Reserach On Pules Timing Modulation Tunable Dye Laser Amplification Technology

Planar Laser Induced Fluorescence imaging technology uses specific wavelength laser to selectively excite the active particles or tracer particles to be measured in the flow field to radiate fluorescence,obtain information such as the spatial distribution of flow field particles for fluorescence imaging,and has non-contact measurement,space-time The advantage of resolution up to nanoseconds and micrometers is one of the important technical methods to study the flow field and combustion.High-speed PLIF imaging diagnosis technology requires that the excitation source works at high repetition rate and outputs ultraviolet laser with large single pulse energy and wide tuning range.Aiming at the high-frequency PLIF imaging diagnostic system's demand for high repetition rate and large energy tunable laser amplification efficiency,this paper carried out the research of pulse timing modulation tunable dye laser amplification technology.The research contents are as follows:First,the effect of different working medium characteristics on the output characteristics of laser dyes was studied.According to the absorption line of hydroxyl groups and the experimental results,methanol was used as the dye solvent.The concentration of Rhodamine 590 was 50 mg/L,and the blending ratio of Rhodamine 590 and Pyrromethene 597 was 2 : 1.The co-doped system of is used as dye solute.By changing the beam expansion ratio of the beam shaping system to change the seed optical characteristics,the optical transmission matrix of the Gaussian beam is used to analyze the influence of the beam expansion ratio on the seed optical characteristics,and the effect of different beam expansion ratios on the efficiency of the amplification stage is experimentally measured.Under the pump light energy of 29.5m J,the amplification efficiency of the shaped optical path with a beam expansion ratio of 1:6 can reach up to 26.5%,and the highest amplification efficiency of a shaped optical path with a beam expansion ratio of 1:3 is only 22.9%,indicating that the beam expansion When the ratio is 1:6,higher amplification efficiency can be obtained,which is in line with theoretical expectations.Then change the angle between the amplification dye box and the seed light to explore the influence of the angle of the seed light and the flow direction of the dye on the amplification efficiency.Next,the influence of the timing energy characteristics of the pump light on the stability of the output laser pulse train in the pulse timing modulation operating mode is studied.When the pump energy is 29.5m J,the standard deviation of the energy between the sub-pulses in the pulse train is the smallest,and the pump The correlation between the light and the output light of the amplifier stage is best.Through the study of the number of sub-pulses in the pump light pulse string,it is determined that the amplification efficiency is the highest when there are 18 pulses in the string,and the maximum amplification efficiency can reach 26.5% when the pump energy is 26.5m J,as the pump energy increases,The amplification efficiency gradually stabilizes.Finally,the effect of the polarization characteristics of the pump light of the amplification stage on the amplification efficiency is studied.Through experiments,the influence rule of the polarization direction of the pump light on the amplification efficiency is obtained.Experiments have found that the amplification efficiency of the elliptically polarized pump light when the polarization long axis direction coincides with the seed light's polarization direction is extremely large.When the pump's polarization short axis direction coincides with the seed light's polarization direction,the amplification efficiency is extremely small,so the amplification efficiency varies The change of the polarization state of the pump light shows an experimental phenomenon of periodic fluctuations.