Ultrafast space-time light field measurement system

Abstract

The utility model discloses an ultrafast space-time light field measuring system, which performs dispersion separation on an interference light field generated after superposition of a laser pulse to be measured and a reference pulse, and performs wavelength screening on the interference light field after dispersion separation by using a wavelength screening element to obtain a laser light field with a target wavelength. Acquiring light field complex amplitude information corresponding to the laser light field of the target wavelength; and reconstructing according to the light field complex amplitude information to obtain a light field corresponding to the laser pulse to be measured. According to the system disclosed by the utility model, the delay between the signal light and the reference light in the measured laser pulse does not need to be regulated and controlled, and the ultrafast space-time light field can be reconstructed only by enabling the same-frequency components to interfere in the same spatial position to obtain the interference pattern of each frequency. The system provided by the utility model has the characteristics of convenience in implementation, interference resistance, low background noise, low data volume, high measurement efficiency and high measurement result accuracy.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of light measurement, especially relates to a kind of ultrafast space-time light field measurement system. BACKGROUND

[0002] Fourier transform pulse control technology realizes the fine control of femtosecond pulse by 4f Fourier transform system, and generates space-time structured light field.

[0003] When measuring ultrafast space-time light field, a measurement means with time resolution is needed to fully characterize the space-time light field. In the prior art, the interference measurement technology based on signal light and reference light delay scanning is usually used to reconstruct the ultrafast space-time light field by accumulating a large amount of delay interference fringe data. However, this method needs to adjust the delay between the signal light and the reference light, so the efficiency is low and the measurement result cannot meet the accuracy requirement.

[0004] Therefore, the prediction system in the prior art needs further improvement. UTILITY MODEL CONTENT

[0005] In view of the deficiencies in the above-mentioned related technology, the purpose of the utility model is to provide an ultrafast space-time light field measurement system to overcome the defects of the prior art that the ultrafast space-time light field measurement system cannot meet the requirement of efficient and accurate reconstruction of the ultrafast space-time light field.

[0006] The technical solution adopted by the utility model to solve the technical problems is as follows:

[0007] In the first aspect, the application provides an ultrafast space-time light field measurement system, which comprises:

[0008] A diffraction element is used to disperse and separate the interference light field generated after the superposition of the to-be-measured laser pulse and the reference pulse.

[0009] A wavelength selection element is arranged on the optical path of the interference light field and is used to select the wavelength of the dispersed and separated interference light field to obtain a laser light field of a target wavelength.

[0010] An imaging element is arranged on the optical path of the laser light field of the target wavelength and is used to obtain the light field complex amplitude information corresponding to the laser light field of the target wavelength, so that the light field reconstruction element reconstructs the light field corresponding to the to-be-measured laser pulse according to the light field complex amplitude information.

[0011] Optionally, a collimating element is further arranged between the diffraction element and the wavelength selection element.

[0012] The collimating element is used to collimate the light of the dispersed and separated interference light field received and output to the wavelength selection element.

[0013] Optionally, the diffraction element is a grating, a metasurface grating, or a liquid crystal grating; the collimation element is a cylindrical lens, a metasurface cylindrical lens, or a liquid crystal cylindrical lens; and the wavelength selection element is a slit, a metasurface slit, or a liquid crystal slit grating.

[0014] Optionally, a first pulse splitting element is arranged on an optical path of the interference light field and the laser light field of the target wavelength.

[0015] After the to-be-measured laser pulse and the reference pulse are superimposed, the first pulse splitting element is passed through, and the interference light field is transmitted into the diffraction element; and after the laser light field of the target wavelength is transmitted out of the wavelength selection element, the laser light field of the target wavelength is incident on the first pulse splitting element, and after the first pulse splitting element is passed through, the laser light field of the target wavelength is transmitted to the imaging element.

[0016] Optionally, the system further comprises a second pulse splitting element and a spectrometer.

[0017] The second pulse splitting element is located between the first pulse splitting element and the imaging element, is used to receive a light beam output by the first pulse splitting element, and divides the light beam into two parts, one part of the light beam is input to the imaging element, and the other part is input to the spectrometer.

