Plasma chemistries for dry etching of NiFe and NiFeCo

Plasma chemistries based on chlorine, bromine, or iodine have been investigated for inductively coupled plasma etching of NiFe and NiFeCo. There is clear evidence of a chemically enhanced etch mechanism with both Cl₂- and I₂- based mixtures, with no enhancement present for Br₂ chemistries. Etch yields are typically low (≤0.25), emphasizing the need for high ion fluxes in order to achieve practical material removal rates.     

Optical networking update

This paper presents an inventory of the current state and future prospects for networks in which signal paths between end user nodes remain entirely in optical form without intervening electronic conversions. The emphasis is on wavelength-division multiplexing (WDM). The applications and system aspects are stressed relative to details of the supporting technologies. The case to be made for optical networks as the basis of an entire possible future generation of networking is examined, after which the various architectural choices are discussed. Next, the limits on what can be achieved, mostly arising from limitations within the available technology, are treated. After a review of the history of all-optical networking, the paper concludes with speculations about where the applications, the technology and the architectural character of these systems will be going in the years ahead     

Functional reentry's influence on intracellular calcium in the LRd membrane equations

This paper examines relationships between transmembrane potential (Vm), [Ca2+]i dependent membrane ionic currents, and [Ca2+]i handling by the sarcoplasmic reticulum (SR) in a two-dimensional model of cardiac tissue. Luo-Rudy dynamic (LRd) membrane equations were used because they include detailed formulations for triggered SR Ca2+ release dependent on membrane Ca2+ influx (CICR) and for spontaneous SR Ca2+ release following calsequestrin buffer overload (SCR). Reentry's rapid rate (110-ms cycle length) elevated [Ca2+]i and limited CICR, which in turn promoted SCR that occurred at intervals of 320-350 ms, was preferential at sites located inside the functional center, and destabilized the reentrant activation sequence. Although adjustment of LRd parameters for SR Ca2+ modified SCR interval and peak [Ca2+]i in voltage clamp simulations with a command waveform representing Vm time course within the functional center, SCR persisted. Using the same command waveform, SCR also occurred with an alternate SR Ca2+ formulation that represented subcellular details underlying CICR. LRd parameter adjustments to promote CICR and limit SCR in subsequent reentry simulations failed to eliminate SCR completely, as they modulated SCR intervals in a manner consistent with the voltage clamp simulations. Taken together, our findings support a destabilizing influence of functional reentry on [Ca2+]i handling. However, [Ca2+]i instabilities did not always fractionate depolarization wavefronts during reentry. Fractionation depended, in part, upon CICR and SCR parameters in the LRd formulation for SR Ca2+ release.     

Passive alignment optical subassemblies for military/aerospacefiber-optic transmitter/receiver modules

Under the DARPA sponsored Avionics Optoelectronic Module Technology program, new passive alignment carrier (PAC) optical subassemblies (LED-PAC and PIN-PAC) ruggedized for military/aerospace avionics fiber-optic transmitter and receiver applications have been developed, LED-PAC and PIN-PAC silicon micro-optical bench substrates were fabricated together on a 5 in diameter silicon wafer via multistage photolithography, thin-film, and substrate processing. Alignment v-grooves designed for passive optical alignment of 100/140 μm multimode optical fiber to the optoelectronic devices were terminated by solder locking the fiber to the silicon PAC substrates. The LED-PAC comprising a surface emitting LED die-bonded onto a novel precision molded AM submount passively mounted onto the silicon microbench achieves the required high coupling efficiency to 100/140 μm multimode optical fiber to meet stringent avionics transmitter output power requirements. The 100/130 μm multimode optical fiber-pigtailed PIN-PAC with a refractive lens etched into the p-i-n photodiode backside surface exhibited responsivities greater than 0.8 A/W at 1.3 μm wavelength. The LED-PAC and PIN-PAC optical subassemblies integrated with Boeing ARINC 636 (FDDI) transmitter and receiver thick film multichip (MCM-C) circuitry are capable of meeting both ARINC 636 and FDDI physical layer requirements     

Application of multiattribute decision analysis to quality functiondeployment for target setting

