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Summary In this paper, we propose a Load‐Balancing and Coding‐Aware Multicast (LCM) protocol for mobile ad hoc networks. In LCM protocol, a new route metric named Expected Transmission Time with Coding and Load Balancing (ETTCL) is presented at first, aiming at effectively selecting the path not only that has the possible coding opportunity but also where overflow due to network overload can be prevented. Then, we describe the route discovery phase by constructing the node‐disjoint multicast tree on the basis of ETTCL and employ network coding to encode the data flows for route maintenance. The effectiveness of LCM protocol is simulated and analyzed by NS‐2, which shows that this protocol has good performance in reducing average end‐to‐end delay and control overhead and can improve packet delivery ratio compared with the existing protocol. Copyright © 2015 John Wiley & Sons, Ltd.

Abstract:We report the generation of a 12.6W average power, 50MHz repetition rate pulse train, compressible to high fidelity 170fs pulses, from an ultrafast ytterbium-doped fiber laser system via adaptive amplitude and phase pre-shaping. IntroductionYtterbium-doped fibre laser systems, coupled with the chirped-pulse amplification (CPA) technique, have allowed the realization of compact ultrafast laser systems producing high average power at various repetition rates [1]. Power scaling in fibre CPA systems is non-trivial, because a number of factors can degrade the pulse fidelity at the output, such as uncompensated material dispersion, nonlinearity, and a non-uniform spectral gain profile with finite width. Due to the optical confinement and long interaction length of the fiber geometry, nonlinear effects, most notably self-phase modulation (SPM), are a critical consideration in constructing fiber CPA laser systems. However, conventional approaches in mitigating SPM have limitations; temporal stretching is physically limited by the finite size of the grating compressor, while the scaling of large-mode-area (LMA) fibers will eventually undermine the advantages of fiber geometry. Hence, novel approaches in mitigating SPM are necessary for further power scaling in fiber CPA laser systems while maintaining pulse fidelity.Adaptive pulse shaping allows for the generation of high-fidelity pulses by controlling the spectral phase profile [2]. However, due to damage limitations, pulse shaping often needs to be implemented prior to high power amplification in CPA systems [3]. In fiber CPA systems, amplitude-only shaping has recently been demonstrated to control the nonlinear-phase modulation induced by SPM at low energy [4], but it cannot compensate for higherorder spectral phase due to the material dispersion. Our group recently demonstrated a phase-only shaping to produce high-quality pulses in a high-energy fiber laser system [5].In this paper, we report our latest experimental result in generating high-fidelity femtosecond pulses in a fiber CPA system by adaptive amplitude and phase pre-shaping [6]. A pulse shaper based on a dual-layer liquid crystal spatial light modulator (LC-SLM) was implemented in the fiber CPA system for amplitude and phase shaping prior to amplification. The LC-SLM was controlled using a differential evolution (DE) algorithm, to maximize a two-photon absorption (TPA) detector signal produced by the compressed fiber CPA output pulses. We show that our approach compensates for both accumulated phase from higher-order material dispersion and nonlinear phase modulation. A train of pulses with an average power of 12.6 W at a 50 MHz repetition rate was produced from the fiber CPA system, compressible to high fidelity pulses with a full-width at half-maximum (FWHM) duration of 170 fs.

We report a high-performance active image sensor pixel design by utilizing amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) with a circular structure. The TFT, configured with the inner electrode as source and outer electrode as drain, typically exhibits good saturation electrical characteristics, where the device has a constant drive current despite variations in drain voltage. Due to the very high output resistance exhibited by this asymmetric TFT structure with a circular shape, the pixel circuit considered here in common-drain configuration provides a higher gain of operation than a pixel circuit implemented with rectangular a-IGZO TFTs. They can be used as driving TFTs in active image sensor circuits. They are, therefore, good candidates for digital X-ray detectors in applications such as medical diagnostic procedures.