A device for real-time analysis of multi-dimensional information of space-time mode-locked pulses in an all-fiber structure

Abstract

This invention discloses a device for real-time analysis of multidimensional information of spatiotemporally mode-locked pulses using an all-fiber structure, belonging to the field of ultrafast optics technology. It includes an all-fiber spatiotemporally mode-locked laser platform, a raw pulse beam profile measurement module, an optical circulator, a sub-pulse beam profile measurement module, and a dispersive Fourier transform and real-time spectral information detection module. Based on the generalized multimode nonlinear Schrödinger equation, this invention constructs a theoretical model of the spatiotemporally mode-locked laser, explores the multidimensional parameter coupling mechanism during spatiotemporal mode-locking, clarifies the mapping relationship between modes and frequencies, and provides a theoretical basis and method for high-precision mode differentiation and multidimensional real-time information extraction. This invention aims to rationally design the parameters of each fiber grating according to the spectral width and temporal interval of the spatiotemporally mode-locked pulse, reflecting more sub-pulses while ensuring that the pulse temporal domains do not overlap, achieving high-precision spatial mode resolution, and maximizing pulse broadening to obtain high-resolution real-time spectral information.

Description

Technical Field

[0001] This invention belongs to the field of ultrafast optics technology, and more specifically, relates to a device for real-time analysis of spatiotemporal mode-locked pulse multidimensional information using an all-fiber structure. Background Technology

[0002] Ultrashort laser pulses, as an indispensable tool in the development of ultrafast science, play a unique role in fundamental research fields such as high-energy physics, chemical observation, and biological imaging. In recent years, spacetime mode-locking technology has broken through the limitations of traditional one-dimensional mode-locking techniques, achieving synchronous spatial and temporal locking and obtaining ultrashort pulses containing multiple higher-order spatial modes. The nonlinear effects of multimode fibers inevitably lead to rich and complex high-dimensional nonlinear dynamics in spacetime mode-locked lasers. However, due to the difficulty in accurately distinguishing the spatial modes of spacetime mode-locked pulses, and the fact that technologies for real-time acquisition of multidimensional information are still under development, research on the dynamics of spacetime mode-locking remains in its early stages. Therefore, designing a high-precision multidimensional parameter measurement method to acquire the spatial-temporal-spectral information of spacetime mode-locked pulses in real time, and revealing the dynamic characteristics of the transient evolution of multidimensional ultrashort pulses, is beneficial for expanding the dimensions of ultrashort pulses in nonlinear science and provides a theoretical basis for obtaining high-power, narrow-pulse-width laser pulses.

[0003] Since its inception in 2017, spacetime mode-locking technology has rapidly become a research hotspot in ultrafast lasers, exhibiting numerous mode-locking states similar to those of conventional mode-locked lasers, including multi-pulse, bound-state pulses, self-similarities, and wavelength tunability. However, due to limitations in spatial sampling resolution, the distinction between different spatial modes remains unclear, making comprehensive analysis of the dynamic characteristics of different modes within spacetime mode-locked pulses challenging. Therefore, a real-time multi-dimensional parameter measurement method based on high-precision mode resolution technology is essential for acquiring multi-dimensional information about spacetime mode-locked pulses and clarifying their dynamic processes.

[0004] In spatiotemporal mode-locked pulses, multidimensional parameters determine the pulse characteristics, and the frequency-time mapping can be obtained through dispersive Fourier transform. However, the mapping relationship between spatial modes, frequency, and time remains unclear, which is key to exploring high-precision mode resolution methods and an urgent problem to be solved in the study of real-time dynamic characteristics of multidimensional pulses. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a device for real-time analysis of multidimensional information of spatiotemporal mode-locked pulses using an all-fiber structure, with the goal of real-time detection, analysis, and reconstruction of multidimensional parameters of spatiotemporal mode-locked pulses.

