Abstract

By using an exact electromagnetic model, a sharp resonance phenomenon in dielectric waveguides loaded with a periodic structure (a grating) has been predicted.¹ The attendant very small linewidth, in terms of wavelength or frequency, may allow use in optical filtering and switching. The resonance linewidth can be controlled by the magnitude of the periodic modulation of the permittivity of the waveguide. Since only a small modulation is needed, it may be possible to dynamically alter the passband and thus scan in frequency. These resonances are fundamentally related to the guided modes of the corresponding unmodulated slab waveguide, which is approached in the limit as the permittivity modulation amplitude of the waveguide grating vanishes. To quantify these properties, theoretical results indicating spectral linewidths, conversion efficiencies, and parametric locations for typical optical materials and geometries are given. For example, spectral curves in the visible and the near-infrared regions are presented. The variation of the lineshapes with the bulk permittivity, implementable using the electrooptic effect, is also calculated. The use of the resonance effects for static and tunable optical filters and electrooptic switches is explained and possible embodiments of selected devices are shown.

© 1991 Optical Society of America