nils-herrmann/clean_scirepeval huggingface dataset:
Discrete Green's function diakoptics — A toy problem

In Green's function diakoptics, wave-field interactions between disjoint domains in space are described in terms of interacting multi-port subsystems. In addition to integral-equation based Green's function diakoptics for time-harmonic fields, a demonstrably stable discrete space-time Green's function diakoptics scheme has been reported to be effective for proximate regions. For distant regions it is necessary to retain a long field history. Upon considering a diakoptics toy problem involving two disjoint domains consisting of a single point each, the resulting boundary operator may be expressed in terms of two distinct discrete Green's functions only, describing the intra- and inter-domain unit-source field responses, respectively. There are various integral representations and asymptotic expansions for the discrete Z-domain Green's functions, and it is even possible to construct representations for the discrete space-time Green's functions consisting of nested finite sums, which turn out to be difficult to evaluate due to severe cancellations.
Dynamic modal analysis of monolithic and multi-GHz mode-locked semiconductor lasers

The authors' approach makes use of the fact that in many practical devices, the lasing spectrum is restricted to only a few longitudinal modes, either by virtue of high repetition rate or by an artificial spectrally selective element such as a distributed Bragg reflector. These lasers therefore render themselves more naturally, not to the fully-time-domain analysis, but to a time-frequency-domain approach. The model is applicable to a wide variety of realistic actively, passively and hybridly mode-locked structures, and takes into account both slow and fast nonlinearities in the active medium. With this model, we can describe, on the same footing, a wide variety of transient as well as steady-state regimes including CW lasing, fully or partially rendered mode-locking (ML), and more complex dynamics including self-pulsing and chaotic instabilities. In our approach, the lasing light is decomposed into a set of longitudinal modes of the realistic (open and inhomogeneous) cavity. We first apply the model to a Fabry-Perot passively mode-locked (F=100 GHz) laser; the resulting steady-state spectra agree well with distributed time-domain model (DTDM) simulations, whilst providing an increase of about an order of magnitude in computation speed. Next, the model is applied to colliding-pulse ML (CPM) lasers (F-200 GHz); as expected, all the "odd" modes die out during the first 1-2 ns of the transient regime and are suppressed by at least 20 dB in the resulting spectrum, which corresponds to a full repetition frequency doubling of the ML pulse train. We also apply the model to harmonic sub-terahertz mode-locking.
DC and RF Characterization of Sub-100-nm-Gate-Length Strained Ge-on-Insulator p-MOSFETs

In this paper, the fabrication and characterization of strained Ge-on-insulator transistors with gate lengths down to 65 nm is described and also, for the first time, RF characteristics of sub-100-nm gate-length Ge MOSFET are reported. It is concluded that considerable further improvement is possible in both the performance and the short-channel characteristics by increasing the strain in the channel, and by the use of halo implants.
Time-domain finite-difference beam propagation method

A new technique to model the behavior of pulsed optical beams in waveguides is proposed and analyzed. The technique is an extension of the traditional continuous-wave beam propagation method (BPNI) to include time dependence, therefore called the time-domain BPM (TD-BPM). The method was tested using different waveguide examples and it is concluded that the technique is simple and accurate. Compared with the finite-difference TD method, the new TD-BPM is more efficient in terms of computer memory and execution time especially for large optical devices.
Integrated asymmetric Mach-Zehnder interferometer WDM (de)multiplexer using quantum well intermixing

An InGaAs/InAlGaAs monolithically integrated asymmetric Mach-Zehnder interferometer WDM (de)multiplexer has been fabricated using quantum well intermixing. Wavelength tuning using current injection is demonstrated and a channel extinction ratio >25 dB is achieved.
FDTD electrodynamics of 1-electron atom in a central potential on a discrete space-time lattice

