A single-shot ultrafast multi-modal temporal phase imaging device

Abstract

The present invention provides a single-shot ultrafast multimodal temporal phase imaging device, which relates to the technical fields of ultrafast optical imaging and computational optical imaging. The imaging device includes: a light source system for generating linearly polarized femtosecond laser pulses; a chirped laser pulse generation system for generating chirped laser pulses based on the femtosecond laser pulses; a pulse shaping system for generating a time series of multi-wavelength sub-pulses based on the chirped laser pulses; and a coherent modulation imaging system for performing coherent modulation imaging based on the time series of multi-wavelength sub-pulses, and using a joint constraint inverse diffraction algorithm of wavelength and modulation coding to achieve single-shot ultrafast multimodal temporal phase imaging. After converting the femtosecond laser pulses into chirped pulses, the pulse shaping technology is used to generate a time series of multi-wavelength sub-pulses with tunable coaxial time resolution and tunable number of sub-pulses.

Description

Technical Field

[0001] The present invention relates to the technical fields of ultrafast optical imaging and computational optical imaging, and particularly relates to a single-shot ultrafast multimodal temporal phase imaging device. Background Art

[0002] Ultrafast optical imaging, as an important optical detection means for detecting the evolution process of ultrafast events, has always attracted much attention. Current ultrafast imaging can be roughly divided into two categories: intensity imaging and complex amplitude imaging. The current photography frequency of intensity imaging can already reach the terahertz level, but it cannot obtain phase information, such as laser-induced plasma and the interaction between ultrashort pulses and matter. To comprehensively record these phenomena, complex amplitude recording means need to be used. Complex amplitude recording mainly includes holographic recording and coherent diffraction imaging methods. Spatial-domain femtosecond holography can obtain scenes at certain instantaneous moments of ultrafast processes by using different multiplexing recording methods, but the system is huge and complex and cannot describe the entire process; frequency-domain femtosecond holography can perform complex amplitude recording of the entire process of ultrafast events, but it is limited by the slit and cannot obtain complete spatial information.

[0003] With the development of computational imaging, coherent diffraction imaging has also begun to emerge. Only one diffraction spot is used to obtain the wavefront distribution of an object. Currently, in the method of realizing ultrafast single-shot multi-frame phase imaging based on coherent modulation imaging, there is a way to control the time delay between incident pulses by integrating the illumination system on a silicon photon chip. Its system time resolution is achieved by reducing the spatial resolution, and its applicability is greatly reduced in the case of high time and spatial resolution requirements; there is also a way to control the time delay between incident pulses by fiber coupling. The sub-pulses pass through fibers of different lengths and are used to detect the measured event in turn with small angular differences, realizing quantitative ultrafast complex amplitude imaging without reducing the spatial resolution. However, its time resolution is affected by the fiber and can only reach the picosecond level. These methods have a common problem: since the incident pulses all enter the object at different angles, this inevitably leads to the situation that the light beams are non-coaxial, thus causing a parallax problem in phase imaging, which in turn affects the accuracy of ultrafast phase measurement. In addition, it is difficult to coordinate the time delay and pulse width between its incident pulses, that is, the time resolution is not adjustable, which poses a challenge to the detection of ultrafast events with different time resolution requirements. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a single-shot ultrafast multimodal temporal phase imaging device. Through ultrafast multimodal phase imaging technology and assisted by computational imaging means, it aims to capture the spatio-temporal characteristics and phase information of atomic time transient events that cannot be repeated. By adopting a parallel sub-pulse train imaging device, the present invention can generate multiple coaxially transmitted sub-pulse trains with a certain time delay in a single operation and record multiple temporal images. At the same time, for multimodal diffraction images, a joint constraint inverse diffraction algorithm based on wavelength and modulation coding is developed, and only a single ordinary intensity sensor is required to obtain the amplitude and phase information of the event, providing a powerful research tool for revealing scientific problems such as the development law of atomic time transient processes and promoting innovative research in basic science and major scientific projects.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] Based on the above object, the present invention provides a single-shot ultrafast multimodal temporal phase imaging device, which includes:

[0007] A light source system for generating linearly polarized femtosecond laser pulses;

[0008] A chirped laser pulse generation system for generating chirped laser pulses based on the femtosecond laser pulses output by the light source system;

[0009] A pulse shaping system for generating a time series of multi-wavelength sub-pulses with tunable time resolution and tunable number of sub-pulses coaxially based on the generated chirped laser pulses;

[0010] A coherent modulation imaging system for performing coherent modulation imaging based on the time series of multi-wavelength sub-pulses generated by the pulse shaping system and using a joint constraint inverse diffraction algorithm based on wavelength and modulation coding to achieve single-shot ultrafast multimodal temporal phase imaging.

