Radio over free space optical link using a directly modulated two-electrode high power tapered laser

The analog modulation performance of a high-power two-electrode tapered laser is investigated. A 25dB dynamic range for 2.4GHz 802.11g signals is achieved with a 26dB loss budget, showing a >1km free space range is possible. © 2010 Optical Society of America.

Gigabit/s modulation of twin-electrode high-brightness tapered laser with high modulation efficiency

Simultaneous high modulation speed and high modulation efficiency operation of a two-electrode tapered laser is reported. 1Gb/s direct data modulation is achieved with 68mA applied current swing for a 0.95W output optical modulation amplitude. © 2009 Optical Society of America.

An analysis of electrode patterns in capacitive touch screen panels

In the design of capacitive touch-screen panels, electrodes are patterned to improve touch sensitivity. In this paper, we analyze the relationship between electrode patterns and touch sensitivity. An approach is presented where simulations are used to measure the sensitivity of touch-screen panels based on capacitance changes for various electrode patterns. Touch sensitivity increases when the touch object is positioned in close proximity to fringing electric fields generated by the patterned electrodes. Three new electrode patterns are proposed to maximize field fringing in order to increase touch sensitivity by purely electrode patterning means. Simulations showed an increased touch sensitivity of up to 5.4%, as compared with the more conventional interlocking diamonds pattern. Here, we also report empirical findings for fabricated touch-screen panels. © 2005-2012 IEEE.

Growth mechanism of graphene on platinum: Surface catalysis and carbon segregation

A model of the graphene growth mechanism of chemical vapor deposition on platinum is proposed and verified by experiments. Surface catalysis and carbon segregation occur, respectively, at high and low temperatures in the process, representing the so-called balance and segregation regimes. Catalysis leads to self-limiting formation of large area monolayer graphene, whereas segregation results in multilayers, which evidently "grow from below." By controlling kinetic factors, dominantly monolayer graphene whose high quality has been confirmed by quantum Hall measurement can be deposited on platinum with hydrogen-rich environment, quench cooling, tiny but continuous methane flow and about 1000°C growth temperature. © 2014 AIP Publishing LLC.

Patterns and levels of PCDD/F in a Chinese graphite electrode sludge

The graphite electrode sludge was sampled from a huge chloralkali plant in central China. The total level of PCDD/F was found as high as 378.85 mu g/kg sludge (dry weight). The patterns of PCDD/F in each homologue indicated the predominance of tetra- to octa-chlorinated PCDFs, Furthermore, the toxic 2,3,7,8-substituted PCDFs constituted over 80% of the total PCDFs in the sludge and the corresponding PCDDs were only at 15 mu g/kg level. The calculated value of the international toxic equivalence (I-TEQ) in sludge was 21.65 mu g/kg sludge (dry weight). This typical "dioxin chloralkali pattern" was apparently identified in the sediments near the effluent outlet of the chloralkali plant.

Electrolyte electroreflectance spectroscopy studies on the interfacial behavior of the near-surface In0.15Ga0.85As/GaAs quantum well electrode vertical bar non-aqueous electrolyte

Electrolyte electroreflectance spectra of the near-surface strained-layer In0.15Ga0.85As/GaAs double single-quantum-well electrode have been studied at different biases in non-aqueous solutions of ferrocene and acetylferrocene. The optical transitions, the Franz-Keldysh oscillations (FKOs) and the quantum confined Stark effects (QCSE) of In0.15Ga0.85As/GaAs quantum well electrodes are analyzed. Electric field strengths at the In0.15Ga0.85As/GaAs interface are calculated in both solutions by a fast Fourier transform analysis of FKOs. A dip is exhibited in the electric field strength versus bias (from 0 to 1.2 V) curve in ferrocene solution. A model concerning the interfacial tunneling transfer of electrons is used to explain the behavior of the electric field. (C) 2001 Elsevier Science B.V. All rights reserved.

Photoelectrochemical behavior of a novel composite In0.15Ga0.85As/GaAs vertical bar GaAs/Al0.3Ga0.7As multiple quantum well electrode

A novel composite InxGa1-xAs/GaAs/GaAs/AlxGa1-xAs multiple quantum well material with different well widths was studied as a new kind of photoelectrode in a photoelectrochemical cell. The photocurrent spectrum and photocurrent-electrode potential curve were measured in ferrocene nonaqueous solution. Pronounced quantization effects and strong exciton absorption were observed in the photocurrent spectrum. The effects of surface states and interfacial states on the photocurrent-electrode potential curve are discussed. (C) 2000 Elsevier Science S.A. All rights reserved.

Interfacial behaviour of a quantum well electrode/electrolyte: EER spectra of an SQW GaAs/AlxGa1-xAs electrode in HQ+BQ non-aqueous electrolyte

The quantum-confined Stark effect and the Franz-Keldysh oscillation of a single quantum well (SQW) GaAs/AlxGa1-xAs electrode were studied in non-aqueous hydroquinone + benzoquinone solution with electrolyte electroreflectance spectroscopy. By investigation of the relation of the quantum-confined Stark effect and the Franz-Keldysh oscillation with applied external bias, the interfacial behaviour of an SQW electrode was analysed. (C) 1997 Elsevier Science S.A.

