Logic gate for optical input using monostable-bistable transitionof serially connected resonant tunnelling transistors

The authors demonstrate a novel optical logic gate consisting of two resonant tunnelling transistors connected in series. The logic gate is characterised by an optically controlled bistability of the gate and a small optical input power of 10 μW realised by using the monostable-bistable transition of the gate     

Polarization-controlled single-mode VCSEL

Relative intensity noise (RIN) in a vertical-cavity surface-emitting laser (VCSEL) was greatly reduced through the use of polarization control to eliminate competition between two orthogonal polarization states by ensuring there was only one polarization state. Polarization was stable with optical feedback of up to 10%. Polarization control was achieved by inducing a small loss anisotropy in fundamental transversal mode VCSEL's. Anisotropic post structures, such as a rectangular post, an oblique post, or a zigzag-sidewall post, were found to be effective in creating loss anisotropy without serious degradation of other VCSEL characteristics such as light-output power or beam profile     

High performance of silicided silicon-sidewall source and drain (S4D) structure

A silicided silicon-sidewall source and drain (S⁴D) structure is proposed for sub-0.1-μm devices. The merit of the S⁴D structure is that the series resistance of the source and drain is significantly reduced since the silicide layer is attached very close to the gate electrode and the silicon sidewall can be doped very highly. Thus, very high drain current drive can be expected, Another advantage of this structure is that the source and drain extensions are produced by the solid-phase diffusion of boron from the highly doped silicon-sidewall. Thus, shallow extensions with very high doping can be realized. A 75-nm gate length pMOSFET fabricated with this structure is shown to exhibit excellent electrical characteristics     

Residential photovoltaic energy storage system

This paper introduces a residential photovoltaic (PV) energy storage system, in which the PV power is controlled by a DC-DC power converter and transferred to a small battery energy storage system (BESS). For managing the power, a pattern of daily operation considering the load characteristic of the homeowner, the generation characteristic of the PV power, and the power-leveling demand of the electric utility is prescribed. The system looks up the pattern to select the operation mode, so that powers from the PV array, the batteries and the utility are utilized in a cost-effective manner. As for the control of the system, a novel control technique for the maximum power-point tracking (MPPT) of the PV array is proposed, in which the state-averaged model of the DC-DC power converter, including the dynamic model of the PV array, is derived. Accordingly, a high-performance discrete MPPT controller that tracks the maximum power point with zero-slope regulation and current-mode control is presented. With proposed arrangements on the control of the BESS and the current-to-power scaling factor setting, the DC-DC power converter is capable of combining with the BESS for performing the functions of power conditioning and active power filtering. An experimental 600 W system is implemented, and some simulation and experimental results are provided to demonstrate the effectiveness of the proposed system     

Reliability of rare-earth-doped fluoride fibers for optical fiberamplifier application

We have clarified the strength and estimated lifetime of fluoride fibers for optical amplifier use. We fabricated a UV-curable epoxy-acrylate coated fluoride fiber with a strength of 542 MPa. We estimated the lifetime of the fluoride fiber to be longer than 25 years at 80°C and 50% RH     

Optimized offset to eliminate first-order mode excitation at thejunction of straight and curved multimode waveguides

Applications to equip semiconductor phased-array wavelength demultiplexers with nonbirefringent waveguides are increasing. In several applications, the waveguides are multimodal and elimination of first-order mode excitation is required for their design. The optimized offset for eliminating the first-order mode excitation at the junction of straight and curved waveguides with a two-dimensional (2-D) structure is analyzed theoretically. We assume that the waveguide has a laterally symmetric index profile. By the perturbation method, the offset is obtained to the first order in the inverse of the bending radius. The offset is simply expressed by the effective refractive indices of the straight waveguide     

Very compact double C-patch antenna

A miniaturised C-patch antenna excited by means of a coaxial probe is described. The antenna consists of two stacked C-shaped elements connected together with a vertical conducting plane. The antenna is designed on an air substrate and offers attractive dimensions, being five times lower than those of a conventional half wavelength microstrip patch antenna operating at the same frequency. A 10 dB bandwidth of 3% is obtained. The voltage standing wave ratio, radiation patterns, and electric surface current density are presented     

Throughput improvement scheme in multi-code CDMA

In multi-code CDMA, there is no self-interference among the sub-codes of a single user. By taking advantage of this property, the authors propose a new scheduling scheme to improve throughput, and derive the system throughputs of two cases with the proposed scheme applied and not applied. Analysis results show that the proposed scheme considerably improves the system throughput     

20 Gbit/s soliton transmission using alternating dispersionarrangement in standard fibre systems

An alternating dispersion arrangement is proposed for soliton systems with dispersion compensation to improve soliton stabilisation. A transmission experiment at 20 Gbit/s over 2600 km long singlemode fibre was successfully demonstrated by employing this novel dispersion arrangement     

Direct observation of local strain field for ULSI devices

The in-depth profile of strain distribution from the silicon surface is one of the most important pieces of information for optimizing the device performance. The convergent-beam electron diffraction(CBED) method has been applied to analyze the local strain filed of the active regions for both test structure with the shallow trench isolation(STI) and the conventional LOCOS on a cross-sectional surface. As a result, strain distribution was observed successfully. It was found that the compressive stress exist all over the survey regions. The active region close to the bottom corner of the STI shows a larger stress than that of the conventional LOCOS. It is demonstrated that the CBED technique is very effective for the determination oflocal strain field in a small area of semiconductors and the optimizing of the STI structure andfabrication process.