Abstract

Laser light incident upon materials may induce a substantial degree of charge transfer in the constituent molecules if their electronic energy levels are resonant with the incoming photon energy. The use of intense laser light also allows the possibility that two photons whose combined energy is equivalent to the excitation energy can produce the charge transfer effect. In this paper, it is shown how composite materials comprising any such charge-transfer component may nonetheless exhibit off-resonant two-photon absorption through a cooperative process in which two distinct species are simultaneously promoted to electronic excited states. Such processes have already been the subject of extensive theoretical and experimental study with regard to their occurrence in matrix-isolated species, doped crystals, etc. However, recent work has shown how charge-transfer species in particular may enhance such cooperative effects.

© 1994 IEEE