PROCEEDINGS ARTICLE | February 18, 2010
Proc. SPIE. 7594, MOEMS and Miniaturized Systems IX
KEYWORDS: Actuators, GRIN lenses, Thin films, Mirrors, Beam splitters, Reflection, Interferometers, Etching, Interferometry, Micromirrors
A MEMS-based interferometric sensor is produced using the multi-user MEMS processing standard (MUMPS)
micromirrors, movable by thermal actuation. The interferometer is comprised of gold reflection surfaces, polysilicon
thermal actuators, hinges, latches and thin film polarization beam splitters. A polysilicon film of 3.5 microns reflects and
transmits incident polarized light from an external laser source coupled to a multi-mode optical fiber. The input beam is
shaped to a diameter of 10 to 20 microns for incidence upon the 100 micron mirrors. Losses in the optical path include
diffraction effects from etch holes created in the manufacturing process, surface roughness of both gold and polysilicon
layers, and misalignment of micro-scale optical components. Numerous optical paths on the chip vary by length, number
of reflections, and mirror subsystems employed. Subsystems include thermal actuator batteries producing lateral
position displacement, angularly tunable mirrors, double reflection surfaces, and static vertical mirrors. All mirror
systems are raised via manual stimulation using two micron, residue-free probe tips and some may be aligned using
electrical signals causing resistive heating in thermal actuators. The characterization of thermal actuator batteries
includes maximum displacement, deflection, and frequency response that coincides with theoretical thermodynamic
simulations using finite-element analysis. Maximum deflection of 35 microns at 400 mW input electrical power is
shown for three types of actuator batteries as is deflection dependent frequency response data for electrical input signals
up to 10 kHz.
