Evanescent wave spectroscopy for the determination of the optical constants of thin silver films deposited on a silver-halide fiber

Abstract

An unclad silver-halide fiber was coated with a 0.1-microm silver layer and immersed in ethyl alcohol, and the fiber transmission in the range 2-20 microm was measured. The loss, induced by the metallic layer, was used to calculate the extinction coefficient, kappa', and the index of refraction, n', of the layer by fitting the experimental data with the time-independent perturbation theory in the complex region. The dependence of the extinction coefficient on the wavelength was found to be logarithmic, kappa'(lambda) = kappa(0)' exp(a lambda), and not linear, as predicted by others. This simple technique may be used to study the optical constants of thin metallic films.

Generalization of the Rouard method to an absorbing thin-film stack and application to surface plasmon resonance

“…SPR has proven to be useful in the development of biosensors, specifically, in the determination of molecular interactions. 7 The phenomenon of SPR emerges from the existence of a plasmon wave. 8,9 The plasmon wave is an induced effect of the coupling between an electromagnetic field and the oscillation of a plasma.…”

“…5 Later, the Rouard method was described for various applications but still in a complex way. 6,7 In this paper, we first briefly review the Rouard method, explicitly written for transparent media. We then discuss the generalization of this method to any number of absorbing layers.…”

Analysis of Surface Leaching Processes in Vitrified High-Level Nuclear Wastes Using In-Situ Raman Imaging and Atomistic Modeling - Final Report

“…These types of systems are useful only as a measure of a known system's stability over time, and can only be used to measure quantitative changes if a calibration curve is used and the system is known completely. [50,51] Current remote optical sensors that are capable of more than stability monitoring include Raman methods, photoluminescence, evanescent wave spectroscopy and broad band transmission methods [50][51][52][53][54][55][56][57][58][59][60]. The design of these types of sensors usually takes the form of one of the three shown in Figure 7.1.…”

Use of Analyte-Modulated Modal Power Distribution in Multimode Optical Fibers for Simultaneous Single-Wavelength Evanescent-Wave Refractometry and Spectrometry

“…To address the selectivity problem encountered with these types of sensors, several techniques can be useful. For example, moderately and highly absorbing samples can be treated by means of a Kramers-Kronig analysis and by time-independent perturbation theory . Such samples can be also studied with surface-plasmon resonance spectroscopy, in which surface plasmons are simultaneously excited at multiple angles and multiple wavelengths. , If weakly absorbing samples are being investigated, the change in refractive index can often be ignored; even anomalous dispersion that occurs in the vicinity of an absorption band is smaller than the typical (1−6) × 10 -5 refractive-index resolution of most optical-waveguide refractometers. ,,, Also, the contributions of a variable refractive index and absorbance of a weakly absorbing sample can sometimes be differentiated by means, respectively, of the baseline shift and the magnitude of the absorption peak in a collected evanescent-wave spectrum. , Unfortunately, all these techniques require recording of a complete spectrum of an absorption feature, including frequencies that do not undergo absorption.…”