Heterodyne interferometers using orthogonally polarized and two-frequency shifted light sources with superhigh extinction ratio

Noboru Nakatani

doi:10.1117/12.347720

7 May 1999 Heterodyne interferometers using orthogonally polarized and two-frequency shifted light sources with superhigh extinction ratio

Noboru Nakatani

Author Affiliations +

Proceedings Volume 3740, Optical Engineering for Sensing and Nanotechnology (ICOSN '99); (1999) https://doi.org/10.1117/12.347720
Event: Optical Engineering for Sensing and Nanotechnology (ICOSN '99), 1999, Yokohama, Japan

Abstract

This paper describes the heterodyne interferometers using orthogonally polarized and two-frequency shifted light sources of two types with super-high extinction ratio for reducing non-linearity of the interferometer due to polarization cross- talk. The acousto-optic modulators are used for shifting light frequencies. In the first interferometer the light source with Glan-Thomson prisms of very high extinction ratio (50 dB) is used for making the polarization cross-talk very small. The Glan-Thomson prisms are put before the combiner of the polarizing beams. In the second interferometer the light source of frequency shifted beams with small crossing angle (2.5 mrad approximately 10 mrad) is used for excluding completely non-linearity of the interferometer due to polarization cross-talk. By measuring thickness of a vacuum evapolation film, it was demonstrated that the interferometers are useful to measure thickness of a thin film in nanometer order.

Citation Download Citation

Noboru Nakatani "Heterodyne interferometers using orthogonally polarized and two-frequency shifted light sources with superhigh extinction ratio", Proc. SPIE 3740, Optical Engineering for Sensing and Nanotechnology (ICOSN '99), (7 May 1999); https://doi.org/10.1117/12.347720

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