fig.13 It is a flow chart of a single-shot imaging method based on grating encoding and optical Kerrgate gating provided in a specific embodiment of the present invention.

[0052] Wherein, the reference numerals of the above-mentioned drawings are as follows:

[0053] 1. Signal light to be measured; 2. Optical beam splitter; 3. Time delay adjustment module; 4. Grating encoding module; 5. Optical beam combiner; 6. Optical Kerr gate; 7. Imaging module; 8. Transient event device to be measured; 9. Pump beam splitter; 10. First beam splitter; 11. First signal light beam combiner; 12. Second beam splitter; 16. 1 / 2 wave plate; 19. First polarizer; 20. Focusing lens; 21. Second polarizer; 22. Kerr medium; 23. Pump light time delay adjustment module; 25. Fourth reflector; 29. ​​Far-field imaging lens; 30. Imaging beam combiner; 31. Camera; 301. First time delay adjustment module; 302. Second time delay adjustment module; 401. First grating encoding module; 402. Second grating encoding module; 303. Third time delay adjustment module; 403. Third grating encoding module. DETAILED DESCRIPTION

[0054] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings of the present invention. Based on the embodiments in this application, other similar embodiments obtained by ordinary technicians in this field without making creative work should belong to the scope of protection of this application. All features disclosed in this specification, or all steps in the disclosed methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

[0055] Any feature disclosed in this specification, unless otherwise stated, may be replaced by other alternative features that are equivalent or have similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features. In addition, the directional terms mentioned in the following embodiments, such as "up", "down", "left", "right", etc., are only referenced to the directions of the accompanying drawings. Therefore, the directional terms used are used to illustrate rather than limit the invention.

[0056] The present invention will be further described below in conjunction with the accompanying drawings and preferred embodiments.

[0057] Embodiment 1

[0058] See also Figure 1 This embodiment provides a single-shot imaging device based on grating encoding and optical Kellgate gating, comprising:

[0059] The signal light to be measured 1, the optical beam splitter 2, the time delay adjustment module 3, the grating encoding module 4, the optical beam combiner 5, the optical Kerr gate 6, the imaging module 7 and the frequency domain identification and analysis module connected to the imaging module 7 in communication are arranged in sequence along the laser transmission direction.

[0060] It can be understood that the working process of the single-shot imaging device in this embodiment includes: splitting the signal light 1 to be measured through the optical beam splitter 2, and using the time delay adjustment module 3 to set different time delays for each sub-beam; then, each sub-beam is modulated and encoded by the grating in different spatial orientations in the grating encoding module 4, and the encoded sub-beams are combined by the optical beam combiner 5 and incident on the optical Kerr gate 6 to achieve the gating of different time slices of different sub-beams; finally, the composite light field information after gating is recorded by the imaging module 7, and the light field information at different times is restored by the frequency domain recognition and analysis module.

[0061] See also Figure 1 The optical beam splitter 2 may include a plurality of beam splitters with different branches, such as Figure 1 201, 202, ... 20n (n is a natural number), the time delay adjustment module 3 may include a plurality of time delay adjustment modules arranged on the branches, such as Figure 1 301, 302, ... 30n in the figure, the raster encoding module 4 may include a plurality of raster encoding modules arranged on the branches, such as Figure 1 401, 402, …40n.

[0062] Specifically, the optical beam splitter 2 is used to split the signal light 1 to be measured into multiple sub-beams;

[0063] In a specific embodiment, the optical beam splitter 2 is composed of a series of splitters with different splitting ratios, which are used to split the signal light 1 to be measured into multiple sub-beams. Preferably, the splitting ratio of the splitter is adjusted to make the energy of each sub-beam as equal as possible, so that the response of each component in the imaging device to each sub-beam can be more uniform and accurate, thereby improving the accuracy of the entire imaging device in measuring the signal light.

[0064] See also Figure 2 The optical beam splitter 2 may include a pump beam splitter 9, a first beam splitter 10, and a second beam splitter 12. The pump beam splitter 9 splits the signal light 1 to be measured into a pump light and a signal light. The first beam splitter 10 and the second beam splitter 12 are used to distribute the signal light 1 to be measured to three signal light branches respectively.

