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 polymer-dispersed liquid crystal (PDLC) mixtures to fabricate holographic gratings. Following formation, the grating is irradiated by a single Ar⁺ laser beam while probed by a He-Ne laser. Experimental results indicate that the first-order diffracted intensity of the probe beam significantly increases. Such an optically switchable diffraction effect is attributed to thermal expansion. The G-206 dye absorbs Ar⁺ laser, subsequently resulting in thermal expansion. The liquid crystal (LC) droplets are then squeezed so that the LC molecules within the droplets are reoriented collectively. Thus, the refractive index difference between the LC-rich and polymer-rich stripes, Δn, increases