Abstract

Nonuniform Bragg gratings, having periods or modulation depths which vary slowly over the length of the grating, have interesting properties and provide extra degrees of freedom in the design of structures which exploit their reflectance characteristics. Physical insight into the relationship between the slowly varying grating structure and its reflectance spectrum is obtained by displaying the variations in the position and extent of the local photonic bandgap as a function of distance along the grating. This diagrammatic technique provides qualitative information on reflectance strengths and the locations of transmission resonances in the spectrum. This qualitative approach is supplemented by semi-analytical results based on the WKB method.

© 1993 Optical Society of America