[0065] The grating encoding module 4 includes a plurality of gratings arranged in different spatial orientations, and the gratings are used to modulate and encode each sub-beam;

[0066] See also Figure 2 The grating encoding module 4 may include a first grating encoding module 401, a second grating encoding module 402, and a third grating encoding module 403. The first grating encoding module 401, the second grating encoding module 402, and the third grating encoding module 403 are respectively arranged in the first signal optical branch, the second signal optical branch, and the third signal optical branch, and are used to modulate and encode the sub-beams on each signal optical branch respectively.

[0067] Preferably, a Ronchi grating or a sinusoidal amplitude grating can be selected to modulate and encode each sub-beam, and each sub-beam has a different spatial orientation. The Ronchi grating structure is relatively simple, usually composed of equally spaced transparent and opaque stripes. This simple structure makes it easier to achieve high-precision processing during the manufacturing process and can effectively modulate light in space; the sinusoidal amplitude grating has special optical properties, and its modulation of light is based on the amplitude change in the form of a sinusoidal function. This modulation method has unique advantages in certain optical systems. Therefore, the present invention can select a Ronchi grating or a sinusoidal amplitude grating to modulate and encode each sub-beam.

[0068] The optical beam combiner 5 is used to combine the modulated and coded sub-beams.

[0069] In a specific embodiment, the optical combiner 5 is generally composed of a multi-stage combiner.

[0070] See also Figure 2 The optical combiner 5 may include a first signal light combiner 11 and an imaging combiner 30. The first signal light combiner 11 is used to combine the sub-beams of the first signal light branch and the second signal light branch after optical delay and grating encoding into a beam of light. The imaging combiner 30 is used to integrate the optical signals in the optical path so that the signal light meets the imaging requirements.

[0071] Specifically, the time delay adjustment module 3 includes at least any one of the following:

[0072] A combination of an electric displacement platform and a reflector group, and an adjustable optical path element;

[0073] The time delay adjustment module 3 is used to set different time delays for each sub-beam.

[0074] In a specific implementation scheme, the time delay adjustment module 3 is used to set different time delays for each sub-beam, and is generally composed of a reflector group and an electric displacement platform, and can also be composed of an adjustable optical path element, for accurately adjusting the time delay of each sub-beam.

[0075] See also Figure 2 The time delay adjustment module 3 may include a first time delay adjustment module 301, a second time delay adjustment module 302, and a third time delay adjustment module 303. The first time delay adjustment module 301, the second time delay adjustment module 302, and the third time delay adjustment module 303 are respectively arranged on the first signal light branch, the second signal light branch, and the third signal light branch, and are used to set different time delays for the sub-beams on the three branches. The time delay adjustment module 3 may also include a pump light time delay adjustment module 23, which is used to set different time delays for the pump photon beams.

[0076] Specifically, the optical Kerr gate 6 includes a Kerr medium 22 and two polarizers whose polarization directions are perpendicular to each other. The optical Kerr gate 6 is used to perform gating on each sub-beam at different time slices.

[0077] Specifically, the Kerr medium 22 is located between two polarizers whose polarization directions are perpendicular to each other.

[0078] It should be further explained that when a linearly polarized strong laser acts on the isotropic Kerr medium 22, it will induce the anisotropy of the refractive index of the medium, that is, produce the Kerr birefringence effect, so that another signal light will produce a phase difference in two directions parallel and perpendicular to the excitation light field when passing through the medium. This effect is the Kerr effect.

[0079] See also Figure 2 , the Kerr medium 22 is placed between two polarizers with perpendicular polarization directions. When there is no pump light, the signal light cannot reach the detector; when a beam of pump light with a polarization direction that forms a certain angle with the first polarizer 19 acts on the medium, linear birefringence is induced, and the polarization state of the signal light passing through the pump light area is changed. A part of the signal light is detected through the second polarizer 21. The Kerr medium 22 and the two polarizers with perpendicular polarization directions constitute an optical Kerr gate 6. Under the control of the pump light, different sub-beams with different time slices are selected. The optical Kerr gate 6 tries to use a Kerr medium 22 with a high nonlinear refractive index, a fast medium polarization response speed, and a good transmission surface, such as CS 2 , to achieve ultrafast time resolution.

