Diffractive MEMS: the polychromator and related devices

Abstract

MEMS and optics are a natural match. There are several reasons: MEMS devices have dimensions and achievable actuation distances comparable to the wavelength of light; smooth surfaced dielectrics, semiconductors, and metals can be used in various combinations; and, photons don't weigh anything, so relatively feeble MEMS actuators can easily manipulate them. Moveable and tiltable mirrors and pop-up structures have held center stage in optical MEMS for several years, with uses in displays, micro-optical benches, scanners, and a variety of optical telecom switching applications. Less noticed, but perhaps equally important in the long run, is a family of diffractive MEMS structures that represent paradigm shifts in display technology, infrared spectroscopy, and optical telecom. The polychromator, uses a set of parallel mirror elements, each one of which is individually actuatable with an analog signal, achieving continuous rather than binary control of the mirror element position As a result, an aperiodic diffraction grating is realized with a fully programmable optical transfer function. When illuminated with white light, the spectral content at a fixed viewing angle can be controlled by adjustment of the various mirror element positions.