[0011] As a further aspect of the present invention, the femtosecond laser pulses generated by the light source system serve as the laser source of the imaging system.

[0012] As a further aspect of the present invention, the light source system adopts a titanium sapphire femtosecond laser to output femtosecond laser pulses with a central wavelength of 800 nm, a pulse width between 30 and 100 femtoseconds, and a spectral width between 30 and 80 nanometers.

[0013] As a further aspect of the present invention, the chirped laser pulse generation system broadens the femtosecond laser pulses through a disperser to form picosecond-level chirped laser pulses with adjustable time delay.

[0014] As a further aspect of the present invention, the pulse shaping system includes two gratings with the same parameters, two lenses with the same parameters, and a multi-slit with adjustable width; the two lenses are combined to form a 4f system, the two gratings are respectively placed on the front and rear focal planes of the 4f system, and the multi-slit is placed on the confocal plane of the 4f system.

[0015] As a further aspect of the present invention, when the pulse shaping system generates a time-series multi-wavelength sub-pulse, the chirped laser pulse generated by the chirped laser pulse generation system is emitted to the first grating, and sequentially passes through the first lens, the multi-slit, the second lens, and the second grating to generate a coaxial time-series multi-wavelength sub-pulse with tunable time resolution and tunable number of sub-pulses.

[0016] As a further aspect of the present invention, the coherent modulation imaging system includes a phase plate and a detector. The coherent modulation imaging system loads the ultrafast event information onto the time-series multi-wavelength sub-pulses generated by the pulse shaping system. After the time-series multi-wavelength sub-pulses are modulated by the phase plate, the detector records the diffraction pattern, and the event reconstruction is performed using the joint constraint back diffraction algorithm of wavelength and modulation coding to obtain the phase information of the atomic time transient event.

[0017] Compared with the prior art, a single-shot ultrafast multi-modal time-sequence phase imaging device proposed by the present invention has the following beneficial effects:

[0018] 1. The ultrafast single-shot multi-frame phase imaging device of the present invention realizes the precise measurement of phase imaging and tunable high time resolution. After converting the femtosecond laser pulse into a chirped pulse, the pulse shaping technology is used to generate a coaxial time-series multi-wavelength sub-pulse with tunable time resolution and tunable number of sub-pulses. In this way, the width of the pulse and the time interval between sub-pulses can be effectively regulated, so as to control the time resolution of imaging to adapt to ultrafast imaging events with different time resolutions. Moreover, these sub-pulses perform phase detection in the coaxial direction, avoiding the phase measurement error caused by parallax in the case of non-coaxial.

[0019] 2. In addition, the highest time resolution can theoretically reach the femtosecond level, and the time resolution can be tuned according to the detection event requirements for chirping and sub-pulse width. Without a complex interference device, assisted by computational imaging means, 4-8 non-repeatable phase information of atomic time transient events with a time resolution in the order of hundreds of femtoseconds can be obtained by single-shot recording. The structure is simple and the system is stable.

[0020] These aspects or other aspects of the present application will be more clearly understood in the following description of the embodiments. It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. Brief Description of the Drawings

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or in the related art, the following will briefly introduce the drawings required for the description of the exemplary embodiments or the related art. The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation to the present invention. In the drawings:

[0022] Figure 1 It is a schematic structural diagram of a single-shot ultrafast multimodal temporal phase imaging device according to an embodiment of the present invention.

[0023] Figure 2 It is a schematic structural diagram of a pulse shaping system in a single-shot ultrafast multimodal temporal phase imaging device according to an embodiment of the present invention.

[0024] Figure 3 It is a schematic structural diagram of a coherent modulation imaging system in a single-shot ultrafast multimodal temporal phase imaging device according to an embodiment of the present invention.

