Refractive Index Profiles of Copper Ion Exchange Glass Planar Waveguides

Glass planar optical waveguides are fabricated by the copper ion-exchange technique. The refractive index (RI) profiles of waveguides are reconstructed by the inverse Wentzel–Kramers–Brillouin (IWKB) method. Cu⁺ and Cu²⁺ ion concentrations are calculated by solving the diffusion equation, and the mechanism of RI changes is analyzed. The model between the RI and ion concentrations is proposed by taking both Cu⁺ and Cu²⁺ into account, according to polarizability changes among Cu⁺, Cu²⁺ and Na⁺. The results show that the contribution of Cu²⁺ is not negligible, and the reason for the RI change is of Cu⁺ and Cu²⁺. With the exchange time increasing, the redox process between Cu⁺ and Cu²⁺ will play an important role on RI profiles.