[0006] This invention is based on a spacetime mode-locked laser model using the generalized multimode nonlinear Schrödinger equation (GMMNLSE). First, it describes the mode field of the spacetime mode-locked pulse. The transmission process in passive multimode fiber is expressed as follows:

[0007]

[0008] in for m Dispersion term of the order, n 2 represents the refractive index of the optical fiber. The center angular frequency, For Raman components, For the Raman response of the medium, for different modes P This invention simulates the transmission of multimode pulses by coupling a series of equations. First, the dispersion parameters corresponding to each mode in the multimode fiber are numerically calculated, and the transmission process in the few-mode gain fiber is simplified to that in a single-mode fiber. In this case, multimode excitation occurs when the pulse enters the multimode fiber from the gain fiber, and a spatial filtering process occurs when it enters the gain fiber from the multimode fiber. This invention uses a saturable absorber in the single-mode field instead of spatiotemporal mode-locking. This significant simplification greatly reduces the computational load in obtaining spatiotemporal mode-locking, providing a theoretical tool for studying the common characteristics of spatiotemporally mode-locked pulses. To address the different dispersion parameters of different spatial modes in the multimode fiber, the results of inter-mode interactions are resolved through coupled equations, resulting in stable spatiotemporally mode-locked pulses. To further investigate the influence of more parameters on spatiotemporal mode-locking, this invention constructs a multidimensional generalized nonlinear Schrödinger equation to more directly describe multidimensional pulses. The evolution in a fully multimode fiber laser cavity is expressed as follows:

[0009]

[0010] in The term represents the nonlinear coefficient, and the last term represents the amplification in the gain fiber, where the gain fiber is not simplified to a single-mode field. Simultaneously, a complete spatiotemporal field saturable absorber is crucial for gain saturation and stable solutions. Based on full-field spatiotemporal simulations, this invention delves into the stable propagation process of multidimensional pulses in graded-mode waveguides, comprehensively analyzing the evolutionary trends of parameters such as time, frequency, and mode, clarifying the parameter coupling mechanism and mapping rules, and providing a theoretical foundation for achieving high-precision spatial mode resolution in the future.

[0011] This invention proposes a multidimensional pulse real-time evolution analysis technique, which builds a device with an all-fiber structure for real-time analysis of spatiotemporal mode-locked pulse multidimensional information. It realizes real-time detection, analysis and reconstruction of multidimensional parameters of spatiotemporal mode-locked pulses, which is beneficial to expanding the research on pulse multidimensional dynamics.

[0012] This invention constructs a theoretical model of a spacetime mode-locked laser based on the generalized multimode nonlinear Schrödinger equation, explores the multidimensional parametric coupling mechanism during spacetime mode-locking, clarifies the mapping relationship between modes and frequencies, and provides a theoretical foundation for high-precision mode differentiation and multidimensional real-time information extraction. Employing an all-fiber structure, and based on the mapping relationship between spatial modes and frequencies, it indirectly distinguishes different spatial modes in spacetime mode-locked pulses by using a frequency separation method, solving the problem of difficulty in distinguishing spatial modes in direct spatial sampling. By adjusting the characteristic parameters of the fiber grating, it achieves the differentiation of reflected light with different center wavelengths and bandwidths, changes the spatial mode sampling interval, improves the system's tunability, overcomes the limitation of spatial sampling resolution of spacetime mode-locked pulses, and provides technical support for studying the dynamic processes of different spatial modes.

