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Photonic crystal

About: Photonic crystal is a research topic. Over the lifetime, 43424 publications have been published within this topic receiving 887083 citations.


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TL;DR: These results reveal that in the wavelength regime of interest evanescent waves are not transmitted by the transparent multilayer, metallo-dielectric photonic band gap structure, and that the main underlying physical mechanisms for sub-wavelength focusing are resonance tunneling, field localization, and propagation effects.
Abstract: We numerically demonstrate negative refraction of the Poynting vector and sub-wavelength focusing in the visible part of the spectrum using a transparent multilayer, metallo-dielectric photonic band gap structure. Our results reveal that in the wavelength regime of interest evanescent waves are not transmitted by the structure, and that the main underlying physical mechanisms for sub-wavelength focusing are resonance tunneling, field localization, and propagation effects. These structures offer several advantages: tunability and high transmittance (50% or better) across the visible and near IR ranges; large object-image distances, with image planes located beyond the range where the evanescent waves have decayed. From a practical point of view, our findings point to a simpler way to fabricate a material that exhibits negative refraction and maintains high transparency across a broad wavelength range. Transparent metallo-dielectric stacks also provide an opportunity to expand the exploration of wave propagation phenomena in metals, both in the linear and nonlinear regimes.

172 citations

Journal ArticleDOI
TL;DR: The main physical effects of patterning are focused on, namely a reduction of reflection losses, diffraction of light in air or inside the cell, and coupling of incident radiation into quasi-guided optical modes of the structure, which is characteristic of photonic light-trapping.
Abstract: We theoretically investigate the light-trapping properties of one- and two-dimensional periodic patterns etched on the front surface of c-Si and a-Si thin film solar cells with a silver back reflector and an anti-reflection coating. For each active material and configuration, absorbance A and short-circuit current density Jsc are calculated by means of rigorous coupled wave analysis (RCWA), for different active materials thicknesses in the range of interest of thin film solar cells and in a wide range of geometrical parameters. The results are then compared with Lambertian limits to light-trapping for the case of zero absorption and for the general case of finite absorption in the active material. With a proper optimization, patterns can give substantial absorption enhancement, especially for 2D patterns and for thinner cells. The effects of the photonic patterns on light harvesting are investigated from the optical spectra of the optimized configurations. We focus on the main physical effects of patterning, namely a reduction of reflection losses (better impedance matching conditions), diffraction of light in air or inside the cell, and coupling of incident radiation into quasi-guided optical modes of the structure, which is characteristic of photonic light-trapping.

172 citations

Journal ArticleDOI
TL;DR: Guided modes propagating in dielectric material surrounded by periodic two-dimensional photonic band-gap material are theoretically studied using the plane-wave expansion and a supercell as discussed by the authors.
Abstract: Guided modes propagating in dielectric material surrounded by periodic two‐dimensional photonic band‐gap material are theoretically studied using the plane‐wave expansion and a supercell. Two opposite boundary designs heavily affecting optical feedback at zone edge (Bragg reflection) are investigated. Limits to the validity range of simple bi‐mode coupling schemes in these periodic guides are emphasized and coupling coefficients presented in adequate cases. Mode symmetries are studied and related to dispersion and frequency‐width relationship. Finally, the smallest guide thickness allowing for a midgap mode is found to be much smaller than the analogous one‐dimensional case, raising prospects for enhanced light‐matter interaction.

172 citations

Journal ArticleDOI
TL;DR: In this paper, a tunable nanophotonic device concept based on flexible photonic crystal, which is comprised of a periodic array of high-index dielectric material and a low-index flexible polymer, is reported.
Abstract: We report a tunable nanophotonic device concept based on flexible photonic crystal, which is comprised of a periodic array of high-index dielectric material and a low-index flexible polymer. Tunability is achieved by applying mechanical force with nano-/microelectromechanical system actuators. The mechanical stress induces changes in the periodicity of the photonic crystal and consequently modifies the photonic band structure. To demonstrate the concept, we theoretically investigated the effect of mechanical stress on the anomalous refraction behavior and observed a very wide tunability in the beam propagation direction. This concept provides a means to achieve real-time, dynamic control of photonic band structure and will thus expand the utility of photonic crystal structures in advanced nanophotonic systems.

172 citations

Journal ArticleDOI
TL;DR: Numerical result shows that very high modal birefringence with a magnitude of the order of 10(-2) around 1550 nm has been obtained and large normal dispersion appears over a wide range of wavelengths in both orthogonal polarizations.
Abstract: We propose a novel polarization-maintaining index-guiding photonic crystal fiber (PCF). It is composed of a solid silica core and a cladding with squeezed-hexagonal-lattice elliptical air holes. Using a full-vector finite-element method, we study the modal birefringence of the fundamental modes in such PCFs. Numerical result shows that very high modal birefringence with a magnitude of the order of 10−2 around 1550 nm has been obtained. Furthermore, large normal dispersion appears over a wide range of wavelengths in both orthogonal polarizations.

172 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023748
20221,590
20211,207
20201,455
20191,643
20181,683