There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Modern electronics based on semiconductors is meeting the fundamental speed limit caused by the interconnect delay and large heat generation when the sizes of components reach nanometer scale. Photons as a carrier of the information are superior to electrons in bandwidth, density, speed, and dissipation. More over, photons could carry intensity, polarization, phase, and frequency information which could break through the limitation of binary system as in electronic devices. But due to the diffraction limitation, the photonic components and devices can not be fabricated small enough to be integrated densely. Surface plasmon polariton is quanta of collective oscillations of free electrons excited by photons in metal nanostrucrures, which offers a promising way to manipulate light at the nanoscale and to realize the miniaturization of photonic devices. Hence, plasmonic circuits and devices have been proposed for some time as a potential strategy for advancing semiconductor-based computing beyond the fundamental performance limitations of electronic devices, as epitomized by Moore's law. A variety of individual plasmonic nanodevices have been intensively studied recently, but the crucial and necessary step to enable nanophotonic circuits for future information technology, namely cascade logics integrated on-chip, has not been achieved. Here we demonstrate that a nanophotonic binary logic NOR gate can be realized by cascading plasmonic OR and NOT gates in four-terminal nanowire networks. We explain the operating principle for the device based on quantum dot luminescence imaging, which reveal the interferences for different logic functions between propagating plasmon wave packets in the nanowire network in great detail. Since the NOR gate is logic complete, i.e. any Boolean logic gate can be constructed from it, our results could have a key role in defining a viable path for the development of novel subwavelength optical processor architectures.

Cascaded Logic Gates in Nanophotonic Plasmon Networks

A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

Supercontinuum generation, photonic crystal fiber

As a key component in the wind turbine system, the power electronic converter and its power semiconductors suffer from complicated power loadings related to environment, and are proven to have high failure rates. Therefore, correct lifetime estimation of wind power converter is crucial for the reliability improvement and also for cost reduction of wind power technology. Unfortunately, the existing lifetime estimation methods for the power electronic converter are not yet suitable in the wind power application, because the comprehensive mission profiles are not well specified and included. Consequently, a relative more advanced approach is proposed in this paper, which is based on the loading and strength analysis of devices and takes into account different time constants of the thermal behaviors in power converter. With the established methods for loading and lifetime estimation for power devices, more detailed information of the lifetime-related performance in wind power converter can be obtained. Some experimental results are also included to validate the thermal behavior of power device under different mission profiles.

Thermal Loading and Lifetime Estimation for Power Device Considering Mission Profiles in Wind Power Converter

Chemi-resistive sensors based on hybrid functional materials are promising candidates for gas sensing with high responsivity, good selectivity, fast response/recovery, great stability/repeatability, room-working temperature, low cost, and easy-to-fabricate, for versatile applications. This progress report reviews the advantages and advances of these sensing structures compared with the single constituent, according to five main sensing forms: manipulating/constructing heterojunctions, catalytic reaction, charge transfer, charge carrier transport, molecular binding/sieving, and their combinations. Promises and challenges of the advances of each form are presented and discussed. Critical thinking and ideas regarding the orientation of the development of hybrid material-based gas sensor in the future are discussed.

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Gas Sensors Based on Chemi-Resistive Hybrid Functional Nanomaterials

Methane gas sensing properties of Pd-doped SnO2/reduced graphene oxide synthesized by a facile hydrothermal route

Design of a tunable graphene plasmonic-on-white graphene switch at infrared range

Surface plasmon resonance (SPR) is a spotlight technique for environmental monitoring. In this regard, an optical gas sensor based on SPR is investigated and analyzed here. The sensor is used for detection of toxic gases such as cyanogen, ethanol, propane, nitrogen dioxide, and phosgene. The performance of the sensor is inspected and optimized by considering different parameters such as the thickness of the metal layer, the material used for the prism, and the incident light angle and wavelength. The finite-difference time-domain method is used for simulation, and the optimization algorithm is particle swarm optimization. Simulation results show that the best metal thickness for gold, silver, aluminum, and copper is 44.39 nm, 43.16 nm, 18.195 nm, and 32.5 nm, respectively. Also, utilizing different materials such as SiO2, PMMA, BCB, MgF2, and cyclomer for the prism and the effect of temperature variation on these materials are studied, and it is shown that MgF2 demonstrates better performance. Furthermore, the results of the optimization indicate that the most suitable incident light angles (wavelengths) are 44.43° (900.59 nm), 45.5° (599.7 nm), 44.56° (300.1 nm), and 44.41° (899.4 nm) for gold, silver, aluminum, and copper, respectively. The sensor shows the best full-width at half-maximum and quality factor (Q) of 4.2 nm and 214.28, respectively, for the combination of MgF2 prism and a gold layer. The maximum sensitivity and figure of merit for gold layer are >120 (nm/RIU) and >20, and for copper layer are >270 (nm/RIU) and >30, respectively.

Particle swarm optimization and finite-difference time-domain (PSO/FDTD) algorithms for a surface plasmon resonance-based gas sensor

In this paper, we propose a narrowband DWDM filter structure, whose reflection band characteristics, meets the ITU-T standard. The proposed filter structure is based on Fibonacci quasi-periodic structures composed of multilayers with large index differences. Studying the effects of the optical and geometrical parameters of Fibonacci quasi-periodic structures on its filtering properties, we have realized that to achieve the ITU-T standard, we need to cascade two successive structures both with the same generation numbers j=4 and orders n=25 and apodized refractive indices. The apodization process helps to minimize the stop band sidelobes. We have also demonstrated that beside Fibonacci’s order, n, the layers dimensions, and their refractive index ratios are the main design parameters.

Narrowband DWDM filters based on Fibonacci-class quasi-periodic structures

In this paper, a metal-insulator-metal plasmonic biosensor based on two adjacent disk resonators and the unidirectional reflectionless propagation effect is proposed and investigated. The numerical results obtained from the finite difference time domain simulations are verified analytically by means of the coupled-mode theory. The resonant properties of the proposed structure including the full-width at half-maximum and quality factor are optimized by determining the suitable geometrical parameters. The presented biosensor is then utilized to detect some biomaterials such as ether, ethyleneglycol, chlorobenzene, and quinoline. It is shown that the proposed structure shows high sensitivity of ~1500nm/RIU, large figure of merit of 242.66RIU−1 and large quality factor of 242.8, compared to the previously reported optical biosensors. Moreover, the effect of the dielectric used in the waveguides is also inspected.

Abbas Zarifkar

Papers

Methane gas sensing properties of Pd-doped SnO2/reduced graphene oxide synthesized by a facile hydrothermal route

Design of a tunable graphene plasmonic-on-white graphene switch at infrared range

Particle swarm optimization and finite-difference time-domain (PSO/FDTD) algorithms for a surface plasmon resonance-based gas sensor

Narrowband DWDM filters based on Fibonacci-class quasi-periodic structures

A Plasmonic Nano-Biosensor Based on Two Consecutive Disk Resonators and Unidirectional Reflectionless Propagation Effect