[0013] To achieve the above objectives, this invention provides a device for real-time analysis of multidimensional information of spatiotemporally mode-locked pulses using an all-fiber structure. The device includes an all-fiber spatiotemporally mode-locked laser platform, a raw pulse beam profile measurement module, an optical circulator, a sub-pulse beam profile measurement module, and a dispersive Fourier transform and real-time spectral information detection module. The spatiotemporally mode-locked pulse beam output from the all-fiber spatiotemporally mode-locked laser platform is received by the raw pulse beam profile measurement module, which measures the raw pulse profile of the pulse beam. The pulse beam coupled out by the raw pulse beam profile measurement module is input to the first port of the optical circulator and transmitted through the second port to the sub-pulse beam profile measurement module. The sub-pulse beam profile measurement module measures the beam profiles of different sub-pulses to obtain the spatial mode distribution of the spatiotemporally mode-locked pulse within different frequency ranges. The chirped fiber gratings of different apodizations in the sub-pulse beam profile measurement module are reflected back to the second port of the optical circulator, transmitted through the optical circulator to the third port, then through the chirped Bragg fiber grating again to the fourth port, and finally transmitted through the photodetector to the high-speed oscilloscope. The chirped Bragg fiber grating, photodetector, and high-speed oscilloscope constitute a dispersive Fourier transform and real-time spectral information detection module. This module performs a dispersive Fourier transform on the spatiotemporally mode-locked pulse and measures its spectral information. The original pulse information measured by the original pulse beam profile measurement module, the sub-pulse information measured by the sub-pulse beam profile measurement module, and the pulse spectral information measured by the dispersive Fourier transform and real-time spectral information detection module are combined and processed to achieve real-time pulse information analysis.

[0014] Furthermore, the pump source is a current-driven laser diode, connected to the optical path of the ring laser resonator via a wavelength division multiplexer to inject pump light energy into the laser. During operation, the output pump light power can be adjusted synchronously by regulating the driving current. The erbium-doped fiber is connected to the wavelength division multiplexer, absorbing the pump light energy injected from the pump source and continuously providing gain for the laser pulses transmitted within the pulsed laser platform. The polarization controller is used to change the local optical polarization state of the optical path inside the laser resonator. During operation, the polarization controller is placed in the laser resonator to adjust the spatiotemporal mode-locking state of the laser pulses. The saturable absorber is composed of a first single-mode fiber, a graded multimode fiber, and a second single-mode fiber. It has nonlinear saturable absorption properties, enabling the introduction of a spatiotemporal mode-locking mechanism into the laser, thereby generating multi-transverse mode-locked laser pulses. The spectral filter is a few-mode fiber, utilizing the multimode interference effect of the few-mode fiber-graded multimode fiber-few-mode fiber structure to achieve spectral filtering, solving a key problem in the spatiotemporal mode-locking process. The first output coupler has two output ports. The first output port is connected to the optical path of the resonant cavity, and the second output port leads to the outside of the laser for outputting pulsed laser. When working, the laser input to the first output coupler will be split into two beams according to a certain power ratio. One beam is output from the second output port, and the other beam returns from the first output port to the optical path of the laser resonant cavity to continue to propagate along the current path.

[0015] Furthermore, the original pulse beam profile measurement module consists of a second output coupler and a first CCD image sensor. The second output coupler is connected to the all-fiber spatiotemporal mode-locked laser platform and has two output ports. The first output port, with a power percentage of 99%, is connected to the first port of the optical circulator, while the second output port, with a power percentage of 1%, is externally connected to output pulsed laser light, which enters the first CCD image sensor for measuring the original pulse profile.

[0016] Furthermore, the optical circulator includes four ports: a first port, a second port, a third port, and a fourth port.

[0017] Furthermore, the sub-pulse beam profile measurement module includes several cascaded sub-pulse beam profile measurement structure groups. Each sub-pulse beam profile measurement structure group sequentially includes a third output coupler, a second CCD image sensor, and a first apodized chirped fiber grating; a fourth output coupler, a third CCD image sensor, and a second apodized chirped fiber grating; and a fifth output coupler, a fourth CCD image sensor, and a third apodized chirped fiber grating. Apodized chirped fiber gratings with different center wavelengths are arranged in series at certain intervals, forming sub-pulses containing different frequency components from different bands in the reflected pulse. Each sub-pulse is connected to the CCD via a 1% output port of the coupler in front of the fiber grating to record the beam profile of different sub-pulses, obtaining the spatial mode distribution within different frequency ranges of the spatiotemporally mode-locked pulse. The 99% output port is connected to the second port of the optical circulator.

