Ultra-precise determination of thicknesses and refractive indices of optically thick dispersive materials by dual-comb spectroscopy
Precise measurements of the geometrical thickness of a sample and its refractive index are important for materials science, engineering, and medical diagnosis. Among the possible non-contact evaluation methods, optical interferometric techniques possess the potential of providing superior resolution...
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Veröffentlicht in: | Optics express 2022-01, Vol.30 (2), p.2734-2747 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | Precise measurements of the geometrical thickness of a sample and its refractive index are important for materials science, engineering, and medical diagnosis. Among the possible non-contact evaluation methods, optical interferometric techniques possess the potential of providing superior resolution. However, in the optical frequency region, the ambiguity in the absolute phase-shift makes it difficult to measure these parameters of optically thick dispersive materials with sufficient resolution. Here, we demonstrate that dual frequency-comb spectroscopy can be used to precisely determine the absolute sample-induced phase-shift by analyzing the data smoothness. This method enables simultaneous determination of the geometrical thickness and the refractive index of a planar sample with a precision of five and a half digits. The thickness and the refractive index at 193.414 THz (λ = 1550 nm) of a silicon wafer determined by this method are 0.5204737(19) mm and 3.475625(58), respectively, without any prior knowledge of the refractive index. |
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ISSN: | 1094-4087 1094-4087 |
DOI: | 10.1364/OE.445134 |