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 b een etched in a mixture of HF and HNO3 acids, under simultaneous illuminati on from a similar to 100 mW 488 nm wavelength Ar ion laser light source, fo cused to power densities of similar to 50 W cm(-2) at the crystal surface e xposed to the etchant. Etching is partially inhibited in illuminated region s, and the degree of inhibition shows a systematic latency: sites illuminat ed early in the etch run resist further etching even after the light is rem oved. Etched structures additionally exhibit regular periodic features of s imilar to0.5 mum scale length. Details of these structures are shown, and t he latent etching effect is discussed. (C) 2000 American Institute of Physi cs. [S0003-6951(00)00844-5].