Exploration of self-writing and photosensitivity in ion-exchanged waveguides

We have demonstrated that self-written channel waveguides can be formed reproducibly in K+-ion-exchanged Nd-doped Bk7 glass by making use of a photosensitive index change of ~6 x 10-5 induced by illumination at 457 nm. The guidance characteristics of these waveguides have been investigated from 457 to 1550 nm. Detailed experiments have been carried out by exploration of the self-writing process, and these are also used to investigate the photosensitivity of the material. We find that an intensity threshold exists below which photosensitivity does not occur. Numerical simulations of both the evolution and the guidance properties of the self-written waveguides provide excellent agreement with observations