[0018] The spectrometer is located on one side of the second pulse splitting element, is used to receive a light beam divided by the second pulse splitting element, and is used to detect a wavelength corresponding to the received light beam.

[0019] Optionally, the system further comprises a reflecting element.

[0020] The reflecting element is located on an optical path of the laser light field of the target wavelength output by the wavelength selection element, is used to reflect light in the received laser light field of the target wavelength, so that the reflected light is sequentially input to the first pulse splitting element through the collimation element and the diffraction element.

[0021] Optionally, the first pulse splitting element is a half-reflective half-transmissive lens.

[0022] Optionally, the imaging element is a color CCD camera, and the light field reconstruction element is a computer.

[0023] Optionally, the reflecting element is a mirror.

[0024] Optionally, the second pulse splitting element is a half-reflective half-transmissive lens.

[0025] Beneficial effects:

[0026] The embodiment discloses a kind of ultrafast space-time light field measurement systems, utilize diffraction element to the interference light field generated after superposition of to-be-measured laser pulse and reference pulse is dispersed, then wavelength screening element is used to the interference light field after dispersion is wavelength screened, the laser light field of target wavelength is obtained, the light field complex amplitude information corresponding to the laser light field of target wavelength is acquired;According to the light field complex amplitude information, the light field corresponding to the to-be-measured laser pulse is reconstructed.The system disclosed in this embodiment, the delay between signal light and reference light in the measured laser pulse is not needed to be regulated and controlled, only need to make the same frequency component interfere in the same spatial position, the interference pattern of each frequency is obtained, and ultrafast space-time light field can be reconstructed.The system provided in the application has the characteristics of convenient implementation, anti-interference, low background noise, low data volume, high measurement efficiency and high measurement result accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is the structure schematic diagram of the ultrafast space-time light field measurement system of the embodiment;

[0028] Figure 2 It is the principle schematic diagram of the ultrafast space-time light field measurement system in the embodiment;

[0029] Figure 3 It is the light field intensity distribution diagram of to-be-measured first-order space-time optical vortex in the embodiment on x-t plane;

[0030] Figure 4 It is the light field intensity distribution diagram of different frequency light on x-y plane after interference light field is dispersed by grating in the embodiment;

[0031] Figure 5 It is the light field intensity distribution diagram of different frequency light on x-y plane after interference light field dispersed by grating is focused collimation by cylindrical lens in the embodiment;

[0032] Figure 6 It is the light intensity distribution diagram of setting slit according to the spatial distribution of different frequency light and making specific frequency light pass in the embodiment;

[0033] Figure 7 It is the light field intensity distribution diagram of different frequency light on x-y plane after to-be-measured light collimation passes through slit in the embodiment;

[0034] Figure 8 It is the light field recovery intensity diagram of to-be-measured space-time ultrafast light field on x-t plane in the embodiment;

[0035] Figure 9 It is the step flow chart of the ultrafast space-time light field measurement method in the embodiment. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0037] Femtosecond lasers have unique advantages such as ultra-short spatial resolution, ultra-wide spectral bandwidth, and ultra-high peak power, not only becoming the core driving force in precision fields such as advanced manufacturing, precision measurement, and optical communication, but also promoting the development of basic and applied sciences in physics, chemistry, and biomedical science. The ultrafast control technology of femtosecond pulses is to precisely control the phase, amplitude, and polarization dimensions, so as to shape femtosecond pulses with different shapes to meet the needs of scientific research and industry.

[0038] In the technology of pulse control, Fourier transform pulse control technology is usually used to achieve precise control of femtosecond pulses through a 4f Fourier transform system, and then obtain spatiotemporal structured light fields that meet different needs. Among them, ultrafast spatiotemporal light fields have important applications in the interaction of light and matter in nonlinear optics due to their ultrafast time characteristics and high peak power. For example: spatiotemporal optical vortices (STOV) can be regarded as a kind of ultrafast spatiotemporal light field, whose phase singularity is located in the x-t plane, carrying transverse orbital angular momentum (OAM), and exhibiting different light field dynamic characteristics. Since the STOV light field structure is embedded in the x-t plane, it cannot be directly captured by imaging devices, and the imaging devices only obtain the time-averaged intensity distribution, so it is difficult to fully reveal its dynamic characteristics. Therefore, a measurement method with time resolution is needed to fully characterize the spatiotemporal optical vortex.

