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Zhang B.,Beijing University of Posts and Telecommunications | Li S.,Beijing University of Posts and Telecommunications | Huang J.,Beijing University of Posts and Telecommunications | Huang J.,Key Laboratory of Information Photonics and Optical Communications
Electronics Letters | Year: 2015

A compact and high selective lowpass filter (LPF) with wide stopband is presented using coupled rhombic stubs. The proposed LPF unit is constructed by loading a rhombic stub on a transmission line. Then, a folded three-element LPF is proposed to achieve compact size and high selectivity by introducing coupling between adjacent rhombic stubs. The operating mechanism of the filter is investigated and explained, by adopting the physically-based LC-equivalent circuit model. The implemented final LPF exhibits a wide stopband of up to 11.5 fc with a rejection level of better than 35 dB. Furthermore, the final LPF features a compact size of 0.12λg × 0.10λg, where λg is the guide wavelength of fc, and a very high figure-of-merit (FOM) of 27 142. © The Institution of Engineering and Technology 2015.


Chen Z.-H.,KTH Royal Institute of Technology | Chen Z.-H.,Key Laboratory of Information Photonics and Optical Communications | Hellstrom S.,KTH Royal Institute of Technology | Ning Z.-J.,KTH Royal Institute of Technology | And 2 more authors.
Journal of Physical Chemistry C | Year: 2011

We study the exciton polariton contribution to the Stokes shift in colloidal quantum dots (QDs). By detailed quantum mechanical description of light?matter interaction and temporal analysis of incident electromagnetic field across the QD using the finite-difference time-domain method, we have shown that the optical excitation of an exciton in the QD and its coupling with the excitation radiation (i.e., exciton polariton) induce strong variations in the dielectric constant of the QD which contribute significantly to the Stokes shift and cause modifications in the absorption spectrum that agrees well with experiments. © 2011 American Chemical Society.


Hussain A.,Key Laboratory of Information Photonics and Optical Communications | Sang X.,Wah Engineering College
Applied Mechanics and Materials | Year: 2012

In this paper the wavelength conversion in a 1cm long silicon-on-insulator (SOI) waveguide has been investigated numerically. The wavelength conversion efficiency is optimized by analyzing free carriers absorption (FCA) loss generated by two-photon-absorption (TPA). The free carriers life time is focused while other factors influencing noise figure are also considered. © (2012) Trans Tech Publications, Switzerland.


Ahmed J.,HITEC University | Hussain A.,HITEC University | Adeel F.,HITEC University | Siyal M.Y.,Nanyang Technological University | Yu C.,Key Laboratory of Information Photonics and Optical Communications
Optik | Year: 2013

Silicon-on-insulator (SOI) waveguide devices are emerging for the realization of optical signal processing systems for the last couple of years. The recent technological advancement in silicon photonics is the main driving force at the back of these devices. Using non-linear optical phenomenon in silicon wires and their compatibility with CMOS devices provide the stage for integrated photonic devices. All-optical signal processing devices are being investigated at present, but the chip-scale solution provided by the silicon photonics is the most promising. In this research we have investigated all-optical signal processing in a 10 mm long SOI waveguide by exploiting well established coupled wave equations. We consider single pulsed pump to analyze frequency shifting by four-wave-mixing (FWM). For the wavelengths 20-30 nm far from the pump, the gain overcomes nonlinear losses resulting in higher frequency conversion efficiency. © 2012 Elsevier GmbH.


Cao H.,Key Laboratory of Information Photonics and Optical Communications | Lu P.,Key Laboratory of Information Photonics and Optical Communications | Yu Z.,Key Laboratory of Information Photonics and Optical Communications | Chen J.,CAS Beijing Institute of Applied Physics And Computational Mathematics | And 2 more authors.
Superlattices and Microstructures | Year: 2014

First-principles calculations have been performed to investigate the electronic and magnetic properties of V-doped AlN nanosheet under in-plane biaxial strains. It is found that V atom favors to substitute for Al site with the lowest formation energy. The magnetic coupling of three different configurations are studied and configuration I is demonstrated to possess room temperature ferromagnetism. The stable ferromagnetic coupling is mediated by double exchange mechanism. In addition, the in-plane biaxial strains corresponding to tensile and compressive strains can affect and manipulate the magnetic interaction of V-doped AlN nanosheet in different ways. These results are conductive to design AlN based two dimensional diluted magnetic semiconductors. © 2014 Elsevier Ltd. All rights reserved.

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