Numerically efficient modal decomposition approach to self-writing processes

We develop a modal decomposition technique to describe wave propagation in dynamically varying waveguides such as those predicted to occur in photosensitive materials. In particular, we use this method to examine the self-writing of a channel waveguide in a slab of photosensitive glass. This method is up to two orders of magnitude faster than the numerical technique used previously, which is based on a conventional beam-propagation treatment. Hence it is a powerful tool for exploring the waveguides that form under a wide range of conditions. (C) 1997 Optical Society of America.