Modal cutoff of an optical waveguide having a lemniscate of Bernoulli-type core cross section

Abstract

With the use of the scalar field approximation a study has been made of a guide having a shape of the lemniscate of Bernoulli as its cross section. This structure represents approximately the situation when two cores are embedded in the same cladding. This is often done in practice. In this case one expects a kind of cross talk (or coupling between the two cores). The present study incorporates a detailed analysis of the modal cutoff condition for such a guide. A comparative study of the modal cutoff values of the present guide and the guides with cardiodic, circular, and elliptical cross sections has been reported. As a basis for comparison all these guides are assumed to have equal cross-sectional areas. It has been found that the presence of two adjacent cores reduces the cutoff value, which ultimately proliferates the modes. © 1997 John Wiley & Sons, Inc.