[0080] Specifically, the imaging module 7 is used to record the composite light field information after the optical Kerr gate 6 is gated;

[0081] The frequency domain identification and analysis module is used to perform frequency domain identification and analysis on the composite light field information recorded by the imaging module 7 to restore the light field information of different time slices.

[0082] Specifically, the device further comprises a transient event device 8 to be detected, and the transient event device 8 to be detected is arranged on the optical path of laser transmission.

[0083] See also Figure 2 , the transient event device 8 to be measured is placed in front of the optical beam splitter 2, specifically between the pump beam splitter 9 and the first beam splitter 10, and a uniform illumination light source is used to illuminate the transient event device 8 to achieve ultrafast time-resolved imaging of transient events. Therefore, the present invention can not only image the light field itself, but also characterize transient events in research fields such as physical chemistry, and is suitable for the study of non-repetitive and difficult-to-reproduce ultrafast phenomena, further expanding the application scenarios of the present invention.

[0084] See also Figure 2-Figure 5, the specific parameter design and selection scheme of the single-shot imaging device based on grating encoding and optical Kerrgate gating proposed in this embodiment, as well as the working mechanism of the device are described in detail below through a specific example:

[0085] See also Figure 2 The overall design of the device includes: the signal light 1 to be measured is divided into three sub-beams by a series of optical beam splitters 2, and then, an electric displacement platform and two reflectors are used as time delay adjustment modules to set time delays of 0ps, 0.4ps and 0.8ps for the three sub-beams respectively; then, the three sub-beams are modulated and encoded by gratings with spatial orientations of 0° and ±8.3° to form encoded sub-beams; the encoded sub-beams are combined by an optical beam combiner 5 and incident on the CS 2 On the optical Kerr gate 6 composed of the medium, under the control of the pump light, the optical Kerr gate 6 selects different time slices of different sub-beams; finally, the selected light field information is imaged on the camera 31 (imaging module), and the light field images at three different times are restored through the frequency domain recognition and analysis module.

[0086] The specific steps are described in detail below:

[0087] See also Figure 2 , an ultrashort pulse laser with a central wavelength of 1030nm, a pulse width of 1ps, and a diameter of 3mm is used as the signal light 1 to be measured. At the same time, the ultrashort pulse laser is also used as pump light, which is obtained by beam splitting by a pump beam splitter 9. The beam splitting ratio of the pump beam splitter 9 is 30:70, that is, 70% of the laser energy is used as pump light, and 30% of the laser energy is used as signal light;

[0088] See also Figure 2 The signal light 1 to be measured is divided into two branches by the first beam splitter 10, and the splitting ratio of the first beam splitter 10 is 80:20, that is, 80% of the laser energy is distributed to the first signal light branch and the second signal light branch, and 80% of the laser energy is divided into the first signal light and the second signal light by the second beam splitter 12 and distributed to the first signal light branch and the second signal light branch respectively, and the splitting ratio of the second beam splitter 12 is 50:50. The first signal light branch and the second signal light branch are optically delayed by the first time delay adjustment module 301 and the second time delay adjustment module 302 respectively, and then modulated and encoded by the first grating encoding module 401 and the second grating encoding module 402 respectively. In addition, the third signal light branch is incident on the third time delay adjustment module 303 after being deflected by the fourth reflector 25 for optical delay, and grating encoded by the third grating encoding module 403. The above-mentioned time delay adjustment module 3 is composed of an electric translation stage and two 90° reflectors.

[0089] It should be noted that the grating encoding module uses 10l p / mm Ronchi grating encoding, the focal length of the focusing lens 20 is 150mm, and the separation distance between the 0th order diffraction and the 1st order diffraction in the far-field spectrum space is 1.55mm. In order to achieve 3-framing, the focal spots between different sub-beams do not overlap, the offset angle of the grating in the direction of the beam cross section (vertical incident direction of light) is 8.3°, and the spatial orientations of the three gratings are 0 and ±8.3° respectively. Since the commercial grating specifications are square (1 inch * 1 inch), in order to achieve precise adjustment of the grating spatial orientation, a custom square-circular adapter fixture is processed. Here, a 2-inch circular wave plate frame is used to embed a 1-inch square grating, which is fixed by a fixture in the middle.

