Self-writing of a channel waveguide in As/sub 2/S/sub 3/: experiment and model

Summary form only given. We have recently shown the self-writing of a channel waveguide in a As/sub 2/S/sub 3/ slab waveguide by two-photon absorption (2PA). We observed that As/sub 2/S/sub 3/ is photosensitive by two-photon absorption in the 800 nm wavelength range, where the penetration depth is up to 2 cm. This combination is the key to induce the self-writing of a channel waveguide. A low intensity Gaussian beam incident into a planar waveguide is initially diffracted. When the intensity is high and the exposure long, the refractive index is increased along the central axis. The beam thus creates a channel and further increases the refractive index along this channel. A permanent channel waveguide is thus self-written.