Abstract

An asymmetric coupler consisting of two dissimilar waveguides can be designed to operate as a narrowband filter if the propagation constants of the individual guides coincide at one wavelength, λ_o. The filter response is approximately a (sinc)² function with high sidelobes of -9 dB, undesirable for WDM applications. The sidelobes can be reduced by controlling the coupling coefficient k(z) along the coupler by varying the interguide separation t according to certain window functions. This was demonstrated theoretically by solving the coupled-wave equations¹ and experimentally with one-dimensional waveguides.²

© 1991 Optical Society of America