Sbs-Pcm Characteristic of Sub-Nanosecond Laser Based on Rotating Wedge

Abstract

One major setback in the applications of high-power solid-state lasers in areas like high energy density physics and laboratory astrophysics is the beam quality that deteriorate with increasing pump power. To solve this problem, we proposed to develop a high beam quality and stable stimulated Brillouin scattering phase conjugation mirror (SBS-PCM) using a filtration approach and a careful design geometry that includes a rotating wedge to operate under a high repetition rate laser. Upon reducing the micro-impurities to 100 nm, the accumulated heat at the focus reduced greatly, resulting in improved beam quality and better phase fidelity. At 6.5 mJ input energy and below 100 Hz repetition rates, there is no observable optical breakdown or obvious thermal effects as oppose to unfiltered medium that experience optical break down at 0.5 mJ and 50 Hz repetition rate. The simulated temperature gradient at the focus shows that the material absorbed the laser within a short distance from the irradiation side, and the temperature probe reveals that the temperature increases with pumping power and time due to heat accumulation at the focus. To disperse the heat accumulation through a large area within the pool, we design and introduce a rotating wedge, which calls for a customized SBS cell. The impact of the rotating wedge was much noticeable when the system works at higher pump power compared to when operated at lower pump power.

Keywords: stimulated Brillouin scattering, phase conjugation mirror, repetition rate, energy reflectivity, temperature probe