We revisit the formulation within the FDTD method of the Abraham-Lorentz model of a 1-electron atom coupling to an external electromagnetic field via the dipole interaction between the field and the moving charge. This classical problem is reformulated for a purely discrete space in discrete-time by specifying the electromagnetic potentials and the electron charge density only at discrete spatial points or edges in a mesh decomposition of space. A systematic simplicial complex structure is used which preserves classical field theorems such as Gauss's Law, Stokes' and Green's Theorems in the discrete domain. The role of the radiation reaction field which permeates the electron charge is identified.
FDTD simulation of the nonlinear gain dynamics in active optical waveguides and semiconductor microcavities

We use the finite-difference time-domain (FDTD) solution of the full-wave vectorial Maxwell-Bloch equations for a two-level quantum system developed earlier , to investigate the nonlinear gain spatio-temporal dynamics of active optical waveguides and semiconductor microcavities. The numerical model has been successfully validated against density matrix theory of gain saturation in homogeneously broadened two-level quantum systems for optical waveguides containing resonant gain nonlinearities. The semiclassical equations have been extended employing the Langevin formalism to account for the quantum noise and the spontaneous emission. We have numerically demonstrated the time evolution of the coherent oscillations build up at the output laser facet identifying the lasing threshold and the fast relaxation oscillations until the settlement of a steady-state emission. Our simulation predictions of the lasing wavelength in a number of vertical-cavity surface-emitting laser geometries, when the spontaneous emission is the only source of radiation, agree very well with standard results and, thus, allow us to infer and subsequently optimize important emission characteristics, such as the spontaneous emission rate, the laser line shape, and the relaxation oscillation frequencies and decay rates.
FDTD simulation of the nonlinear gain dynamics and modulation response of a semiconductor microcavity

The method of FDTD solution of the full-wave vectorial Maxwell-Bloch equations for a two-level quantum system in 1D is applied to investigate the nonlinear gain spatio-temporal dynamics in an active semiconductor microcavity. The test structure used was 15 /spl mu/m long active medium slab (GaAs) at the left boundary of which a continuous-wave sinusoid source field (after smooth turn-on within 5 periods) at the atomic transition frequency (/spl lambda/ = 1.5 /spl mu/m) is launched.
A low jitter passively mode locked laser diode at 40 GHz using regenerative feedback via an optical fiber loop

Mode-locked laser diodes (MLLDs) are excellent candidates for generating ultrashort high frequency pulses for a number of applications, including optical clocking, sampling, and clock recovery. Although more prone to noise than active MLLDs, passive MLLDs do not require any external electrical oscillator. But many applications for such lasers require highly stable optical pulses with sub-picosecond timing jitter and in this paper we report a technique for reducing the RF phase noise in a passive MLLD. Regenerative mode locking is a technique used to significantly reduce the timing jitter by providing a self-referencing mechanism to continuously correct the phase timing of the pulses [1, 2]. However, many of the current techniques used are based on electrical extraction and high-Q RF filtering of the pulses, which adds several components and considerable system complexity. Here we present a simplified all-optical regenerative mode locking technique which can provide significant reductions in phase noise and timing jitter.
Mobility Scaling in Short-Channel Length Strained Ge-on-Insulator P-MOSFETs

The hole transport characteristics in partially strained (0.5%) Ge p-channel MOSFETs formed on silicon-germanium-on-insulator (SGOI) substrates were investigated for gate lengths down to 65 nm. We demonstrate that high hole mobility is maintained down to the shortest channel lengths. The channel conductance from these devices is measured and compared to state-of-the-art high-performance Si channel P-MOSFETs.
Control of the nonlinear polarisation dynamics in a semiconductor waveguide with a periodic magnetic field