In the product design and development process, quality function deployment (QFD) provides a comprehensive, systematic approach to support the design of new products intended to meet or exceed customer expectations. The authors use multiattribute value theory to support new product design and hence to augment a design team's experience and judgment. We introduce the concept of a target set, the set of all value score vectors that are at least as preferred as the value score vectors of any of the given design alternatives. Assuming mutually preferential independence, we characterize the target set and indicate how it can be used to support selecting targets: 1) for the level of customer satisfaction to be attained by the new product, for each customer requirement and 2) for design requirements, presumably based in part on information from engineering competitive assessments. We then use the target set concept to augment the product planning phase of QFD. The concepts are illustrated and evaluated through the retrospective application of the methodology to an actual surgical product (universal converter). Although the analysis was performed retrospectively, without knowledge of the market success of the product and its competitors, the results were consistent with product acceptance and provided valuable insights to the lead engineer     

Dielectric characterization of low-loss materials a comparison oftechniques

Measurements on low-loss materials using closed and open cavity resonators, and dielectric resonator methods are presented. Results indicate that consistent measurement results can be obtained with a number of well-characterized fixtures. Uncertainties associated with each method are addressed. Measurements also were performed on materials used in previous intercomparisons     

An Overview of Analog Feedback Part II: Amplifier Configurations in Generic Device Technologies

In this second installment of a two part paper that overviews analog feedback circuits, computationally efficient and general feedback analysis techniques applicable to virtually all three and four terminal device technologies are formulated. As developed in Part I, these techniques coalesce signal flow and two port network theories in a way that clearly illuminates the loop gain, driving point I/O impedances, and other characteristics of any type of feedback configuration. More than simply developing the signal flow-two port methodology, this paper demonstrates its design-oriented utility by applying the new technique to the problem of assessing the performance attributes and limitations of four single loop and two dual loop feedback architectures.Three advantages are gleaned by the signal flow-two port method of feedback network analysis. The first advantage is its amenability to a straightforward application of the stability theories and compensation strategies discussed in Part I. The second is its ability to underscore the magnitude of potentially troublesome feedforward factors associated with the feedback network. Once the extent of this parasitic feedforward is highlighted, the topological nature of appropriate feedforward compensation is relatively easy to innovate. The third advantage of signal flow-two port analytical methods is its ability to simplify the analysis of dual loop feedback architectures. This last advantage is noteworthy in view of the fact that dual feedback loops offer the only practical analog mechanism for desensitizing the gain and I/O impedances with respect to uncertainties in open loop parameters.     

Surface wave excitation from open microstrip discontinuities

Radiation properties of open microstrip discontinuities are investigated using a full-wave integral equation technique. Formulas are presented to characterize power loss from open microstrip discontinuities. The technique utilizes microstrip current distributions obtained with the method of moments. The formulas allow the separation of total loss into the individual contributions of space wave and surface wave radiation and indicate the direction in which surface wave power is propagating within the substrate. Patterns depicting the power propagating in the substrate have been computed and verified experimentally     

The relationship between optical guiding and the relative phase infree-electron lasers

The relative phase in this case is defined as the shift in the wavenumber from the vacuum value integrated over the interaction length. The relative phase is studied from the standpoint of the linear stability analysis in both the high- and low-gain regimes, and the qualitative implications in each of these regimes of the relative phase on the refractive guiding of the signal are identical. Specifically, the relative phase is found to be negative at the low-frequency end of the gain band. The relative phase increases with increasing frequency over this band until it turns positive at a frequency approximately 10% below the frequency of peak gain. Thus optical guiding is indicated over a large portion, but not all, of the gain band. The specific example of interest involves the low-gain regime prior to saturation. In this case, it is shown that the analytic result is in substantial agreement with the calculation of the relative phase     

Physical design issues for very large ATM switching systems

The authors examine the physical design issues associated with terabit/second switching systems, particularly with regard to the customer access portion of the switch. They determine the physical design requirements in the areas of backplane interconnections, integrated circuit packaging, and circuit board technology and identify areas where existing- or near-future physical design technologies are inadequate to meet the requirements of this application. A new 3D interconnection architecture that solves some of the problems encountered at the backplane level is suggested. It is also suggested that multichip module technology will help meet some of the speed and density requirements at the chip packaging level. Some of the system-level consequences of the proposed model are discussed