1,721,050 research outputs found
A probabilistic model of the electron transport in films of nanocrystals arranged in a cubic lattice
No full textThe fabrication of nanocrystal (NC) films, starting from colloidal dispersion, is a very attractive topic in condensed matter physics community. NC films can be employed for transistors, light emitting diodes, lasers, and solar cells. For this reason the understanding of the film conductivity is of major importance. In this paper we describe a probabilistic model that allows the prediction of the conductivity of NC films, in this case of a cubic lattice of Lead Selenide or Cadmium Selenide NCs. The model is based on the hopping probability between NCs. The results are compared to experimental data reported in literature
Periodic transmission peaks in non-periodic disordered one-dimensional photonic structures
No full textBand gap splitting and average transmission lowering in ordered and disordered one-dimensional photonic structures composed by more than two materials with the same optical thickness
No full textThe optical properties of photonic structures made with more than two materials are very interesting for optical filtering and lighting applications. Herein, we compared the transmission properties of one-dimensional photonic crystals made with three, four and five materials, showing that, with a photonic crystal made of t different materials, the band gap splits in t-1 bands. The same optical thickness for the different materials layers results in split photonic band gaps with the same intensity. Photonic crystals with more than two materials are simple structures that could be used for multi-feature optical filters, or that could provide feedback for multi-peak distributed feedback lasers. Furthermore, we analysed the transmission properties of ternary and quaternary random photonic structures. These materials could very interesting for light trapping in photovoltaic devices. (C) 2014 Elsevier B.V. All rights reserved
Three material and four material one-dimensional phononic crystals
No full textIn this work, we studied one-dimensional phononic structures for selective acoustic filtering. The structures are composed of three and four materials which have different elastic properties. We have observed that the phononic band gaps split in two and three transmission valleys for the three-material and the four-material based phononic structures, respectively. Furthermore, the number of transmission peaks between the split gaps is directly related to the number of unit cells composing the phononic structures. The observations of this work can be useful for the fabrication of acoustic filters with the possibility to select the transmission of particular frequencies
Colloidal‐Doped Semiconductor Nanocrystals Embedded in One‐Dimensional Photonic Crystals for Ultrafast Photonics
No full textThe optical properties of strongly doped semiconductor nanocrystals depend strongly on the carrier density of the nanocrystals. These characteristics can be exploited for the design of innovative optical devices based on ultrafast switching potentially in the THz modulation bandwidth. In this study, the optical response of one-dimensional photonic crystals incorporating colloidal nanoparticles of a highly doped semiconductor such as indium tin oxide (ITO) is investigated, taking into consideration the angular dependence of the photonic band gap and the position dependence of the photonic band gap on the light-induced tunability of the ITO doping
Periodic transmission peak splitting in one dimensional disordered photonic structures
No full textIn the present paper we present ways to modulate the periodic transmission peaks arising in disordered one dimensional photonic structures with hundreds of layers. Disordered structures in which the optical length nd (n is the refractive index and d the layer thickness) is the same for each layer show regular peaks in their transmission spectra. A proper variation of the optical length of the layers leads to a splitting of the transmission peaks. Notably, the variation of the occurrence of high and low refractive index layers, gives a tool to tune also the width of the peaks. These results are of highest interest for optical application, such as light filtering, where the manifold of parameters allows a precise design of the spectral transmission ranges
Magneto-optical switching in microcavities based on a TGG defect sandwiched between periodic and disordered one-dimensional photonic structures
Full text linkThe employment of magneto-optical materials to fabricate photonic crystals gives the unique opportunity to achieve optical tuning by applying a magnetic field. In this study we have simulated the transmission spectrum of a microcavity in which the Bragg reflectors are made with silica (SiO2) and yttria (Y2O3) and the defect layer is made with TGG (Tb3Ga5O12). We show that the application of an external magnetic field results in a tunable splitting of the defect mode of the microcavity. In the simulations we have considered the wavelength dependence of the refractive indexes and the Verdet constants of the materials. A tuning of the defect mode of about 22Â nm with a magnetic field of 5Â T, at low temperature (8Â K), is demonstrated. Furthermore, we discuss the possibility to tune a microcavity with disordered photonic structures as reflectors. In the presence of the magnetic field such microcavity shows a shift of resonances in a broad range of wavelengths. This study presents a method of contactless optical tuning
Tunable light filtering by a Bragg mirror/heavily doped semiconducting nanocrystal composite
Full text link© 2015 Kriegel and Scotognella. Tunable light filters are critical components for many optical applications in which light in-coupling, out-coupling or rejection is crucial, such as lasing, sensing, photovoltaics and information and communication technology. For this purpose, Bragg mirrors (band-pass filters with high reflectivity) represent good candidates. However, their optical characteristics are determined during the fabrication stage. Heavily doped semiconductor nanocrystals (NCs), on the other hand, deliver a high degree of optical tunability through the active modulation of their carrier density, ultimately influencing their plasmonic absorption properties. Here, we propose the design of an actively tunable light filter composed of a Bragg mirror and a layer of plasmonic semiconductor NCs. We demonstrate that the filtering properties of the coupled device can be tuned to cover a wide range of frequencies from the visible to the near infrared (vis-NIR) spectral region when employing varying carrier densities. As the tunable component, we implemented a dispersion of copper selenide (Cu2-xSe) NCs and a film of indium tin oxide (ITO) NCs, which are known to show optical tunablility with chemical or electrochemical treatments. We utilized the Mie theory to describe the carrier-dependent plasmonic properties of the Cu2-x Se NC dispersion and the effective medium theory to describe the optical characteristics of the ITO film. The transmission properties of the Bragg mirror have been modelled with the transfer matrix method. We foresee ease of experimental realization of the coupled device, where filtering modulation is achieved upon chemical and electrochemical post-fabrication treatment of the heavily doped semiconductor NC component, eventually resulting in tunable transmission properties of the coupled device
Black phosphorus-based one-dimensional photonic crystals and microcavities
No full textThe latest achievements in the fabrication of thin layers of black phosphorus (BP), toward the technological breakthrough of a phosphorene atomically thin layer, are paving the way for their use in electronics, optics, and optoelectronics. In this work, we have simulated the optical properties of one-dimensional photonic structures, i.e., photonic crystals and microcavities, in which few-layer BP is one of the components. The insertion of the 5-nm black phosphorous layers leads to a photonic band gap in the photonic crystals and a cavity mode in the microcavity that is interesting for light manipulation and emission enhancement
One dimensional disordered photonic structures characterized by uniform distributions of clusters
No full text© 2014 Elsevier B.V. We investigated one dimensional disordered photonic structures by grouping high refractive index layers in clusters, randomly distributed within layers of low refractive index. We control the maximum size of the high refractive layer clusters and the ratio of the high–low refractive index layers, which we call the dilution of the system. By studying the total transmission of the disordered structure within the photonic band gap of the ordered structure as a function of the maximum cluster size, we observe a dip of the total transmission for a specific maximum cluster size. This value increases with increasing dilution. Moreover, within one dilution we observe oscillations of the total transmission with increasing cluster size
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