Computational electromagnetic analysis of partially-filled rectangular waveguide at X-band frequencies

In this paper, the full-wave analysis of the direct scattering problem in the rectangular waveguide is derived. The numerical calculation results of the scattering characteristics are presented. To show the advantage of our proposed model, we compared direct problem results with three-dimensional simulation software Ansys HFSS calculations. An excellent agreement is observed when compared these two approaches

Electromagnetic Compatibility Analysis of DVB-T and LTE Systems

In 2012 the Communications Regulatory Authority of Lithuania reallocated 790–862 MHz band used by terrestrial TV operators for mobile communications purposes following an International Telecommunication Union decision. The aim of this paper is to experimentally investigate electromagnetic compatibility of Digital Video Broadcasting - Terrestrial receivers operating below 790 MHz band with LTE base stations operating in 800 MHz band and derive an analytical model suitable for further electromagnetic compatibility analysis. An experimental testbed using LTE hardware and DVB-T receivers was used for evaluation of adjacent channel LTE downlink signal interference impact on digital TV system. Also, effect of using third party hardware such as band-pass filters and wideband preamplifiers on interference was analyzed. The results obtained provide protection ratio and overloading threshold for the digital TV receivers in different operating scenarios which serve as a reference guide for regulatory authority, mobile operators and terrestrial TV providers

Spin dynamics in semiconductors

This article reviews the current status of spin dynamics in semiconductors which has achieved a lot of progress in the past years due to the fast growing field of semiconductor spintronics. The primary focus is the theoretical and experimental developments of spin relaxation and dephasing in both spin precession in time domain and spin diffusion and transport in spacial domain. A fully microscopic many-body investigation on spin dynamics based on the kinetic spin Bloch equation approach is reviewed comprehensively.Comment: a review article with 193 pages and 1103 references. To be published in Physics Reports

Ultrafast single photon emitting quantum photonic structures based on a nano-obelisk

A key issue in a single photon source is fast and efficient generation of a single photon flux with high light extraction efficiency. Significant progress toward high-efficiency single photon sources has been demonstrated by semiconductor quantum dots, especially using narrow bandgap materials. Meanwhile, there are many obstacles, which restrict the use of wide bandgap semiconductor quantum dots as practical single photon sources in ultraviolet-visible region, despite offering free space communication and miniaturized quantum information circuits. Here we demonstrate a single InGaN quantum dot embedded in an obelisk-shaped GaN nanostructure. The nano-obelisk plays an important role in eliminating dislocations, increasing light extraction, and minimizing a built-in electric field. Based on the nano-obelisks, we observed nonconventional narrow quantum dot emission and positive biexciton binding energy, which are signatures of negligible built-in field in single InGaN quantum dots. This results in efficient and ultrafast single photon generation in the violet color region

Optical investigation of non-equilibrium carrier dynamics in differently doped VGF-grown ZnTe single crystals

We applied a time-resolved FWM technique to study the dynamics of photoexcited carriers in differently doped VGF-grown ZnTe crystals at room temperature. We observed a fast carrier trapping to deep levels in phosphorus doped and undoped samples. The measurements at below and above band-gap excitations revealed the much higher concentration of these levels near the surface than in the bulk in both samples. The concentration of deep traps has been estimated for phosphorus doped sample N=(1-2)e15 cm–3 in the bulk and N=(3-5)e18 cm–3 near the surface. In the undoped sample these traps are present at much higher concentration. The electron and hole mobilities µn=(500±28) cm2/Vs and µh=(16±6) cm2/Vs were estimated from the measured diffusion coefficient values D=(12.5±0.7) cm2/s in the p-type sample and D=(0.8±0.3) cm2/s in the semi-insulating one