Lamellar-Grating-Based MEMS Fourier Transform Spectrometer

Abstract

Design, fabrication, and characterization of a high-performance micromachined lamellar-grating-interferometer-based Fourier transform spectrometer are presented. The device is designed to give high deflections with very low dynamic deformation and good mode separation. Mechanical self-stoppers are introduced to withstand accelerations larger than 500 g due to shock. The clear aperture area of the grating is about 10 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The maximum deflection while electrostatically actuated at ambient conditions is ±356 μm at 71.2 V and 340 Hz, setting a record for comparable devices. At a pressure of 8.6 Pa, the same deflection is reached at 4.3 V. Six hundred eighty spectra per second can be recorded with a resolution of 14 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . With a HeNe laser at 633 nm, a spectral resolution of 0.54 nm (22 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ) is reached using electrostatic actuation. The microelectromechanical systems device is integrated into a compact Fourier transform spectrometer setup including a blackbody source, an infrared (IR) detector, and a visible laser using the device back side for reference. Early results with IR interferograms are also reported. In addition, the devices are actuated with pressure waves in the ambient air to reach deflections up to ±700 μm. With this setup, the spectrum of a red laser is measured with a resolution of 0.3 nm (12.4 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ).