Silicon spatial light modulator

Abstract

A spatial light modulator including a silicon backplate having an insulating layer and a standoff grid of insulating material deposited on the backplate to define an array of cells. An electrode is deposited in each cell on said backplate. A thin membrane of doped silicon is mounted to the standoff grid and over said array of cells and electrodes. Mirrors are laid on the membrane to create an array of reflective pixels over the array of cells. When an electrode is selectively charged the portion of the membrane overlying that cell is deflected by electrostatic attraction between the membrane and the electrode. Taken overall, a pattern is assumed by the array of pixels which corresponds to the state of the electrical signals placed on the electrodes. A vent hole formed in each cell from the electrode side of the backplate to the opposite side thereof for venting gas from the cell when said diaphragm is deflected, and grooves extend across the face of the backplate and over the cell to intersect the vent hole to assist in venting gas out of the cell and through the hole. The vent hole is preferably of a size and constructed for critical damping of the movement of the mass of the deflected diaphragm at said cell to control the movement caused by the electrostatic deflection. Flexures of reduced cross-section are formed in the diaphragm along a closed line extending around the inside perimeter of the stand off grid, so that said diaphragm moves more nearly in piston mode within the flexure.