WAVELENGTH DEMULTIPLEXING BY CHIRPED WAVE-GUIDE GRATINGS

The performance of a chirped waveguide grating as a wavelength demulti plexer has been investigated. Considerations include TE-TE, TE-TM and TM-TM mode coupling for different incident angles and waveguide parame ters. The spectral response of the chirped sinusoidal surface relief g rating in the optical waveguide has been studied by means of Local Nor mal Mode Expansion (LNME) theory to account for the varying thickness of a corrugated waveguide. A matrix technique has been applied to acco unt for the varying grating period, the grating being divided into seg ments with constant periods and coupling coefficients. A nonslanted fi rst-order diffraction grating is considered and contradirectional coup ling between guided modes in phase synchronism at arbitrary incident a ngles. We show the effect of geometry and waveguide parameters on the performance of the chirped grating as a wavelength demultiplexer. Also , we demonstrate how the bandwidth of the filtering and demultiplexing characteristics and the spectral shift between different polarization modes can be controlled.