[0018] Furthermore, the dispersive Fourier transform and real-time spectral information detection module includes a chirped Bragg fiber grating, a photodetector, and a high-speed oscilloscope. The chirped Bragg fiber grating is connected to the third port of the optical circulator and is used to broaden each sub-pulse, mapping the frequency domain of the pulse to the time domain. After the dispersive Fourier transform, the pulse is reflected back to the third port, transmitted through the optical circulator, and output from the fourth port. The fourth port is connected to the photodetector and the high-speed oscilloscope, which are used to acquire and record the time-domain information of each sub-pulse, i.e., the real-time spectral information.

[0019] Compared with the prior art, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0020] 1. This invention designs a spectral filter and a saturable absorber based on multimode fiber to build an all-fiber spatiotemporal mode-locking system, achieving stable spatiotemporal mode-locking and outputting various spatiotemporal mode-locked pulses, providing a platform for studying multidimensional dynamic processes; based on the multidimensional pulse mode-frequency mapping relationship, a high-precision spatial mode resolution method is designed to improve spatial sampling resolution and effectively extract sub-pulses containing different transverse modes, providing a foundation for further measurement of their real-time information; combined with dispersive Fourier transform technology, a high-precision mode-resolved multidimensional information real-time measurement system is built to detect the real-time spectrum of different mode sub-pulses and obtain multidimensional real-time information of spatiotemporal mode-locked pulses.

[0021] 2. This invention proposes for the first time a high-resolution mode differentiation method based on fiber Bragg gratings. Based on the mapping relationship between spatial modes and frequencies, it indirectly distinguishes different spatial modes in spatiotemporally mode-locked pulses by separating frequencies. By adjusting the characteristic parameters of the fiber Bragg grating, it is possible to differentiate reflected light with different center wavelengths and bandwidths, thereby changing the spatial mode sampling interval. The system exhibits extremely high tunability, breaking through the limitations of spatial sampling resolution in spatiotemporally mode-locked pulses and providing technical support for studying the dynamic processes of different spatial modes.

[0022] 3. This invention adopts an all-fiber structure, requiring no external components, and features high beam quality, resistance to electromagnetic interference, high conversion efficiency, good stability, high feasibility, compact structure, low cost, and easy heat dissipation and maintenance.

[0023] 4. This invention can detect in real time and is versatile. As a multi-mode real-time detection system, it can be applied to many fields such as optical fiber communication and optical fiber sensing, and has rich scientific research significance and engineering application value. Attached Figure Description

[0024] Figure 1 This is a block diagram of the device for real-time analysis of spatiotemporal mode-locked pulse multidimensional information using an all-fiber structure provided by the present invention.

[0025] Figure 2 This is a structural diagram of an all-fiber spatiotemporal mode-locked laser platform;

