Investigation On 800nm Sub-Nanosecond Pulse Laser With OPO And SBS

Sub-nanosecond laser pulse at 800 nm has an important application in the field of micro-particle acceleration,THz technology and laser medical due to the combination of narrow pulse duration and high energy.At present,800 nm laser pulse is mainly obtained through Ti:sapphire lasers,alexandrite lasers and dye lasers.However,the former two is relatively costly and for the third one,dyes dissolved in liquid solvents are toxic.These factors are not conducive to the application of 800 nm lasers.The development of compact and stable 800 nm laser is a vital promotion of the scientific and medical study.Optical parametric oscillator(OPO)and Stimulated Brillouin scattering(SBS)are used to obtain nanosecond laser pulse at 800 nm.SBS compressor has an uncomplicated structure but high energy reflectivity and pulse duration compression ratio,which can offer sub-nanosecond pulse with tunable pulse duration and high energy to OPO process.OPO has a wide range of wavelength tuning and high conversion efficiency,which can output 800 nm pulses on the basis of SBS by optimizing the nonlinear optical crystal parameters.In this paper,the work revolves the key to the proposed technical route and the main contents are as follows.In terms of SBS,the one-dimensional transient model is derived based on the optical wave equation and the Navier-Stokes equation.The finite difference method is used to simulate the influence of the SBS process and the injected energy on the output sub-nanosecond pulse.FC-770 is chosen as the medium in the experiment and the simulation results are verified by experiments.Sub-nanosecond pulses with stable pulse duration is obtained at an optimum injected energy.In terms of OPO,the nanosecond laser pulse is used to study the 800 nm OPO.The experimental result is utilized to optimize the parameters of sub-nanosecond OPO.Based on the theory of nonlinear polarization intensity,the methods of phase matching in nonlinear optical crystal are analyzed by using physical model of optical parametric process in OPO.The effect of pump and cavity parameters on OPO energy conversion efficiency is obtained by numerical simulation and experiment.The time domain characteristics of signal pulses are also discussed.According to the results of nanosecond OPO,the experiments on acquisition of 800 nm sub-nanosecond laser based on SBS and OPO are carried out.The influence of pump energy on energy conversion efficiency under different cavity parameters is analyzed experimentally and the main factors which limit the energy conversion efficiency in sub-nanosecond OPO process are also discussed.Under the condition of double-beam-path pump structure,20.3% energy conversion efficiency is measured at 46 mJ pump energy.To the best of our knowledge,it is the highest energy conversion efficiency in the sub-nanosecond OPO research currently.