Large refractive index change induced by ion implantation in lithium niobate

Large but negative refractive index change (∼ 10% at 632.8-nm line) is observed in several lithium niobate samples, each occurring in a thin layer induced by implantation of argon or neon ions. Implantation energy is 60 kV and the ion dose is 1016 cm−2 or more in each sample. Mechanisms causing the refractive index change and possible applications for integrated optics are discussed.