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Optical Review

, Volume 6, Issue 5, pp 443–448 | Cite as

Heterodyne Interferometers Using Orthogonally Polarized and Two-Frequency Shifted Light Sources with Super-high Extinction Ratio

  • Noboru Nakatani
OPTICAL SYSTEMS AND TECHNOLOGIES

Abstract

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

Key words

heterodyne interferometer frequency shifted light source high extinction ratio non-linearity polarization cross-talk 

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References

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    N. Nakatani: Japan patent No. 2807965 (1998) (Contribution Filed 1994-No. 108922).Google Scholar

Copyright information

© The Optical Society of Japan 1999

Authors and Affiliations

  1. 1.Ashiya UniversityDepartment of Industrial EducationHyogoJapan

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