Lamellar-Grating-Based MEMS Fourier Transform Spectrometer

Abstract

Design, fabrication, and characterization of a highperformance micromachined lamellar-grating-interferometerbased 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 2 . 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 −1 . With a HeNe laser at 633 nm, a spectral resolution of 0.54 nm (22 cm −1 ) 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 −1 ).[2011-0252] Index Terms-Fourier transform spectroscopy (FTS), infrared (IR) spectroscopy, interferometer, lamellar grating, microoptoelectromechanical systems. I. INTRODUCTIONF OURIER transform spectroscopy (FTS) has evolved into a standard analytical technique in the fields of physical, biological, and chemical sciences, as well as a tool for quality and process control, bomb detection, mining industry, and gas detection. Compared to other spectroscopy methods, it provides high accuracy, high throughput, a compact form factor, and low cost. The conventional FTS devices make use of a Michelson Manuscript

Review of MEMS Based Fourier Transform Spectrometers

“…A maximum peak to peak deflection of 355 µm was achieved under 76 V and 971 Hz excitation environment. Seren et al implemented another out-of-plane resonant mode electrostatic MEMS for Lamellar grating based FTS in 2010 [41]. The device had a clear aperture of 10 mm × 10 mm.…”

“…However, high voltage is required, and hundreds of volts only produce several tens of micrometers. Moreover, high voltage introduces electronics Seren et al implemented another out-of-plane resonant mode electrostatic MEMS for Lamellar grating based FTS in 2010 [41]. The device had a clear aperture of 10 mm × 10 mm.…”

Wafer-Level Vacuum-Packaged Translatory MEMS Actuator with Large Stroke for NIR-FT Spectrometers

“…In addition to the actuation mechanism, MEMS-based FTS can be subclassified by the principle of optical FTS instrumentation: (i) Michelson interferometer-based FTS, e.g., [ 7 , 12 , 23 , 24 , 25 , 26 , 27 ], or (ii) lamellar grating-based FTS, enabling a simplified interferometer set-up without optical beam splitter [ 6 , 8 , 28 , 29 , 30 , 31 , 32 ]. MEMS technology was also used to simplify the optical system integration of FTS; early approaches using bulk [ 5 , 6 , 33 ] and surface micromachining [ 34 ] were reported.…”

Nondestructive On-Site Detection of Soybean Contents Based on An Electrothermal MEMS Fourier Transform Spectrometer

“…It is capable of miniaturizing spectrometers and various MEMS based spectrometers have been developed [5], [6]. MEMS spectrometers can be classified into three categories: dispersive gratings [7]- [9], tunable filters [10]- [12], and Fourier transform infrared (FTIR) spectrometers [13]- [16]. MEMS-based FTIR, or μFTIR, has the advantages of higher signal to noise ratio (SNR) and spectral resolution as well as potentially low cost as only single IR photodetectors, instead of expensive IR detector arrays, are needed.…”