Topic
Total external reflection
About: Total external reflection is a research topic. Over the lifetime, 829 publications have been published within this topic receiving 22213 citations.
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TL;DR: In this paper, the intensity of light signal transmitted through an optical fiber, whose cladding over a finite length is removed, is used as a sensor of refractive index of liquids, in which the fiber is immersed.
Abstract: The intensity of light signal transmitted through an optical fiber, whose cladding over a finite length is removed, is used as a sensor of refractive index of liquids, in which the fiber is immersed. The transmitted light intensity is measured as a function of liquid refractive index for different lengths of the unclad section of the fiber and at each unclad length its sensitivity to change in refractive index of liquid is monitored. The liquid refractive index studied ranges from below the refractive index of the cladding to above that of the core. A plot of normalized light intensity as a function of liquid refractive index for a short unclad length shows a local maximum at a liquid refractive index equal to the refractive index of the fiber core. This maximum becomes less prominent as length of unclad region increases and finally disappears. These observations are interpreted in terms of frustrated total internal reflection of light rays. Sensitivity to refractive index differential, of the sensor response, increases with increase in refractive index of the liquid pair, below that of the fiber core. In this range of refractive index, we observe a maximum in this sensitivity at an intermediate unclad length of the fiber. When liquid refractive index equals core refractive index, at the rising edge of the local maximum observed in sensors of shorter unclad length, the sensitivity maximum disappears. The sensitivity to refractive index differential diminishes as liquid refractive index exceeds fiber core refractive index. Measurements have been performed with five different unclad sensor lengths and a core diameter of 400 and 800 μm. The results for the two core diameters show similar qualitative features.
20 citations
TL;DR: Using X-ray reflectivity, this article investigated UVCVD and PECVD silica thin films deposited on germanium substrates and showed that the use of this specific part of the reflectivity profile provided a significant improvement of the density determination of thin films giving an accuracy close to one per cent.
Abstract: Using X-ray reflectivity, we investigate UVCVD and PECVD silica thin films deposited on germanium substrates Under our experimental conditions, an accurate measurement of the total external reflection on the substrate can be obtained We show that the use of this specific part of the reflectivity profile provides a significant improvement of the density determination of thin films giving an accuracy close to one per cent This procedure is used to compare the silica densities of films made by UVCVD, PECVD and thermal oxidation In UVCVD films a stationary deposition regime exists above a critical thickness
20 citations
TL;DR: In this article, a harmonic analysis is applied to study the reflection and refraction patterns of thermal waves from a surface and an interface between dissimilar materials, and the physical envelope for complete transmission and physical conditions for complete reflection are discussed in detail.
20 citations
Journal Article•
20 citations
TL;DR: In this article, the 2D reflected light distributions from front surfaces of silicon cells textured in various ways are characterised by an appropriate optical setup, and the results are compared to those of conventional ray tracing.
20 citations