[0039] Currently, the system based on measuring ultrafast spatiotemporal light fields is usually an interference measurement technology based on signal light and reference light delay scanning, which realizes the accurate reconstruction of the three-dimensional distribution of STOV by accumulating a large amount of delay interference fringe data. However, this system not only has high requirements for hardware, complex operation, long reconstruction time, but also has noise and system effect, which affects the contrast of the interference fringes and the accuracy of the phase data, so it may introduce additional noise and errors. Therefore, the reconstruction system in the prior art needs to face the problems of large hardware resource consumption, long reconstruction time, noise and system effect interference.

[0040] To address the aforementioned problems in the prior art, this embodiment provides an ultrafast spatiotemporal optical field measurement system. The system first performs dispersion separation on the interference optical field generated by the superposition of the laser pulse to be measured and the reference pulse. Then, it performs wavelength filtering on the dispersion-separated interference optical field to obtain the laser optical field of the target wavelength, acquiring the complex amplitude information of the optical field corresponding to the target wavelength laser optical field. Based on the complex amplitude information, the optical field corresponding to the laser pulse to be measured is reconstructed. The system disclosed in this embodiment does not require adjusting the delay between the signal light and the reference light in the laser pulse to be measured. It only needs to make the co-frequency components interfere at the same spatial position and acquire the interference patterns of each frequency to reconstruct the ultrafast spatiotemporal optical field. Therefore, the system of this application is convenient to implement, highly efficient, and highly accurate.

[0041] The following description, in conjunction with the accompanying drawings, further illustrates an ultrafast spatiotemporal optical field measurement system disclosed in this embodiment.

[0042] Firstly, this application provides an ultrafast spatiotemporal optical field measurement system, such as Figure 1 As shown, the measurement system includes:

[0043] The diffraction element 131 is used to perform dispersion separation on the interference light field generated by the superposition of the laser pulse to be tested and the reference pulse. In this embodiment, the light field formed by the laser pulse to be tested is the ultrafast spatiotemporal light field to be tested. The laser pulse to be tested and the reference pulse (without time delay) are combined and incident on the diffraction element. Due to the diffraction effect of the diffraction element, light fields of different frequencies can be separated in space, thereby achieving modulation of light of different frequencies. The diffraction element can be a diffractive optical element (DOE), a grating, or a phase plate, etc.

[0044] In one implementation, the diffraction element is a grating, a metasurface grating, or a liquid crystal grating. A grating is an optical device composed of a large number of parallel slits of equal width and spacing. These slits can be etched or lens-shaped, causing diffraction and interference phenomena as light passes through them. A metasurface grating is an optical element that combines metasurface technology and grating technology. The design of a metasurface grating is typically based on the simultaneous application of the generalized Snell's law and the grating equations, calculating the phase gradient of the desired unit structure. Then, a suitable unit structure is selected through dispersion modulation and arranged according to a certain pattern to form the metasurface grating. This design process gives the metasurface grating specific diffraction and reflection characteristics. A liquid crystal grating is an optical element that combines liquid crystal technology and grating technology. It utilizes the orientation change of liquid crystals under the influence of an electric or magnetic field to control the propagation direction and polarization state of light. A liquid crystal grating typically consists of two glass substrates filled with liquid crystal molecules. A conductive film is coated on the substrates to form electrodes, and an alignment layer is then coated on the electrodes to control the alignment of the liquid crystal molecules in a certain direction.

[0045] The wavelength selection element 133 is arranged in the light path of the interference light field, and is configured to perform wavelength selection on the interference light field after dispersion separation, so as to obtain a laser light field of a target wavelength.

