1,721,013 research outputs found
Optical properties and diffraction effects in opal photonic crystals
No full textIl lavoro contiene una formulazione teorica che permette di calcolare le proprietà ottiche di cristalli fotonici tridimensionali quali gli opali artificiali, con varie applicazioni.
Abstract: Optical properties of fcc opals oriented along the [111]direction are calculated by means of a scatteringmatrix approach based on approximating each sphere with cylindrical slices. The use of a plane-wave basis in
each layer allows distinguishing zero-order reflection and transmission from higher-order diffraction spectra.
Optical spectra at large values of the angle of incidence indicate the presence of diffraction effects and of
polarization mixing along the LW orientation. Reflectance and transmittance in the high-energy region show a rich spectral dependence and compare reasonably well with recent experimental observations on polystyrene opals. Diffraction spectra as a function of the number of layers display an oscillatory behavior, pointing to the existence of a Pendellösung phenomenon, related to the exchange of energy between two propagating modes in the investigated three-dimensional photonic crystal. This phenomenon could be observed in transmittance experiments on high-quality opals with controlled thickness
Gap maps, diffraction losses and exciton-polaritons in photonic crystal slabs
No full textA theory of photonic crystal (PhC) slabs is described, which relies on an expansion in the basis of guided modes of an effective homogeneous waveguide and on treating the coupling to radiative modes and the resulting losses by perturbation theory. The following applications are discussed for the case of a high-index membrane: gap maps for photonic lattices in a waveguide; exciton–polariton states, when the PhC slab contains a quantum well with an excitonic resonance; propagation losses of line-defect modes in W1 waveguides, also in the presence of disorder; the quality factors of photonic nanocavities. In particular, we predict that disorder-induced losses below 0.2 dB/mm can be achieved in state-of-the-art samples by increasing the channel width of W1 waveguides
Quantum theory of photonic crystal polaritons
No full textWe formulate a full quantum mechanical theory of the interaction between electromagnetic modes in photonic crystal slabs and quantum well excitons embedded in the photonic structure. We apply the formalism to a high index dielectric layer with a periodic patterning suspended in air. The strong coupling between electromagnetic modes lying above the cladding light line and exciton center of mass eigenfunctions manifests itself with the typical anticrossing behavior. The resulting band dispersion corresponds to the quasi-particles coming from the mixing of electromagnetic and material excitations, which we call photonic crystal polaritons. We compare the results obtained by using the quantum theory to variable angle reflectance spectra coming from a scattering matrix approach, and we find very good quantitative agreement
Photonic Bandgap Materials
No full textA review of the main concepts underlying the photonic band structure of photonic band gap materials is presented. 1D, 2D, 3D and waveguide-embedded photonic crystals are treated
Photonic Bands and Gap Maps in a Photonic Crystal Slab
No full textAbstract—The photonic bands of a two-dimensional (2-D) lat-tice patterned in a planar waveguide are calculated by expanding the magnetic field on the basis of waveguide modes. The method yields both the truly guided modes of the structure as well as the quasi-guided modes (or guided resonances) which lie above the light line in the first Brillouin zone. Representative results for the photonic bands are shown in the cases of strong- and weak-con-finement waveguides patterned with a triangular lattice of holes. The gap maps as a function of hole radius are calculated and show significant differences with respect to the ideal 2-D case. A compar-ison of the photonic bands with those extracted from the calculated surface reflectance shows very good agreement, thereby indicating the reliability of the approach. Index Terms—Modeling, optical materials, waveguides. I
Silver high-aspect-ratio micro- and nanoimprinting for optical applications
No full textMetal direct nanoimprinting is a fabrication technique based on plastic deformation of ductile metals
such as silver and gold pressed into a structured rigid mold. While this process can be exploited to
manufacture metallic micro- and nanoparts by removing the mold after processing, it can also be
used as a metallization method for producing two-dimensional metallo-dielectric composites. Dense
silver-pillar arrays with diameters down to 140 nm, aspect ratios up to 13, and excellent uniformity
over large areas were fabricated. The sample quality was confirmed by near-infrared optical
reflectances of Si–Ag photonic crystals, which showed strong collective surface plasmon-polarito
Light-matter interaction in complex photonics systems: introduction
Full text linkThis feature issue presents original work on light-matter interaction in complex photonics systems, which has been a continuously growing area of optics and photonics, in terms of both importance and breadth. From disordered systems to highly controlled micro- and nanostructures, recent decades have witnessed the onset of random media, photonic crystals, metamaterials, plasmonics, and, more recently, metasurfaces.This article is published as Agio, Mario, Xunya Jiang, Maria Kafesaki, and Thomas Koschny. "Light-matter interaction in complex photonics systems: introduction." JOSA B 38, no. 9 (2021): LMI1-LMI2.
DOI: 10.1364/JOSAB.441711.
Copyright 2021 Optical Society of America.
Posted with permission.
DOE Contract Number(s): AC02-07CH1135
Cavity modes in one-dimensional photonic crystal slabs
No full textA theoretical study of cavity modes in one-dimensional photonic crystal slabs embedded in Silicon-on-Insulator structures is reported. Three different methods are employed, namely a guided-mode expansion in which the coupling to radiative modes is treated by perturbation theory, a grating or scattering-matrix method for calculating the surface reflectance, and a Fourier modal expansion for in-plane transmission calculations. It is shown that all methods lead to the same values for the quality factors of cavity modes for both first- and second-order Bragg mirrors. We conclude that the quality factor of a cavity mode can be determined with optical reflectance from the surface of the slab
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