Silicon nanostencils with integrated support structures

We describe the fabrication of single crystal silicon membranes for stencil mask deposition. The membranes are created using standard microfabrication techniques combined with focussed ion beam milling to give structures with openings hundreds of micrometers to 50 nm in size. Deflection of the membrane structures under the deposition of highly stressed metals films is measured for vacuum deposited tantalum films, and used to estimate a film stress of 1.3 ± 0.1 GPa. In order to overcome these significant deflections, we have integrated simple stiffening structures into the membranes themselves which both preserve line of sight to the sample as well as provide a sufficiently large bending moment to resist vertical deflections which would otherwise cause noticeable feature broadening. Deposition of metallic nanowires on the surface shows good agreement with the calculated and measured deflections of the reinforced structures.     

Analysis of bandpass filtering behaviour of singlemodedepressed-core-index photonic-bandgap fibre

The propagation of light into a depressed-core-index photonic bandgap fibre is strongly dependent on the wavelength. The transmission spectrum is experimentally measured and successfully compared with theoretical predictions     

Spatial power combining for two-dimensional structures

The two-dimensional (2-D) hybrid dielectric slab-beam open and closed waveguide systems are suitable for the design of planar quasi-optical integrated circuits and devices. An open system consisting of an active E-plane amplifier array consisting of Vivaldi-type antennas with MESFET and monolithic microwave integrated circuit (MMIC) devices was investigated. The 4×1 MESFET amplifier array generated 11 and 4.5 dB of amplifier and system gain, respectively, at 7.12 GHz, and the cascade MMTC Vivaldi-type antenna produced 24 dB of amplifier gain at 8.4 GHz. Also, experiments on a new 2-D H-plane parallel-plate closed system with a stripline slot antenna is introduced, and the wavebeam-mode theory is presented. The new system minimizes scattering and isolation losses associated with open structures. The amplifier gain of the closed system based on slot antennas is compared to the open system based on Vivaldi antennas     

QoS support for integrated services over CATV

Cable TV has emerged as a promising access network infrastructure for the delivery of voice, video, and high-speed data traffic. A central issue in the design of protocols for CATV networks is to support different levels of QoS for diverse user applications. While CATV service providers and equipment have standardized, in the so-called MCNS protocol, the basic network architecture and interfaces, issues in the MAC layer for QoS support are likely to be left for differentiation in vendor products. This article first presents an overview of the basic CATV network architectural assumptions and the set of QoS requirements for supporting integrated services over CATV. It then discusses a MAC layer scheduling protocol that can efficiently multiplex constant bit rate traffic, such as voice over IP with guaranteed delay bound, and best-effort traffic, such as data services with minimum bit rate guarantee, while achieving fairness on any excess available bandwidth. The performance of this algorithm is illustrated by simulation results using Opnet. We also discuss a dynamic polling mechanism that enhances the link utilization while preserving delay bounds for latency-critical traffic     

Test structures for propagation delay measurements on high-speed integrated circuits

The accuracy of high-speed wafer-level measurements on digital IC's is limited by the probe interface. This limitation strongly encourages the use of built-in on-chip test hardware to reduce the number of critical off-chip high-speed interfaces. A novel synchronous propagation delay test structure is described which will provide accurate parametric data under typical automatic test conditions. Built-in test features added to complex combinational circuits are shown which are useful for delay measurement and which reduce the total number of high-speed I/O connections while still providing acceptable fault coverage in many cases.     

Cube probe structures for integrated near-field scanner module

Two new miniature near-field 'cube probe' structures for EMC/EMI measurements are proposed. Their performances are compared to those of the classical H-field loop probe in two orthogonal planes. The single cube probe effectively replaces three conventional orthogonally oriented loops. An array of cube probes is also proposed to form a near-field scan module dedicated to the characterisation of integrated circuit radiated emissions.     

A two-dimensional hot carrier injector for electron waveguide structures

The current-voltage characteristics for a constriction in a quantum waveguide channel are calculated. The constriction forms an effective barrier which can be employed as a tunneling injector. We find that such a structure may be useful in providing high-energy electrons in a single mode of the waveguide. We also examine the current in the far-from-linear response regime. Away from the linear region the current through the constriction saturates and the conductance falls to zero.     