[0046] The wavelength selection element is arranged behind the diffraction element and receives the light beam output by the diffraction element, so that the wavelength selection element is arranged in the light path of the interference light field output by the diffraction element, and is configured to perform wavelength selection on the light field processed by the diffraction element, so as to obtain a laser light field of a target wavelength.

[0047] Specifically, the wavelength selection element is an optical element for separating light of a specific wavelength or wavelength range from polychromatic light. In specific implementation, the wavelength selection element can be a filter, a grating, a tunable wavelength selector, a prism or a slit. In an embodiment, in order to realize the selection of light of a specific wavelength in the interference light field, the wavelength selection element uses a slit, and by adjusting the position of the slit in the interference light field, the selection of the light field of the target wavelength is realized. Further, the slit can also be designed to be replaced by a metasurface or a liquid crystal to realize the function of wavelength selection.

[0048] The imaging element 17 is arranged in the light path of the laser light field of the target wavelength, and is configured to obtain the light field complex amplitude information corresponding to the laser light field of the target wavelength.

[0049] The laser light field of the target wavelength output by the wavelength selection element is output to the imaging element, and after being captured by the imaging element, the light field complex amplitude information corresponding to the laser light field is obtained. The imaging element is used to collect the light field complex amplitude information of a certain wavelength, and therefore needs to have the ability to detect interference patterns and the resolution needs to meet the requirements, for example, a color CCD camera with a pixel of 1920x1080 and a resolution of 5-8um. In specific implementation, the resolution (size of a single pixel) is 7um.

[0050] The light field reconstruction element is configured to reconstruct the light field corresponding to the to-be-measured laser pulse according to the light field complex amplitude information. After the imaging element obtains the light field complex amplitude information corresponding to the laser light field of the target wavelength, the superfast spatiotemporal light field corresponding to the to-be-measured laser pulse can be reconstructed based on the obtained light field complex amplitude information. Specifically, the interference complex amplitude information of all frequencies recorded by the imaging unit can be recovered into the to-be-measured superfast spatiotemporal light field through inverse Fourier transform from frequency domain to time domain.

[0051] Further, as shown in Figure 2 In order to obtain more accurate wavelength selection effect, a collimating element 132 is further arranged between the diffraction element 131 and the wavelength selection element 133.

[0052] The collimating element is configured to collimate the light received after dispersion separation of the interference light field and output the light to the wavelength selection element.

[0053] The collimating element receives the light beam output by the diffraction element and collimates the received light beam, and then inputs the collimated light beam to the wavelength screening element. The collimating element can be a cylindrical lens, or a super-surface cylindrical lens made by super-surface technology and lens technology, or a liquid crystal cylindrical lens made by liquid crystal technology and lens technology. The liquid crystal cylindrical lens generally consists of a liquid crystal layer and a cylindrical lens. The liquid crystal molecules in the liquid crystal layer can rotate under the action of an electric field, thereby controlling the transmission and reflection of light. The cylindrical lens has a cylindrical surface that can concentrate and stretch the image in a certain dimension. When the light passes through the liquid crystal cylindrical lens, the liquid crystal molecules will rotate according to the change of the electric field, thereby changing the propagation direction of the light. At the same time, the cylindrical lens will concentrate and stretch the light.

[0054] Further, as shown in Figure 1 The first pulse beam splitting element 15 is arranged on the optical path of the interference light field and the target wavelength laser light field. After the to-be-measured laser pulse and the reference pulse are superimposed, they pass through the first pulse beam splitting element 15 and enter the diffraction element 131. After the target wavelength laser light field is transmitted from the wavelength screening element 133, it is incident on the first pulse beam splitting element 15 and then transmitted to the imaging element 17.

[0055] In specific implementation, the first pulse beam splitting element is a half-mirror. Since the half-mirror can reflect 50% of the incident light energy and transmit 50% of the incident light energy, the light beam after the to-be-measured laser pulse and the reference pulse are superimposed can be divided into two beams.

[0056] Further, as shown in Figure 1 The system further includes a second pulse beam splitting element 16 and a spectrometer 18. The second pulse beam splitting element 16 is located between the first pulse beam splitting element 15 and the imaging element 17, and is used to receive the light beam output by the first pulse beam splitting element 15 and divide the light beam into two parts. One part of the light beam is input to the imaging element 17, and the other part is input to the spectrometer 18.