[0090] See also Figure 2 , the first signal light branch and the first signal light branch are coaxially combined into a beam of light by the first signal light combiner 11 after optical delay and grating encoding. Then, the third signal light branch is coaxially combined by the optical combiner 5. At this time, all the encoded sub-beams are combined into one beam; the timing of the pump light branch is precisely adjusted by a series of reflectors and a pump light time delay adjustment module 23 to achieve a strict correlation with the timing of the signal light. There is a time delay difference between each sub-beam of the signal light. By adjusting the electric translation stage, the time delay relative to the pump light is set to 0ps, 0.4ps and 0.8ps.

[0091] See also Figure 2 Under the control of the pump light, the optical Kerr gate 6 selects different time slices of different sub-beams. The optical Kerr gate 6 is composed of two polarizers (the first polarizer 19 and the second polarizer 21) with perpendicular polarization directions and a Kerr medium 22 in the middle. The Kerr medium is selected from CS with a high nonlinear refractive index coefficient. 2 , whose nonlinear refractive index is 290e-7cm 2 / GW, for optical Kerr gate 6, a geometric cross Kerr gate configuration is selected, and the crossing angle between the pump light and the signal light is 10°.

[0092] The optical Kerr gate switch efficiency can be expressed as η(t) = sin 2 (2θ)sin 2 (πLn 2 (t)I pump (t) / λ probe ). η is the switching efficiency, θ is the angle between the polarization direction of the pump light and the transmission direction of the second polarizer 21, and L is the effective action length; λ probe is the wavelength of the detection light, I pump is the pump light intensity, n 2is the nonlinear refractive index of the medium. When θ=45°, the switching efficiency is the highest. The 1 / 2 wave plate 16 is used to control the polarization direction of the pump light. The 1 / 2 wave plate 16 is rotated so that the polarization direction of the pump light is at an angle of 45° relative to the polarization direction of the signal light.

[0093] See also Figure 3 The time response characteristics of the optical Kerr gate are tested by the step-scan method. The test equipment includes an electric displacement platform, an energy calorimeter, a camera, and an oscilloscope. First, the signal light and the pump light are adjusted to coincide with each other, and the time selection signal is observed on the energy calorimeter (camera or oscilloscope). The pump light excitation time is changed by the electric displacement platform, and the response amplitude of the signal light is tested synchronously. The time response curve of the Kerr gate is measured by scanning point by point. Figure 3 To adopt CS 2 As an optical Kerr medium, the temporal resolution of the system is based on CS 2 The time resolution of the Kerr medium is 1.2 ps (half-maximum width) and 3.8 ps (10% bottom width).

[0094] The coded imaging optical path is designed based on the single-lens imaging principle, the object plane is located at the grating, the grating coding module of each sub-beam is at the same distance from the Kerr medium 22, which is 2 times the focal length. A camera 31 is placed at 2 times the focal length behind the Kerr medium 22, which can realize near-field imaging of the light beam of the signal light to be measured in different time segments. Based on the single-lens imaging principle, adaptation to a wide spectrum light source can be achieved, which is not limited to a specific wavelength range and is suitable for a variety of spectral measurement needs, providing a powerful tool for laser performance optimization and ultrafast phenomenon research.

[0095] Figure 4-Figure 11 This is the time-resolved near-field experimental result of a single shot of the present invention, where: Figure 4 is the original image captured by the camera, Figure 5 is the spatial frequency domain image corresponding to the original image, Figure 6 is the spatial frequency domain shift diagram at the first moment, Figure 7 is the restored image corresponding to the spatial frequency domain frequency shift image at the first moment; Figure 8 is the spatial frequency domain frequency shift diagram at the second moment, Fig. 9 is the restored image corresponding to the spatial frequency domain frequency shift map at the second moment; Fig.10 is the spatial frequency domain shift diagram at the third moment, Fig.11 The restored image corresponds to the spatial frequency domain shift map at the third moment. By performing frequency domain operations such as Fourier transform, spatial frequency domain shift, low-pass filtering and inverse Fourier transform in the frequency domain recognition and analysis module, the near-field images at different moments are successfully restored.

[0096] like Fig.12As shown, a single far-field imaging lens 29 is used to image the far-field focal position of each sub-beam, and the far-field of the light field at different times can be obtained. The experimental results show that the device successfully realizes the spatiotemporal resolution measurement of the near-field and far-field information of the laser pulse itself, with a time resolution of 1.2ps (half-maximum width).

