Emission enhancement in dielectric nanocomposites

We consider emitting nanoparticles in dielectric nanocomposites with varying refractive index contrast and geometry. For that we develop a simple and universal method to calculate the emission enhancement in nanocomposites that employs solely the calculation of the effective refractive index and electric field distributions from three quasistatic calculations with orthogonal polarizations. The method is exemplified for dilute nanocomposites without electromagnetic interaction between emitting particles as well as for dense nanocomposites with strong particle interaction. We show that the radiative decay in dielectric nanocomposites is greatly affected by the shape and arrangement of its constituents and give guidelines for larger enhancement

Comment on 'Nonreciprocal light propagation in a silicon photonic circuit'

We show that the structure demonstrated by Feng et al. (Reports, 5 August 2011, p. 729) cannot enable optical isolation because it possesses a symmetric scattering matrix. Moreover, one cannot construct an optical isolator by incorporating this structure into any system as long as the system is linear and time-independent and is described by materials with a scalar dielectric function

Nonreciprocal nanophotonic structures

Diese Arbeit präsentiert neue Konzepte für die Integration von nicht-reziproken optischen Komponenten. Es werden ein Isolator, ein Zirkulator, ein magneto-optischer Schalter sowie ein Faraday Rotator vorgestellt.This work proposes new concepts for integrated nonreciprocal optical components. An isolator, a circulator, a magneto-optical switch as well as a Faraday rotator are presented

Limit of efficiency of generation of hot electrons in metals and their injection inside a semiconductor using a semiclassical approach

Hot electron generation in a metal and injection into a semiconductor is a crucial mechanism to convert sub band gap photons into free electrical charges inside a semiconductor. This process is of paramount importance for solar photocatalysis since the semiconductors involved often have a band gap too large for direct excitation with sun light, thus requiring a carrier transfer from an adjacent effective absorber, which in our case is a metal, to the semiconductor in order to initiate the envisaged photochemical reactions. Single interaction of a hot electron with a metal-semiconductor boundary is described by Fowler's law. In nanometer sized metals hot electrons, before they lose their energy, can interact several times with the boundary, which increases the probability of injection. To understand the efficiency of this process, to find ways to optimize it, and to determine its limits, an electron transport model based on a Monte Carlo approach is proposed. The numerical calculations provide an in-depth understanding of the impact of size and shape of the metal on the injection efficiency. Values are obtained that exceed the usual efficiency limits described by Fowler's theory