One- and Two-Dimensional Coherently Coupled Implant-Defined Vertical-Cavity Laser Arrays

Loss between elements of coherently coupled vertical-cavity surface-emitting laser (VCSEL) arrays typically causes out-of-phase operation with on-axis intensity nulls in the far-field. We show that in-phase evanescently coupled VCSEL arrays may be defined by proton implantation. An advantage for implanted in-phase coherently coupled VCSEL arrays is that this approach employs a simple and reliable fabrication process where the absence of loss between elements leads to in-phase coupling. We present data for 2, 3, and 4 element in-phase implant-defined coherently coupled VCSEL arrays.     

从二维到三维虚拟演播系统的实践运用

本文通过对TRINITY及MAGICSET两套虚拟演播系统基本特性的分析及使用心得介绍，阐明虚拟演播系统从二维到三维的技术发展及对电视制作实践运用的意义。     

Recent Progresses and Future Prospects of Two- and Three-Dimensional Photonic Crystals

Photonic crystals, in which the refractive index changes periodically, provide an exciting new tool for the manipulation of photons and have received keen interest from a variety of fields. This paper reviews the recent progress and future prospects of photonic crystals and their applications to photonic-nanostructure devices     

Three-Dimensional Electromagnetic and Electrical Simulation of HgCdTe Pixel Arrays

We have investigated the combined electromagnetic and electrical response of HgCdTe-based pixel detector arrays with different geometries. We have computed the propagation of the optical signal in the detector structure by solving Maxwell’s curl equations using a finite-difference time-domain approach. From the field distribution inside the device, we have evaluated the optical carrier generation rate. Using this information in a three-dimensional (3D) numerical model based on a drift–diffusion approach, we have computed the quantum efficiency and photoresponse of a number of pixel geometries. Specifically, we have analyzed the response of both mesa-type and planar detector arrays with and without CdZnTe substrate. Furthermore, the electromagnetic response has also been evaluated for different metal contact dimensions and configurations. It is found that, for mesa-type arrays without the substrate, significant reflection effects take place in the device that lead to resonance peaks in the photoresponse.     

A Two- or Three-Dimensional Green's Function Which can be Applied to Hyperfrequency Microelectronic Transmission Lines (Letters)

Knowing Green's function and the charge density found on different conductors, the diverse capacities can eventually be calculated by solving an integral equation. This has been dealt with only for simple dielectric-conductor configurations. In Coen's article, the integral representation of log (Z) is employed in calculating Green's function for microstrips (with or without an upper ground plane). Electrostatically speaking, the boundary conditions along conductors or dielectric interfaces are represented by means of infinite charge series.     

One- and Two-Stage Tunable Receivers

In this paper, we propose and assess a CFAR detector that can adjust its “directivity” through a real scalar parameter. It relies on the usual assumption that a set of homogeneous training data is available and encompasses as special cases the well-known Kelly's GLRT and the recently introduced W-ABORT detector. More important, it can be tuned in order to control the level to which sidelobe signals are rejected. Such functionality is particularly important to contain the number of false alarms in presence of mismatched signals. We also consider a parametric detector which resorts to a diagonally loaded sample covariance matrix commonly adopted to take advantage of the presence of strong interferers. The performance assessment of such detector has shown that it can significantly outperform Kelly's GLRT in terms of prediction probabilities for matched signals and in terms of selectivity, but it is not strictly CFAR. We also propose to use the CFAR parametric detector as second stage of a two-stage tunable detector and show that such a two-stage detector can outperform already proposed tunable receivers in terms of selectivity. The analysis of the detectors is conducted assuming a homogeneous Gaussian environment; with reference to this scenario and to the CFAR detectors we derive analytical expressions for the probability of false alarm and the probability of detection for both matched and mismatched signals.      

