Tapered edge ridge waveguides for integrated optics

We propose a tapered edge ridge (TER) waveguide as a flexible means for interconnecting devices in integrated optics. Since the guiding film itself is in the form of a ridge, the maximum acceptance angle can be very large. The tapered edges of the ridge help to make the scattering losses negligible. Our experiments with a tantulum oxide guide on a 7059 glass substrate show that scattering losses from the tapered edges are small if any. We have coupled light at 20 degrees to waveguide axis with light propagation occurring with no apparent loss from scattering at the edges. We have developed a theory that can be used to compute ray trajectories in the tapered regions and have devised an expression (similar to the critical angle in total specular reflection) for the maximum acceptance angle that happens to be approximately 42 degrees for our structure.