High-power phase-conjugating mirror based on stimulated Brillouin scattering in solids

The possibility has been investigated that the optical glasses could be used as a solid-state phase conjugator for high power lasers. The solid SBS (stimulated Brillouin scattering) materials as effective phase conjugator can be performed with stable operation for improving the beam quality of high- average-power lasers. The advantage using solid material as phase-conjugating media is its reliability, environmental harmlessness and easy handling. An optical fiber offers a low power SBS threshold and stable performance at input energies of a few mJ level. Using a bulk optical glass, flint glass of SF-6 showed a much lower SBS threshold at 1.06 micrometer wavelength than fused silica glass because of its high SBS gain coefficient (9 cm/GW). However, the operating energy range of flint glass is limited by its low damage threshold. For long pulse duration using a longer focusing lens, fused- silica glass had high SBS reflectivity over 90% without any damage occurrence at the incident energy of 600 mJ in 18 ns at a repetition rate of 10 Hz. It shows also high SBS reflectivity of approximately over 95% at a single shot operation with no damage observation at a pumping energy of 2.3 J in 18 ns. These properties of the fused-silica are almost comparable with those of highly performed gases or liquids. Damage-free operation using a fused-silica as a better phase conjugation material would lead to construct more compact laser-diode pumped all-solid-state laser system.