CN-116519151-B - Device for analyzing space-time mode locking pulse multidimensional information in real time by all-fiber structure

CN116519151BCN 116519151 BCN116519151 BCN 116519151BCN-116519151-B

Abstract

The invention discloses a device for analyzing space-time mode locking pulse multidimensional information in real time by an all-fiber structure, and belongs to the technical field of ultrafast optics. The device comprises an all-fiber space-time mode-locked laser platform, an original pulse beam profile measuring module, an optical circulator, a sub-pulse beam profile measuring module and a dispersion Fourier transform and real-time spectrum information detecting module. The invention constructs a theoretical model of the space-time mode-locked laser based on a generalized multimode nonlinear Schrodinger equation, explores a multidimensional parameter coupling mechanism in the space-time mode locking process, and provides a theoretical basis and a method for high-precision mode distinction and multidimensional real-time information extraction by adopting a mapping relation between a li-qing mode and a frequency. According to the invention, each fiber grating parameter is designed reasonably according to the spectral width and time domain interval of the space-time mode-locked pulse, more sub-pulses are reflected on the premise of ensuring that the pulse time domains are not overlapped, high-precision spatial mode resolution is realized, and the stretched pulse is maximized, so that high-resolution real-time spectral information is obtained.

Inventors

XIA RAN
CHEN XI
YUAN QINYUN
WANG XIUZHENG
ZHANG ZHIBO
XU GANG
TANG XIAHUI

Assignees

华中科技大学

Dates

Publication Date: 20260505
Application Date: 20230425

Claims (6)

1. The device for analyzing the space-time mode-locked pulse multidimensional information in real time by the all-fiber structure is characterized by comprising an all-fiber space-time mode-locked laser platform (1), an original pulse beam profile measuring module (2), an optical circulator (3), a sub-pulse beam profile measuring module (4), a dispersion Fourier transform and real-time spectrum information detecting module (5), wherein the space-time mode-locked pulse beam output by the all-fiber space-time mode-locked laser platform (1) is received by the original pulse beam profile measuring module (2), the original pulse beam profile measuring module (2) is used for measuring the original pulse profile of a pulse beam, the pulse beam coupled by the original pulse beam profile measuring module (2) is input to a first port (301) of the optical circulator, transmitted to the sub-pulse beam profile measuring module (4) through a second port (302) of the optical circulator, the sub-pulse beam profile measuring module (4) is used for measuring the beam profiles of different sub-pulses, the spatial mode distribution in different frequency ranges of the space-time mode-locked pulse beam profile measuring module (4) is obtained, the different chirped light beams reflected by the original pulse beam profile measuring module (2) are reflected by the original pulse profile measuring module (2), the second port (501) of the chirped light grating (3) is transmitted to a fourth port (303), the chirped light grating (303) is transmitted to a fourth port (303), the system is transmitted to a high-speed oscilloscope (503) after passing through a photoelectric detector (502), wherein the chirped Bragg fiber grating (501), the photoelectric detector (502) and the high-speed oscilloscope (503) form a dispersion Fourier transform and real-time spectrum information detection module (5), and the dispersion Fourier transform and real-time spectrum information detection module (5) is used for carrying out dispersion Fourier transform on space-time mode-locked pulses and measuring spectrum information of the pulses; The all-fiber space-time mode-locked laser platform (1) comprises a pumping source (101) and a ring laser resonant cavity which is 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), wherein the pumping source (101) is connected with a ring laser resonant cavity optical path through the wavelength division multiplexer (102) and is used for injecting pumping light energy into a laser, the erbium-doped fiber (103) is connected with the wavelength division multiplexer (102) and is used for absorbing the pumping light energy injected from the pumping source (101) and continuously providing gain for laser pulses transmitted inside the all-fiber space-time mode-locked laser platform (1), the polarization controller (104) is used for changing the local light polarization state of an optical path inside the ring laser resonant cavity, the first output coupler (105) comprises two output ports, one path of laser input to the first output coupler (105) is output from the second output port and is used for outputting pulse laser, the other path returns to the current output port along the resonant cavity optical path, and can be continuously led to the spectral filter (109) through the saturation mode-locked filter after the laser pulses are continuously transmitted from the first output port to the first output port and the current port, and the laser pulses pass through the saturation mode-locked filter and the spectral filter is continuously.
2. The device according to claim 1, wherein the saturable absorber comprises a first single mode fiber (106), a graded multimode fiber (107), a second single mode fiber (108) connected in sequence.
3. The apparatus according to claim 1, wherein the raw pulse beam profile measurement module (2) comprises a second output coupler (201), a first CCD image sensor (202), the spatiotemporal mode-locked pulse first passing through a 1:99 coupler, 1% of the fraction entering the CCD for measuring the raw pulse profile, the remaining 99% entering the optical circulator first port (301).
4. The device according to claim 1, wherein the sub-pulse beam profile measurement module (4) comprises a plurality of groups of cascaded sub-pulse beam profile measurement structure groups, each group of sub-pulse beam profile measurement structure groups sequentially comprises 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), the first apodization chirped fiber grating (403), the second apodization chirped fiber grating (406) and the third apodization chirped fiber grating (409) are arranged in series at a preset distance interval, and are used for reflecting different parts of pulses corresponding to the central wavelength thereof, forming sub-pulses containing different frequency components, each sub-pulse enters the CCD through the coupler output 1% before the fiber grating, records the different sub-pulses, and returns to the annular pulse profile of the second apodization chirped fiber grating (99) to the annular pulse mode.
5. The device according to claim 4, wherein the dispersion fourier transform and real-time spectrum information detection module (5) comprises a chirped bragg fiber grating (501), a photoelectric detector (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 used for stretching each sub-pulse, mapping the frequency domain of the pulse to the time domain, realizing the reflection of the pulse back to the third port (303) of the optical circulator after the dispersion fourier transform, and outputting the pulse from the fourth port (304) of the optical circulator after the dispersion fourier transform, wherein the photoelectric detector (502) and the high-speed oscilloscope (503) are used for collecting and recording the time domain information, namely the real-time spectrum information, of each sub-pulse.
6. The apparatus according to claim 1, characterized in that the pump source (101) is a flow-driven laser diode.

