Giant nonlinearities of organic based crystals

The nonlinear effects of organic based crystals in which the Frenkel type of excitons are realized were studied. Using the nonequilibrium Green function method it is shown that significant nonlinearities can arise in such type of crystals at moderate pump intensities owing to interaction of excitons. The study of transmission of intensive quasiresonant electromagnetic wave by crystal showed that at natural (nonlinear) boundary condition the multistability effects can arise with very sharp and big change of transmission. The switching devices similar to optical key can be realized.