Silicon Micromachined Tunable Infrared Polarizer

Abstract

Active polarizers that consist of parallel metal wires are fabricated by silicon micromachining techniques. If wavelength of incident radiation is larger than the period of the wire grid, the wire grid reflects incident radiation with the electric field parallel to the grid line, while transmits the other. Polarization of infrared light can be succussfully modulated by changing the period of the grid or changing the geometrical configuration. Two kinds of silicon structures are fabricated and demonstrated. One of them is electrostatic driven structure composed of mechanically flexible grid. The period of the grid can be modulated by itself with electrostatic actuation. The other is piezo driven structure, which consists of a pair of fingers (wire grid) and a torsional resonator. It changes the geometrical configuration of the wire grid. These mechanical behaviors and optical characteristics for infrared modulation are presented.