Research On Pusle Laser Frequency Locking Method Based On Molecular Absorption

Our country is a country with frequent meteorological disasters.In recent years,global climate change has further exacerbated the trend of frequent meteorological disasters such as drought and hail in our country,causing serious economic losses and casualties.Drought and hail disasters seriously threaten our country's food security,water security and ecological security,and restrict the sustainable development of social economy.Water resources have become an important material basis for the sustainable development of our country's social economy.Artificial rain increase is the most direct,effective,and cost-effective way to increase local precipitation using atmospheric water resources.The precipitation potential of the cloud system is determined by the macro conditions of the cloud,which mainly depends on the water vapor supply and the distribution of the updraft.In order to solve the lack of measurement of cloud bottom temperature and humidity and cloud bottom rise rate in the detection of cloud precipitation potential,the cloud precipitation precipitation detection lidar integrates multi-wavelength technology,hyperspectral technology,Raman technology and rice scattering single-edge technology to achieve the detection of bottom height,atmospheric humidity,atmospheric temperature and wind speed.The stability of the frequency of the laser emission system directly determines the measurement accuracy of the atmospheric temperature and wind speed of the lidar for detection of cloud precipitation potential.Lidar for detection of cloud precipitation potential has proposed 0.5K atmospheric temperature observation accuracy and 0.3?0.5m/s cloud bottom vertical wind speed observation accuracy.However,the current commercial laser has a large frequency drift range and cannot provide a stable frequency detection light source for lidar for detection of cloud precipitation potential to achieve its detection accuracy of atmospheric temperature and wind speed.In this thesis,a set of pulsed laser frequency locking method based on frequency discrimination of Iodine molecular absorption spectrum is proposed.The absorption spectrum of the Iodine molecular absorption cell at different temperatures was measured and calibrated.Based on the size of the linear region and the frequency discrimination sensitivity,the Iodine absorption spectrum at different temperatures was compared and analyzed to determine the optimal spectrum to achieve laser frequency monitoring of laser emission.A computer measurement and control system based on a graphical programming language development environment and a data acquisition card was built.The measurement and control system,under the control of a trigger signal at the same frequency as the pulse laser,realizes the functions of collection,preservation and feedback control of the pulse laser output laser frequency.The feedback control signal output from the measurement and control system is loaded on the tunable seed laser to tune the output frequency of the seed laser,and the seed injection technology is used to control the output laser frequency of the pulse laser,so that the pulse laser output laser frequency is between the set target frequency.The deviation of is continuously reduced and stabilized within the ideal range to achieve pulse laser frequency locking.The frequency locking results show that the frequency drift of the pulsed laser is less than±1.4MHz in 25 minutes,the temperature measurement error caused by the frequency drift after frequency locking is less than 0.16K,and the wind measurement error is less than 0.37m/s,which reaches the detection system of cloud precipitation potential.Radar's requirements for atmospheric temperature and wind field detection accuracy.The pulse laser frequency locking method based on Iodine molecular absorption spectrum frequency discrimination can not only stabilize the frequency drift of the seed laser,but also reduce the frequency drift of the pulse laser due to the influence of temperature and vibration on the resonant cavity.At the same time,the research results of this thesis can provide a solid technical guarantee for the detection of atmospheric temperature and wind field by the lidar of the precipitation potential of the cloud system,and solve the limitation of the detection accuracy of the laser source frequency stability in the field of lidar remote sensing.