Semi-analytical approach to short-wavelength dispersion and modal properties of photonic crystal fibers

We consider photonic crystal fibers made from arbitrary base materials and derive a unified semi-analytical approach for the dispersion and modal properties which applies to the short-wavelength regime. In particular we calculate the dispersion and the effective index and comparing to fully-vectorial plane wave simulations we find excellent agreement. We also calculate asymptotic results for the mode-field diameter and the V-parameter and from the latter we predict that the fibers are endlessly single mode for a normalized air-hole diameter smaller than 0.42, independently of the base material.Comment: 3 pages including 3 figures. Accepted for Opt. Let

Introduction

Crime-preventing neurointerventions (CPNs) are increasingly being used or advocated for crime prevention. There is increasing use of testosterone-lowering agents to prevent recidivism in sexual offenders, and strong political and scientific interest in developing pharmaceutical treatments for psychopathy and anti-social behaviour. Recent developments suggest that we may ultimately have at our disposal a range of drugs capable of suppressing violent aggression, and it is not difficult to imagine possible applications of such drugs in crime prevention. But should neurointerventions be used in crime prevention, and may the state ever permissibly impose CPNs as part of the criminal justice process? It is widely thought that preventing recidivism is one of the aims of criminal justice, yet existing means of pursuing this aim are often poorly effective, restrictive of basic freedoms, and harmful. Incarceration, for example, tends to be disruptive of personal relationships and careers, detrimental to physical and mental health, highly restrictive of freedom of movement and association, and rarely more than modestly effective at preventing recidivism. Neurointerventions hold the promise of preventing recidivism in ways that are more effective and more humane, but the use of CPNs in criminal justice raises several ethical concerns. CPNs could be highly intrusive and may threaten fundamental human values, such as bodily integrity and freedom of thought, and humanity has a track record of misguided, harmful, and unwarrantedly coercive use of neurotechnological ‘solutions’ to criminality. This collection brings together original contributions from emerging scholars and internationally renowned moral and political philosophers to address these issues

Localization of light on a cone: theoretical evidence and experimental demonstration for an optical fiber

The classical motion at a conical surface is bounded at one (narrower) side of the cone and unbounded at the other. However, it is shown here that a dielectric cone with a small half-angle gamma can perform as a high Q-factor optical microresonator which completely confines light. The theory of the discovered localized conical states is in excellent agreement with experimental data. It provides both a unique approach for extremely accurate local characterization of optical fibers (which usually have gamma ~10^-5 or less) and a new paradigm in the field of high Q-factor resonators

Investigation into the role of sodium chloride deposited on oxide and metal substrates in the initiation of hot corrosion

Sodium chloride is deposited on the surface of alumina substrates and exposed to air containing 1% SO2 at temperatures between 500 C and 700 C. In all cases the sodium chloride was converted to sodium sulfate. The volatilization of sodium chloride from the original salt particles was responsible for the development of a uniform coating of sodium sulfate on the alumina substrate. At temperatures above 625 C, a liquid NaCl-Na2SO4 autectic was formed on the substrate. The mechanisms for these reactions are given. One of the main roles of NaCl in low temperature hot corrosion lies in enabling a corrosive liquid to form

Two-dimensional photonic band-gap structures as quasi-metals

By considering waves that propagate out of the transverse plane, we show that common high index materials (eg GaAs) with a 2D array of air holes can act in some ways like a 3D photonic band-gap structure. In particular, we describe a dielectric "quasi-metal" that reflects all propagating light incident from free space