Strain Sensitivity in the Nitrogen 1s NEXAFS Spectra of Gallium Nitride

The Nitrogen 1s near edge X-ray absorption fine structure (NEXAFS) of gallium nitride (GaN) shows a strong natural linear dichroism that arises from its anisotropic wurtzite structure. An additional spectroscopic variation arises from lattice strain in epitaxially grown GaN thin films. This variation is directly proportional to the degree of strain for some spectroscopic features. This strain variation is interpreted with the aid of density functional theory calculations.Comment: 20 pages, 6 figures, http://www.sciencedirect.com/science/article/pii/S0169433214015980 or Applied Surface Science 316, 232 (2014

Plasmonic, photonic, or hybrid? Reviewing waveguide geometries for electro-optic modulators

Electro-optic modulators are key elements in high-speed optical telecommunication links and preferably rely on materials with a linear electro-optic effect. Choosing adequate waveguide geometries is a key challenge in the design of electro-optic modulators. While all-dielectric geometries promise high-speed modulation with low propagation loss, their modulation efficiency suffers from low confinement and weak electrical fields, resulting in lengthy devices. Plasmonic geometries, on the other hand, allow for most compact devices featuring highest electro-optical bandwidths, but at the cost of higher losses. Alternatively, hybrid photonic–plasmonic solutions open a sweet spot for high-speed modulators with moderate loss. In this review, we discuss the three waveguide types by analyzing and comparing their performance and their sensitivity to variations in geometry with respect to a choice of the electro-optical Pockels-effect material.ISSN:2378-096