A study of periodic gratings in planar dielectric waveguides

Abstract

Periodic gratings in waveguides act as frequency selective mirrors making them very useful as spectral filters for wavelength division multiplexing applications and as end mirrors for narrow linewidth lasers. A study of the spectral characteristics of both single and double gratings in planar dielectric waveguides is presented.

The analysis of light propagation in a planar dielectric waveguide with sinusoidal boundary perturbations is carried out using coupled-mode theory. Power reflection and transmission coefficients are calculated for single gratings as well as two gratings of the same period and depth but arbitrary lengths and separated by a specified distance.

The spectral response is examined for several cases. The influence of grating period, depth, and length in the single-grating case as well as separation of the gratings in the case of a double grating is investigated. Numerical results for example cases are presented. The results of this study are valuable for designing grating devices which are becoming increasingly attractive to broadband fiber-optic communication systems.