A two-dimensional time-domain finite element formulation for periodic structures

A formulation is presented for a two-dimensional time-domain finite-element method (FEM-TD) that incorporates periodic boundaries. The specifics of the method are shown for scattering problems, but it should be straightforward to extend it to radiation problems. The method solves for a transformed field variable (instead of solving directly for the electric field) in order to easily enable periodic boundary conditions in the time domain. The accuracy and stability of the method is demonstrated by a series of examples where the new formulation is compared with reference solutions. Very accurate results are obtained when the excitation (frequency range) and the geometry are such that no higher order Floquet modes are present. The accuracy is degraded in the presence of higher order modes due to the rather simple absorbing boundary condition that is used with the present formulation. The method is found to be stable even for angles of incidence close to grazing.     

Improved microwave imaging procedure for nondestructive evaluations of two-dimensional structures

An improved microwave procedure for detecting defects in dielectric structures is proposed. The procedure is based on the integral equations of the inverse scattering problem. A hybrid genetic algorithm (GA) is applied in order to minimize the obtained nonlinear functional. Since in nondestructive evaluations the unperturbed object is completely known, it is possible off-line to numerically compute the Green's function for the configuration without defects. Consequently, a very significant computation saving is obtained, since the "chromosome" of the GA codes only the parameters describing the unknown defect.     

Optimization of diode structures for monolithic integrated microwave circuits

Device requirements of a medium power Ku-band reflective phase shifter are reviewed indicating a requirement for a diode with a 4-Terrahertz cut-off frequency. Various structures are examined to test their suitability for integration and feasibility for meeting specifications. A "pocket version" of a surface oriented device design is chosen and described. It is shown to meet or exceed all electrical requirements while providing for compatibility with final integration into the circuit.     

基于HLA的装备保障全要素集成模拟训练系统设计

为提高装备保障训练效果,从装备保障全要素集成训练需求出发,设计了装备保障全要素集成模拟训练系统功能层次结构,设立了三种训练模式,合理区分了训练层次。基于HLA设计了模拟训练系统的体系结构,并提出了系统软件设计总体方案。最后系统阐述了装备保障全要素模拟集成训练系统的工作流程。该模拟训练系统可为装备装备保障全要素集成训练提供训练平台支撑。     

New low-loss bend structures for high-density integrated opticalswitch arrays

A technique for lowering the loss around discrete bends in weakly guiding integrated optical circuits proposed, and modeling based on the beam-propagation method predicts a large improvement in the bend losses when it is applied. The idea of inserting an outrigger waveguide of high-refractive index appears to be novel, is relatively easily implemented practically, and shows considerable potential. The development of this idea is an excellent example of the use of numerical CAD (computer-aided design) tools in device design, since it is unlikely that it would have been discovered by experimentation alone. A CAD package for running the BPM (BEAMER) has been used to iterate towards low-loss bend geometries     

Deployment and support of complex integrated solutions

BT needs to bring new products and services faster into the market-place. Consequently, network and system components must be deployed more rapidly than ever. Successful integration and launch processes demand efficient, effective delivery and commissioning of new components followed by equally efficient day-to-day operational support. This paper discusses the support framework needed to satisfy these demands.     

Monolithically integrated two-dimensional arrays of surface-emitting photonic-crystal terahertz lasers

We demonstrate two-dimensional arrays of surface-emitting THz frequency photonic-crystal quantum cascade lasers covering a broad spectral range. The arrays are made of 16 unit elements, each of them spectrally single mode and featuring a narrow divergence emission pattern. The array emission frequencies cover a range of ≈0.2 THz around an emission frequency of ≈2.75 THz. Large size and small size devices have been developed. The former devices operate up to a maximum temperature of ≈90K with 2 to 3 mW output power in continuous wave regime.     

Transient analysis of multiple-input integrated digital structures

This paper presents an insight into the transient performance and propagation delay of complex integrated multiple-input structures in relation to a large digital system, taking into account the intrinsic parameters associated with device geometry. Modeling is therefore performed at the gate level. A piecewise linear model is used for the various transient intervals and the analysis employs fixed time steps. Experimental observations give ample evidence of good agreement between the theoretical and computed results, for which various values of input rise and fall times and different values of fan-out, β0, and fTare used. An accurate appraisal of the storage time associated with the gate is thus possible. Detailed solutions determine the main factors that offer scope for improvement for the structure studied, and suggest means of optimizing the transient response using the derived analytical expressions.     

