Abstract

Ion-exchange in glass produces guides with a large increase in refractive index (∆_n = 0.1) and low propogation loss. Hence the technique is useful for devices requiring tight confinement such as ring resonators^(1),(2) and passive power dividers⁽³⁾. The large ∆_n, however, results in large mode mismatch between single mode channel guides and fibers. A typical single mode, ion-exchanged channel guide in glass has a width of 2μm. It is not possible to mode match to a fiber merely by tapering the width to 5-10μm at the device input since this makes the input end multimode. An alternate approach is to thermally taper the channel guide by postbaking it in a suitable temperature gradient. Thus the guide dimension at the input end is increased to 5-10μm; however, Δn decreases since the exchanged ion species is distributed over a larger volume and the guide remains single mode.

© 1988 Optical Society of America