In Vivo Two- and Three-Dimensional Imaging of Artificial and Real Fingerprints With Optical Coherence Tomography

Fingerprint recognition is one of the dominant methods among all biometric techniques. However, current commercial fingerprint reader systems are based on analysis of surface topography of a finger and, thus, have tremendous security vulnerability for simply made artificial fingerprint dummies. In this letter, we demonstrate that a novel optical coherence tomography-based method for depth-resolved 2-D and 3-D imaging and assessment of artificial and real fingerprints could significantly enhance spoof-proofing of fingerprint reader systems as well as provide information of both artificial and real ridge and furrow patterns (that form the fingerprint patterns) simultaneously.     

One- and two-level filter-bank convolvers

In a recent paper, it was shown in detail that in the case of orthonormal and biorthogonal filter banks we can convolve two signals by directly convolving the subband signals and combining the results. In this paper, we further generalize the result. We also derive the statistical coding gain for the generalized subband convolver. As an application, we derive a novel low sensitivity structure for FIR filters from the convolution theorem. We define and derive a deterministic coding gain of the subband convolver over direct convolution for a fixed wordlength implementation. This gain serves as a figure of merit for the low sensitivity structure. Several numerical examples are included to demonstrate the usefulness of these ideas. By using the generalized polyphase representation, we show that the subband convolvers, linear periodically time varying systems, and digital block filtering can be viewed in a unified manner. Furthermore, the scheme called IFIR filtering is shown to be a special case of the convolver     

推进农网双向改造,加快三网融合业务发展

三网融合在即,在做好城市有线电视网络双向改造的同时,广电应根据自身的实际情况积极推进农村有线电视双向网络,以期符合三网融合业务发展的网络基础要求。     

Low-Cost, Precision, Self-Alignment Technique for Coupling Laser and Photodiode Arrays to Polymer Waveguide Arrays on Multilayer PCBs

The first, to our knowledge, passive, precision, self-alignment technique for direct coupling of vertical cavity surface emitting laser (VCSEL) and photodiode (PD) arrays to an array of polymer buried channel waveguides on a rigid printed circuit board (PCB) is reported. It gives insertion losses as good as the best achieved previously, to within experimental measurement accuracy, but without the need for costly active alignment nor waveguide facet polishing and so is a major step towards a commercially realizable low cost connector. Such an optical connector with four duplex channels each operating at 10 Gb/s (80 Gb/s aggregate) was designed, constructed, and its alignment precision assessed. The alignment technique is applicable to polymer waveguide interconnections on both rigid and flexible multilayer printed circuit boards (PCBs). The dependence of optical coupling loss on misalignments in $x$, $y$ and $z$ of the VCSEL and PD arrays allows the precision of alignment to be assessed and its reproducibility on multiple mating cycles of the connector is reported. The first recorded measurements of crosstalk between waveguides when the connector is misaligned are reported. Lateral misalignments of the connector to within its tolerance are shown to have no effect on the signal to crosstalk ratio (SCR), to within experimental measurement accuracy. The insertion loss repeatability is similar to that of single mode fiber mechanically transferable (MT) connectors.      

XY拾音制式与MS拾音制式的等效转换

从传声器指向性系数的角度入手,简单介绍了XY制式和MS制式的拾音原理,提出了XY制式与MS制式等效转换的一种计算方法,并对其进行了讨论。     

One-, two-, and three-photon pumped lasing in a novel liquid dye salt system

We report the observation of one-, two-, and three-photon pumped lasing in the same medium, a novel liquid dye salt system when excited by pulsed 0.532-, 1.06-, and /spl sim/1.49-/spl mu/m coherent radiation pulses, respectively. Since the gain medium is a liquid and not a solution, it contains a significantly higher effective dye concentration and, therefore, is highly suitable for multiphoton pumped lasing and optical power limiting applications. The lasing spectra, temporal waveforms, near- and far-field intensity distributions, and output/input efficiency were measured under the conditions of one-, two-, and three-photon pump configurations.     

