Device for generating multiple beams of time sequence light based on single-circle light spring

Abstract

The invention provides a device for generating multiple beams of time sequence light based on a single-circle light spring, and relates to the technical field of ultrafast imaging, and the device comprises a leading edge tilt pulse generation system which is used for generating a long elliptical leading edge tilt pulse; the light spring generation system comprises a polarizer, a first wave plate, a diaphragm, a geometric conversion device, a convex lens, a phase compensator and a second wave plate which are sequentially arranged along the pulse propagation direction, and generates a single circle of light spring pulse based on the long elliptical leading edge tilt pulse output by the leading edge tilt pulse generation system; and the time sequence light beam generation system is used for dividing the single-circle light spring pulse into a plurality of beams of time sequence light through a circular porous diaphragm and a lens group. According to the invention, multiple beams of time sequence pulses can be generated as a coherent shutter to interfere with a signal light beam carrying ultrafast event information, multiple beams of time sequence light can be efficiently generated, multi-beam interference noise is optimized, and efficient image separation of ultrafast imaging is realized.

Description

Technical Field

[0001] The present invention relates to the field of ultrafast imaging technology, and in particular to a device for generating multiple beams of sequential light based on a single-loop optical spring. Background Art

[0002] The development of ultrafast imaging technology has always revolved around how time dimension is encoded into other dimensions. There are various types of ultrafast imaging technologies, such as spectral encoding, frequency-domain holography, spatial spectrum encoding, compressed sensing ultrafast imaging, etc.

[0003] As a classical method, pump-probe imaging technology achieves sub-femtosecond time resolution and high signal-to-noise ratio through dual-pulse timing control. However, it relies on repeatable experimental conditions, cannot capture single irreversible transient events, and is difficult to synchronously obtain spatial spectral information. Compressed ultrafast imaging innovatively introduces a compressed sensing algorithm, breaks through the traditional Nyquist limit through sparse sampling and non-linear reconstruction, and achieves an ultra-high frame rate of trillions of frames per second in a single exposure, significantly expanding the observation ability of non-repetitive processes. However, limited by algorithm complexity and the problem of motion blur suppression, its spatial resolution still faces challenges in high-speed dynamic scenarios. Spectral encoding technology realizes the efficient coupling of spatio-temporal and spectral information by mapping time information to the spectral dimension: on the one hand, it can capture the dynamic evolution of multiple wavelengths in a single exposure without mechanical scanning, significantly improving data throughput; on the other hand, spectral resolution ability is combined with ultrashort pulses.

[0004] Spatial spectrum encoding encodes the imaging at different times near different spatial frequencies, and the imaging is performed on a photosensitive element. Subsequently, the images at each time are separated by using a spatial spectrum filtering method. Here, spatial spectrum encoding uses multiple pulses with different time delays, that is, sequential light, to illuminate the ultrafast process at different azimuth angles. And a single-loop optical spring has different time delays in spatial distribution, and can generate multiple beams of sequential pulses to interfere with a signal beam carrying ultrafast event information as a coherent shutter.

[0005] Currently, the method for generating multiple beams of sequential light based on a single-loop optical spring still has certain limitations, mainly reflected in the limited accuracy of the time interval of sequential light beams. Mechanical vibration or thermal drift easily causes time delay errors, reducing time resolution; insufficient scalability. When increasing the number of sequential pulses, the non-linearity of the spring's dynamic response intensifies, and it is difficult to achieve a uniform delay distribution. Therefore, how to efficiently generate multiple beams of sequential light and optimize the interference noise of multiple beams to achieve efficient image separation in ultrafast imaging is an important challenge in the current technology. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide a device for generating multiple beams of sequential light based on a single - loop optical spring, which can generate multiple beams of sequential pulses to interfere with a signal beam carrying ultrafast event information as a coherent shutter, can efficiently generate multiple beams of sequential light, optimize the interference noise of multiple beams, and achieve efficient image separation for ultrafast imaging.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] Based on the above object, the present invention provides a device for generating multiple beams of sequential light based on a single - loop optical spring, including the following components:

[0009] A leading - edge tilted pulse generation system for generating a long - elliptical leading - edge tilted pulse;

[0010] An optical spring generation system for generating a single - loop optical spring pulse based on the long - elliptical leading - edge tilted pulse output by the leading - edge tilted pulse generation system;

[0011] A sequential light beam generation system for dividing the single - loop optical spring pulse into multiple beams of sequential light through a circular multi - aperture diaphragm and a lens group.

[0012] As a further aspect of the present invention, the long - elliptical leading - edge tilted pulse is a femtosecond laser pulse with a pulse width in the order of hundreds of femtoseconds.

[0013] As a further aspect of the present invention, the wavelength of the long - elliptical leading - edge tilted pulse is 1030 nm, and the diameters (full width at half maximum) of the long - elliptical leading - edge tilted pulse in the horizontal and vertical directions are 15 mm and 1.5 mm respectively.

[0014] As a further aspect of the present invention, the optical spring generation system includes a polarizer, a first wave plate, a diaphragm, a geometric transformation device, a convex lens, a phase compensator, and a second wave plate arranged in sequence along the pulse propagation direction; after the long - elliptical leading - edge tilted pulse passes through them in sequence, it is transformed into a single - loop optical spring pulse.

[0015] As a further aspect of the present invention, the vibration direction of the long - elliptical leading - edge tilted pulse after passing through the polarizer forms an angle of - 45° or 135° with the fast and slow axes of the first wave plate, converting the long - elliptical leading - edge tilted pulse into a left - hand circularly polarized light.

[0016] As a further aspect of the present invention, both the first wave plate and the second wave plate are quarter - wave plates, the focal length of the convex lens is 500 mm, and the clear aperture of the diaphragm is 13 mm.

[0017] As a further aspect of the present invention, both the geometric transformation device and the phase compensator are phase modulators, and are respectively located at the front focal plane and the rear focal plane of the convex lens. The geometric transformation device, the convex lens, and the phase compensator form an inverse logarithmic coordinate transformation system.

[0018] As a further solution of the present invention, the small holes in the circular porous diaphragm are circular, distributed in a ring shape and corresponding to the position of the single-loop optical spring.

[0019] As a further solution of the present invention, the lens group is composed of three convex lenses, and the focal lengths are 500 mm, 250 mm, and 500 mm in sequence.

[0020] Compared with the prior art, a device for generating multiple beams of time-sequential light based on a single-loop optical spring proposed by the present invention can use the multiple beams of time-sequential light generated as a coherent shutter to interfere with a signal beam carrying ultrafast event information. By using Fourier filtering technology to collect images, each frame of the image can be separated, thus realizing ultrafast imaging. The present invention has the following beneficial effects:

[0021] A device for generating multiple beams of time-sequential light based on a single-loop optical spring proposed by the present invention generates multiple beams of time-sequential pulses with different time delays in spatial distribution by regulating the deformation characteristics of the single-loop optical spring. These multiple beams of time-sequential pulses irradiate ultrafast events at a specific azimuth angle, precisely controlling the pulse interval through the elastic deformation of the optical spring, constructing a spatio-temporal coupled optical field with a linear correlation between space and time. The separation of the interference pattern is realized by using Fourier filtering technology. Compared with traditional multi-pulse systems, its advantages lie in its simple and compact structure, without the need for complex mechanical delay lines. The deformation of the optical spring directly maps the time delay, with high stability. The spatially distributed time-sequential light can reduce the multi-beam interference noise. Combined with a pseudo-random coding mask plate, continuous scanning imaging in two-dimensional space and one-dimensional time can be achieved. The device of the present invention is used as a coherent shutter for single-shot ultrafast imaging, and multiple beams of time-sequential light can be used as a coherent shutter to interfere with a signal beam carrying ultrafast event information.

[0022] 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

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following will briefly introduce the drawings required for the description of the exemplary embodiments or related technologies. The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention. In the drawings:

[0024] Figure 1 is a schematic structural diagram of a device for generating multiple beams of time-sequential light based on a single-loop optical spring according to an embodiment of the present invention.

[0025] Figure 2This is a schematic structural diagram of the optical spring generation system in a device for generating multiple beams of sequential light based on a single-turn optical spring according to an embodiment of the present invention.

[0026] Figure 3 This is a schematic structural diagram of the sequential light beam generation system in a device for generating multiple beams of sequential light based on a single-turn optical spring according to an embodiment of the present invention.

