Single-layer antireflection coatings on absorbing substrates for the parallel and perpendicular polarizations at oblique incidence

Azzam, R. M. A.

doi:10.1364/ao.24.000513

Cited by 12 publications

(4 citation statements)

References 11 publications

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“…This can be attributed to the presence of the transparent dielectric layer (SiO 2 ) on an absorbing substrate (in our case a multilayer stack). [ 40 ] The peak in the ellipsometric ψ plot further confirms the observation of generalized Brewster effect. Zero‐reflection of the s‐polarization is manifested as a peak in the ψ spectrum, approaching the value of 90°.…”

Section: Differential Phase Sensor Design and Responsesupporting

confidence: 68%

Reusable Biosensor Based on Differential Phase Detection at the Point of Darkness

Samdani

Kala

Kaurav

et al. 2021

Advanced Photonics Research

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A differential phase sensor based on a narrowband perfect absorber uses the phase singularity at the point of darkness (100% absorption). Herein, a structure with a top SiO2 layer is proposed that is index matched with a glass flow cell that shows the point of darkness for both s‐ and p‐polarizations. Detailed numerical results to optimize the structure, study the role of fluctuation in thickness and roughness of analyte layer show that the proposed structure has refractive index sensitivity of 147.3° RIU−1. Experimental results of launch angle independent ≈99.9% absorption in the 45°–73° range are reported, with the highest reported till date quality factor in planar narrowband absorbers of ≈42, and high figure of merit of 556 for p‐polarization. The structure also exhibits the generalized Brewster effect with a perfect absorption (≈99.99%) for s‐polarization at ≈74° angle. Experimental results are presented to demonstrate the sensor operation for two different biomolecules at the p‐polarization resonance. The configuration presented is ideal for reusable and cost‐effective biosensors.

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Section: Differential Phase Sensor Design and Responsesupporting

confidence: 68%

Reusable Biosensor Based on Differential Phase Detection at the Point of Darkness

Samdani

Kala

Kaurav

et al. 2021

Advanced Photonics Research

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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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“…Anti-reflective (AR) coatings are necessary in several applications where losses from reflection of incident optical radiation need to be eliminated 16 . Reflective losses from metallic surfaces can be eliminated by depositing ultra-thin films of absorbing dielectrics on the metal surface 17 18 19 . Mikhail et al .…”

Section: Mechanism Of Visualizationmentioning

confidence: 99%

“…Anti-reflective (AR) coatings are necessary in several applications where losses from reflection of incident optical radiation need to be eliminated [16].Reflective losses from metallic surfaces can be eliminated by depositing ultra-thin films of absorbing dielectrics on the metal surface [17,18,19]. Mikhail et al [10] used ultra-thin Ge films (5-25 nm thick) deposited on gold to achieve anti-reflection condition for enhancing solar energy conversion efficiency.…”

Section: Mechanism Of Visualizationmentioning

confidence: 99%

Bright-field Nanoscopy: Visualizing Nano-structures with Localized Optical Contrast Using a Conventional Microscope

Suran

Bharadwaj

Raghavan

et al. 2016

Sci Rep

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Most methods for optical visualization beyond the diffraction limit rely on fluorescence emission by molecular tags. Here, we report a method for visualization of nanostructures down to a few nanometers using a conventional bright-field microscope without requiring additional molecular tags such as fluorophores. The technique, Bright-field Nanoscopy, is based on the strong thickness dependent color of ultra-thin germanium on an optically thick gold film. We demonstrate the visualization of grain boundaries in chemical vapour deposited single layer graphene and the detection of single 40 nm Ag nanoparticles. We estimate a size detection limit of about 2 nm using this technique. In addition to visualizing nano-structures, this technique can be used to probe fluid phenomena at the nanoscale, such as transport through 2D membranes. We estimated the water transport rate through a 1 nm thick polymer film using this technique, as an illustration. Further, the technique can also be extended to study the transport of specific ions in the solution. It is anticipated that this technique will find use in applications ranging from single-nanoparticles resolved sensing to studying nanoscale fluid-solid interface phenomena.

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Single-layer antireflection coatings on absorbing substrates for the parallel and perpendicular polarizations at oblique incidence

Cited by 12 publications

References 11 publications

Reusable Biosensor Based on Differential Phase Detection at the Point of Darkness

Reusable Biosensor Based on Differential Phase Detection at the Point of Darkness

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

Bright-field Nanoscopy: Visualizing Nano-structures with Localized Optical Contrast Using a Conventional Microscope

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