Analytical Description of Backward Stimulated Raman Scattering Short Pulse Gain factor for Gaussian and Square Pulses

• Main Authors: Figueroa, Humberto, Sinclair, Mitchell, Joshi, Chan
• Format: Journal Article
• Language: English
• Published: 18-11-2024
• Subjects: Physics - Plasma Physics
• DOI: 10.48550/arxiv.2411.12093

This work analytically compares the growth of Backward Stimulated Raman
Scattering (B-SRS) induced by temporal laser pulses on the order of a few tens
of laser cycles or a couple of picoseconds for nominally 10 um wavelength IR
pulse with Gaussian versus the constant intensity profile assumed in the
original theory, both delivering an equivalent energy. By evaluating the growth
factors of these two pulse shapes, we demonstrate that the temporal structure
of the laser pulse significantly influences the maximum growth rate of the
instability. Specifically, while the growth rate for a square pulse increases
linearly with time, the Gaussian pulse resultant growth rate tracks with the
temporal intensity profile of the pulse. We utilize the newly calculated total
maximum growth that a temporally varying pulse delivers above the B-SRS
threshold and then determine the normalized intensity for a pulse that has same
duration. and contains the same amount of total energy. We show that these
energy equivalent square pulses yield the same total B-SRS growth as the
Gaussian pulses.