Nonlinear polarisation dynamics in semiconductor waveguides is a topic of current interest with applications in vectorial spatial solitons and all-optical switching schemes. It is generally found that as the change in refractive index induced by the Kerr nonlinearity becomes comparable to the birefringence of the waveguide, the single-polarised (TE and TM) stable stationary eigenmode becomes unstable and there is an emergence of a pair of mixed-polarised stable stationary eigenmodes (i.e. bifurcation). The bifurcation in the mode with the lower propagation constant is attributable to the anisotropy in the nonlinear refraction between the TE and TM polarisations. These phenomena have been scrutinised both in the plane-wave and spatial soliton cases obtaining analytic results for the bifurcation threshold. Of interest is the additional degree of control obtained with a longitudinal magnetic field through the magneto-optic effect which may, for example, allow the polarisation state to be switched from one stationary state to another. The polarisation dynamics are analysed in terms of the Stokes parameters allowing the evolution trajectories to be mapped on a Poincare sphere for the non-dissipative case. We derive the Hamiltonian for the system consisting of terms for the anisotropic Kerr nonlinearity, waveguide birefringence and longitudinal magneto-optic effect. From the Hamiltonian the evolution equations in terms of the Stokes parameters can be subsequently obtained.
Soliton pulse-position modulation

The phenomenon of a train of optical fibre solitons, modulated in some way by impressed disturbances, is increasingly being identified as a new type of dynamical system, with interesting dynamical behaviour which can be studied both experimentally and mathematically. This perception leads rather naturally to an investigation of the behaviour of this system when subjected to various forms of pulse-analogue modulation, to which this chapter is devoted. The principal motivation for the study of solitons in pulse position modulation (PPM) arises from the fact that PPM with short pulses permits a greater transmission rate than longer pulses, and intense pulses exhibit higher signal-to-noise ratio than weak pulses. Consequently, intense short pulses are desirable for PPM, but fibre dispersion limits the minimum width an individual pulse can have after linear transmission. This consideration leads naturally to speculation on solitons in PPM because the soliton does not suffer dispersion. However, this is only one example of a general interest which is developing in the understanding of dynamical phenomena involving solitons, to which this work is addressed.
Ultrashort pulse lossless propagation through a degenerate three-level medium in nonlinear optical waveguides and semiconductor microcavities

The authors develop and apply a novel group-theoretical approach for studying the coherent dynamics of ultrashort pulse propagation in nonlinear optical waveguides and passive semiconductor microresonators. The resonant nonlinearity is modeled by a degenerate three-level system of saturable absorbers in order to allow for a two-dimensional medium polarization. The resulting Maxwell-pseudospin equations are solved in the time domain using the finite-difference time-domain method. Conditions of onset of the self-induced transparency (SIT) regime of propagation are investigated. Numerical evidence of multidimensional solitons localized both in space and in time is given for the planar optical waveguides. Pattern formation and cavity SIT-soliton formation are demonstrated for a passive semiconductor microcavity filled with saturable absorbers.
Current injection tunable monolithically integrated InGaAs-InAlGaAs asymmetric Mach-Zehnder interferometer using quantum-well intermixing

A compact highly efficient wavelength (de)multiplexer with channel spacing of 100 GHz has been realized with a monolithically integrated asymmetric 2 /spl times/ 2 Mach-Zehnder interferometer using a single step sputtered SiO/sub 2/-annealing quantum-well intermixing process. Wavelength tunability and asymmetric loss rebalancing of the device is demonstrated using current injection. Wavelength tuning over 0.8 nm is achieved with only 6 mA of injected current. An extinction ratio of more than 27 dB is obtained.
A perceptually efficient VBR rate control algorithm

This paper describes a rate control algorithm for a variable bit-rate (VBR) video coder. The algorithm described varies the quantizer step size of the coder according to properties of an image sequence that affect the perception of errors. The algorithm also limits the output bit-rate of the coder without the use of buffers to more efficiently use network bandwidth. It is shown that a VBR encoder using this algorithm will provide decoded image sequences with a consistent perceived quality that is comparable with, or better than, the perceived quality of images coded with a CBR encoder.
Theory of mixed-polarization spatial solitons in anisotropic cubic media