[0026] Figure reference numerals: 1-All-fiber spatiotemporal mode-locked laser platform, 101-Pump source, 102-Wavelength division multiplexer, 103-Erbium-doped fiber, 104-Polarization controller, 105-First output coupler, 106-First single-mode fiber, 107-Graded multimode fiber, 108-Second single-mode fiber, 109-Spectral filter, 2-Raw pulse beam profile measurement module, 201-Second output coupler, 202-First CCD image sensor, 3-Optical circulator, 301-First port of optical circulator, 302-Second port of optical circulator, 303-Third port of optical circulator, 304- The optical circulator has four ports; 4-sub-pulse beam profile measurement module; 401-third output coupler; 402-second CCD image sensor; 403-first apodization chirped fiber grating; 404-fourth output coupler; 405-third CCD image sensor; 406-second apodization chirped fiber grating; 407-fifth output coupler; 408-fourth CCD image sensor; 409-third apodization chirped fiber grating; 5-dispersion Fourier transform and real-time spectral information detection module; 501-chirped Bragg fiber grating; 502-photodetector; 503-high-speed oscilloscope. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0028] This invention provides a device for real-time analysis of spatiotemporal mode-locked pulse multidimensional information using an all-fiber structure, such as... Figure 1 As shown, the system includes an all-fiber spatiotemporal mode-locked laser platform 1, a raw pulse beam profile measurement module 2, an optical circulator 3, a sub-pulse beam profile measurement module 4, and a dispersive Fourier transform and real-time spectral information detection module 5. The spatiotemporal mode-locked pulse beam output from the all-fiber spatiotemporal mode-locked laser platform 1 is received by the raw pulse beam profile measurement module 2, which measures the raw pulse profile of the pulse beam. The pulse beam coupled out by the raw pulse beam profile measurement module 2 is input to the first port 301 of the optical circulator and transmitted through the second port 302 to the sub-pulse beam profile measurement module 4. The sub-pulse beam profile measurement module 4 measures the beam profile of different sub-pulses, obtaining the spatial mode distribution of the spatiotemporal mode-locked pulse within different frequency ranges. After reflection by different apodized chirped fiber gratings, the beam returns to the optical circulator. The signal from the second port 302 of the circulator is transmitted to the third port 303 of the optical circulator via the optical circulator 3. After passing through the chirped Bragg fiber grating 501, it returns to the third port 303 of the optical circulator, then passes through the optical circulator 3 to the fourth port 304 of the optical circulator. After passing through the photodetector 502, it is transmitted to the high-speed oscilloscope 503. The chirped Bragg fiber grating 501, the photodetector 502, and the high-speed oscilloscope 503 constitute the dispersive Fourier transform and real-time spectral information detection module 5. The dispersive Fourier transform and real-time spectral information detection module 5 is used to perform dispersive Fourier transform on the spatiotemporally mode-locked pulse and measure the spectral information of the pulse. The original pulse information measured by the original pulse beam profile measurement module 2, the sub-pulse information measured by the sub-pulse beam profile measurement module 4, and the pulse spectral information measured by the dispersive Fourier transform and real-time spectral information detection module 5 are combined and processed to realize real-time pulse information analysis.

[0029] The original pulse beam profile measurement module 2 includes a second output coupler 201 and a first CCD image sensor 202. The spatiotemporal mode-locked pulse first passes through a 1:99 coupler, 1% of which enters the CCD to measure the original pulse profile, and the remaining 99% enters the first port 301 of the optical circulator.

[0030] The sub-pulse beam profile measurement module 4 includes several cascaded sub-pulse beam profile measurement structure groups. Each sub-pulse beam profile measurement structure group sequentially includes a third output coupler 401, a second CCD image sensor 402 and a first apodization chirped fiber grating 403, a fourth output coupler 404, a third CCD image sensor 405 and a second apodization chirped fiber grating 406, a fifth output coupler 407, a fourth CCD image sensor 408 and a third apodization chirped fiber grating 409, and so on. A first apodized chirped fiber grating 403, a second apodized chirped fiber grating 406, a third apodized chirped fiber grating 409, etc., are arranged in series at preset intervals to reflect different band portions of the pulse corresponding to its center wavelength, forming sub-pulses containing different frequency components. Each sub-pulse outputs 1% through the coupler in front of the fiber grating and enters the CCD to record the beam profile of different sub-pulses, thereby obtaining the spatial mode distribution of the spatiotemporally mode-locked pulse within different frequency ranges. 99% of the sub-pulses return to the second port 302 of the optical circulator.

[0031] The dispersive Fourier transform and real-time spectral information detection module 5 includes a chirped Bragg fiber grating 501, a photodetector 502, and a high-speed oscilloscope 503. The chirped Bragg fiber grating 501 is connected to the third port 303 of the optical circulator and is used to broaden each sub-pulse, mapping the frequency domain of the pulse to the time domain, so that the dispersive Fourier transform is reflected back to the third port 303 of the optical circulator, and after transmission, it is output from the fourth port 304 of the optical circulator. The photodetector 502 and the high-speed oscilloscope 503 will collect and record the time domain information of each sub-pulse, that is, the real-time spectral information.

