A Novel Wet-Etching Method Using Electric-Field-Assisted Proton Exchange in LiNbO<tex>₃</tex>

This paper presents a novel wet etching method for LiNbO/sub 3/ using electric-field-assisted proton exchange. By applying voltage with appropriate polarity on designed electrodes placed on both sides of substrate, the induced electric-field distribution can effectively suppress or enhance proton diffusion in the lateral and depth directions. Thus, the proton-exchanged range in LiNbO/sub 3/ can be expertly manipulated. Because the proton-exchanged region can be removed by using a mixture of HF/HNO/sub 3/ acids, the proposed wet-etching method can effectively control the shape of the etched region in the LiNbO/sub 3/ substrate. Under appropriate electrode and proton-exchange parameters, a vertical sidewall with smooth surface is successfully produced, which makes fabricating reflection mirrors and T-junctions in LiNbO/sub 3/ possible. By utilizing the proposed wet-etching method, optical integrated circuits with higher integration density can be fabricated in LiNbO/sub 3/.