Chalcogenide glasses as passive thin film structures for integrated optics

One approach to obtaining electro-optic or magneto-optic modulation in an integrated optic structure is to use a transparent film on an “active” (electro- or magneto-optic) optical substrate. Since the most useful active optical materials have relatively high refractive indices which preclude the use of oxide glasses as the transparent thin film, we have investigated the possibility of using higher index chalcogenide glasses in this configuration. Preliminary waveguiding studies were performed on a model system consisting of an As₂S₃ film on a LiNbO₃ substrate which demonstrated the feasibility of using chalcogenide glasses in this regard. The optical and mechanical properties of a suitable glass system, As-Ge-S, were then characterized. The characterization consisted of developing empirical formulas based on the type of bonding present in the glass which can be used to predict the relevant properties of a glass as a function of its composition. These formulas allow selection of optimum glass compositions to match a variety of electro-optic and magneto-optic substrates.     

Periodic slow-wave low-loss structures for monolithic GaAs microwave integrated circuits

Slow-wave structures on GaAs semi-insulating substrate, obtained by periodically loading a coplanar line with high-Q overlap capacitors, are described. They operate up to X-band, reducing significantly the signal phase velocity by a factor nearly independent of the frequency. Owing to their low transmission losses, they are particularly suitable for monolithic GaAs f.e.t. circuits.     

Block decomposition structures for the fast modular implementation of two-dimensional digital filters

A general structure is presented for the block realization of two-dimensional infinite impulse response digital filters, which is based on the two-dimensional matrix convolution equations and the decomposition of their associated transfer function matrices. The proposed decomposition may be considered as an extension of the scalar decomposition technique, which has already been used for the realization of two-dimensional digital filters associated with two-variable polynomials. The decomposition structure is considered in two different forms, which correspond to the direct forms I and II. It is shown that if a given two-dimensional single-input, single-output filter is realizable, then realizable block decomposition structures may be always selected. The proposed approach is general and applies without any restriction for the block implementation of any two-dimensional filter. The resulting structures are characterized by high inherent parallelism, modularity, regularity, reconfigurability, local interconnections, and very high sampling and throughput rates. Thus they are well suited for VLSI implementation and implementation via multiprocessor systems and array processors, such as systolic and wavefront arrays.     

Sensitivity analysis of a fiber ring resonator based on an air-core photonic-bandgap fiber

The fiber ring resonator (FRR) is the core sensing element in a resonator fiber optic gyroscope (R-FOG), and its sensitivity determines the performance of the R-FOG. This paper presents an in-depth analysis of the sensitivity of the FRR which is made of an air-core photonic-bandgap fiber (PBF), in which the characteristics of the FRR using PBF are compared with that of an FRR using a conventional single mode fiber. When using PBF instead of conventional fiber, it is found that the resonance curve is changed, and the sensitivity of the FRR is decreased a little when a narrow spectral linewidth laser is used. However, the degree of the decrease in sensitivity is not big enough to deny the advantages of PBF in improving the performance of the R-FOG considering that PBF is much better than conventional fiber in reducing the drift. Also, the optimal parameters of the directional coupler for sensitivity are discussed. It is found that the optimal intensity coupling coefficient when using PBF is nearly two times larger than that when using conventional fiber, and the optimal coupler intensity loss when using PBF is smaller than that when using conventional fiber.     

A two-dimensional integrated device/circuit numerical model for GaAs DCFL gate simulation

A two-dimensional integrated numerical device/circuit model for GaAs/MESFET DCFL gate simulation is presented. It is different from previous publications in that (a) transient carrier transport equations of the FETs are calculated with consideration for the interaction between interconnected FETs in a circuit, (b) the numerical calculations are carried out for the coupled equations to provide accuracy and (c) with the new algorithm used, the numerical calculation can be carried out with high efficiency. A “dynamic method” and a “single gate method” have been developed to simulate the steady state transfer and ring oscillator transient characteristics, respectively, which have proved to be much more efficient than the previously used methods. Based on the model, a gate level two-dimensional numerical simulator, LADES2G, has been developed and successfully applied to GaAs DCFL circuit design.