[0057] The spectrometer is located on one side of the second pulse beam splitting element and is used to receive the light beam divided by the second pulse beam splitting element and detect the wavelength corresponding to the received light beam. The wavelength information detected by the spectrometer corresponds to the wavelength information screened by the wavelength screening unit. The wavelength information detected by the spectrometer is used to verify the wavelength information screened by the wavelength screening unit. At the same time, the target wavelength to be screened in the wavelength screening unit can be adjusted according to the wavelength detected by the spectrometer, so as to obtain accurate measurement results of the to-be-measured ultrafast spatiotemporal light field.

[0058] The system further includes a reflective element 14; the reflective element 14 is located on the optical path of the laser light field of the target wavelength output by the wavelength filtering element 133, and is used to reflect the light in the laser light field of the received target wavelength so that the reflected light passes through the collimating element 132 and the diffraction element 131 in sequence and is input to the first pulse beam splitter 15.

[0059] In the measurement system disclosed in this embodiment, a reflective element reflects the light beam output from the wavelength selection element back to the collimating element and the diffraction element. After passing through the first pulse beam splitter and the second pulse beam splitter, the beam is received by the imaging unit. Both the first pulse beam splitter and the second pulse beam splitter are semi-reflective mirrors. The light, resulting from the superposition of the reference pulse and the measured laser pulse, is reflected by the first pulse beam splitter to the diffraction element. After dispersion separation by the diffraction element, it is transmitted to the collimation element. The collimation element collimates the received beam before it is input to the wavelength selection element. After passing through the wavelength selection element, the light field of the target wavelength is transmitted to the reflection element. Since the wavelength selection element, collimation element, and diffraction element are arranged sequentially in front of the reflection element, the light field of the target wavelength incident on the reflection element, after reflection, passes sequentially through the wavelength selection element, collimation element, and diffraction element before being input to the first pulse beam splitter. After transmission through the first pulse beam splitter, it is input to the second pulse beam splitter. The second pulse beam splitter splits the received beam into two beams, one of which is input to the imaging unit, where the complex amplitude information of the measured light field is received. The amplitude and phase spatiotemporal structure of the measured ultrafast light field are reconstructed through algorithms and data processing, thus achieving the reconstruction of the measured ultrafast spatiotemporal light field.

[0060] Combination Figure 2 The diagram shown is a schematic representation of the test system disclosed in this embodiment. Wherein, E(x,y,t) represents the ultrafast spatiotemporal optical field to be tested; Let E(x,y,t) be the light field after undergoing a one-dimensional Fourier transform (FT) from the time domain to the frequency domain, as shown in Equation (1-1).

[0061]

[0062] Where T is the total duration of the pulse.

[0063] for The light field after the two-dimensional Fourier transform (2D FT) is shown in Equation (1-2).

[0064]

[0065] Wherein, X is the length range of the incident light field, Y is the width range of the incident light field.

[0066] For The light field after two-dimensional filtering (Two dimensional filtering, 2D Filtering); For The light field after two-dimensional inverse Fourier transform (Two dimensional inverse Fourier transform, 2D iFT), as shown in equation (1-3).

[0067]

[0068] Wherein, KX is the length range of the light field after 2D FT, KY is the width range of the light field after 2D FT.

[0069] E''(x, y, t) is The final recovered light field after one-dimensional inverse Fourier transform (One dimensional inverse Fourier transform, iFT) from frequency domain to time domain, as shown in equation (1-4).

[0070]

[0071] Wherein, Ω is the total frequency number of the pulse after FT.

[0072] From the above principle, when the interference information of the to-be-measured ultrafast spatiotemporal light field and the reference light under all frequencies is collected, the inverse Fourier transform from frequency domain to time domain can be used to recover the light field intensity diagram of the to-be-measured ultrafast spatiotemporal light field on the x-t plane, and further realize the reconstruction of the to-be-measured ultrafast spatiotemporal light field.

