Novel etching fluids for potassium dihydrogen phosphate

摘要

Absorbing defects such as fractures and contaminants are a leading cause of surface damage in nanosecond pulsedlasers. Etching such defects has proven to be a powerful technique for increasing the laser damage threshold of fusedsilica, but to date no etching process has been reported for potassium dihydrogen phosphate (KH_2PO_4 or KDP) or itsdeuterated analog (DKDP). We show that physical dissolution in water is a viable strategy for etching DKDP surfacesbut surface-redeposited byproducts can serve as laser damage precursors. We use a water-in-oil microemulsion to etchengineered surface fractures in DKDP. Etching widens surface fractures laterally and decreases their optical activity, asmeasured by photoluminescence. The removal of 1 μm of the surface of a DKDP crystal increases the laser damagethreshold (λ = 355 nm, 7 ns) of the engineered surface fractures by 2-4 J/cm~2 (15-30%).