Electrically Switchable Diffraction Grating Based on Electrophoretic Redistribution of Carbon Black Nanoparticles

We investigate a novel concept of a switchable diffractor in which the slit spacing can be switched by controlling carbon black (CB) nanoparticles. The slit width varies depending on the driving mode, where the nanoparticle positions are controlled by vertical electric fields generated between the planar electrode on the top substrate and the interdigitated electrodes on the bottom substrate. The diffraction angle of the proposed diffractor can be adjusted by controlling the slit spacing, operating in either wide-slit or narrow-slit modes. The diffractor also exhibits bistability, maintaining both slit modes without an applied field when the solution is optimized with a thickening agent. Furthermore, the device demonstrates a wide operating temperature range from −50°C to at least 100°C. In addition, the CB diffractor operates independently of the polarization state of incident light. Accordingly, this tunable diffractor utilizing CB nanoparticles exhibits outstanding potential for application in various advanced photonic devices.