[0073] Next, taking a spatiotemporal optical vortex (Spatiotemporal Optical Vortices, STOV) as the to-be-measured ultrafast spatiotemporal light field, a diffraction element as a grating, a collimating element as a cylindrical lens, a wavelength selection element as a slit, and an imaging element as a CCD camera, the test system disclosed by the utility model is further described.

[0074] Combined Figure 3 As shown in the figure, the first-order STOV (E(x, y, t), E(x, y, ω) ) is combined with the reference pulse and transmitted into the first pulse beam splitting element, reflected to the grating through the first pulse beam splitting element, and the grating disperses and separates the interference light field after the combination of the STOV and the reference pulse, so that the light of different frequencies in the interference light field is separated in space (set as the X direction), forming the dispersed and separated interference light field The modulation of different frequencies ω is shown in equation (1-5):

[0075]

[0076] where β is the dispersion coefficient of the grating; ω0is the center frequency of the incident pulse. In the specific implementation, the grating constant can be 600 lines / mm to 1800 lines / mm.

[0077] Figure 4 Figures (a), (b) and (c) of the drawing show the light field intensity distribution of the light of three different frequencies (ω0+Δω, ω0, ω0-Δω) after passing through the grating, where, Figure 4 Figure (a) of the drawing shows the light field intensity distribution of the light of frequency ω0-Δω after passing through the grating, Figure 4 Figure (b) of the drawing shows the light field intensity distribution of the light of frequency ω0after passing through the grating, Figure 4 Figure (c) of the drawing shows the light field intensity distribution of the light of frequency ω0+Δω after passing through the grating. The spatially dispersed light passes through a cylindrical lens and is focused and collimated in the x direction as shown in the modulation equation (1-6).

[0078]

[0079] where F is the focal length of the cylindrical lens. The cylindrical lens is used to collimate the spatially dispersed spectrum, and the focal length is generally 150 mm to 300 mm. As shown in the drawing, Figure 5 Figures (a), (b) and (c) of the drawing show the light field intensity distribution of the light of three different frequencies (ω0+Δω, ω0, ω0-Δω) after passing through the cylindrical lens, where, Figure 5 Figure (a) of the drawing shows the light field intensity distribution of the light of frequency ω0-Δω after passing through the cylindrical lens, Figure 5 Figure (b) of the drawing shows the light field intensity distribution of the light of frequency ω0after passing through the cylindrical lens, Figure 5 Figure (c) of the drawing shows the light field intensity distribution of the light of frequency ω0+Δω after passing through the cylindrical lens. Figure 6 Figures (a), (b) and (c) of the drawing show the light intensity distribution of the light of different frequencies passing through the slit according to the spatial distribution of the light, where, Figure 6 Figure (a) of the drawing shows the light intensity distribution of the light of frequency ω0-Δω passing through the slit according to the spatial distribution of the light, Figure 6 Figure (b) of the drawing shows the light intensity distribution of the light of frequency ω0passing through the slit according to the spatial distribution of the light, Figure 6 Figure (c) of the drawing shows the light intensity distribution of the light of frequency ω0+Δω passing through the slit according to the spatial distribution of the light. According to the Fourier transform translation theorem, the frequency shift amount of the spatial frequency domain is calculated, and the position of the slit for light of different frequencies is shown in equation (1-7), and the modulation of the pulse by the slit is shown in equation (1-8).

[0080]

[0081] wherein G τ is a gate function.

[0082] In a specific implementation, the slit width is less than 1 mm, and the wavelength of the screening light is changed by changing the position of the slit. Ideally, a specific slit only allows a single frequency of light field to pass through, but in the actual process, since the frequency of the ultrafast spatiotemporal light field is not discrete but continuous distribution, the light transmitted by the specific slit will have interference of other frequency light. As Figure 7 shows the light field intensity distribution diagram of three different frequency lights after passing through the slit Finally, the reflected spectrum of the reflecting element (mirror) transmits the column lens The grating, the first pulse splitting element and the second pulse splitting element, by means of the spectrometer monitoring the corresponding wavelength, record the interference complex amplitude information of all frequencies, and then the inverse Fourier transform of the frequency domain to time domain can be used to restore the measured ultrafast spatiotemporal light field (E''(x, y, t)), and the first-order STOV recovered is as Figure 8 shown.

