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Optically excited and interrogated micromechanical silicon cantilever structure

Optisch angeregte und abgetastete mikromechanische Silizium-Balkenstruktur
: Woelfelschneider, H.; Knoll, G.; Ramakrishnan, S.; Hoefflin, H.; Kist, R.

Langenbeck, P. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
In-process optical metrology for precision machining
Bellingham/Wash.: SPIE, 1987 (Proceedings of SPIE 802)
ISBN: 0-89252-837-0
5 pp. : Abb.,Lit.
International Symposium on Optical and Optoelectronic Applied Science and Engineering <4, 1987, The Hague>
Conference Paper
Fraunhofer IPT ()
Frequenzcodierung; Mikromechanik; Sensor(faseroptisch)

Micromechanical silicon cantilever structures of typical dimensions 1 mm x 80 micrometers x 5 micrometers have been excited by absorption of pulsed light from diode laser at 790 nm or a LED at 830 nm respectively. The excitation motion of the cantilevers was measured by means of a fiber-optic Michelson interferometer as well as a reflective multimode fiber optic pick up. In addition to the optical signal the electrical signal of a thin film piezoresistive transducer localized at the base of the cantilever has been measured. The optimal fiber position with respect to the cantilever was determined experimentally. At this position a signal to noise ratio of about 6 could be realized for the detected signal at 5 kHz bandwidth for optical power levels of 56 micrometers. Using a 125 micrometers diameter optical fiber this corresponds to an optical power density of 4.6 mW/square millimeters which is below the critical value of 5 mW/square millimeters suggested for explosive environments.