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Translatory MEMS actuators for optical path length modulation in miniaturized fourier-transform infrared spectrometers

: Sandner, T.; Drabe, C.; Schenk, H.; Kenda, A.; Scherf, W.


Journal of micro/nanolithography, MEMS and MOEMS 7 (2008), Nr.2, Art. 021006
ISSN: 1537-1646
ISSN: 1932-5150
ISSN: 1932-5134
Fraunhofer IPMS ()

We present several types of translatory MOEMS actuators developed for fast optical-path-length modulation [e.g., in confocal microscopes or Fourier-transform infrared (FTIR) spectrometers] and their application on miniaturized FTIR spectrometers capable of performing time-resolved measurements from the near infrared to the mid infrared. The MOEMS devices are manufactured in a complementary metal oxide semi conductor compatible silicon-on-insulator process. They are electrostatically resonant, driven using in-plane comb drives. A first translatory 5-kHz MOEMS device is used in a first prototype of a miniaturized MOEMS-based FTIR spectrometer where the MOEMS actuator replaces the macroscopic mirror drive, enabling a miniaturized, robust, and low-cost FTIR system. The mirror plate of 1.65 mm2 is suspended by bending springs. Due to the resonant operation, a 200-µm stroke can be achieved with low voltages (<40 V) at an ambient pressure below 500 Pa. Consequently, this yields a spectral resolution of 25 cm?1 and an acquisition time of 200 µs per spectrum. In addition, we present a novel MOEMS device with an increased mirror aperture of 7.1 mm2 and pantograph-like mirror suspension enabling up to a 500-µm stroke. This device is specifically optimized for miniaturized FTIR spectrometers to enable an improved spectral resolution of 10 cm?1 and a signal-to-noise ratio of >1000:1.