Research On Transmission Characteristics And Beam Shaping Of Laser Energy Supply System

The laser energy supply system has the advantages of anti-electromagnetic interference and high voltage,and it has important application in military,civilian,and industrial environments.Laser energy supply system generally uses laser battery as photoelectric conversion element.The material of the laser battery can accept a laser beam with a narrow line width,which greatly explores the conversion efficiency of the laser battery and reduces the occurrence of thermal effects.In addition,the high power density and high unidirectionality of the laser beam enable a small area laser battery to obtain high-power energy conversion;beam shaping can ensure the uniformity of the incident laser,and solve the high-intensity unevenness of the laser battery carried by the fiber.Long distance laser energy transmission can be achieved by energy transfer fiber.However,the distribution of laser energy output by fiber is not uniform,resulting in speckle,dark area,decrystallization and other problems when irradiated to laser battery.By shaping the output beam,the uniformity of incident laser can be improved to solve the above problems.The conversion efficiency and output power of laser battery are the most critical parameters in its output performance.Based on the introduction of the working principle of laser battery and the theory of beam shaping,this paper studies the photoelectric conversion characteristics of laser under the irradiation of the beam shaping,explores its influencing factors and makes theoretical derivation and experimental research in many aspects,and designs a set of beam shaping system to obtain the adaptive laser beam.The main contents include(1)A set of laser energy supply system was established to verify the effects of the laser battery material and working temperature,incident laser uniformity,shape matching and other factors on the output performance of the battery.In the natural cooling state,the power density of the incident laser was gradually increased,and the output power of the laser battery first increased rapidly and then reached saturation.With the increase of the operating temperature of the laser cell,the photoelectric conversion efficiency decreases.The conversion efficiency of uniform beam is higher than that of Gaussian beam.In this experiment,the maximum conversion efficiency of Si and GaAs laser cells is 20.6% and 46.5% respectively at 280 K temperature and1W/cm2 power density irradiation.The results show that increasing the incident power density,decreasing the operating temperature,improving the spot uniformity and matching degree can improve the photoelectric conversion efficiency of the laser cell.(2)Design a beam shaping system based on an aspherical lens,using the theory of aspherical mirrors to achieve flat top distribution of light spots,achieve rectangular distribution of light spots through fast and slow axis alignment,and a rectangular spot with 83% uniformity was obtained.On the basis of this system,a variable magnification beam expansion system based on fiber optic end caps is designed,which uses fiber optic end caps to replace aspherical lenses.The output surface of the end caps is aspherical,which can not only transmit large energy but also achieve flat top distribution of light spots.By using a "negative positive negative" structure variable magnification beam expansion mirror group,the shape and size of the light spot can be adjusted,the beam expansion ratio is adjustable from 1 to 24 times,and the maximum spot radius is 24 mm,providing a feasible solution for the matching and coupling of the shaped beam and the size of the laser battery.