Abstract
Stimulated Raman backscattering in plasma is potentially an efficient method of amplifying laser pulses to reach exawatt powers because plasma is fully broken down and withstands extremely high electric fields. Plasma also has unique nonlinear optical properties that allow simultaneous compression of optical pulses to ultra-short durations. However, current measured efficiencies are limited to several percent. Here we investigate Raman amplification of short duration seed pulses with different chirp rates using a chirped pump pulse in a preformed plasma waveguide. We identify electron trapping and wavebreaking as the main saturation mechanisms, which lead to spectral broadening and gain saturation when the seed reaches several millijoules for durations of 10’s – 100’s fs for 250 ps, 800 nm chirped pump pulses. We show that this prevents access to the nonlinear regime and limits the efficiency, and interpret the experimental results using slowly-varying-amplitude, current-averaged particle-in-cell simulations. We also propose methods for achieving higher efficiencies.
Highlights
Stimulated Raman backscattering in plasma is potentially an efficient method of amplifying laser pulses to reach exawatt powers because plasma is fully broken down and withstands extremely high electric fields
These systems are based on chirped pulse amplification (CPA)[3] and utilise solid state media, but the step is very challenging because the low damage threshold of optical elements results in very large amplifiers and compressors
This constraint has led to the suggestion of stimulated Raman backscattering (SRBS) in plasma[4] as an alternative amplification method[5] suitable for high field intensities, where energy is directly transferred from a pump beam to a short seed beam
Summary
Because of fluctuations in measurements mainly due to laser pointing and capillary discharge jitter, for each data set, only the analysis of the single best acquisition for the amplified seed is kept. APIC is a 1-dimensional, averaged particle-in-cell (PIC) code developed for the simulation of Raman amplification in plasma[38]. It employs envelope equations for the two laser pulses and a particle description for the plasma, where motion on fast time scales is eliminated. Modifications have been made to the original code, which include implementation of chirped laser pulses, single-pulse ponderomotive contributions (which drive Raman forward scattering and wakefield generation), a dispersive model for the laser solver, and a time-dependent temperature function.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
