Chopping of near- and mid-infrared radiation using a curled electrostatic MEMS actuator

Abstract

An electrostatic MEMS actuator known as the "Artificial Eyelid" can be used as a micromechanical chopper for IR detectors. The actuator structure consists of a curled polymer/metal film stack which is microfabricated and released from an IR transparent substrate. The film stack is uncurled by applying an electric field between the curled film and the transparent fixed electrode on the substrate. These flexible film actuators can act as IR choppers, providing transmission of radiation to the sensor elements when open (curled) and reflection when closed (uncurled). Arrays of actuators were fabricated on ITOcoated glass substrates and ranged in size from 4 x 4 mm to 7.5 x 15 mm with individual elements ranging from 250 to 500 µm on a side. Actuation for devices with average radius of curvature of 120 µm was consistently achieved at 150-170 V operation with 98-100% of the elements functioning and long lifetimes. IR chopper characteristics were measured using a blackbody source and pyroelectric detector by applying sine and square wave voltage to the actuators at a frequency of 30 Hz. The capability of the artificial eyelid for chopping near-and mid-IR radiation, including future fabrication of devices using NiCo 2 O 4 or NiRh 2 O 4 films for IR transparent electrodes, will be discussed.

Transmission functions of optical choppers for Gaussian beam distributions: modeling and simulations

“…This is the major drawback -and limitation -of this type of choppers and one of the reasons for developing micro-choppers [5][6][7], which can go beyond this limit. As a remark, other macroscopic choppers do have this advantage as well, but they can work only with coherent light -such as acousto-optic devices, which can provide MHz modulation frequencies.…”