[0097] It should be noted here that the present invention realizes single-shot ultrafast optical imaging based on grating encoding and ultrafast optical Kerrgate gating, and can capture multiple spatiotemporally resolved images of the entire light field evolution in a single exposure through frequency domain recognition and analysis. The single-shot imaging device in the present invention is simple in composition and does not need to be equipped with precise optical and mechanical instruments, which greatly reduces the cost and greatly improves the usability and reliability of the present invention. Based on the single-shot ultrafast imaging device provided by the present invention, a transient event device to be measured is set on the laser transmission optical path, and a uniform illumination light source is used to illuminate the transient event device to be measured, so as to realize ultrafast time-resolved imaging of transient events. Therefore, the present invention can not only image the light field itself, but also characterize transient events in research fields such as physical chemistry, and is suitable for the study of non-repetitive and difficult-to-reproduce ultrafast phenomena.

[0098] Embodiment 2

[0099] See also Fig.13 This embodiment provides a single-shot imaging method based on grating encoding and optical Kerrgate gating, the method comprising:

[0100] S100, splitting the signal light 1 to be measured passing through the optical beam splitter 2 into a plurality of sub-beams;

[0101] S200, using the time delay adjustment module 3 to set different time delays for each sub-beam;

[0102] S300, modulating and encoding each sub-beam using gratings at different spatial orientations in the grating encoding module 4 to form coded sub-beams;

[0103] S400, combining the encoded sub-beams through an optical beam combiner 5 to form a first combined beam;

[0104] S500, passing the first combined beam through an optical Kerr gate 6, and gating each sub-beam at different time slices;

[0105] S600, overlapping and imaging the gated composite light field information on the imaging module 7;

[0106] S700 , processing the composite light field information recorded by the imaging module 7 through the frequency domain recognition and analysis module to restore the light field information of different time slices.

[0107] Specifically, the composite light field information recorded by the imaging module 7 is processed by the frequency domain recognition and analysis module to restore the light field information of different time slices, including:

[0108] The overlapping composite light field information in the spatial domain is analyzed and reconstructed into light field information of different time slices through frequency domain calculation.

[0109] Specifically, the frequency domain calculation includes:

[0110] Fourier transform, spatial frequency shift, low-pass filtering, inverse Fourier transform.

[0111] It can be understood that the frequency domain recognition and analysis module mainly includes Fourier transform, spatial frequency shift, low-pass filtering, inverse Fourier transform, etc. Through a series of frequency domain operations, the overlapping composite light field information in the spatial domain is analyzed and reconstructed into separate light field information at different times, such as Figure 4-Figure 11 As shown, Figure 4 is the original composite light field image collected by the camera, Figure 5 is the spatial frequency domain diagram obtained by Fourier transform, Figure 6 , Figure 8 , Fig.10 The frequency domain shift diagrams at three different moments are shown in Figure 1. The light field segments at the corresponding moments are moved to near zero frequency. In the frequency domain analysis, low-pass filtering is used to eliminate the mutual interference between different sub-beams. Since the sub-beams modulated by gratings in different directions have overlapping spectral components in the frequency domain, low-pass filtering can separate the spectrum of a single sub-beam, thereby avoiding mutual interference between the sub-beams. Figure 7 , Fig. 9 , Fig.11 The light field images at three different times are restored by inverse Fourier transform analysis.

[0112] It should be noted here that the present invention splits the signal light to be measured by an optical beam splitter, and uses a time delay adjustment module to set different time delays for each sub-beam; then each sub-beam is modulated and encoded by the grating in different spatial orientations in the grating encoding module, and the encoded sub-beams are combined by the optical combiner and incident on the optical Kerr gate to achieve gating of different time slices of different sub-beams; finally, the composite light field information after gating is recorded by the imaging module, and the light field information at different times is restored by the frequency domain identification and analysis module, which is suitable for the study of non-repetitive and difficult to reproduce ultrafast phenomena, greatly improves the imaging efficiency, and achieves the ability of ultrafast time resolution. The number of image divisions is further increased by grating coding multiplexing, and ultrafast time resolution measurement can be achieved by ultrafast optical Kerr gate gating. Based on the imaging principle of the single-shot imaging device in the present invention, a wide spectral response can be achieved, which is not limited to a specific wavelength range and is suitable for a variety of spectral measurement requirements, providing a powerful tool for laser performance optimization and ultrafast phenomenon research.

