Optical bistability and differential gain resulting from absorption increasing with excitation

An extended theoretical discussion of a novel general method of obtaining optical bistability is given. The method uses absorption that increases as the material becomes more excited and requires no mirrors or other external feedback. Criteria for bistability and differential gain are derived for a simple case, and specific illustrative analytic results are given. Limiting relations are derived for the switching powers and the width of the bistable region. It is shown that this general class of bistability encompasses at least six previous independent and unrelated investigations of mirrorless bistability in specific physical systems. The common general requirements for this bistability are discussed together with its attributes.