Optimal direction and propagation of mid-IR light inside rough and polished diamonds for highly-sensitive transmission measurements of nitrogen content

• Published in: Diamond and related materials Vol. 128; p. 109278
• Main Authors: Khmelnitsky, Roman A., Kovalchuk, Oleg E., Gulina, Yulia S., Nastulyavichus, Alena A., Kriulina, Galina Y., Boldyrev, Nikolay Y., Kudryashov, Sergey I., Levchenko, Alexey O., Shiryaev, Vladimir S.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-10-2022
• Subjects: Faceted diamond; Immersion material; Nitrogen defects; Optical transmission/absorption measurement; Rough diamond; Signal dynamic range; Faceted diamond; Signal dynamic range; Optical transmission/absorption measurement; Nitrogen defects; Immersion material; Rough diamond
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2022.109278

Optical transmission/absorption measurements in diamond provide a way for determining content of basic nitrogen defects, with their concentrations varying in different crystals by many orders of magnitude. In a traditional scheme of transmission measurement in many diamond crystals only a small fraction of incident light is transmitted and detected due to light refraction and multiple reflections. This significantly reduces signal-to-noise ratio, narrows the dynamic range of measured signal magnitudes and the corresponding range of measurable defects concentrations. In this work optimal input/output points and optical propagation paths of mid-IR light inside most characteristic forms of rough and faceted diamonds were searched and analyzed. Practical acquisition recommendations and measurement configurations are proposed, enabling to expand signal dynamic range by acquiring multiple mid-IR light reflection/transmission replica, using an integrating sphere and immersion material.
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•Direction of mid-IR light on the pavilion facets parallel to the girdle plane in round-cut diamonds was demonstrated as the optimal measurement scheme.•Direct spectral comparison of mid-IR light transmitted through round-cut diamonds and their rough precursors shows their good correspondence, enabling mid-IR acquisition of impurity-defect composition and gem tracing.•Chalcogenide glass Ge7Se93 has proven itself as a good mid-IR immersion material for reducing scattering losses.