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Miniaturized MOEMS spectrometer for NIR applications

: Grüger, H.; Heberer, A.; Zimmer, F.; Wolter, A.; Schenk, H.


Hatheway, A.E. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Optomechanics 2005 : Spie Conference on Optomechanics 2005, 31 July - 4 August 2005, San Diego, Calif.; proceedings
Bellingham/Wash.: SPIE, 2005 (SPIE Proceedings Series 5877)
ISBN: 0-8194-5882-1
Conference on Optomechanics <2005, San Diego/Calif.>
Fraunhofer IPMS ()

Optical spectroscopy is a common tool for many applications. Micro systems most often use fixed gratings and array detectors. In the infrared wavelength range above the limit for Si-detectors (1100nm) and Ge-detectors (1700nm) respectively, this is either very expensive or almost impossible. Micro opto electro mechanical systems (MOEMS) offer very promising options. A movable grating can be realized by a silicon chip, using the technology of a well established scanner mirror chips in combination with the realization of a reflective grating either through etching of the aluminium mirror layer or even a more sophisticated technology. The patented resonant drive realizes a mechanical angle of ±7° with CMOS compatible voltages of approximately 20V. This technology leads to the realization of a set up close to a classical Czerny-Turner spectrometer using a single detector only. The device offers the capability to be scaled down to the size of a cigarette box. The spectrometer presented here was adjusted to 900...2500nm range. The scanning grating chip has either 500, 625 or 714 lines/mm. As detector serves a fast InGaAs photodiode, read out through a 12 Bit AD converter. The sinusoidal movement is unfolded by a signal processor (TI TMS320F2812) which also computes the spectrum. Acquired data can be shown by a display or transmitted to a host PC. System tests have been performed using infrared LEDs. Wavelengths have been 1300, 1400 or 1550nm for example. The spectrometer is working accurately. First result of micro shaped grating structures to enhance the sensitivity are presented.