Direct-Write e-beam Sub-Micron Domain Engineering in Liquid Phase Epitaxy LiNbO_3 Thin Films

摘要

By using a direct-write e-beam technique with liquid phase epitaxy LiNbO3 thin films, we have successfully produced sub-micron domain structures for achieving dynamically switchable filters in a periodically poled lithium niobate (PPLN) waveguide. Sub-micron domain (～200 nm) structures with a period ～1.2 μm are realized in liquid phase epitaxy LiNbO3 films on congruent LiNbO_3 substrates by using the direct-write e-beam domain engineering method. In comparison with single crystal congruent LiNbO_3 (CLN) and stoichiometric LiNbO_3 (SLN), we show that LPE LiNbO_3 is the most promising material for producing superior domain regularities and finer domain sizes than single crystals. A physical model is presented to qualitatively explain the observed differences in structure and regularity of the induced periodic domains among the three different materials we studied. We postulate that the higher Li/Nb ratio in LPE LN than in CLN enhances domain inversion initiation. Also, we believe that the vanadium incorporation and distortion due to the lattice mismatch between films and substrates enhance electron localization, domain wall pinning and domain nucleation in LPE materials, giving rise to better structures.