[0025] Reference numerals:

[0026] 11 - Light source system, 12 - Chirped laser pulse generation system, 13 - Pulse shaping system, 131 - Grating, 132 - Lens, 133 - Multi-slit, 14 - Coherent modulation imaging system, 141 - Event, 142 - Phase plate, 143 - Detector. Detailed implementation manners

[0027] Next, in combination with the drawings and the specific implementation manners, the present application will be further described. It should be noted that, on the premise of non-conflict, the following-described embodiments or technical features can be arbitrarily combined with each other to form new embodiments.

[0028] To make the purpose, technical solutions and advantages of the present invention clearer and more understandable, the following will further elaborate on the embodiments of the present invention in detail with reference to the specific embodiments and the drawings. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0029] It should be noted that all the expressions using "first" and "second" in the embodiments of the present invention are used to distinguish two non-identical entities or non-identical parameters with the same name. It can be seen that "first" and "second" are only for the convenience of expression and should not be construed as a limitation to the embodiments of the present invention. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units inherently includes other steps or units.

[0030] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0031] The following will describe in detail some embodiments of the present application in conjunction with the accompanying drawings. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0032] Since the incident pulses all enter the object at different angles, this inevitably leads to the situation that the light beams are non-coaxial, thus causing a parallax problem in phase imaging, which in turn affects the accuracy of ultrafast phase measurement. In addition, it is difficult to harmonize the time delay and pulse width between its incident pulses, that is, the time resolution is not adjustable, which poses a challenge to the detection of ultrafast events with different time resolution requirements. The present invention proposes a single-shot ultrafast multimodal temporal phase imaging device, aiming to capture the spatio-temporal characteristics and phase information of non-repeatable atomic time transient events. Through ultrafast multimodal phase imaging technology, assisted by computational imaging means, by using a parallel sub-pulse train imaging device, multiple coaxial transmitted sub-pulse trains with a certain time delay can be generated in a single operation, and multiple temporal images can be recorded; at the same time, for multimodal diffraction images, a joint wavelength and modulation coding constrained back-propagation algorithm is developed, and the amplitude and phase information of the event can be obtained only by a single ordinary intensity sensor, providing a powerful research tool for revealing scientific problems such as the development law of atomic time transient processes, and being able to promote the innovative research of basic science and major scientific projects.

[0033] See Figure 1 As shown, an embodiment of the present invention provides a single-shot ultrafast multimodal temporal phase imaging device, which includes a light source system 11, a chirped laser pulse generation system 12, a pulse shaping system 13, and a coherent modulation imaging system 14. The light source system 11 is used to generate linearly polarized femtosecond laser pulses; the chirped laser pulse generation system 12 generates chirped laser pulses based on the femtosecond laser pulses output by the light source system 11; the pulse shaping system 13 generates a coaxial time series of multi-wavelength sub-pulses with adjustable time resolution and adjustable number of sub-pulses based on the generated chirped laser pulses; the coherent modulation imaging system 14 performs coherent modulation imaging based on the time series of multi-wavelength sub-pulses generated by the pulse shaping system 13, and uses a joint wavelength and modulation coding constrained back-propagation algorithm to achieve single-shot ultrafast multimodal temporal phase imaging.

[0034] Specifically, in this embodiment, the femtosecond laser pulses generated by the light source system 11 are delivered into the chirped laser pulse generation system 12. After receiving the femtosecond laser pulses, the chirped laser pulse generation system 12 broadens the femtosecond laser pulses through its own dispersion characteristics, so that the femtosecond laser pulses are broadened into picosecond-level chirped laser pulses. The chirped laser pulses generated by the chirped laser pulse generation system 12 are input into the pulse shaping system 13, and the pulse shaping system 13 converts the chirped laser pulses generated by the chirped laser pulse generation system 12 into coaxial time-resolvable and sub-pulse-number-resolvable time-series multi-wavelength sub-pulses and inputs them into the coherent modulation imaging system 14; the coherent modulation imaging system 14 loads the ultrafast event information onto the coaxial time-resolvable and sub-pulse-number-resolvable time-series multi-wavelength sub-pulses generated by the pulse shaping system 13, and then reconstructs the phase information at different moments of the event through the wavelength and modulation coding joint constraint back-propagation algorithm.

