Sinusoidal wavelength-scanning interferometric reflectometry

Osami Sasaki; Tomokazu Kuwahara; Ryohta Hara; Takamasa Suzuki

doi:10.1117/12.347759

7 May 1999 Sinusoidal wavelength-scanning interferometric reflectometry

Osami Sasaki, Tomokazu Kuwahara, Ryohta Hara, Takamasa Suzuki

Proceedings Volume 3740, Optical Engineering for Sensing and Nanotechnology (ICOSN '99); (1999) https://doi.org/10.1117/12.347759
Event: Optical Engineering for Sensing and Nanotechnology (ICOSN '99), 1999, Yokohama, Japan

Abstract

We propose an interferometric reflectometry using a sinusoidal wavelength-scanning tunable laser diode to detect positions and profiles of multiple reflecting surfaces. An objective signal extracted from an interference signal contains the modulation amplitude Z and the phase (alpha) which are related to positions and profiles of multiple reflecting surfaces, respectively. By using values of the object signal at special times, we can produce an image intensity which shows where the reflecting surfaces exist. To obtain exact values of Z or values of (alpha) the objective signal is estimated with a conjugate gradient method. Experiments results show that a resolution of two-optical path difference (OPD) in the image intensity is 87 micrometer, and a final OPD accuracy is 2 micrometer and 8 micrometer for the two and three reflecting surfaces, respectively, in the case of the wavelength-scanning width of 7 nm. Profiles of front and rear surfaces of a silica glass plate with thickness of 20 micrometer are measured with an accuracy of about 10 nm.

Citation Download Citation

Osami Sasaki, Tomokazu Kuwahara, Ryohta Hara, and Takamasa Suzuki "Sinusoidal wavelength-scanning interferometric reflectometry", Proc. SPIE 3740, Optical Engineering for Sensing and Nanotechnology (ICOSN '99), (7 May 1999); https://doi.org/10.1117/12.347759

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