Design Of 780nm High Spectral Resolution Lidar Based On Laser Diode

The atmospheric aerosol is a complicated multiphase system composed of atmosphere and kinds of particles suspending in it.High spectral resolution lidar is an indispensable tool for retrieving the extinction coefficient of aerosols by detecting Mie scattering signal from aerosols and Rayleigh scattering signal from atmospheric molecules independently.In order to retrieve the optical properties of aerosols at 780nm finely and extend the application of high spectral resolution lidar into more wavebands,the 780nm high spectral resolution lidar system is designed based on semiconductor laser.The laser emission system and high spectral resolution spectroscopic system are designed with emphasis.Then the performances of the lidar system have been analyzed.The spectrum of Mie scattering signal from aerosols and Rayleigh scattering signal from atmospheric molecules is analyzed,then the detection principle and inversion algorithm of high spectral resolution lidar are expounded in detail.The laser emission system of the 780nm high spectral resolution lidar is designed,in which the DFB laser is used as the seed source and the tapered semiconductor optical amplifier is driven by pulse current.The pulse driver of optical amplifier is designed based on high-speed MOSFET.The cylindrical lens and aspherical mirror are used to reduce the beam divergence of the tapered semiconductor optical amplifier.The central wavelength of the laser emission system is 780.246nm and the bandwidth is 0.6MHz.In the case of repetition frequency of 1kHz,the pulse width is 250ns and the pulse energy is 1?J.The output spot is elliptic,the long axis is 31 mm and the short axis is 4.8mm.The divergence angles of the output beam in the fast axe and slow axe are 0.2mrad and 0.035mrad respectively.The spectroscopic system of 780nm high spectral resolution lidar is designed by interference filter,FP etalon and Rb cell,and the parameters of FP etalon and operating temperature of Rb cell are optimized.The bandwidth of the interference filter is 0.5nm.The FWHM of the transmission peak of FP etalon is 2.8GHz,and the free spectrum range is 98.62GHz.The cavity length of Rb cell is 71.80mm,the operating temperature is 338K.The inhibition rate to the Mie scattering signal can reach 37.3dB.The results show that the spectroscopic system can effectively separate the Mie scattering signal from Rayleigh scattering signal.Finally,the performance of the 780nm high spectral resolution lidar is simulated numerically based on the American standard atmospheric model.The results show that the effective detection heights of the Mie channel and Rayleigh channel are 4.9km and 5.4km respectively at night,and 2.0km and 1.9km respectively in the daytime,which the threshold of SNR is 10.The 780nm high spectral resolution lidar system is an important application extension of the high spectral resolution lidar,and can provide important supplement to the existing aerosol detection data.In addition,the 780nm high spectral resolution lidar system has the advantages of eye safety and convenient maintenance.In summary,the research has great significance for the development of fine detection technology of aerosols and the productization of high spectral resolution lidar.