[0035] In this embodiment, the femtosecond laser pulses generated by the light source system 11 serve as the laser source of the imaging system. Among them, the light source system 11 can adopt a titanium-sapphire femtosecond laser, the central wavelength of the output femtosecond laser pulses is 800 nm, the pulse width is between 30 and 100 femtoseconds, and the corresponding spectral width is between 30 and 80 nanometers.

[0036] In this embodiment, the chirped laser pulse refers to a laser pulse whose instantaneous frequency changes with time. The chirped laser pulse generation system 12 broadens the femtosecond laser pulses through a disperser to form picosecond-level chirped laser pulses with adjustable generation time delay. It should be noted that in specific implementation, the femtosecond laser pulses can also be broadened into pulse widths of other magnitudes according to actual needs.

[0037] In this embodiment, see Figure 1 and Figure 2 As shown, the pulse shaping system 13 includes two gratings 131 with the same parameters, two lenses 132 with the same parameters, and a multi-slit 133 with adjustable width; the two lenses 132 are combined to form a 4f system, the two gratings 131 are respectively placed on the front and rear focal planes of the 4f system, and the multi-slit 133 is placed on the confocal plane of the 4f system.

[0038] Among them, when the pulse shaping system 13 generates time-series multi-wavelength sub-pulses, based on the chirped laser pulses generated by the chirped laser pulse generation system 12, they are incident on the first grating, and then pass through the first lens, the multi-slit, the second lens, and the second grating in sequence to generate coaxial time-resolvable and sub-pulse-number-resolvable time-series multi-wavelength sub-pulses.

[0039] It should be noted that in this embodiment, the fixing method of the pulse shaping system 13 composed of the grating 131, the lens 132, and the multi-slit 133 is a prior art, such as being fixed through the housing structure; the slit width and the number of slits can be adjusted according to actual requirements during specific implementation.

[0040] In this embodiment, the coherent modulation imaging system 14 loads the ultrafast event information onto a time-series multi-wavelength sub-pulse with coaxial tunable time resolution and tunable number of sub-pulses, and reconstructs the event information by using the wavelength and modulation coding joint constraint back-propagation algorithm. Refer to Figure 1 and Figure 3 As shown, the coherent modulation imaging system 14 includes a phase plate 142 and a detector 143. The coherent modulation imaging system 14 loads the ultrafast event 141 information onto the time-series multi-wavelength sub-pulses generated by the pulse shaping system 13. After being modulated by the phase plate 142, the time-series multi-wavelength sub-pulses are recorded by the detector 143 for the diffraction pattern, and the event 141 is reconstructed by using the wavelength and modulation coding joint constraint back-propagation algorithm to obtain the phase information of the atomic time transient event 141.

[0041] It should be noted that different distributed phase plates can be designed according to actual requirements during specific implementation.

[0042] The ultrafast single-shot multi-frame phase imaging device of the present invention realizes the precise measurement of phase imaging and tunable high time resolution. After converting the femtosecond laser pulse into a chirped pulse, the pulse shaping technology is used to generate a time-series multi-wavelength sub-pulse with coaxial tunable time resolution and tunable number of sub-pulses. In this way, the width of the pulse and the time interval between sub-pulses can be effectively regulated, so as to control the time resolution of imaging to adapt to ultrafast imaging events with different time resolutions. Moreover, these sub-pulses perform phase detection in the coaxial direction, avoiding the phase measurement error caused by parallax in the case of non-coaxial.

[0043] In addition, the highest time resolution can theoretically reach the femtosecond level, and the time resolution can be tuned according to the detection event requirements for chirping and sub-pulse width. Without a complex interference device, assisted by computational imaging means, 4-8 non-repeatable phase information of atomic time transient events with a time resolution in the order of hundreds of femtoseconds can be obtained in a single record, with a simple structure and a stable system.

[0044] In summary, the ultrafast single-shot multi-frame phase imaging device of the present invention realizes coaxial single-shot multi-frame coherent modulation imaging, avoids phase measurement errors caused by different parallaxes in the background of non-coaxiality, and improves the accuracy and stability of phase measurement. The time resolution can be adjusted according to the detection requirements of ultrafast events for the chirp amount and sub-pulse width. The structure is simple and the system is stable. By adjusting the chirp amount and sub-pulse width, the system can achieve the best performance under different time resolution requirements. The structure of the present invention is simple and the system is stable, which helps to overcome the challenges that may be encountered in the detection of ultrafast events at different time resolutions, and improves the accuracy and reliability of data acquisition and analysis.

