Optically switchable gratings based on polymer-dispersed liquid crystal films doped with a guest-host dye

In this work, we add a small amount of a guest-host dye G-206 in the polyme r-dispersed liquid crystal mixtures to fabricate holographic gratings. Foll owing formation, the grating is irradiated by a single Ar+ laser beam while probed by a He-Ne laser. Experimental results indicate that the first-orde r diffracted intensity of the probe beam increases significantly. Such an o ptically switchable diffraction effect is attributed to thermal expansion. The G-206 dye absorbs the Ar+ laser, subsequently resulting in thermal expa nsion. The liquid crystal (LC) droplets are then squeezed so that the LC mo lecules within the droplets are reoriented collectively. Thus, the refracti ve index difference between the LC-rich and polymer-rich stripes Delta n in creases. (C) 1999 American Institute of Physics. [S0003-6951(99)04318-1].