Analysis And Experimental Research On Pumping Parameters Of Laser Guide Sodium Star

Obtaining a high-luminance sodium guide star is an important condition for accurate detection of atmospheric wavefront distortion.The intensity of backward resonance fluorescence scattering of sodium guiding stars is closely related to many factors such as atmospheric transmission efficiency,geomagnetic field,season,transmitting system parameters,receiving system parameters,and pump laser parameters.Investigate the physical relationship between the pumping parameters of the laser sodium guide star and the intensity of the return light,and conduct experimental verification to guide the design of sodium guide lasers with efficient excitation performance,conduct sodium guide star experiments,and obtain high signal-to-noise guide satellite return Optical signals have an important role in the development of adaptive optics technology for deep space exploration in the astronomical field.This article starts from the theoretical model of sodium atom ultrafine spectroscopy,and conducts in-depth research and exploration theoretically and experimentally.The main research contents and innovations are as follows:(1)A numerical model of a two-level system that directly correlates the laser pumping parameters and the intensity of the return light was established;the physical parameter setting model of the sodium guide star was established,and the sodium guide star experimental system parameters and atmospheric condition parameters with practical reference significance were completed Set;Based on the density matrix software,by solving the steady state solution of the matrix p in the thermal equilibrium state,the calculated expected value of the fluorescence operator of the Bloch equation is obtained,and the resonance fluorescence characteristics of the sodium atom are simulated.Based on the above work,the numerical simulation of sodium resonance fluorescence intensity under the conditions of widening of various spectral lines in the 2-level system is completed;the output laser wavelength tuning,polarization state conversion,power density adjustment,line width adjustment,single/Numerical Simulation of Sodium Resonance Fluorescence Intensity under Two-line Excited Iso-pumped State The simulation results show that:on the one hand,the pump laser line broadening technology is beneficial to excite more sodium atom velocity groups and enhance the resonance fluorescence;and the double-line circular polarization 100 Hz laser pump that matches the double peaks of the sodium atom absorption spectrum Pu is the optimal excitation mode for sodium guide stars.On the other hand,after the pump laser mode is effectively optimized,the light return efficiency is less affected by the pump intensity and can be effectively maintained at high power density;as the pump power increases,no strict light return occurs Intensity saturation,increasing pump intensity has a significant contribution to enhancing back light.(2)Carry out laboratory sodium pool experiments.An experimental system was set up using a sodium cell device and a 589nm laser with high-precision wavelength tuning control,and experiments were performed on the resonance fluorescence intensity characteristics of the sodium cell under the conditions of output laser wavelength tuning,polarization state conversion,line width adjustment,and single-line/double-line excitation.The experimental results are consistent with the theoretical analysis.(3)Establish an experimental system for high-efficiency launching/receiving of sodium guide stars,and conduct experiments on sky sodium guide stars.A variety of laser parameter pumping modes were used to detect the return intensity of the pulsed sodium guide star.By adjusting the polarization state of the output laser,the center wavelength of the excitation spectral line,and the spectral line width parameters and other technical methods,high-energy-based A series of 100-second pulsed sodium guide lasers with multiple longitudinal mode pulsed sodium guide lasers pump a series of back light intensity data that are consistent with the theoretical analysis results.Experimentally,a comprehensive comparison between the light return characteristics of sodium guide stars and light source parameters is obtained.Understanding of the regularity of physical relationships.The experimental results show that the precise control of the pump laser line is an important means to obtain the stable light return intensity of the sodium guide star.The working mode of the sodium guide star based on the circularly polarized double-line stretched pumping system is to achieve efficient excitation and obtain the sodium layer atoms.An effective way for high brightness back light.(4)It is proposed to use the synchronous detection technology to realize the focusing non-iso-halo measurement of sodium guide stars within the Greenwood time constant of the atmosphere.Simultaneous detection of the Hartmann lattice in the visible light band,and obtaining a single-frame wavefront of the return light of the sodium guide star.The experimental results were analyzed from the aspects of wavefront consistency comparison,Zernike coefficient comparison,and analog imaging correction.The experimental results show that under the current experimental conditions,although the imaging contrast of a single-frame Hartmann lattice of a pulsed sodium guide star is relatively low,which restricts the accuracy of wavefront recovery,the two sets of wavefronts measured simultaneously can always maintain similarity.The coefficients have good consistency in the first 36 steps.The simulation results show that the detection surface of the sodium guide star can help to effectively correct the imaging of natural stars.The deviation of the focus anisotropic halo after subtracting the wave surface recovery error is less than 0.1 rad2,which is very close to the theoretical result.