[0032] like Figure 2 As shown, the all-fiber spatiotemporal mode-locked laser platform 1 includes a pump source 101 and a ring laser resonator cavity sequentially connected by a wavelength division multiplexer 102, an erbium-doped fiber 103, a polarization controller 104, a first output coupler 105, a saturable absorber, and a spectral filter 109. The pump source 101 is connected to the optical path of the ring laser resonator cavity through the wavelength division multiplexer 102, injecting pump light energy into the laser. The erbium-doped fiber 103 is connected to the wavelength division multiplexer 102, absorbing the pump light energy injected from the pump source 101, thus providing power to the all-fiber spatiotemporal mode-locked laser platform 1. The transmitted laser pulses continuously provide gain; the polarization controller 104 is used to change the local optical polarization state of the optical path inside the ring laser resonator; the first output coupler 105 includes two output ports, one of the lasers input to the first output coupler 105 is output from the second output port for outputting pulsed laser, and the other is returned from the first output port to the laser resonator optical path to continue propagating along the current path, passing through a saturable absorber, introducing a spatiotemporal mode-locking mechanism to generate multi-transverse mode-locked laser pulses, which are then filtered by the spectral filter 109 and returned to the wavelength division multiplexer 102.

[0033] The saturable absorber includes a first single-mode fiber 106, a graded multimode fiber 107, and a second single-mode fiber 108 connected in sequence.

[0034] Example

[0035] The system includes a 980 nm pump source, a 980 / 1550 nm wavelength division multiplexer, three meters of erbium-doped fiber, a polarization controller, a 1*2 output coupler with a split ratio of 10:90, four 1*2 output couplers with a split ratio of 1:99, two single-mode fibers, one graded multimode fiber, one few-mode fiber, three apodized chirped fiber gratings, one chirped Bragg fiber grating, a 4-port optical circulator, four CCD image sensors, a high-speed photodetector with a sampling rate of 25 GS / s, and a high-speed oscilloscope with a sampling rate of 20 GS / s.

[0036] Among them, the pump source 101 is a current-driven laser diode. The output optical power and operating temperature are monitored in real time through the integrated current stabilization and heat dissipation device of the pump source, and the output pump optical power is adjusted synchronously by adjusting the driving current.

[0037] The wavelength division multiplexer 102 has a 980 nm pump light input port and two 1550 nm transmission ports. The 980 nm port is used to connect to the pump source 101 and couple the pump light energy into the laser optical path.

[0038] Erbium-doped fiber 103 is connected to the 1550nm port of wavelength division multiplexer 102, absorbing the input 980nm pump light energy and providing gain for pulsed laser through stimulated emission light amplification effect.

[0039] One end of the polarization controller 104 is connected to the end of the erbium-doped fiber 103, which can control the local polarization state of the light, thereby adjusting the working state of the mode-locked laser in the optical path. The other end is connected to the first output coupler 105. The pulsed laser input to the coupler is split into two beams of unequal power. One beam is output to the outside through the 10% splitting ratio port for subsequent system detection, and the other beam returns to the laser through the 90% splitting ratio port to continue transmission.

[0040] The saturable absorber consists of a first single-mode fiber 106, a graded multimode fiber 107, and a second single-mode fiber 108 connected in sequence. The saturable absorber is connected to the 90% output port of the first coupler 105. It has saturable absorption properties, retains more field dimensions compared to nonlinear polarization rotation, and introduces a spatial filtering effect, realizing multiple uses for a single device and introducing spatiotemporal mode locking for the laser.

[0041] The spectral filter 109 is connected to a saturable absorber. The spectral filter utilizes the multimode interference effect of a few-mode fiber-graded multimode fiber-few-mode fiber structure to achieve spectral filtering, solving a key problem in the spatiotemporal mode-locking process.

