Analysis of a riblike waveguide structure consisting of three dielectric films shows that properly chosen film thicknesses permit the lateral containment of any selected waveguide mode, with the unselected modes radiating laterally away from the rib structure. The waveguide consists of two high-index films separated by a low-index layer in which the fields are evanescent. A perturbation in the thickness of the low-index layer increases the local effective index for some planar waveguide modes while decreasing it for others. Hence a ridge or trough in the low-index layer can guide certain selected modes along its axis if the high-index-layer thicknesses are correctly chosen. Unlike mode-stripping structures based on preferential absorption of the unwanted modes, this all-dielectric structure introduces no loss to the selected mode other than the unavoidable scattering and residual absorption in the dielectric media. Also, unlike mode-selecting structures based on Bragg effects, no maintenance of phase-matched conditions over controlled propagation lengths is required.
© 1983 Optical Society of AmericaFull Article | PDF Article
OSA Recommended Articles
A. B. Buckman
J. Opt. Soc. Am. 72(6) 688-691 (1982)
J. Opt. Soc. Am. 73(5) 680-683 (1983)
S. L. Chuang and J. A. Kong
J. Opt. Soc. Am. 73(5) 669-679 (1983)