Low potential detection of glutamate based on the electrocatalytic oxidation of NADH at thionine/single-walled carbon nanotubes composite modified electrode

A glutamate biosensor based on the electrocatalytic oxidation of reduced nicotinamide adenine dinucleotide (NADH), which was generated by the enzymatic reaction, was developed via employing a single-walled carbon nanotubes/thionine (Th-SWNTs) nanocomposite as a mediator and an enzyme immobilization matrix. The biosensor, which was fabricated by immobilizing glutamate dehydrogenase (GIDH) on the surface of Th-SWNTs, exhibited a rapid response (ca. 5 s), a low detection limit (0.1 mu M), a wide and useful linear range (0.5-400 mu M), high sensitivity (137.3 +/- 15.7) mu A mM(-1) cm(-2), higher biological affinity, as well as good stability and repeatability. In addition, the common interfering species, such as ascorbic acid, uric acid, and 4-acetamidophenol, did not cause any interference due to the use of a low operating potential (190 mV vs. NHE). The biosensor can be used to quantify the concentration of glutamate in the physiological level. The Th-SWNTs system represents a simple and effective approach to the integration of dehydrogenase and electrodes, which can provide analytical access to a large group of enzymes for wide range of bioelectrochemical applications including biosensors and biofuel cells.

PHOTOELECTROCHEMICAL BEHAVIOR OF THE GAAS/ALXGA1-XAS SUPERLATTICE ELECTRODE/ELECTROLYTE INTERFACE

Single and multiple quantum wells of lattice-matched superlattices material GaAs/AlxGa1-xAs have been studied as photoelectrodes in photoelectrochemical cells containing nonaqueous electrolyte. Structural photocurrent spectra in the potential range of -1.8 to 1.0 V (vs standard calomel electrode) were obtained. The quantum yields for both superlattice electrodes were estimated and compared.

Interfacial behaviour of quantum well electrode/electrolyte: effect of redox species on EER spectra of a single quantum well GaAs vertical bar AlxGa1-xAs electrode

The EER spectra of a single quantum well GaAs\AlxGa1-xAs electrode were studied as a function of applied reverse bias in ferrocene, p-methyl nitrobenzene and hydroquinone+benzoquinone non-aqueous solutions. EER spectra were compared for different redox species and showed that a pronounced quantum-confined Stark effect and a Franz-Keldysh oscillation for a single quantum well electrode were obtained in the p-methyl-nitrobenzene- and hydroquinone+benzoquinone-containing solutions. A surface interaction of the single quantum well electrode with ferrocene led to fewer changes in the electric field of the space charge layer for reverse bias; this was suggested to explain the weak quantum-confined Stark effect and Franz-Keldysh oscillation effect observed for the single quantum well electrode in the ferrocene-containing solution. (C) 1997 Elsevier Science S.A.

EER studies of the single quantum well GaAs/AlxGa1-xAs electrode/nonaqueous solution interface

The interfacial behavior of the single quantum well (SQW) GaAs/AlxGa1-xAs electrode in HQ/BQ and Fc/Fc(+) electrolytes was characterized respectively by studying the quantum confined Stark effect and Franz-Keldysh oscillation with electrolyte electroreflectance spectroscopy. The interaction of the surface state of the SQW electrode with redox species and its effects on the distribution of external bias at the interface of the SQW electrode are discussed.

Transient photocurrent investigation of photo-processes of lattice-matched MQW GaAs/AlxGa1-xAs electrode

Transient photocurrents induced by short light pulses at lattice-matched GaAs/AlxGa1-xAs multiple quantum well (MQW) electrodes were studied as a function of electrode potential. Dual exponential photocurrent decay transients were observed at various potentials. By analysis of the dual exponential decay transients, information on steady state photocurrents (I-s), surface collection of photoexcited minority carriers (G(0)) and lifetimes of surface states (T-s) was obtained. The kinetic behaviors of photoprocesses at illuminated MQW/electrolyte interface were discussed.

Lithography-independent and large scale fabrication of a metal electrode nanogap

A lithography-independent and wafer scale method to fabricate a metal nanogap structure is demon-strated. Polysilicon was first dry etched using photoresist (PR) as the etch mask patterned by photolithography.Then, by depositing conformal SiO_2 on the polysilicon pattern, etching back SiO_2 anisotropically in the perpendic-ular direction and removing the polysilicon with KOH, a sacrificial SiO_2 spacer was obtained. Finally, after metal evaporation and lifting-off of the SiO_2 spacer, an 82 nm metal-gap structure was achieved. The size of the nanogap is not determined by the photolithography, but by the thickness of the SiO_2. The method reported in this paper is compatible with modern semiconductor technology and can be used in mass production.