[0042] The second output coupler 201 is connected to the 10% port of the first output coupler 105. The output spatiotemporal mode-locked pulse is divided into two beams with a ratio of 1:99. One of the beams, representing 1%, is connected to the first CCD image sensor 202 to monitor the profile of the spatiotemporal mode-locked pulse spot and to analyze its transverse mode distribution.

[0043] The 4-port optical circulator 3 has unidirectional transmission characteristics, and the spatiotemporal mode-locked pulse is transmitted clockwise. The first port 301 of the optical circulator is connected to the 99% port of the second output coupler 201; the second port 302 of the optical circulator is connected to the 99% port of the third output coupler 401; the third port 303 of the optical circulator is connected to the chirped Bragg fiber grating 501, where the spatiotemporal mode-locked pulse is broadened by the grating to achieve dispersive Fourier transform; the fourth port 304 of the optical circulator is connected to the photodetector 502.

[0044] The input port of the third output coupler 401 is connected to the first apodized chirped fiber grating 403. Using a specific center wavelength, the apodized chirped fiber grating reflects the selected sub-pulse back. After passing through the output coupler, the input port is connected to the second CCD image sensor 402 to detect the beam shape profile of the sub-pulse. In the sub-pulse beam profile measurement module 4, each detection structure consisting of an apodized chirped fiber grating, an output coupler, and a CCD image sensor separates and detects the beam profile of a sub-pulse within a specific wavelength range. Combined with the light source mode used in actual applications, the beam profile of each sub-pulse can be detected by selecting different center wavelengths of the apodized chirped fiber grating and adjusting the angle. In actual use, it is not necessary to be limited to the three detection structures shown in the reference figure; the number of detection structures can be increased or decreased as needed.

[0045] The photodetector 502 receives the spatiotemporally mode-locked pulses broadened by the chirped Bragg fiber grating 501, converts the frequency domain signal of the spatiotemporally mode-locked pulses into an electrical signal, and connects it to a high-speed oscilloscope 503. The oscilloscope allows for real-time observation of the time-domain information (i.e., real-time spectral information) of each sub-pulse of the spatiotemporally mode-locked pulse. The instrument used to detect the spectral characteristics of the output optical signal can be replaced with any other signal analysis instrument for different signal analysis needs, such as a power meter, oscilloscope, spectrum analyzer, autocorrelator, etc.

[0046] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A device for real-time analysis of spatiotemporal mode-locked pulse multidimensional information using an all-fiber structure, characterized in that, The system includes an all-fiber spatiotemporal mode-locked laser platform (1), a raw pulse beam profile measurement module (2), an optical circulator (3), a sub-pulse beam profile measurement module (4), and a dispersive Fourier transform and real-time spectral information detection module (5). The spatiotemporal mode-locked pulse beam output by the all-fiber spatiotemporal mode-locked laser platform (1) is received by the raw pulse beam profile measurement module (2), which measures the raw pulse profile of the pulse beam. The pulse beam coupled out by the raw pulse beam profile measurement module (2) is input to the first port (301) of the optical circulator and transmitted to the sub-pulse beam profile measurement module (4) through the second port (302) of the optical circulator. The sub-pulse beam profile measurement module (4) measures the beam profile of different sub-pulses to obtain the spatial mode distribution of the spatiotemporal mode-locked pulse within different frequency ranges. After being reflected by different apodized chirped fiber gratings of the sub-pulse beam profile measurement module (4), the beam returns to the first port (301) of the optical circulator. The two-port (302) is transmitted to the third port (303) of the optical circulator (3) after passing through the chirped Bragg fiber grating (501), and then returns to the third port (303) of the optical circulator. After passing through the optical circulator (3) to the fourth port (304), it is transmitted to the high-speed oscilloscope (503) after passing through the photodetector (502). The chirped Bragg fiber grating (501), the photodetector (502), and the high-speed oscilloscope (503) form a dispersive Fourier transform and real-time spectral information detection module (5). The dispersive Fourier transform and real-time spectral information detection module (5) is used to perform dispersive Fourier transform on the spatiotemporally mode-locked pulse and measure the spectral information of the pulse. The original pulse information measured by the original pulse beam profile measurement module (2), the sub-pulse information measured by the sub-pulse beam profile measurement module (4), and the pulse spectral information measured by the dispersive Fourier transform and real-time spectral information detection module (5) are combined and processed to realize real-time pulse information analysis. The all-fiber spatiotemporal mode-locked laser platform (1) includes a pump source (101) and a ring laser resonator consisting of a wavelength division multiplexer (102), an erbium-doped fiber (103), a polarization controller (104), a first output coupler (105), a saturable absorber, and a spectral filter (109) connected in sequence. The pump source (101) is connected to the optical path of the ring laser resonator via the wavelength division multiplexer (102) to inject pump light energy into the laser. The erbium-doped fiber (103) is connected to the wavelength division multiplexer (102) to absorb the pump light energy injected from the pump source (101), thus providing all-fiber spatiotemporal mode-locked laser energy. The laser pulse transmitted inside the device platform (1) continuously provides gain; the polarization controller (104) is used to change the local optical polarization state of the optical path inside the ring laser resonator cavity; the first output coupler (105) includes two output ports, one of the lasers input to the first output coupler (105) is output from the second output port for outputting pulsed laser, and the other is returned from the first output port to the optical path of the laser resonator cavity to continue transmission along the current path. After passing through the saturable absorber, a spatiotemporal mode-locking mechanism is introduced to generate multi-transverse mode-locked laser pulses, which are then filtered by the spectral filter (109) and returned to the wavelength division multiplexer (102).

