Technology for integrated spatial light modulators based on reflective membranes

摘要

Two approaches toward the fabrication of a spatial light modulator are presented. The first approach uses a pixelated nitride membrane that is suspended by a grid structure over an electrode array. Deformation of each membrane segment is achieved by means of electrostatic attraction. By using a continuous reflective surface, we achieve a 100% optical fill factor. Since we can coat with any metal or combination of materials, these devices can, in principle, handle high optical loads over a wide spectral range. We have tried different spacer materials and dimensions with this approach. In the second approach, the membrane rests on a viscoelastic carrier layer. During fabrication we use the thin nitride membrane to ensure uniformity of the elastic layer after which it is used as an etch stop for the bulk silicon etchant. This type of device is more robust, can use smaller pixel sizes, but has less sensitivity at low voltages. To achieve an optimal, but simple fabrication procedure, the membranes and electronics are fabricated in different processes, ensuring a higher optical quality of the membrane and increasing yield at lower costs. Applications lie in the field of projection displays, optical lithography, optical communication networks, etc.