Optically-based methods and apparatus for performing sorting, coding and authentication using a gain medium that provides a narrowband emission

Abstract

Disclosed are methods and apparatus for at least one of authenticating, sorting or counting documents, as well as to security structures contained within documents and to documents containing security structures. A security device or structure includes an optical gain medium and a structure having boundaries that impart an overall geometry to the structure that, in combination with at least one material property of the structure, supports an enhancement of electromagnetic radiation emitted from the gain medium for favoring, in one embodiment, the creation of at least one mode that enhances an emission of electromagnetic radiation within a narrow band of wavelengths. Suitable, but not limiting, shapes for the structure comprise elongated, generally cylindrical shapes such as filaments, a sphere shape, a partial-sphere shape, a toroidal shape, a cubical and other polyhedral shape, and a disk shape. The structure is preferably comprised of at least one of a monolithic structure or a multi-layered structure or an ordered structure that may provide for distributed optical feedback. In a preferred embodiment of this invention the security device forms a part of a currency, a passport, a lottery ticket, a negotiable security, a credit card or debit card, or any substrate or carrier which it is desired to at least one of authenticate, count, encode, sort or verify.