Reserach On Pules Timing Modulation Tunable Dye Laser Doubling Frequency Technology

Combustion is the main form of energy conversion.The combustion process is very hot and the environment is complicated and complicated.In the measurement method of the combustion field,Planar laser-induced fluorescence has the advantages of non-contact measurement,high resolution and rich measurement information.PLIF is a general technology for combustion diagnosis.In recent years,in order to meet the research of high-speed flow fields such as engine ignition,aircraft wind tunnel test and hypersonic aircraft,High-speed PLIF technology has gradually become a hot research topic.Dye laser as the core source of PLIF technology.When operating at high repetition frequency,the single-pulse energy of the output ultraviolet band is low,which cannot meet the needs of high-speed PLIF diagnosis.Aiming at the demand of tunable laser source for highspeed PLIF technology,this paper studies the frequency doubling efficiency of dye laser under high energy.First,the construction of the experimental device for frequency doubling efficiency research was completed.In the experiment,Rhodamine 6G was dissolved in methanol solution.The experimental device mainly comprises a pump source,an oscillating stage,a beam shaping system,an amplification stage and a frequency doubling module.Changing the laser output by change the beam shaping lens spacing.The influence of the beam shaping lens spacing on the seed beam waist position,divergence angle and the amplitude of the base beam of the amplification stage is measured.The shaping principle is analyzed by the light propagation matrix of Gaussian beam,and the experimental results are in line with the theory.The experimental results show that the seed light collimation effect is best when the mirror spacing is 110.9mm.Using a CCD camera shoot the seed light and the amplified fundamental frequency spot separately.The light intensity distribution is analyzed by Matlab software.The results show that the beam shaping system can change the quality of the fundamental beam of the amplification stage.Keep the fundamental frequency optical pulse output energy 7.5mJ,The second harmonic pulse energy at the waist position of different fundamental frequency beams was measured separately.When the beam position is 28.2cm,the frequency doubling efficiency is the highest,reaching 21.43%.The effects of fundamental frequency optical power density,fundamental frequency light divergence,fundamental frequency beam waist position and frequency doubling crystal cutting angle on laser doubling efficiency of large energy tunable dyes were studied.It is found that the effect of the separation effect and the angle of crystal cutting on the frequency doubling efficiency can be neglected.The frequency doubling efficiency is mainly affected by the fundamental beam waist position and the fundamental frequency optical power density.