Single-Shot, High-Speed, Thermal-Interface Characterization of Semiconductor Laser Arrays

Through a detailed characterization of thermally induced output power degradation it is possible to use junction heating as a tool to resolve thermal interfaces on mus timescales using a single-shot characterization technique. In this work, the deleterious effect junction heating has on the optical output power of a laser array is characterized and then used to infer the time-dependent junction temperature in response to current pulses of varying widths. The extracted parameters are also used numerically to model the laser as a temperature-dependent heat source for thermal simulations. This treatment allows realistic packaging and emitter-placement studies to be parametrically performed by incorporating the relationship between temperature and output power/efficiency for each emitter. In this respect, once the temperature behavior of a single emitter is quantified, the operating temperature and output power performance can be accurately predicted for any realistic physical arrangement of laser array and packaging. The experimental method presented in this work is also compared to other techniques and numerical simulations using the nonlinear heat source; this demonstrates the utility of this approach and the convenience of using easily measured parameters in thermal simulations.     

阵列式场致发射结构的电特性

我们报道了湿法腐蚀的阵列式硅场致发射锥尖的实验结果。给出了Ⅰ-Ⅴ测试结果和角分辨的电子发射能谱。我们发现场致发射发生在具有极小曲率半径的有效表面积中的很小一部分。能谱仪测定的结果表明了硅中在低于费米能级以下几电子伏的地方产生发射,并给出了△E=0.28eV的半高宽(FWHM)。     

有线电视双向网接入技术选择

EPON技术因其高带宽、无源分配、易维护、支持多业务等优势,近年来正在成为宽带接入的主要技术之一,也非常适合于有线电视网络开展双向数据业务。在接入技术方面有EoC、LAN,部分广电有线电视网络已经进行了基于Cable Modem方式的HFC双向网改造,那么如何选择宽带接入方式呢？对HFC、EPON以及几种接入技术做技术分析、投入成本分析以及网络现状分析,以此选择适合有线电视网宽带接入的技术方式。     

Two- and three-dimensional calculation of substrate resistance

A two- and three-dimensional solution of the Laplace equation for the calculation of the substrate resistance for rectangular contacts is presented. After the calculations are performed for a uniform substrate, an extension is given to nonuniform doped regions. This solution makes it possible to investigate the influence of buried layers and field implementations on substrate and well resistances     

Direct Assembly of Vertically Oriented,Gold Nanorod Arrays

Although many nanoscale materials such as quantum dots and metallic nanocrystals exhibit size dependent optical properties, it has been difficult to incorporate them into optical or electronic devices because there are currently no methods for precise, large-scale deposition of single nanocrystals. Of particular interest is the need to control the orientation of single nanocrystals since the optical properties are usually strongly anisotropic. Here a method based on electrophoretic deposition (EPD) is reported to precisely assemble vertically oriented, single gold nanorods. It is demonstrated that the orientation of gold nanorods during deposition is controlled by the electric dipole moment induced along the rod by the electric field. Dissipative particle dynamics simulations indicate that the magnitude of this dipole moment is dominated by the polarizability of the solution phase electric double layer around the nanorod. The resulting vertical gold nanorod arrays exhibit reflected colors due to selective excitation of the transverse surface plasmon mode. The EPD method allows assembly of arrays with a density of over one million, visually resolvable, vertical nanorods per square millimeter.     

Controlled One- and Multidimensional Modulations Using Chaotic Maps

Recently, several approaches for communications using chaos have been presented, often showing less than acceptable performance. In this paper, a short introduction to the topic is given, and it is shown that such methods can be efficient—if the information production related to the chaos in the transmitter is controlled and used for the payload of the communication. The influence of minimum distance aspects, a previously ignored key point, to the design of appropriate controlled schemes are studied. In terms of applicable theory, a link between schemes based on one-dimensional and multidimensional chaotic systems (as presented in this paper) and convolutional codes will be established. In order to support our argument, we give simulation results for some a priori examples and results of search procedure for more powerful modulations.     

柔性晶体管阵列

现在市场上出现了柔性晶体管阵列并且前景诱人，但是在柔性阵列技术进入主流市场之前还要克服不少困难。