All-optical light modulation in anthraquinone dye doped waveguides based on an improved prism coupling method

In this paper, an improved all-optical light modulation scheme has been proposed with respect to photo-induced changes of the refractive index of polymer planar waveguides by the m-line spectroscopy technique. An improved prism coupling method was used to realize it. In this prism coupling configuration, the strong pump (writing) beam excited by an Ar+ laser at 514 nm is illuminated on film sample by passing through the upper base of prism, and induces local refractive index changes by heating. A probe (reading) beam, which is coupled into prism coupling system and forms waveguide modes in film, is modulated for its changes of reflectivity due to changes of refractive index of waveguide film. A shift of sharp guided wave resonance is observed and 20 ms of response time is obtained.