Optically switchable Bragg reflectors

One-dimensional holographic photonic crystals that incorporate photochromic azobenzene-derived liquid crystals azobenzene-derived liquid crystals (LCs) have been produced. The additive photochromic molecules disrupt the host LC nematic order, inducing an isothermal phase transition and changing the effective dielectric properties of the LC layer (see Figure). This imparts photo-optic properties to the structure, allowing for its reflectivity to be modulated with exposure to light.