AlGaAs is an attractive material system for the study of the dynamics of Kerr spatial solitons, having a nonlinear coefficient of 1000 times that of silica around the communication wavelength of 1.55 /spl mu/m. However, there are several differences between AlGaAs and silica when the polarization dependence of nonlinear refraction is considered. Cubic semiconductors can display an anisotropic third-order nonlinearity (although in terms of linear optics they are nonbirefringent) and are also usually exploited in the vicinity of an optical resonance (e.g., just below the half-bandgap), so that Kleinmann symmetry cannot be assumed. On considering the propagation of two orthogonal polarization components in such a medium, one obtains not only self-phase modulation, cross-phase modulation, and four-wave mixing, but now with an orientation dependence, but also terms that contribute to anisotropy.
Finite-difference Green's function diakoptics — Domain versus boundary formalisms

The lookback boundary Green's function diakoptics (GFD) schemes reported on before act on field quantities at the boundary set of disjoint domains. This seems a logical and desirable property, but induces computational complexities. It is also possible to construct a domain-based GFD lookback scheme, akin to a discrete Green's function method developed by Vazquez and Parini. We discuss these limited and unlimited lookback boundary and domain based GFD formalisms.
A practical course in digital video communications based on MATLAB

The outline of new course in video coding is presented in which the basic concepts are reinforced by way of a series of graded MATLAB exercises. Following a brief overview of the motion-compensated discrete cosine transform (DCT) encoder, a number of exercises are described in which the student obtains an understanding of image correlations and entropy and the concepts involved in predictive encoding. The data compaction properties of the discrete cosine transform are then illustrated together with interframe motion-estimation and motion-compensated prediction. All aspects of the evolving video encoder are then integrated by way of a simplified encoder syntax that is based upon the standard Moving Picture Experts Group (MPEG) syntax. This allows students to exchange digital bit-streams and decode image sequences that have been encoded by fellow students. Advanced topics such as fast motion estimation techniques, error resilience, and other coding approaches are briefly discussed.
Analysis of membrane support structures for integrated antenna usage on two-dimensional photonic-bandgap structures

The study of the transmission of electromagnetic waves through a photonic crystal with various membranes placed over the surface is presented in this paper. A difference in performance is observed even for a membrane thickness that is unable to support guided substrate modes through total internal reflection. The transmittance has been investigated for two crystal orientations, assuming normally incident external plane waves on a finite thickness two-dimensional (2-D) photonic crystals both with and without a membrane. The angular transmission response is characterized by scanning the incidence angle of the impinging plane wave to cover all available angles within the 2D periodic plane of the structure.
Efficient time-domain beam-propagation method for modeling integrated optical devices

A new efficient technique that models the behavior of pulsed optical beams in homogenous medium, metallic and dielectric waveguides, is introduced and verified using both linear nondispersive and dispersive examples that have analytical predictions. Excellent accuracy results have been observed. The method is called time-domain beam-propagation method (TD-BPM) because it is similar to the classical continuous-wave BPM with additional time dependence. The explicit finite difference and the Du Fort-Frankel approaches were used to discretize the TD-BPM equation. Comparisons between these techniques are also given with the application of the perfectly matched layers as spatial boundary conditions to the Du Fort-Frankel. Then the TD-BPM was successfully applied to model a two-dimensional dielectric Y-junction. It is concluded that the new technique is more efficient than the traditional finite-difference TD method, especially in modeling large optical devices.
Efficient drift-free signal-to-noise ratio scalability

Signal-to-noise ratio (SNR) scalability has been incorporated into the MPEG-2 video-coding standard to allow for the delivery of two services with the same spatial and temporal resolution but different levels of quality. In this paper, we begin by reviewing the performance of a single-loop SNR scalable encoder that is compliant with the MPEG-2 standard and demonstrate that its performance is limited by drift in the base layer. We also look at an alternative single-loop drift-free noncompliant SNR scalable encoder, but discover that its coding efficiency is poor. We then review the performance of an MPEG-compliant two-loop SNR scalable encoder. Finally, we propose a new two-loop noncompliant encoder which achieves improved coding performance at the expense of some increase in encoder and decoder complexity.
Quantification of retinal damage during cardiopulmonary bypass: comparison of computer and human assessment

