Various types of waveguides were studied for single-mode devices. Glasses are one of the promissing candidates for substrate materials because of thier low loss and low cost. In the glass devices, ion-exchange(I/E) processes are well-known. They can be divided into two categories, depending on whether the ion-exchange is performed by one-step or two-step process, and also whether the electric field is assisted or not. The one-step I/E process [1,2], in general, provides semi-embedded waveguides and therefore the coupling efficiency to single-mode fibers (SMFs) are inevitably not high.
© 1988 Optical Society of AmericaPDF Article