Nanoscale light modulators from silicon-liquid crystal hybrids

A novel light modulator device constructed by integrating nanoscale silicon mirrors with nematic liquid crystals is reported. The mirrors are composed of porous silicon Bragg reflectors, prepared via electrochemical etching of crystalline silicon. By controlling the etching parameters, the average pore size can be easily adjusted to accommodate the liquid crystal molecules. In our device, the pores are perpendicular to the multilayer structure and the pore size is 20 - 50 nm. It is shown that when voltage is applied to this composite device, the liquid crystal molecules re-orient such that their long axis aligns along the electric field. The molecular reorientation changes the refractive index of each layer, and accordingly the reflection of the mirrors is electrically modulated. The fabrication, optical characterization, molecular alignment, and operation of this novel device are discussed.