A comparison of retinal fluorescein angiograms taken before cardiopulmonary bypass with those taken just before the end of operation, has shown that microvascular occlusions can develop during operation. Quantification of the retinal damage in terms of the area of nonperfusion depends on careful examination by humans. Assessment of these areas is necessarily subjective and digital image analysis would be preferable to make the measurements more objective. Visual or automatic comparison of images is facilitated by prior geometrical alignment. A method for registering retinal images which has been used successfully on 65 image pairs is described. Techniques for automatically detecting changes in the microvascular structure are illustrated. Using a subset of 40 good quality image pairs, good agreement between computer detected occlusions and human assessment of nonperfusing areas is reported.
Dynamic modal analysis of monolithic mode-locked semiconductor lasers

We analyze the advantages and applicability limits of the mode-coupling approach to active, passive, hybrid, and harmonic mode-locking in diode lasers. A simple, computationally efficient numerical model is proposed and applied to several traditional and advanced laser constructions and regimes, including high-frequency pulse emission by symmetric and asymmetric colliding pulse mode-locking, and locking properties of hybrid mode-locked Fabry-Perot and distributed Bragg reflector lasers.
Preparing to witness a multi-megawatt motor and adjustable speed drive acceptance test — The basics

Adjustable speed drive (ASD) and motors, if selected as a prime mover for compressors, pumps, extruders, etc. can provide various electro-mechanical benefits to its operators and stakeholders. Their benefits and application considerations have been well documented in past papers and tutorials. However, a successful installation of a multi-megawatt motor and ASD system requires detailed application, engineering, manufacturing, testing and installation considerations. Many times testing is requested by the operator and/or consultant, but navigating the types of tests available, test procedures, plans and how they comply with appropriate standards is often not fully understood. This can lead to surprises, shipment delays, price adders and ultimately the equipment itself not being in compliance with the stated project objectives. This paper attempts to address the factory acceptance testing (FAT) phase of a medium voltage motor and ASD system whether procured separately or as a package. Issues such as type of test selection, specifications, standards, preparation, acceptance criteria, and finally string testing will be covered. This paper serves as a guideline of how one can select, prepare, witness and sign off of a medium voltage motor and ASD test.
Reversible image compression bounded by noise

Reversible image compression rarely achieves compression ratios larger than about 3:1. An explanation of this limit is offered, which hinges upon the additive noise the sensor introduces into the image. Simple models of this noise allow lower bounds on the bit rate to be estimated from sensor noise parameters rather than from ensembles of typical images. The model predicts that an 8-b single-band image subject to noise with unit standard deviation can be compressed reversibly to no less than 2.0 b/pixel, equivalent to a maximum compression ratio of about 4:1. The model has been extended to multispectral imagery. The Airborne Visible and Infra Red Imaging Spectrometer (AVIRIS) is used as an example, as the noise in its 224 bands is well characterized. The model predicts a lower bound on the bit rate for the compressed data of about 5.5 b/pixel when a single codebook is used to encode all the bands. A separate codebook for each band (i.e., 224 codebooks) reduces this bound by 0.5 b/pixel to about 5.0 b/pixel, but 90% of this reduction is provided by only four codebooks. Empirical results corroborate these theoretical predictions.
Tungsten and cobalt metallization: A material study for MOL local interconnects

Middle-of-the-line (MOL) interconnect and contact resistances represent significant impacts to high-end IC performance at ≤ 10 nm nodes. CVD W-based metallization has been used for all nodes since the inception of damascene. However, it is now being severely challenged due to limited scaling of the traditional PVD Ti/CVD TiN barrier and ALD nucleation layers. This study reports the use of alternate barriers, along with metal-to-metal contact interface cleans, to reduce contact resistance for W-based MOL metallization. As well, we report the first use of Co metal for MOL contacts and local interconnects, with successful integration below a Cu BEOL dual damascene V0/M1 module. Metal line resistances are compared among the various options, and the challenges with each option are highlighted.