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We consider the design of individual and periodic arrangements of metal or semiconductor nanoparticles for localized electromagnetic field enhancement utilizing a topology optimization based numerical framework as the design tool. We aim at maximizing a function of the electromagnetic field amplitude in a region of space through the introduction of nanoparticles in and/or near the region.
We present an approach to analyse near-field effects on nanostructured gold films by finite element simulations. The studied samples are formed by fabricating gold films near the percolation threshold and then applying laser damage. Resulting samples have complicated structures, which then was captured using scanning transmission electron microscopy (STEM) and the obtained dark field images are used...
The exciton oscillator strength (OS) in type-II quantum dot (QD) nanowires is calculated by using a fast and efficient method. We propose a new structure in Double-Well QD (DWQD) nanowire that considerably increases OS of type-II QDs which is a key parameter in optical quantum gating in the stimulated Raman adiabatic passage (STIRAP) process [1] for implementing quantum gates.
Despite of its many wonderful properties, pristine graphene has one major drawback: it does not have a band gap, which complicates its applications in electronic devices. Many routes have been suggested to overcome this difficulty, such as cutting graphene into nanoribbons, using chemical methods, or making regular nanoperforations, also known antidot lattices. Theoretically, all these ideas lead...
Presently, we investigate the influence of the extent of a ring of exceptional points on the Q-factor of three-dimensional photonic crystal slabs. By changing the thickness of the slab, the extent of the ring of exceptional points is varied, allowing us to recover the Dirac cones in open, non-Hermitian systems. In this case, three bound states in the continuum are exhibited close to the Γ-point. For...
In this work it is showed that compressively strained Ge1−xSnx/Ge quantum wells (QWs) grown on a Ge virtual substrate are very promising TE mode gain medium. Moreover we show how emission wavelength and polarization can be controlled in Ge1−wSnw/SiyGe1−x−ySnx QWs. Demonstration of capabilities of presented QW systems bases on analysis of transverse electric (TE) and transverse magnetic (TM) modes...
In this work we compare numerical simulations of silicon nitride waveguide Bragg gratings based on a 2D+z coupled wave theory implementation against fabricated and measured structures. The coupled wave theory presented here includes additional coupling terms to account for radiative losses inherent to higher order gratings. In conclusion, the presented theory reflects the measured spectra and is therefore...
A TCAD based analysis is presented on the transmission efficiency η of silicon-on-insulator (SOI) and silicon nitride slab waveguides in a high-voltage standard SOI-CMOS technology, for the spectral range of 480 nm–1300 nm, and isotropic optical excitation via monolithic Si-based LEDs. The effects of geometry, wavelength and galvanic isolation on η are reported.
We propose a low loss graded-index optical splitter based on multimode interference effects (MMI). Even without further improvements of the manufacturing diffusion process, the derived excess and insertion loss suggest a theoretical feasibility for MMI-elements with a graded-index profile.
In this work we present how 3-dimensional ferroelectric domains observed in MAPbIs affect the performance of perovskite solar cells. We simulated a 3D system with dimensions of 500 nm × 500 nm × 300 nm, considering domains with 100 nm side length which have been assigned random orientations of the polarization field. Calculations are performed with the simulator TiberCAD using a 3D drift-diffusion...
We demonstrate one-dimensional (1D) electrical modeling of InP nanowire array solar cells. This 1D modeling gives accurate description of the current voltage response even at high surface recombination velocity. The 1D electrical model decreases the simulation time by 3 orders of magnitude compared to a full three-dimensional (3D) model.
Design of nanogratings with graded heights is proposed for solar-cell applications. The designed structure gives rise to absorption enhancement in solar-cells by reducing the reflection losses and focusing the incoming radiation into the photoactive layer. The results show that solar-cell efficiency is increased by 15% with graded height nanogratings.
The effect of silicon quantum wires (SiQWs) diameter of heterojunction solar cells based on SiQWs with rectangular cross sections and graphene (SiQWs/G) is investigated using a coupled optical and electrical model. It is found that SiQWs/G with small cross section area (d2=4 nm2) shows high efficiency. because, the band gap of SiQWs obtained from the distance of energy state of wave function of the...
Hole transport material (HTM) free and WOx based perovskite solar cells are theoretically investigated by using driftdiffusion and small signal models. The influence of interface states and leakage current is studied, and the current-voltage (J-V) and capacitance-voltage (C-V) characteristics are reproduced in reasonable agreement with experimental data, including build in potential (Vbi) variation,...
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