Ultrashort Ultraintense Laser Pulses by Stimulated Raman Backscattering Amplification and Compression in Plasma

Abstract

Stimulated Raman Backscattering (SRBS) in plasma provides a new scheme to generate ultrashort ultraintense laser pulses. By counter propagating two laser pulses, pump and seed, in plasma, a Langmuir wave is excited by the beat between two pulses. This plasma wave can mediate energy transfer from the long pump pulse to short seed pulse under resonance condition. One of the most attractive features of SRBS in plasma is that the seed pulse can undergo simultaneous amplification and compression during nonlinear stage of the interaction.

The thesis presented here concentrates on the experimental research of SRBS amplification and compression in plasma. Theoretical calculations and computer simulations were performed to identify the parameters that affect the gain and examine optimal conditions for improving SRBS amplification and energy transfer efficiency. The experimental setup was developed for SRBS in plasma with an improved seed pulse generation design and longer, uniform plasma channel. By introducing density chirp along the plasma channel in interaction path and employing double-pass design, the amplified seed energy was increased to 5.6 mJ with an effective energy transfer efficiency of ~ 20% according to calculation. Further improvement of the experimental setup included increasing the plasma channel length to 4 mm and expanding the channel diameter to ~ 250 μm. The updated system already delivered enhanced amplified seed energy of more than 16 mJ in a single path 4 mm long plasma channel. The SRBS amplification and compression in plasma was proved to be a potential alternative to Chirped Pulse Amplification (CPA) technique in generating ultraintense ultrashort laser pulses for future development of science and technology.