[0083] In a specific implementation, when the imaging element (such as a color CCD camera) acquires the complex amplitude information, the collected complex amplitude information needs to be reconstructed to obtain the reconstructed complex amplitude information, and then the ultrafast spatiotemporal light field is reconstructed based on the reconstructed complex amplitude information. First, the color CCD camera detects the interference fringes, records the interference fringes, and transmits the recorded interference fringes to the light field reconstruction element (for example, a computer system). The light field reconstruction element performs Fourier transform on the acquired interference fringes to obtain the spectral distribution of the interference fringes. Through frequency domain filtering, the zero-order spectral component and the first-order spectral component are separated. The first-order spectral component is subjected to inverse Fourier transform to obtain the phase distribution of the measured laser pulse wavefront and the amplitude modulation function of the interference fringes. The zero-order spectral component is subjected to inverse Fourier transform to obtain the background light intensity of the interference fringes. Combined with the combined amplitude modulation function of the laser and the background light intensity, the amplitude distribution of the measured laser is calculated, and finally the measured ultrafast spatiotemporal light field is reconstructed based on the amplitude distribution of the measured laser.

[0084] The measurement system provided in the embodiment does not start from the delay time, but realizes the detection of the ultrafast spatiotemporal light field by collecting the interference fringe data of each frequency. Compared with the traditional measurement system, the measurement system does not need to regulate the delay between the signal light and the reference light, but only needs to cooperate the grating and the column mirror to make the same frequency components interfere at the same spatial position, regulate the slit position to capture the interference patterns of each frequency in the imaging device, and then reconstruct the ultrafast spatiotemporal light field. The measurement system designed in the present application aims to provide a more efficient and accurate measurement method for the research of spatiotemporal structured light field.

[0085] Based on the aforementioned measurement system, this embodiment also provides an ultrafast spatiotemporal optical field measurement method, such as... Figure 9 As shown, the measurement method includes:

[0086] Step S1: Perform dispersion separation on the interference light field generated by the superposition of the laser pulse to be tested and the reference pulse.

[0087] Combination Figure 1 As shown, a diffraction element (e.g., a grating) is used to achieve dispersion separation of the interference light field generated by superimposing the laser pulse to be measured and the reference pulse.

[0088] Step S2: Perform wavelength selection on the interference light field after dispersion separation to obtain the laser light field of the target wavelength.

[0089] Combination Figure 1 As shown, the scanning and filtering system 13, composed of a grating, a cylindrical lens, and a slit, filters the wavelength of the interference light field to obtain the laser light field of the target wavelength. The target wavelength is set to correspond to the center wavelength of the laser pulse corresponding to the ultrafast spatiotemporal light field to be measured.

[0090] Step S3: Obtain the complex amplitude information of the laser field corresponding to the target wavelength.

[0091] The light output from the laser field at the target wavelength can be detected and received by a color CCD camera to obtain the complex amplitude information of the laser field.

[0092] Step S4: Reconstruct the optical field corresponding to the laser pulse to be tested based on the optical field complex amplitude information.

[0093] Furthermore, the step of performing wavelength selection on the dispersion-separated interference light field to obtain the laser light field of the target wavelength specifically includes:

[0094] The position of the slit where the interference light field is incident is adjusted to select the laser light field of the target wavelength.

[0095] When reconstructing the ultrafast spatiotemporal optical field corresponding to the laser pulse under test based on the complex amplitude information of the optical field, MATLAB is generally used to reconstruct the optical field based on the complex amplitude information of the optical field.

[0096] Specifically, the steps for reconstructing the ultrafast spatiotemporal optical field based on the complex amplitude information of the optical field include: obtaining time-resolved measurement information based on the complex amplitude distribution of the optical field to obtain the optical field information of the laser pulse under test at different time points; and then constructing the ultrafast spatiotemporal optical field corresponding to the laser pulse under test based on the time-resolved measurement information. This ultrafast spatiotemporal optical field will contain information such as the light intensity and phase of the laser pulse at different time points and spatial locations.

