Technion – Israel Institute of Technology

About: Technion – Israel Institute of Technology is a education organization based out in Haifa, Israel. It is known for research contribution in the topics: Population & Nonlinear system. The organization has 31714 authors who have published 79377 publications receiving 2603976 citations. The organization is also known as: Technion Israel Institute of Technology & Ṭekhniyon, Makhon ṭekhnologi le-Yiśraʼel.

Topological insulator laser: Theory

Abstract: INTRODUCTION Topological insulators emerged in condensed matter physics and constitute a new phase of matter, with insulating bulk and robust edge conductance that is immune to imperfections and disorder To date, topological protection is known to be a ubiquitous phenomenon, occurring in many physical settings, ranging from photonics and cold atoms to acoustic, mechanical, and elastic systems So far, however, most of these studies were carried out in entirely passive, linear, and conservative settings RATIONALE We propose topological insulator lasers: lasers whose lasing mode exhibits topologically protected transport without magnetic fields Extending topological physics to lasers is far from natural In fact, lasers are built on foundations that are seemingly inconsistent with the essence of topological insulators: They require gain (and thus are non-Hermitian), they are nonlinear entities because the gain must be saturable, and they are open systems because they emit light These properties, common to all lasers, cast major doubts on the possibility of harnessing topological features to make a topological insulator laser Despite this common mindset, we show that the use of topological properties leads to highly efficient lasers, robust to defects and disorder, with single-mode lasing even at conditions high above the laser threshold RESULTS We demonstrate that topological insulator lasers are theoretically possible and experimentally feasible We consider two configurations involving planar arrays of coupled active resonators The first is based on the Haldane model, archetypical for topological systems The second model, geared toward experiment, constitutes an aperiodic array architecture creating an artificial magnetic field We show that by introducing saturable gain and loss, it is possible to make these systems lase in a topological edge state In this way, the lasing mode exhibits topologically protected transport; the light propagates unidirectionally along the edges of the cavity, immune to scattering and disorder, unaffected by the shape of the edges Moreover, we show that the underlying topological properties not only make the system robust to fabrication and operational disorder and defects, they also lead to a highly efficient single-mode lasing that remains single-mode even at gain values high above the laser threshold The figure describes the geometry and features of a topological insulator laser based on the Haldane model while adding saturable gain, loss, and an output port The cavity is a planar honeycomb lattice of coupled microring resonators, pumped at the perimeter with a lossy interior We show that under these conditions, lasing occurs at the topological edge mode, which has unidirectional flux and is extended around the perimeter with almost-uniform intensity The topological cavities exhibit higher efficiency than the trivial cavity, even under strong disorder For the topological laser with a small gap, the topological protection holds as long as the disorder level is smaller than the gap size DISCUSSION The concept of the topological insulator laser alters current understanding of the interplay between disorder and lasing, and opens exciting possibilities at the interface of topological physics and laser science, such as topologically protected transport in systems with gain We show here that the laser system based on the archetypal Haldane model exhibits topologically protected transport, with features similar to those of its passive counterpart This behavior means that this system is likely to have topological invariants, despite the nonhermiticity Technologically, the topological insulator laser offers an avenue to make many semiconductor lasers operate as one single-mode high-power laser The topological insulator laser constructed from an aperiodic array of resonators was realized experimentally in an all-dielectric platform, as described in the accompanying experimental paper by Bandres et al

The effects of leadership dimensions, safety climate, and assigned priorities on minor injuries in work groups

Abstract: This study is based on three premises: (a) Leadership style affects the level of concern for subordinate safety; (b) Concern for safety, operationalized with supervisory practices, provides the source for safety climate perceptions; and (c) Safety priority as assigned by higher superiors influences supervisory safety practice independently of leadership style. Assigned safety priority was expected to moderate the relationship between leadership style and injury rate in organizational subunits, with safety climate mediating this leadership–injury relationship due to its demonstrable effect on safety behavior. A within-group split-sample analysis of 42 work groups, coupled with prospective design, indicated that transformational and constructive leadership predicted injury rate, while corrective leadership provided indirect, conditional prediction. Leadership effects were moderated by assigned safety priorities and mediated by commensurate safety-climate variables. The results suggest that transformational and transactional leadership provide complementary modes of (mediated and moderated) influence on safety behavior of group members. Copyright © 2002 John Wiley & Sons, Ltd.

A double-blind, delayed-start trial of rasagiline in Parkinson's disease.

Abstract: In this double-blind trial, we examined the possibility that rasagiline has diseasemodifying effects in Parkinson’s disease. A total of 1176 subjects with untreated Parkinson’s disease were randomly assigned to receive rasagiline (at a dose of either 1 mg or 2 mg per day) for 72 weeks (the early-start group) or placebo for 36 weeks followed by rasagiline (at a dose of either 1 mg or 2 mg per day) for 36 weeks (the delayed-start group). To determine a positive result with either dose, the early-start treatment group had to meet each of three hierarchical end points of the primary analysis based on the Unified Parkinson’s Disease Rating Scale (UPDRS, a 176-point scale, with higher numbers indicating more severe disease): superiority to placebo in the rate of change in the UPDRS score between weeks 12 and 36, superiority to delayed-start treatment in the change in the score between baseline and week 72, and noninferiority to delayed-start treatment in the rate of change in the score between weeks 48 and 72. Results Early-start treatment with rasagiline at a dose of 1 mg per day met all end points in the primary analysis: a smaller mean (±SE) increase (rate of worsening) in the UPDRS score between weeks 12 and 36 (0.09±0.02 points per week in the early-start group vs. 0.14±0.01 points per week in the placebo group, P = 0.01), less worsening in the score between baseline and week 72 (2.82±0.53 points in the early-start group vs. 4.52±0.56 points in the delayed-start group, P = 0.02), and noninferiority between the two groups with respect to the rate of change in the UPDRS score between weeks 48 and 72 (0.085±0.02 points per week in the early-start group vs. 0.085±0.02 points per week in the delayed-start group, P<0.001). All three end points were not met with rasagiline at a dose of 2 mg per day, since the change in the UPDRS score between baseline and week 72 was not significantly different in the two groups (3.47±0.50 points in the earlystart group and 3.11±0.50 points in the delayed-start group, P = 0.60). Conclusions Early treatment with rasagiline at a dose of 1 mg per day provided benefits that were consistent with a possible disease-modifying effect, but early treatment with rasagiline at a dose of 2 mg per day did not. Because the two doses were associated with different outcomes, the study results must be interpreted with caution. (ClinicalTrials. gov number, NCT00256204.)