[0045] The ultrafast single-shot multi-frame phase imaging device of the present invention can be used to study ultrafast optical processes, such as the propagation of laser pulses in matter, optical nonlinear effects, non-reproducible atomic time transient events, etc. By providing a tunable time resolution at the femtosecond level, the present invention can help researchers deeply analyze the time evolution and phase changes of optical processes.

[0046] The above are exemplary embodiments disclosed by the present invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments disclosed by the present invention as defined by the claims. The functions, steps, and / or actions of the method claims according to the disclosed embodiments here do not need to be executed in any specific order. In addition, although the elements disclosed by the embodiments of the present invention can be described or claimed in individual form, they can also be understood as multiple unless explicitly limited to the singular.

[0047] Those of ordinary skill in the art should understand that: the discussion of any of the above embodiments is only exemplary, and is not intended to imply that the scope of the embodiments disclosed by the present invention (including the claims) is limited to these examples; under the idea of the embodiments of the present invention, the technical features between the above embodiments or different embodiments can also be combined, and there are many other variations in different aspects of the embodiments of the present invention as above, which are not provided in detail for the sake of brevity. Therefore, any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of the present invention shall be included in the protection scope of the embodiments of the present invention.

Claims

1. A single-shot ultrafast multi-modal time-series phase imaging device, characterized in that: The imaging device comprises: A light source system (11) for generating linearly polarized femtosecond laser pulses; A chirped laser pulse generating system (12) generates chirped laser pulses based on the femtosecond laser pulses output by the light source system (11); A pulse shaping system (13) generates coaxial time-series multi-wavelength sub-pulses with adjustable time resolution and adjustable number of sub-pulses based on the generated chirped laser pulses; the pulse shaping system (13) comprises two gratings (131) with the same parameters, two lenses (132) with the same parameters, and a multi-slit (133) with adjustable width; the two lenses (132) are combined to form a 4f system, the two gratings (131) are respectively placed on the front and rear focal planes of the 4f system, and the multi-slit (133) is placed on the common focal plane of the 4f system; A coherent modulation imaging system (14) performs coherent modulation imaging based on the time series multi-wavelength sub-pulses generated by the pulse shaping system (13), and uses a wavelength and modulation coding joint constrained anti-derivative algorithm to achieve single ultrafast multi-modal time series phase imaging; the coherent modulation imaging system (14) comprises a phase plate (142) and a detector (143); the coherent modulation imaging system (14) loads ultrafast event (141) information onto the time series multi-wavelength sub-pulses generated by the pulse shaping system (13); after the time series multi-wavelength sub-pulses are modulated by the phase plate (142), the diffraction pattern is recorded by the detector (143); and the event (141) is reconstructed using a wavelength and modulation coding joint constrained anti-derivative algorithm to obtain phase information of the atomic time transient event (141).

2. The single-shot ultrafast multi-modal temporal phase imaging device according to claim 1, characterized in that: The femtosecond laser pulses generated by the light source system (11) serve as the laser source of the imaging system.

3. The single-shot ultrafast multi-modal temporal phase imaging device according to claim 2, characterized in that: The light source system (11) adopts a titanium sapphire femtosecond laser, which outputs femtosecond laser pulses with a central wavelength of 800 nm, a pulse width of 30-100 femtoseconds, and a spectrum width of 30-80 nanometers.

4. The single-shot ultrafast multi-modal temporal phase imaging device according to claim 1, characterized in that: The chirped laser pulse generating system (12) widens the femtosecond laser pulse through a disperser to generate a picosecond chirped laser pulse with adjustable generation time delay.

5. The single-shot ultrafast multi-modal temporal phase imaging device according to claim 1, characterized in that: When the pulse shaping system (13) generates time-series multi-wavelength sub-pulses, the chirped laser pulses generated by the chirped laser pulse generating system (12) are emitted to the first grating, and sequentially pass through the first lens, the multi-slit, the second lens and the second grating to generate coaxial time-series multi-wavelength sub-pulses with adjustable time resolution and adjustable number of sub-pulses.

Images