[0097] The system provided by the embodiment only needs to adjust the position of the slit, change the transmitted light field spectrum, and recover the incident ultrafast space-time light field through the frequency light field complex amplitude information collected by the imaging unit, so that accurate measurement results can be obtained.

[0098] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example" or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or N embodiments or examples in a suitable manner. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples without contradiction.

[0099] The above-described embodiments only express several implementation manners of the application, which are described in detail and specifically, but cannot be understood as the limitation of the scope of the utility model patent. It should be pointed out that for those skilled in the art, without departing from the concept of the application, a number of modifications and improvements can be made, which are all within the protection scope of the application. Therefore, the protection scope of the patent of the application should be subject to the appended claims.

Claims

1. An ultrafast spatiotemporal optical field measurement system, characterized in that, The system comprises: a diffraction element for dispersively separating an interference light field generated after superposition of a to-be-tested laser pulse and a reference pulse; a wavelength screening element arranged in an optical path of the interference light field, for wavelength screening of the dispersively separated interference light field to obtain a laser light field of a target wavelength; an imaging element arranged in an optical path of the laser light field of the target wavelength, for obtaining light field complex amplitude information corresponding to the laser light field of the target wavelength, so that a light field reconstruction element reconstructs a light field corresponding to the to-be-tested laser pulse according to the light field complex amplitude information.

2. The ultrafast spatiotemporal light field measurement system of claim 1, wherein, A collimating element is further arranged between the diffraction element and the wavelength screening element; The collimating element is used for collimating light received after dispersively separating the interference light field and outputting the light to the wavelength screening element.

3. The ultrafast spatiotemporal light field measurement system of claim 2, wherein, The diffraction element is a grating, an ultra-surface grating or a liquid crystal grating; the collimating element is a cylindrical mirror, an ultra-surface cylindrical mirror or a liquid crystal cylindrical mirror; and the wavelength screening element is a slit, an ultra-surface slit or a liquid crystal slit grating.

4. The ultrafast spatiotemporal light field measurement system of claim 1, wherein, A first pulse beam splitting element is arranged in optical paths of the interference light field and the laser light field of the target wavelength; After superposition of the to-be-tested laser pulse and the reference pulse, the light passes through the first pulse beam splitting element and enters the diffraction element; After the laser light field of the target wavelength is output from the wavelength screening element, the light is incident on the first pulse beam splitting element, passes through the first pulse beam splitting element and is then input to the imaging element.

5. The ultrafast spatiotemporal light field measurement system of claim 4, wherein, The system further comprises a second pulse beam splitting element and a spectrometer; The second pulse beam splitting element is located between the first pulse beam splitting element and the imaging element, is used for receiving a light beam output by the first pulse beam splitting element, and divides the light beam into two parts, one part of the light beam being input to the imaging element and the other part being input to the spectrometer; The spectrometer is located at one side of the second pulse beam splitting element, is used for receiving a light beam divided by the second pulse beam splitting element, and is used for detecting a wavelength corresponding to the received light beam.

6. The ultrafast spatiotemporal light field measurement system of claim 4 or 5, wherein, The system further comprises a reflecting element; The reflecting element is located in an optical path of the laser light field of the target wavelength output by the wavelength screening element, is used for reflecting light in the received laser light field of the target wavelength, so that the reflected light enters the first pulse beam splitting element in sequence through the collimating element and the diffraction element.

7. The ultrafast spatiotemporal light field measurement system of claim 5, wherein, The first pulse beam splitting element is a half-reflecting half-transmitting lens.

8. The ultrafast spatiotemporal light field measurement system of claim 1, wherein, The imaging element is a color CCD camera, and the light field reconstruction element is a computer.

9. The ultrafast spatiotemporal light field measurement system of claim 6, wherein, The reflecting element is a mirror.

10. The ultrafast spatiotemporal light field measurement system of claim 5, wherein, The second pulse beam splitting element is a half-reflecting half-transmitting lens.

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