Vertical comb-drive microscanner with 4x4 array of reference micromirrors for phase-shifting Mirau microinterferometry
Résumé
In this paper, we present construction, fabrication and characterization of an electrostatic MOEMS vertical microscanner
for generation of an optical phase shift in array-type interferometric microsystems. The microscanner employs asymmetric
comb-drives for a vertical displacement of a large 4x4 array of reference micromirrors and for in-situ position sensing.
The device is designed to be fully compatible with Mirau configuration and with vertical integration strategy. This enables
further integration of the device within an “active” multi-channel Mirau micro-interferometer and implementation of the
phase shifting interferometry (PSI) technique for imaging applications. The combination of micro-interferometer and PSI
is particularly interesting in the swept-source optical coherence tomography, since it allows not only strong size reduction
of a system but also improvement of its performance (sensitivity, removal of the image artefacts). The technology of device
is based on double-side DRIE of SOI wafer and vapor HF releasing of the suspended platform. In the static mode, the
device provides vertical displacement of micromirrors up to 2.8μm (0 - 40V), whereas at resonance (fo=500 Hz), it reaches
0.7 μm for only 1VDC+1VAC. In both operation modes, the measured displacement is much more than required for PSI
implementation (352nm peak-to-peak). The presented device is a key component of array-type Mirau micro-interferometer
that enables the construction of portable, low-cost interferometric systems, e.g. for in vivo medical diagnostics.