[0027] Reference numerals:

[0028] 11 - Leading-edge tilt pulse generation system, 12 - Optical spring generation system, 13 - Sequential light beam generation system, 21 - Polarizer, 22 - First wave plate, 23 - Diaphragm, 24 - Geometric transformation device, 25 - Convex lens, 26 - Phase compensator, 27 - Second wave plate, 31 - Circular multi-aperture diaphragm, 32 - Lens group. Detailed implementation manners

[0029] Next, in combination with the accompanying drawings and specific implementation manners, the present application will be further described. It should be noted that, on the premise of no conflict, the following-described embodiments or technical features can be arbitrarily combined with each other to form new embodiments.

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the following further details the embodiments of the present invention in combination with specific embodiments and with reference to the accompanying 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.

[0031] It should be noted that all the expressions using "first" and "second" in the embodiments of the present invention are for distinguishing 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 on 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.

[0032] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in combination with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. 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 scope of protection of the present application.

[0033] The flowcharts shown in the accompanying drawings are only illustrative examples and do not necessarily include all the content and operations / steps, nor do they necessarily need to be executed in the described order. For example, some operations / steps can also be decomposed, combined, or partially merged. Therefore, the actual execution order may be changed according to the actual situation.

[0034] 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.

[0035] Referring to Figure 1 As shown, an embodiment of the present invention provides a device for generating multiple beams of time-sequential light based on a single-turn optical spring, including the following components:

[0036] A leading-edge tilted pulse generation system 11 for generating a long elliptical leading-edge tilted pulse;

[0037] An optical spring generation system 12 for generating a single-turn optical spring pulse based on the long elliptical leading-edge tilted pulse output by the leading-edge tilted pulse generation system 11;

[0038] A time-sequential beam generation system 13 for dividing the single-turn optical spring pulse into multiple beams of time-sequential light through a circular multi-aperture diaphragm 31 and a lens group 32.

[0039] In this embodiment, multiple beams of time-sequential light are generated using a single-turn optical spring pulse. Since the single-turn optical spring has different time delays in spatial distribution, multiple beams of time-sequential pulses can be generated. These multiple beams of time-sequential pulses can be used to capture and image ultrafast events. The obtained interference pattern uses the pulse edge tilt technology combined with the spatial coordinate transformation technology to construct a spatio-temporal coupled optical field with linear spatial and temporal correlation. Then, each frame of the image can be separated using Fourier filtering technology.

[0040] In this embodiment, the long elliptical leading-edge tilted pulse is a femtosecond laser pulse with a pulse width in the order of hundreds of femtoseconds. The femtosecond laser pulse first enters the leading-edge tilted pulse generation system 11, and then a long elliptical leading-edge tilted pulse is generated. After the long elliptical leading-edge tilted pulse passes through the optical spring generation system 12, a single-turn optical spring pulse is generated. Then, it passes through the time-sequential beam generation system 13. In the time-sequential beam generation system 13, the single-turn optical spring pulse passes through a customized circular multi-aperture diaphragm 31 and a lens group 32 to generate multiple beams of time-sequential light.

[0041] In this embodiment, the multiple beams of time-sequential light refer to multiple laser pulse signals output by the time-sequential beam generation system 13. The time-sequential beams have different time delays. The multiple beams of time-sequential light generated by the present invention can be used as a coherent shutter to interfere with a signal beam carrying ultrafast event information, such as plasma, ultrafast rotating optical field, etc. After obtaining the interference pattern, it is used to construct a spatio-temporal coupled optical field with linear spatial and temporal correlation as a coherent shutter for single-shot ultrafast imaging. Using this spatio-temporal correlation, time-space frequency encoding between multiple images can be achieved. The collected images can be separated using Fourier filtering technology, thereby realizing ultrafast imaging.

[0042] In this embodiment, referring to Figure 2As shown, the optical spring generation system 12 includes a polarizer 21, a first wave plate 22, a diaphragm 23, a geometric transformation device 24, a convex lens 25, a phase compensator 26, and a second wave plate 27 arranged in sequence along the pulse propagation direction; after the long elliptical front-tilted pulse passes through them in sequence, a single-loop optical spring pulse is formed.

