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Proceedings Paper

New modulation technique for unambiguous measurements of phase changes in diode laser interferometers
Author(s): Igor Koltchanov; Klaus Petermann; Johannes Roths
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Paper Abstract

We present a new powerful modulation/demodulation technique for unambiguous measurements of phase changes in two-beam interferometers. The technique does not require any additional optics besides a basic interferometer setup and resolves the ambiguity of direction of phase changes by use of a simple two-tone modulation of the laser diode wavelength via injection current. The interference of two modulated light beams generates a signal at the photodetector which is similar to that of heterodyne interferometric setup. The optical phase is thus transferred to an electrical carrier frequency, which allows the phase detection by means of conventional electronic FM-signal processing. The new techniques can be used with any two-beam interferometers as e.g. the Michelson or Mach-Zehnder ones. In the present paper it was applied to a laser-diode, 'self- mixing interferometer' where a weak optical feedback from a target results in an interference with internal laser light.

Paper Details

Date Published: 17 September 1997
PDF: 9 pages
Proc. SPIE 3098, Optical Inspection and Micromeasurements II, (17 September 1997); doi: 10.1117/12.281176
Show Author Affiliations
Igor Koltchanov, Technische Univ. Berlin (Germany)
Klaus Petermann, Technische Univ. Berlin (Germany)
Johannes Roths, Kayser-Threde GmbH (Germany)

Published in SPIE Proceedings Vol. 3098:
Optical Inspection and Micromeasurements II
Christophe Gorecki, Editor(s)

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