Cladded optical glass waveguide as planar polarizer

Planar optical waveguide polarizers for TE0/TM0 modes are fabricated on an asymmetric ion-exchanged glass (Na+ --> K+) waveguide. The thickness of the exchanged layer is about 2 mu m, achieved after 2 h of the exchanged treat ment, and is enough to excite a first-order mode in the layer. Polarizers a re fabricated by giving the cladding of various materials on the guide surf ace. For TE0 polarization, metals (-ve dielectric constant) evaporated at 1 0(-5) torr with a thickness of about 250 nm measured using the Tolansky tec hnique are used as a clad Metals like Al Ag. Cu, Pb, and Au are chosen for, study. For TM0 polarization, semiconducting oxide materials (+ve dielectri c constant) like BaTiO3, Al2O3, SnO2, etc, are screen printed and used as a clad The thicknesses of the printed films are measured by a light section microscope with an accuracy of 0.5 mu m, and are about 20 mu m. These sampl es are characterized using the prism-film coupling method. In the case of m etal clads, the TM0 mode has a highel loss than the TE0 mode while passing through the clad. Hence, the length where the TM0/TE0 loss approaches almos t zero is taken as the cutoff length. On the other hand, for semiconducting clads, a slightly higher, attenuation of the TE0 mode is observed than the TM0 mode. Therefore, following the basic law of physics, 1/e times the fal l of the intensity of TE0 is treated as the cutoff condition. The cutoff le ngths are observed experimentally as well as calculated theoretically. It i s seen that both are in good agreement within an error of 5-10%. The cutoff lengths of the metals are compared with the reported values, and are analy zed on the basis of material purity and conductivity. (C) 1999 John Wiley & Sons, Inc.