2. The apparatus according to claim 1, characterized in that, The saturable absorber includes a first single-mode fiber (106), a graded multimode fiber (107), and a second single-mode fiber (108) connected in sequence.

3. The apparatus according to claim 1, characterized in that, The original pulse beam profile measurement module (2) includes a second output coupler (201) and a first CCD image sensor (202). The spatiotemporal mode-locked pulse first passes through the 1:99 coupler, 1% of which enters the CCD to measure the original pulse profile, and the remaining 99% enters the first port (301) of the optical circulator.

4. The apparatus according to claim 1, characterized in that, The sub-pulse beam profile measurement module (4) includes several cascaded sub-pulse beam profile measurement structure groups. Each sub-pulse beam profile measurement structure group sequentially includes a third output coupler (401), a second CCD image sensor (402), and a first apodization chirped fiber grating (403); a fourth output coupler (404), a third CCD image sensor (405), and a second apodization chirped fiber grating (406); and a fifth output coupler (407), a fourth CCD image sensor (408), and a third apodization chirped fiber grating (409). ...; The first apodized chirped fiber grating (403), the second apodized chirped fiber grating (406), the third apodized chirped fiber grating (409) ... are arranged in series at a preset distance to reflect different bands of the pulse corresponding to its center wavelength, forming sub-pulses containing different frequency components. Each sub-pulse outputs 1% through the coupler in front of the fiber grating and enters the CCD to record the beam profile of different sub-pulses and obtain the spatial mode distribution of the spatiotemporally mode-locked pulse in different frequency ranges. 99% of the sub-pulses return to the second port (302) of the optical circulator.

5. The apparatus according to claim 4, characterized in that, The dispersive Fourier transform and real-time spectral information detection module (5) includes a chirped Bragg fiber grating (501), a photodetector (502), and a high-speed oscilloscope (503). The chirped Bragg fiber grating (501) is connected to the third port (303) of the optical circulator to broaden each sub-pulse, map the frequency domain of the pulse to the time domain, and realize the reflection back to the third port (303) of the optical circulator after dispersive Fourier transform. After transmission, it is output from the fourth port (304) of the optical circulator. The photodetector (502) and the high-speed oscilloscope (503) will collect and record the time domain information of each sub-pulse, that is, the real-time spectral information.

6. The apparatus according to claim 1, characterized in that, The pump source (101) is a flow-driven laser diode.

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