High-repetition-rate, high-pulse-energy, and high-beam-quality laser system using an ultraclean closed-type SBS-PCM

Abstract

We present a high-repetition-rate, high-pulse-energy, high-beam-quality, and high-average-power laser system using an ultraclean closed-type stimulated-Brillouin-scattering phase-conjugate mirror (SBS-PCM). By controlling microparticles of SBS-PCM down to 40 nm, thermal load capacity of such closed-type SBS-PCM was greatly improved, which presented the best reported cleanliness. The closed-type SBS-PCM, lacking scanning wedge plates, achieved reflectivity as high as 92% and showed no optical breakdown phenomena or obvious thermal effects at a 500 Hz pulse-repetition frequency (PRF). Operation at 550 W output power, approximately 1.1 J pulse energy, and beam quality M of approximately 2 represents, to our knowledge, the best reported performance. Thermal phase distortion was compensated, and the maximum-output-power pulse-width compression improved from 30 ns to approximately 10 ns.

Roadmap on nonlinear optics–focus on Chinese research

“…Scientific researchers in China have performed well at this stage. As shown in figure 5(a), the SBS-based phase conjugation mirror (PCM) is used to compensate for the wavefront distortion caused by optical defects and thermal distortion, so as to obtain high-quality beam output [33]. In the process of opposite propagation between Stokes and pump, the self-amplification effect of SBS makes the pulse width of the Stokes significantly compressed compared with the pump, as shown in figure 5(b).…”

Output characteristics of high-power stimulated Brillouin scattering pulse compression enhanced by thermal effects based on HT270

“…In SBS pulse compression, the liquid medium used for Brillouin scattering has the advantages of no high pressure, a small absorption coefficient, and a high laser damage threshold compared with gas and solid media, and is most suitable for SBS with high injection energies and long interaction distances [9][10][11][13][14][15][16]. Therefore, SBS pulse compression based on the liquid medium is the most promising technical method for obtaining a high-energy sub-nanosecond laser with a kilohertz-level repetition rate.…”

“…The effective thermal mitigation methods in the literature can be divided into two categories. The first is the liquid purification method to remove large impurity particles in the liquid medium [ 16 , 28 ] , which can appropriately reduce the total heat absorption generated by the laser absorption within the medium and reduce the optical-breakdown probability. The second category is the method involving flowing liquid and a wedge-based moving focal spot [ 27 , 29 ] , which are used to alleviate the local focusing heat accumulation.…”

Developments of Picosecond Lasers Based on Stimulated Brillouin Scattering Pulse Compression

“…By appropriately using SBS-PCMs, except for realizing picosecond pulses, one can also compensate wavefront distortions caused by optical elements during laser transmission and amplification processes, leading to a higher beam quality output [25,26]. For this reason, today, the combination of SBS-PCMs and master oscillator power amplifier (MOPA) is a common method to achieve high peak power, high beam quality, and narrow pulse width lasers [27]. Although showed that the distortion with vortex wavefront will lead to the input "donut-like" pump pluses into peta-like Stokes pluses [28], SBS is always the most effective phase conjugation method for conventional lasers with the fundamental (i.e., TEM 00 ) spatial mode.…”