Abstract
A Fourier transform spectrometer (FTS) that incorporates a closed-loop controlled, electrothermally actuated microelectromechanical systems (MEMS) micromirror is proposed and experimentally verified. The scan range and the tilting angle of the mirror plate are the two critical parameters for MEMS-based FTS. In this work, the MEMS mirror with a footprint of 4.3 mm × 3.1 mm is based on a modified lateral-shift-free (LSF) bimorph actuator design with large piston and reduced tilting. Combined with a position-sensitive device (PSD) for tilt angle sensing, the feedback controlled MEMS mirror generates a 430 µm stable linear piston scan with the mirror plate tilting angle less than ±0.002°. The usable piston scan range is increased to 78% of the MEMS mirror’s full scan capability, and a spectral resolution of 0.55 nm at 531.9 nm wavelength, has been achieved. It is a significant improvement compared to the prior work.
Highlights
Fourier transform spectroscopy is a well-established technique that has been used to determine a variety of unknown substances with applications ranging from chemical and biomedical sensing to hazardous materials detection
An Fourier transform spectrometers (FTS) system enabled by a closed-loop controlled electrothermal MEMS mirror has been
Compared to the prior work, the newly implemented closed-loop control method provides a robust solution on minimizing the tilting of the MEMS mirror during the piston scanning
Summary
Fourier transform spectroscopy is a well-established technique that has been used to determine a variety of unknown substances with applications ranging from chemical and biomedical sensing to hazardous materials detection. The issue of the mirror plate tilting that significantly limits the usable scan range is a bottleneck for electrothermal MEMS mirror-based FTS systems. Wu et al developed a lateral-shift-free (LSF) electrothermal MEMS mirror with 620 μm vertical displacement at 5.3 V, but the mirror plate experienced a tilting as large as 0.7◦ [23]. Open-loop control is very sensitive to any environmental disturbances and degrades quickly over time These electrothermally-actuated MEMS mirrors are summarized in Table 1 in terms of the scan range and tilt angle with and without compensation. An FTS system based on a closed-loop controlled LSF electrothermal MEMS mirror is developed. This LSF electrothermal micromirror can generate a maximum vertical displacement of 550 μm. LSF is lateral-shift-free, CCBA is curled concentric electrothermal bimorph actuator, is inverted-series-connected
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