Search results for " Reflection"

Kerr and Faraday Rotations of Magneto-Optical Multilayers under the Condition of Total Internal Reflection

1999

Photonic transfer through subwavelength optical waveguides

1998

Optical tunneling effect through dielectric junctions with subwavelength transverse sizes has been demonstrated some years ago. In this letter, we demonstrate how similar effects can be exploited to perform photonic transfer through a subwavelength optical wave guide (SOW) by structuring its optical index along the direction of propagation. The optical transmittance of the SOW is computed self-consistently in direct space through the numerical solution of a Dyson equation. We apply this scheme to investigate the optical properties of different SOW architectures. Even under total internal reflection, in which the light is coupled to the SOW by an evanescent mode, an efficient optical transfe…

Interrogation of whispering-gallery modes resonances in cylindrical microcavities by backreflection detection

2009

The excitation of whispering-gallery-mode resonances of cylindrical microcavities, using narrow fiber tapers, produces simultaneously the excitation of spiral modes. The power coupled to the spiral modes leads to a significant broadening of the dips observed in the spectrum of light transmitted through the taper. We demonstrate that whispering-gallery modes resonances of cylindrical microcavities can also be interrogated by measuring the reflection spectrum. Unlike the dips observed in transmission, the peaks in the reflection spectrum are symmetric and narrower than the corresponding transmission dips.

Analytical description of resonances in Fabry–Perot and whispering gallery mode resonators

2021

Whispering gallery mode optical resonators have attracted attention due to their simplicity and applicability for sensing. In this paper, analytical formulas are provided that describe resonance conditions in optical resonators. Basic terms (resonance wavelengths and frequencies, free spectral range, Q -factor, summation principle of Q -factors of various processes, finesse, etc.) are introduced. A description of interference of an infinite number of waves of progressively smaller amplitudes and equal phase differences is given. A description of a Fabry–Perot resonator with nonequal reflection coefficients is also given as well as analysis of all-pass and add-drop optical filters. The prese…

Three-dimensional scattering of dielectric gratings under plane-wave excitation

2003

The problem of scattering of electromagnetic plane waves by one-dimensional (1D) periodic dielectric gratings, under the most general condition of oblique incidence (3D incidence), is rigorously solved. A recently developed vectorial modal method for obtaining the modal spectrum of 1D dielectric periodic guiding media has been extended to consider 3D incidence. Polarization coupling effects are included in the analysis, just demonstrating the impossibility of the separation between the transverse electric and transverse magnetic polarizations traditionally employed in the two-dimensional (2D) case. A study of the scattering parameters of a multilayered dielectric periodic structure is accom…

Plasmon-driven Bessel beams

2012

We report on subwavelength diffraction-free beams with grazing propagation in metal-dielectric devices. The nondiffracting beams are resonantly transmitted through the nanostructured medium leading to light confinement and wave amplification around the beam axis.

Carbon coatings for soft-x-ray reflectivity enhancement

2007

In X-ray astronomical telescopes, the focalization of the radiation is achieved by means of grazing incidence Wolter I (parabola + hyperbola) optics in total reflection regime. In general, high density materials (e.g. Au, Pt, Ir, W) are used as reflecting coatings, in order to increase as much as possible the cut-off angles and energies for total reflection. However these materials present an important reduction of the reflectivity between 0.2 and 5 keV, due to the photoabsorption, and this phenomenon is particularly enhanced in correspondence of the M absorption edges (between 2 and 3.5 keV). In general, this determines a strong decrease of the telescope effective area. To overcome the pro…

Specular reflection of spin-polarized electrons from the W(001) spin-filter crystal in a large range of scattering energies and angles

2015

Extending previous work on the imaging spin-filter technique based on electron diffraction from W(001) in the specular (00)-LEED (low-energy electron diffraction) spot, we studied the scattering-energy and angle-of-incidence landscape of spin sensitivity $S$ and reflectivity ${I/I}_{0}$. The setup includes a spin-polarized GaAs electron source and a rotatable delay-line detector for spatially resolving detection. We measured the intensity and spin asymmetry of the specularly reflected beam for energies between 14 and 37 eV and angles of incidence between ${30}^{\ensuremath{\circ}}$ and ${60}^{\ensuremath{\circ}}$. Resulting energy-angular landscapes show rather good agreement with theory [r…

Asymmetric Conductivity of Strongly Correlated Compounds

2014

In this chapter, we show that the FC solutions for distribution function \(n_0(\mathbf{p})\) generate NFL behavior, and violate the particle-hole symmetry inherent in LFL. This, in turn, yields dramatic changes in transport properties of HF metals, particularly, the differential conductivity becomes asymmetric. As it is demonstrated in Sect. 3.1, Fermi quasiparticles can behave as Bose one. Such a state is viewed as possessing the supersymmetry (SUSY) that interchanges bosons and fermions eliminating the difference between them. In the case of asymmetrical conductivity it is the emerging SUSY that violates the time invariance symmetry. Thus, restoring one important symmetry, the FC state vi…

Quantification of phenolic acids by partial least squares Fourier-transform infrared (PLS-FTIR) in extracts of medicinal plants.

2020

Introduction Phenolic compounds are ubiquitous compounds found in all plants as their secondary metabolites. Phenols are becoming increasingly important particularly because of their beneficial effects on health. Objective To provide a faithful calibration model for the simultaneous determination and quantification of phenolic acids, as salicylic, vanillic, p-hydroxybenzoic acids, eugenol and thymol in different extracts of medicinal plants, a comparative study was made between two methods of infrared measurements based on attenuated total reflectance (ATR) and transmission. Methods Characteristic absorbance peak heights of mid-infrared spectra of individual phenolic acids were measured for…