[0043] Among them, in the front-tilted pulse generation system 11, a Gaussian pulse entering the front-tilted pulse generation system 11 is generated by a fiber femtosecond laser, with a wavelength of 1030 nm and a pulse width in the order of hundreds of femtoseconds. The diameters (full width at half maximum) of the long elliptical front-tilted pulse in the horizontal and vertical directions are 15 mm and 1.5 mm respectively.

[0044] Among them, both the first wave plate 22 and the second wave plate 27 are quarter-wave plates, the focal length of the convex lens 25 is 500 mm, and the clear aperture of the diaphragm 23 is 13 mm.

[0045] In this embodiment, the vibration direction of the long elliptical front-tilted pulse after passing through the polarizer 21 forms an angle of -45° or 135° with the fast and slow axes of the first wave plate 22, converting the long elliptical front-tilted pulse into a left-handed circularly polarized light; in this embodiment, both the geometric transformation device 24 and the phase compensator 26 are phase modulators, and are respectively located at the front focal plane and the rear focal plane of the convex lens 25. The geometric transformation device 24, the convex lens 25, and the phase compensator 26 form an inverse logarithmic coordinate transformation system.

[0046] Among them, the generated optical spring is a single-loop optical spring. Without considering chirp, the distribution characteristics of the single-loop optical spring in the time domain and its frequency domain are shown in formulas (1) and (2);

[0047]

[0048] Among them, E LS (θ, t) represents the time-domain distribution of the single-loop optical spring, A represents the amplitude, is to describe the time-domain characteristics of the pulse (τ p is the pulse width), t represents time, Δω is the spectral width, ω 0 represents the angular frequency of the single-loop optical spring, θ is the azimuth angle, l 0 is the topological charge corresponding to the central frequency, and Δl is the spectral topological charge width corresponding to the spectral width Δω, represents the frequency-domain distribution of the single-loop optical spring, and ω represents the angular frequency.

[0049] In this embodiment, the geometric transformation device (GTE), the convex lens, and the phase compensator (PCE) form a coordinate transformation system. The inverse logarithmic polar coordinate transformation can be performed on the long elliptical front-tilted pulse. The phase distributions of the geometric transformation device and the phase compensation device are shown in formulas (3) and (4):

[0050]

[0051] wherein, φ GTE (x, y) represents the phase distribution of the geometric transformation device, a and b are respectively the light-passing size coefficients of the phase modulator, λ is the wavelength, f is the focal length of the convex lens, (x, y) and (u, v) correspond to the spatial coordinates of the front focal plane and the rear focal plane of the convex lens, and φ PCE (u, v) represents the phase distribution of the phase compensator. The inverse log-polar coordinate transformation implemented by the geometric transformation device (GTE) and the phase compensator (PCE) is a preserving transformation, and the log-polar coordinate transformation can be achieved by exchanging their positions.

[0052] In this embodiment, after a single-loop optical spring pulse is generated by the optical spring generation system 12, it enters the timing beam generation system 13. As Figure 3 shown, the timing beam generation system 13 includes a circular multi-aperture diaphragm 31 with a radius of 8 mm and an inner diameter of 6.5 mm. A number of circular small holes are distributed along the inner diameter. The diameter of each small hole is 0.5 mm, and the number of holes is 12, which are distributed in a ring and correspond to the position of the single-loop optical spring. The lens group 32 in the timing beam generation system 13 consists of three convex lenses with focal lengths of 500 mm, 250 mm, and 500 mm in sequence. The single-loop optical spring pulse passes through the circular multi-aperture diaphragm 31 and then through the lens group 32, and is divided into 12 beams of timing light. It should be noted that here, according to the experimental needs, the interval between the holes can be flexibly set to generate the timing and the number of beams required for the experiment.

