Planar lightwave integrated circuits with embedded actives for board and substrate level optical signal distribution

This paper explores design options for planar optical interconnections integrated onto boards, discusses fabrication options for both beam turning and embedded interconnections to optoelectronic devices, describes integration processes for creating embedded planar optical interconnections, and discusses measurement results for a number of integration schemes that have been demonstrated by the authors. In the area of optical interconnections with beams coupled to and from the board, the topics covered include integrated metal-coated polymer mirrors and volume holographic gratings for optical beam turning perpendicular to the board. Optical interconnections that utilize active thin film (approximately 1-5 /spl mu/m thick) optoelectronic components embedded in the board are also discussed, using both Si and high temperature FR-4 substrates. Both direct and evanescent coupling of optical signals into and out of the waveguide are discussed using embedded optical lasers and photodetectors.     

Quasi-bound states determination using a perturbed wavenumbersmethod in a large quantum box

A perturbed wavenumbers method (PWM) is presented that is capable of determining the quasi-bound-state eigenenergies and their lifetimes for quantum heterostructures having arbitrary potential profiles. The numerical method presented solves the single-band effective-mass Schrodinger equation without using complex energies. It is applicable to quantum structures that are symmetric, asymmetric, unbiased, or biased. For multiple quantum heterostructures, extensive comparisons of this numerical method with other currently used techniques are included. In addition, a modified density of states formulation is presented and applied to these example cases     

X-ray fluorescence in some rare earth and high Z elements excited by 661.6 keV γ-rays

The K-shell X-ray fluorescence cross sections are determined experimentally for 10 elements such as Pb, Hg, Ir, W, Lu, Tm, Dy, Tb, Gd and Nd at excitation energy of 661.6 keV associated with γ-rays of ¹³⁷Cs radioisotope. The technique employed involves the measurement of total intensity of fluorescent K X-rays that follow the photoeffect absorption of a known flux of γ-rays using a well type Nal(Tl) detector. The obtained results are compared with the available theoretical values and other measured values.     

Electrical and optical clock distribution networks for gigascale microprocessors

A summary of electrical and optical approaches to clock distribution within high-performance microprocessors is presented. System-level properties of intrachip electrical clock distribution networks corresponding to three microprocessor families are summarized. It is found that global clock interconnect performance and short-term jitter present the greatest challenges to the continued use of conventional clock distribution methodologies. An extrapolation of trends describing the percentage of clock period consumed by global skew and short-term jitter identifies the 32-nm technology generation of the 2002 International Technology Roadmap for Semiconductors (ITRS) as the first technology generation within which alternate methods of clock distribution may be warranted. Research efforts investigating interboard through intrachip optical clock distribution are also summarized. An optical distribution network compatible with high volume manufacturing in conjunction with a suitable means of providing optical-to-electrical signal conversion comprise the two fundamental challenges facing successful implementation of an optical clock distribution network. It is found that a global guided-wave distribution capable of efficient input and output coupling of optical power is required to meet the first challenge. The identification of a suitable means of optical-to-electrical conversion, however, remains an active topic of research.     

Optimization of multilayer integrated optics waveguides

A numerical method is described that provides the means for optimizing any objective function representing a general multilayer integrated optics waveguide. In this way, the physical parameters of the multilayer structure can be set so that the performance of the device is optimized. The method uses any standard numerical minimization algorithm in conjunction with the argument principle method. The method has been successfully applied for the optimization of a multilayer immunosensor and a TE-mode polarizer. The advantages of the method are its generality, its efficiency, its accuracy, and its applicability to a wide range of planar integrated optics devices     

Quantum interference effects in semiconductors: a bibliography

The bibliography has been compiled as an introduction and study guide to this field. The papers listed describe the extensive theoretical and experimental results that have been obtained on quantum interference effects and discuss possible application areas. Works of a fundamental nature concerning phenomena that are basic to all semiconductor behavior have not been included. Articles on the properties and band structure of semiconductors, which are essential to a complete understanding of quantum interference effects, have not been included. Conference papers, though frequently very important, have not been included to conserve space. The papers are listed alphabetically according to the first author's surname. As in the compilation of any bibliography, numerous valuable and pertinent articles have probably been inadvertently omitted     

The quasibound state model for self-consistent characteristics of semiconductor intersubband devices

The quasibound state model (QBSM) for determining the self-consistent conduction band profile and space charge density of semiconductor intersubband devices is presented. This new method is based on the quasibound (QB) state resonances of quantum structures. For heterostructures, the traditional self-consistent energy continuum model (ECM) calculates space charge by integration over the entire energy continuum, weighted by Fermi–Dirac statistics. In the present approach, the continuum of energy states of the heterostructure is accurately represented by a small number of QB states, and the space charge calculations are performed only at these eigen-energies. This approach significantly reduces the computational burden associated with all self-consistent algorithms. Theoretical formulation of QBSM is compared with the traditional ECM approach. The bound (B) and QB eigenenergies of the structure are obtained by solving the single-band effective-mass Schrödinger equation using the argument principle method. The performance and the accuracy of the QBSM are evaluated for a double-barrier resonant structure and an asymmetric Fabry–Perot electron-wave interference filter. The self-consistent electron density and potential profiles calculated by the present method are shown to be in excellent agreement with the results obtained from the traditional ECM model. In addition to requiring less computational time, the present method is easily implemented and may be applied equally well to biased/unbiased, symmetric/asymmetric heterostructures.     

Quantum reflection pole method for determination of quasibound states in semiconductor heterostructures

The quantum reflection pole method (QRPM) is introduced for determining quasibound state eigenenergies and their lifetimes in symmetric, asymmetric, biased, and unbiased quantum heterostructures. In the QRPM the single-band effective-mass Schrödinger equation is solved without using complex arithmetic. Calculations are much simpler to perform than with previous methods. Further, results are found to be in excellent agreement with other rigorous techniques.     

Parallelized formulation of the maximum likelihood-expectation maximization algorithm for fine-grain message-passing architectures

Recent architectural and technological advances have led to the feasibility of a new class of massively parallel processing systems based on a fine-grain, message-passing computational model. These machines provide a new alternative for the development of fast, cost-efficient Maximum Likelihood-Expectation Maximization (ML-EM) algorithmic formulations. As an important first step in determining the potential performance benefits to be gathered from such formulations, we have developed an ML-EM algorithm suitable for the high-communications, low-memory (HCLM) execution model supported by this new class of machines. Evaluation of this algorithm indicates a normalized least-square error comparable to, or better than, that obtained via a sequential ray-driven ML-EM formulation and an effective speedup in execution time (as determined via discrete-event simulation of the Pica multiprocessor system currently under development at the Georgia Institute of Technology) of well over two orders of magnitude compared to current ray-driven sequential ML-EM formulations on high-end workstations. Thus, the HCLM algorithmic formulation may provide ML-EM reconstructions within clinical time-frames.