All-optical switching of holographic gratings made of polymer-liquid-crystal-polymer slices containing azo-compounds

We present the observation of an all-optical switching effect that takes place when a light beam of suitable wavelength irradiates a 'layered' structure made of polymer slices alternated to films of well aligned liquid crystal (LC) which contain also a small percentage of azo-LC molecules. The simple and reliable fabrication procedure exploits a holographic UV curing technique. The observed switching effect takes place in samples that exhibit diffraction efficiency as high as 85% and is induced in less than 0.5 s by an unfocused pump beam of 245 mW/cm(2) power density.