Total internal reflection and evanescent gain
Journal article, Peer reviewed
MetadataShow full item record
Original versionOptics Express. 2011, 19 (22), 21404-21418. 10.1364/OE.19.021404
Total internal reflection occurs for large angles of incidence, when light is incident from a high-refractive-index medium onto a low-index medium. We consider the situation where the low-index medium is active. By invoking causality in its most fundamental form, we argue that evanescent gain may or may not appear, depending on the analytic and global properties of the permittivity function. For conventional, weak gain media, we show that there is an absolute instability associated with infinite transverse dimensions. This instability can be ignored or eliminated in certain cases, for which evanescent gain prevails.