Locally Er-Doped Near-Stoichiometric LiNbO3 Crystals Prepared by Standard Er Diffusion and Post-VTE Treatment

The feasibility of preparing locally Er-doped near-stoichiometric (NS) LiNbO₃ crystals for integrated optics applications is demonstrated by a two-step process with standard diffusion (1130°C/154 h) of Er metal followed by vapor transport equilibration (VTE) treatment under three different conditions of 1135°C/22 h, 1115°C/50 h, and 1125°C/60 h. Detailed studies on the crystalline phase, Li composition, diffused surface roughness, and emission characteristics of Er³⁺ ions indicate that there is an upper limit on the initial Er metal film thickness: ∼20 nm for an X -cut crystal and ∼30 nm for a Z -cut crystal. When the initial Er film thickness is below this limit, the post-VTE does not induce formation of ErNbO₄ precipitate and the diffused surface retains high quality with a root mean square roughness <3 nm. Depending on the VTE condition adopted, the VTE results in the increase of ([Li]+[Er])/[Nb] ratio in the diffused layer from congruent point (94.5%) to 97.4%–99.4%. Secondary ion mass spectrometry study shows that the post-VTE does not affect the Gauss nature of the Er profile, but leads to the increase of diffusion depth by as much as 1.6 μm. In comparison with the standard Er diffusion, the post-VTE results in the decrease of Er diffusivity by three to nine times. The higher the VTE temperature is, the lower the Er diffusivity is. In addition, the post-VTE also results in definite reduction of OH⁻ content in crystal, slight lengthening of lifetime and slight narrowing of linewidth of Er³⁺ emission at 1530 nm.     

The application of complex Pade approximants to reflection atoptical waveguide facets

We demonstrate that the numerical instabilities associated with the use of the standard real Pade approximation for the reflection operator can be avoided through either a complex Pade expression or a branch-cut rotation in the complex plane     

Interacting with infotainment applications: navigation patterns and mental models

This article investigates the way users interact with typical multimedia infotainment applications. The focus is on the development over time of their navigation behaviours in the information structure and their mental models of it. The experiment involved a multimedia infotainment (CD-i) title with some 150 information items. Subjects were asked to perform a series of exploration, search and drawing tasks; sessions were concluded with an interview and a reconstruction task. Objective navigational data were compared with subjective results concerning the users' mental models, using the terminology of the navigational framework of Edwards and Hardman. It was found that, after 1 hour, only 25% of the information items had been explored. Subjects use the first 20-30 minutes of explorative interaction time to discover the (local) structures in the title. They then start to observe the presentations in a more content-related way. The development of the user's mental model appears to proceed relatively steadily. The perceived distance between information elements mainly depends on the number of steps to be taken.     

High-performance CMOS current comparator

A new high-performance CMOS current comparator is proposed. By adding two inverters in the feedback loop of Traff's comparator, the proposed comparator exhibits significant speed improvement especially for low input currents. Simulated in a 0.18 mum CMOS technology, the comparator achieves a 0.6 ns delay for a 100 nA input current at 1.8 V supply, which is about eight times faster than Traff's comparator.     

Praseodymium Rare Earth Doped Tellurite Glasses

Praseodymium (Pr3+)-doped tellurite glasses suitable for planar waveguide device applications at 1.3μm operation have been fabricated and characterized optically. The maximum phonon band of undoped glasses is at 738 cm-1, and the emission from the Pr3+: 1G4→3H5 transition is at 1.33 μm wavelength with a spectral bandwidth of 100nm,The lifetime of the 1G4 level is ～24 us, and the quantum efficiency is ～ 2.6 % which is similar to that in fluorozirconate glasses. The resonant energy transfer between Pr3+ and Yb3+ in tellurite glasses has been investigated. Energy absorbed by Pr3+ is transferred efficiently to Yb3+, and fluorescence around 1.00 μm is observed.     

Parental language and verbal responsiveness to children in crowded homes.

This article is a secondary data analysis of the University of Kansas Language Acquisition Project, which intensively studied, on a regular basis, parent and child language from age 6 months to 30 months. The association between residential density and parent–child speech was examined. Parents in crowded homes speak in less complex, sophisticated ways with their children compared with parents in uncrowded homes, and this association is mediated by parental responsiveness. Parents in more crowded homes are less verbally responsive to their children. This in turn accounts for their simpler, less sophisticated speech to their children. This mediational pathway is evident with statistical controls for socioeconomic status. This model may help explain prior findings showing a link between residential crowding and delayed cognitive development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Polyphase SC IIR Hubert transformer with reduced sensitivity tofinite gain and bandwidth

A polyphase switched-capacitor (SC) IIR Hubert transformer with reduced sensitivity to finite opamp gain and bandwidth is proposed for high frequency applications. Low sensitivity is achieved by applying a predictive correlated-double-sampling (CDS) technique. Theoretical analysis and SWITCAP simulation results are given     

Relaxation of operational amplifier parameters after pulsed electron beam irradiation

The relaxation of operational amplifier parameters (offset voltage and differential gain) with time after pulsed electron beam irradiation has been studied as a function of total dose and amplifier type. Four types of operational amplifiers were studied viz., general purpose bipolar input (μA 741), super-beta transistor input (LM 308), JFET input (LF 356) and MOSFET input (CA 3140) from different vendors. The experiments were carried out mainly using 500 ns pulses from a Linear Accelerator. The study, the first of its kind, shows that while the electrical transient at the output of the operational amplifier recovers in a few milliseconds, relaxation of parameters can take several to several tens of seconds. This relaxation is attributed to the build up and/or anneal of damage in the oxide or at the interface of the internal transistor structures. The change and relaxation of parameters depend on operational amplifier type and total dose, and can have significant effects in certain application domains as illustrated by the response of a thermocouple amplifier after pulsed irradiation.