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

Abstract

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 ~100 mW 488 nm wavelength Ar ion laser light source, focused to power densities of ~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 ~0.5 µm scale length. Details of these structures are shown, and the latent etching effect is discussed