Latency effects and periodic structures in light-induced frustrated etching of Fe:doped LiNbO3

Single crystals of z-cut 0.05% Fe:doped lithium niobate (Fe:LiNbO3), have been etched in a mixture of HF and HNO3 acids, under simultaneous illumination from a similar to 100 mW 488 nm wavelength Ar ion laser light source, focused to power densities of similar to 50 W cm(-2) at the crystal surface exposed to the etchant. Etching is partially inhibited in illuminated regions, and the degree of inhibition shows a systematic latency: sites illuminated early in the etch run resist further etching even after the light is removed. Etched structures additionally exhibit regular periodic features of similar to0.5 mum scale length. Details of these structures are shown, and the latent etching effect is discussed. (C) 2000 American Institute of Physics. [S0003-6951(00)00844-5].