Nonlinear optical wave mixing and switching in dyedoped polymer saturable absorbers

Abstract

Dye-saturable absorbers are an important class of nonlinear optical materials where nonlinear interactions like four- and two-wave mixing can be observed even at low laser intensities. The modulation of the nonlinear absorption coefficient of the dye medium by an appropriate interaction of laser radiation can be utilized to generate phase conjugate signals both in the backward and the forward FWM geometries. By probing this population grating at time scales less than the dye relaxation times, transient PC signals can be observed. Here we report the generation of the forward and backward PC signals using azo dye-doped polymer films. By modulating the intensity of one of the pump beams an exchange of energy between these two PC signals was observed. The behaviour of phase conjugator as an optical switch due to this pump intensity modulation is also discussed.