Description

Device for analyzing space-time mode locking pulse multidimensional information in real time by all-fiber structure Technical Field The invention belongs to the technical field of ultrafast optics, and particularly relates to a device for analyzing space-time mode locking pulse multidimensional information in real time by an all-fiber structure. Background The ultra-short laser pulse is used as an indispensable tool for the development of ultra-fast science, and plays a unique role in the basic research fields of high-energy physics, chemical observation, biological imaging and the like. In recent years, the space-time mode locking technology breaks through the limitation of one-dimensional locking of the traditional mode locking technology, realizes synchronous locking of space and time, and obtains ultra-short pulse containing a plurality of high-order space modes. The multimode fiber nonlinear effect makes the space-time mode-locked laser have abundant and complex high-dimensional nonlinear dynamics, however, the technology for acquiring the multidimensional information in real time is in a development stage because of the difficulty in distinguishing the space mode of the space-time mode-locked pulse with high precision, so that the dynamics research on the space-time mode-locked laser is still in a starting stage. Therefore, a high-precision multidimensional parameter measurement method is designed, space-time-spectrum information of the space-time mode locking pulse is obtained in real time, dynamics characteristics of transient evolution of the multidimensional ultrashort pulse are revealed, on one hand, the dimension of the ultrashort pulse in nonlinear science is facilitated to be expanded, and on the other hand, a theoretical basis is provided for obtaining high-power and narrow-pulse-width laser pulses. The space-time mode locking technology has been proposed in 2017, and is rapidly becoming one of the research hot spots of ultrafast laser, which shows a great deal of mode locking states similar to those of traditional mode locking lasers, including phenomena such as multipulse, bound state pulse, self-similarity, wavelength tunable and the like. The spatial sampling resolution is limited, the distinction between different spatial modes is not obvious, and the comprehensive analysis of the dynamics characteristics of different modes in the space-time mode locking pulse is still difficult. Therefore, the multi-dimensional parameter real-time measurement method based on the high-precision mode resolution technology is very necessary for acquiring the multi-dimensional information of the space-time mode locking pulse and the dynamic process of the li qing multi-dimensional pulse. The multidimensional parameter in the space-time mode locking pulse determines the characteristics of the pulse, and the frequency mapping result in time can be obtained through dispersion Fourier transformation. However, the mapping relation between the spatial mode and the frequency and time is not clear, is a key for exploring a high-precision mode resolution method, and is a problem to be solved in the process of researching the real-time dynamics characteristics of the multi-dimensional pulse. Disclosure of Invention Aiming at the defects of the prior art, the invention aims to provide a device for analyzing space-time mode-locking pulse multidimensional information in real time by an all-fiber structure, and aims to detect, analyze and reconstruct multidimensional parameters of space-time mode-locking pulses in real time. The invention is based on the space-time mode-locked laser model of generalized multimode nonlinear Schrodinger equation (GMMNLSE), firstly describes the mode field of space-time mode-locked pulseThe transmission process in a passive multimode optical fiber is expressed as follows: Wherein the method comprises the steps of N 2 is the refractive index of the fiber for the m-order dispersion term,Is centered at the angular frequency of the light emitted by the light source,In order for the raman component to be a component,For the raman response of the medium, the transmission of the multimode pulses is simulated by coupling a series of equations for the different modes P. Firstly, calculating dispersion parameters of each mode corresponding to multimode fibers through numerical values, simplifying a few-mode gain fiber into a transmission process in a single-mode fiber, exciting multimode when the gain fiber enters the multimode fiber, and performing spatial filtering when the gain fiber enters the gain fiber. The invention adopts the saturable absorber in the single mode field to replace the space-time mode locking, which greatly reduces the model operation amount in the process of acquiring the space-time mode locking and provides a theoretical tool for researching the common characteristic of the space-time mode locking pulse. Aiming at the difference of transmission dispersion parameters of differ