Strongly index-guided II-VI laser diodes

Ridge-waveguide laser diodes based on Be-chalcogenides have been fabricated by reactive ion etching and planarization with polyimide. Etching close to or even through the active layer is demonstrated to suppress the current spreading efficiently; resulting in a significant reduction of the threshold current as compared to gain-guided structures. This allows the fabrication of narrow, strongly index-guided II-VI laser diodes with a ratio between the vertical and the lateral far-field angle of, e.g., 1.2:1 for L_m=1 μm     

A comparison of three predictors of an individual's memory performance: The individual's feeling of knowing versus the normative feeling of knowing versus base-rate item difficulty.

Compared the memory performance predictions of 168 undergraduates with normative item-difficulty predictions and with normative feeling-of-knowing (FOK) predictions. Ss attempted to recall the answers to general-information questions, made FOK judgments on nonrecalled items, and were subsequently administered a criterion test (relearning, perceptual identification, or 1 of 2 versions of recognition). Results indicate that, for predicting an S's criterion performance, the S's own FOK predictions were intermediate between 2 kinds of normative predictions: Ss' FOK predictions were more accurate than predictions derived from normative FOK ratings but were less accurate than predictions derived from base-rate item difficulty (normative probabilities of correct recall). Subsidiary analyses showed that factors other than unreliability were responsible for the partial inaccuracy of Ss' FOK. Possible ways to improve the accuracy of an individual's FOK predictions are discussed. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Very Large Rashba Spin–Orbit Splitting in HgTe Quantum Wells

A large Rashba spin splitting has been observed in the first conduction subband of n-type modulation doped HgTe quantum wells with an inverted band structure via an investigation of Shubnikov–de Haas oscillations as a function of gate voltage. Self-consistent Hartree calculations of the band structure based on an 8 × 8 k p model quantitatively describe the experimental results. It has been shown that the heavy-hole nature of the H1 conduction subband greatly influences the spatial distribution of electrons in the quantum well and also enhances the Rashba spin splitting at large electron densities. These are unique features of type III heterostructures in the inverted band regime. The k ³ dispersion predicted by an analytical model is a good approximation of the self-consistent Hartree calculations for small values of the in-plane wave vector k . This is in contrast to the commonly used k dispersion for the conduction subband in type I heterojunctions.