High-temperature proton-exchange as an efficient method for fabrication of low-loss LiNbO3 waveguides

An efficient method, the high temperature proton exchange (HTPE), to fabricate high-quality LiNbO3 optical waveguides is studied. The new proton exchange source, the stearic acid diluted by lithium stearate, is proposed for HTPE process. The known Soft Proton Exchange (SPE) process can be realized by HTPE. THere are no phase transitions when the (alpha) -phase waveguides are fabricated by SPE. This phase presents the same crystalline structure as that of LiNbO3 and, as expected, maintains the excellent nonlinear and electro-optical properties of the bulk material. The kinetics of HTPE is studied.