New modulation technique for unambiguous measurements of phase changes in diode laser interferometers

Igor Koltchanov; Klaus Petermann; Johannes Roths

doi:10.1117/12.281176

17 September 1997 New modulation technique for unambiguous measurements of phase changes in diode laser interferometers

Igor Koltchanov, Klaus Petermann, Johannes Roths

Proceedings Volume 3098, Optical Inspection and Micromeasurements II; (1997) https://doi.org/10.1117/12.281176
Event: Lasers and Optics in Manufacturing III, 1997, Munich, Germany

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.

Citation Download Citation

Igor Koltchanov, Klaus Petermann, and Johannes Roths "New modulation technique for unambiguous measurements of phase changes in diode laser interferometers", Proc. SPIE 3098, Optical Inspection and Micromeasurements II, (17 September 1997); https://doi.org/10.1117/12.281176

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