Surface-induced optical bistability in coupled exciton-phonon systems

Nonlinear optical responses of exciton-phonon coupling systems near a reflecting surface are investigated. For a polydiacetylene chain lying parallel to the surface, optical bistability induced by the surface is discovered. It is also found that the threshold and contrast of the bistability can be controlled by adjusting the distance of the system from the surface, and that vacuum fluctuations are reduced whenever the bistability occurs. The nature of the bistability and its origin are discussed.