[0113] The present invention is not limited to the aforementioned specific implementations, nor is it limited to the aforementioned application scenarios, and can be applied to any filtering scenario, and the present invention is not limited to this. In addition, the present invention extends to any new features or any new combination disclosed in this specification, and any new method or process steps or any new combination disclosed.

[0114] The various technical features described above can be combined arbitrarily. Although all possible combinations of these technical features are not described, any combination of these technical features should be considered to be covered by this specification as long as there is no contradiction in such combination.

[0115] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A single-shot imaging device based on grating encoding and optical Kellgate gating, characterized in that: include: A signal light to be measured (1), an optical beam splitter (2), a time delay adjustment module (3), a grating encoding module (4), an optical beam combiner (5), an optical Kerr gate (6), an imaging module (7), and a frequency domain identification and analysis module communicatively connected to the imaging module (7) are sequentially arranged along a laser transmission direction.

2. The single-shot imaging device based on grating coding and optical Kellgate gating according to claim 1, characterized in that: The optical beam splitter (2) is used to split the signal light to be measured (1) into a plurality of sub-beams; The grating encoding module (4) comprises a plurality of gratings arranged in different spatial orientations, and the gratings are used to modulate and encode each sub-beam; The optical beam combiner (5) is used to combine the modulated and coded sub-beams.

3. The single-shot imaging device based on grating coding and optical Kellgate gating according to claim 2, characterized in that: The time delay adjustment module (3) comprises at least any one of the following: A combination of an electric displacement platform and a reflector group, and an adjustable optical path element; The time delay adjustment module (3) is used to set different time delays for each sub-beam.

4. The single-shot imaging device based on grating coding and optical Kellgate gating according to claim 2, characterized in that: The optical Kerr gate (6) comprises a Kerr medium (22) and two polarizers whose polarization directions are perpendicular to each other. The optical Kerr gate (6) is used to select each sub-beam at different time slices.

5. The single-shot imaging device based on grating coding and optical Kellgate gating according to claim 4, characterized in that: The Kerr medium (22) is located between two polarizers whose polarization directions are perpendicular to each other.

6. The single-shot imaging device based on grating coding and optical Kellgate gating according to claim 5, characterized in that: The imaging module (7) is used to record the composite light field information after the optical Kerr gate (6) is gated; The frequency domain identification and analysis module is used to perform frequency domain identification and analysis on the composite light field information recorded by the imaging module (7) to restore light field information of different time slices.

7. The single-shot imaging device based on grating coding and optical Kellgate gating according to claim 1, characterized in that: The device also includes a transient event device (8) to be detected, and the transient event device (8) to be detected is arranged on the optical path of laser transmission.

8. A single-shot imaging method based on grating encoding and optical Kellgate gating, characterized in that: include: S100, splitting the signal light to be measured (1) passing through the optical beam splitter (2) into a plurality of sub-beams; S200, using the time delay adjustment module (3) to set different time delays for each sub-beam; S300, modulating and encoding each sub-beam using gratings at different spatial orientations in a grating encoding module (4) to form coded sub-beams; S400, combining the encoded sub-beams through an optical beam combiner (5) to form a first combined beam; S500, passing the first combined beam through an optical Kerr gate (6), and gating each sub-beam at different time slices; S600, overlapping and imaging the gated composite light field information on an imaging module (7); S700: Processing the composite light field information recorded by the imaging module (7) through a frequency domain recognition and analysis module to restore light field information of different time slices.

9. The single-shot imaging method based on grating coding and optical Kellgate gating according to claim 8, characterized in that: The composite light field information recorded by the imaging module (7) is processed by the frequency domain recognition and analysis module to restore the light field information of different time slices, including: The overlapping composite light field information in the spatial domain is analyzed and reconstructed into light field information of different time slices through frequency domain calculation.

10. The single-shot imaging method based on grating coding and optical Kellmen gating according to claim 9, characterized in that: The frequency domain calculation includes: Fourier transform, spatial frequency shift, low-pass filtering, inverse Fourier transform.

Images