NOVEL ALL-OPTICAL LIGHT-MODULATION BASED ON COMPLEX REFRACTIVE-INDEX CHANGES OF ORGANIC DIE-DOPED POLYMER FILM UPON PHOTOEXCITATION

A novel all-optical light modulation has been proposed based on photoi nduced changes of an imaginary part of complex refractive index in gui ded wave geometry. Very fast and repeated modulation of a reading beam (reflected intensity) was demonstrated at the incident angle correspo nding to a sharp guided wave resonance using phthalocyanine-doped poly (vinyl alcohol) film as a photoresponsive layer and a nanosecond pulse d laser as a writing beam. Such responses were mainly due to the forma tion and decay of excited triplet phthalocyanine. The rise and fall ti me was markedly improved as compared with previous systems based on ph otothermal changes of the refractive index. (C) 1996 American Institut e of Physics.