[0053] The present invention provides a device for generating multiple beams of sequential light based on an optical spring. By modulating the azimuth-time coupling characteristics of ultrashort pulses, an optical field with a helical envelope structure, i.e., a single-loop optical spring, is generated. Combining with a circular multi-aperture diaphragm 31, multiple beams of sequential pulses with different time delays are generated in spatial distribution. These pulses irradiate ultrafast events at specific azimuth angles, and the pulse intervals are precisely controlled through the elastic deformation of the optical spring, constructing a spatio-temporal coupled optical field with a linear correlation between space and time. The separation of the interference patterns is achieved by Fourier filtering technology, and the number of frames can be flexibly modulated by designing the geometric parameters of the spring coil. Compared with traditional multi-pulse systems, the advantages are simple and compact structure, no need for complex mechanical delay lines, the deformation of the optical spring directly maps the time delay, and high stability; strong scalability, by designing the series or parallel connection of multiple-stage springs, the number of sequential pulses can be efficiently increased to meet the requirements of high-frame-rate imaging. The spatially distributed sequential light can reduce the multi-beam interference noise, and combined with a pseudo-random coding mask plate, two-dimensional space-one-dimensional time continuous scanning imaging can be realized. The device of the present invention serves as a coherent shutter for single-shot ultrafast imaging. Through spatio-temporal frequency encoding and Fourier domain decoupling, it provides a highly reliable and low-cost multi-dimensional dynamic observation means for irreversible transient processes.

[0054] 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 herein do not need to be performed in any specific order. In addition, although the elements disclosed by the embodiments of the present invention can be described or claimed in an individual form, they can also be understood as multiple unless explicitly limited to the singular.

[0055] 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 concept 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 device for generating multiple sequential lights based on a single-loop light spring, characterized in that: Includes the following components: A leading edge tilt pulse generating system (11) for generating a long elliptical leading edge tilt pulse; A light spring generating system (12) generates a single-turn light spring pulse based on the long elliptical front tilt pulse output by the front tilt pulse generating system (11); The time-sequential light beam generating system (13) is used for dividing a single-circle light spring pulse into a plurality of time-sequential light beams through a circular multi-aperture aperture (31) and a lens group (32).

2. The device for generating multiple sequential lights based on a single-loop light spring as claimed in claim 1, characterized in that: The long elliptical front tilt pulse is a femtosecond laser pulse, and the pulse width is in the order of hundreds of femtoseconds.

3. The device for generating multiple sequential lights based on a single-loop light spring as claimed in claim 2, characterized in that: The wavelength of the long elliptical front tilt pulse is 1030 nm, and the diameters of the long elliptical front tilt pulse in the horizontal and vertical directions are 15 mm and 1.5 mm respectively.

4. The device for generating multiple sequential lights based on a single-loop light spring as claimed in claim 1, characterized in that: The light spring generating system (12) comprises a polarizer (21), a first wave plate (22), an aperture (23), a geometric transformation device (24), a convex lens (25), a phase compensator (26) and a second wave plate (27) which are sequentially arranged along the pulse propagation direction; and is used for allowing the long elliptical front tilt pulses to pass through sequentially and then transforming them into single-circle light spring pulses.

5. The device for generating multiple sequential lights based on a single-loop light spring as claimed in claim 4, characterized in that: The vibration direction of the long elliptical front tilt pulse after passing through the polarizer (21) and the fast and slow axes of the first wave plate (22) are at an angle of -45° or 135°, so that the long elliptical front tilt pulse is converted into left-handed circularly polarized light.

6. The device for generating multiple sequential lights based on a single-loop light spring as claimed in claim 5, characterized in that: The first wave plate (22) and the second wave plate (27) are both quarter wave plates.

7. The device for generating multiple sequential lights based on a single-loop light spring as claimed in claim 6, characterized in that: The focal length of the convex lens (25) is 500 mm, and the aperture of the aperture (23) is 13 mm.

8. The device for generating multiple sequential lights based on a single-loop light spring as claimed in claim 7, characterized in that: The geometric transformation device (24) and the phase compensator (26) are both phase modulators and are respectively located at the front focal plane and the back focal plane of the convex lens (25). The geometric transformation device (24), the convex lens (25) and the phase compensator (26) form an inverse logarithmic coordinate transformation system.

9. The device for generating multiple sequential lights based on a single-loop light spring as claimed in claim 1, characterized in that: The small holes in the circular multi-aperture aperture (31) are circular, distributed in a ring shape and corresponding to the positions of the single-circle light spring.

10. The device for generating multiple sequential lights based on a single-loop light spring as claimed in claim 9, characterized in that: The lens group (32) consists of three convex lenses, and the focal lengths are 500 mm, 250 mm, and 500 mm respectively.

Images