The precision hand polishing of BBO and LBO

A hand polishing method for generating stain-free surfaces for BBO and LBO having surface figures of 1/10th wave or better, parallelisms of less than 1 are s and surface roughness of 10 Angstrom RMS or less is described. Barium metaborate (BaB2O4, BBO) and lithium triborate (LiB3O5, LBO) are nonlinear crystals characterized by a wide transparency range, small birefringence, a moderate nonlinear optical coefficient, and a high optical damage threshold.(1-3) The realization of these properties depends, to a great extent, on the ability to fabricate quality surfaces for these crystals. The focus of this note is the precise hand polishing of these crystals.