Electrically controlled diffraction employing electrophoresis, supercapacitance, and total internal reflection

Abstract

The reflectance of a surface can be altered by controlling the concentration of dye ions in a region adjacent to an optically transparent and electrically conductive thin film. We present a method for nonmechanical light deflection achieved by altering the reflectance of a diffraction grating, an approach that creates new diffraction peaks that lie between those associated with the original grating spacing. We have demonstrated this effect by applying an electrical potential difference between interdigitated indium-tin oxide (ITO) electrodes and measuring the intensity of one of the new diffraction peaks. The measured diffraction peak intensities were found to reversibly deflect approximately 7% of the reflected light to previously nonexistent peaks. The diffraction grating was formed by patterning a thin film of planar, untreated ITO on a glass substrate using standard photolithography techniques. The size scale for this method of electrically controlled diffraction is limited only by the lithographic process; thus there is potential for the grating to deflect light to angles greater than those achievable using other methods. This approach could be used in applications such as telecommunications, where large deflection angles are required, or other applications where alternate beam-steering methods are cost prohibitive.