Pseudo-Brewster and second-Brewster angles of an absorbing substrate coated by a transparent thin film

Azzam, R. M. A.; Thonn, Tracy F.

doi:10.1364/ao.22.004155

Cited by 20 publications

(5 citation statements)

References 3 publications

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“…The assumption that the reflection occurs from a homogeneous medium can also be violated by creating a multilayer structure where either the s - or the p - polarized light is reflected and the other polarization is extinguished . The generalized Brewster conditions of a lithography-free planar stack of thin films have been theoretically investigated where the inhomogeneity is due to stacking different materials. − In this case, the GBA corresponds to an angle where electric dipoles in the inhomogeneous stack of materials destructively interfere. An experimental realization of GBA effect of a transparent film on an absorbing substrate, however, has not been demonstrated.…”

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confidence: 99%

Generalized Brewster Angle Effect in Thin-Film Optical Absorbers and Its Application for Graphene Hydrogen Sensing

et al. 2019

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The generalized Brewster angle (GBA) is the incidence angle at polarization by reflection for p- or s-polarized light. Realizing an s-polarization Brewster effect requires a material with magnetic response, which is challenging at optical frequencies since the magnetic response of materials at these frequencies is extremely weak. Here, we experimentally realize the GBA effect in the visible using a thin-film absorber system consisting of a dielectric film on an absorbing substrate. Polarization by reflection is realized for both p - and s - polarized light at different angles of incidence and multiple wavelengths. We provide a theoretical framework for the generalized Brewster effect in thin-film light absorbers. We demonstrate hydrogen gas sensing using a single-layer graphene film transferred on a thin-film absorber at the GBA with ∼1 fg/mm 2 aerial mass sensitivity. The ultrahigh sensitivity stems from the strong phase sensitivity near the point of darkness, particularly at the GBA, and the strong light–matter interaction in planar nanocavities. These findings depart from the traditional domain of thin films as mere interference optical coatings and highlight its many potential applications including gas sensing and biosensing.

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Generalized Brewster Angle Effect in Thin-Film Optical Absorbers and Its Application for Graphene Hydrogen Sensing

et al. 2019

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“…Such angles are somewhat analogous to the Brewster angle θ B , at which plane waves polarized in the plane of incidence (p polarized) are fully transmitted: the corresponding reflection coefficient r p θ B 0, giving zero reflected light projected onto an analyzer set in the p-polarization state [10]. Null-reflection angles are not polarizing angles [11,12], but they are interesting in the context of beam shifts, as they occur for arbitrary states of elliptic polarization, when the analyzer is crossed with (orthogonal to) the reflected polarization, and they can be found in regimes of both total and partial reflection.Beams, made up of many plane wave components, do not have] homogeneous polarization after reflection, and hence the projection onto an analyzer polarization is nonzero but possibly shifted. With appropriate choice of initial and final polarizations, the beam shift close to Brewster or null-reflection angles can be very large.…”

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confidence: 99%

Limits to superweak amplification of beam shifts

Götte

Dennis

2013

Opt. Lett.

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The magnitudes of beam shifts (Goos-Hänchen and Imbert-Fedorov, spatial and angular) are greatly enhanced when a reflected light beam is postselected by an analyzer, by analogy with superweak measurements in quantum theory. Particularly strong enhancements can be expected close to angles at which no light is transmitted for fixed initial and final polarizations. We derive a formula for the angular and spatial shifts at such angles (which includes the Brewster angle), and we show that their maximum size is limited by higher-order terms from the reflection coefficients occurring in the Artmann shift formula.

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“…So, we have considered the angle at which the ratio of R p to R s is found to be minimum which is not always equal to the Brewster's angle and referred to here as the second Brewster's angle (θ B2 ). 18 Since refractive index of a medium depends on the wavelength, the Brewster's angle also varies with refractive index. However, for the chosen narrow spectral band of 40 Å between 740 and 780 Å, there is no substantial change in the refractive index of the chosen fluoride coatings as shown in Figure 1.…”

Section: Mirror Coatings and Polarimeter Configurationsmentioning

confidence: 99%

Design concepts of EUV polarimeter

Khan,

Nagaraju,

Phanindra

2023

Optics for EUV, X-Ray, and Gamma-Ray Astronomy XI

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The solar corona is a complex and dynamic region primarily controlled by the magnetic fields. Hence the routine measurement of these fields is crucial. Magnetic field information remains embedded in the polarization profiles of the spectral lines, which can be quantified through spectropolarimetry. Differential Hanle effect is a promising diagnostic tool to probe weak coronal magnetic fields and their vector properties. In a recent study we have found several combinations of spectral lines located in the wavelength range 100 to 1210 Å suitable for the above purpose whose critical Hanle field lies in the range of 0.01-200 Gauss. Since the background emission from the Sun’s underlying layers, such as the photosphere and the chromosphere, is almost negligible at these short wavelengths, the coronagraphic technique is not required to study the solar corona, thereby enabling both on-disk and off-limb measurements. Yet there is no EUV polarimeter built for solar observations. In this context we explored a few polarimeter concepts based on the configurations of two and three reflecting mirrors. The performances of these configurations are studied in terms of their throughput and polarizing power using Zemax software in the wavelength range 740-780 Å. They are also compared with different coating materials namely, BaF2, MgF2 and LiF. It is found that BaF2 has significantly higher throughput and polarizing power in the above stated wavelength range.

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Pseudo-Brewster and second-Brewster angles of an absorbing substrate coated by a transparent thin film

Cited by 20 publications

References 3 publications

Generalized Brewster Angle Effect in Thin-Film Optical Absorbers and Its Application for Graphene Hydrogen Sensing

Generalized Brewster Angle Effect in Thin-Film Optical Absorbers and Its Application for Graphene Hydrogen Sensing

Limits to superweak amplification of beam shifts

Design concepts of EUV polarimeter

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