Optical surface waves in periodic layered media

A generalized analysis of wave propagation in periodic layered media is applied to the special case of optical surface waves. These waves, confined to the interface between a periodic layered medium and a homogeneous medium, are formally analogous to electronic surface states in crystals. Single-mode surface-wave propagation along the surface of a GaAs-AlGaAs multilayer stack (grown by molecular-beam epitaxy) has been observed experimentally

Electromagnetic propagation in periodic stratified media. I. General theory

The propagation of electromagnetic radiation in periodically stratified media is considered. Media of finite, semi-infinite, and infinite extent are treated. A diagonalization of the unit cell translation operator is used to obtain exact solutions for the Bloch waves, the dispersion relations, and the band structure of the medium. Some new phenomena with applications to integrated optics and laser technology are presented

Diffraction efficiency of strong volume holograms

We investigate the diffraction efficiency of strong volume holograms in which the coupling parameter is several times that needed for maximum diffraction efficiency. We discuss the implications of our findings on photorefractive implementations of various neural network systems

Prediction of Pesticide Distribution on the Ground Based on Boom Sprayer Movements

Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is a Technical Paper from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 4 (2002): D. Pochi and D. Vannucci. Prediction of Pesticide Distribution on the Ground Based on Boom Sprayer Movements. Vol. IV. December 2002

Dynamics of grating formation in photovoltaic media

The Kukhtarev equations are solved taking into account the photovoltaic effect and different boundary conditions. In the case of open circuit, the voltage across the crystal is found to vary with a time scale similar to the photorefractive time constant. This effect explains the dynamic behavior observed experimentally

Phase-locked sustainment of photorefractive holograms using phase conjugation

A method for sustaining multiply exposed photorefractive holograms, in a phase-locked fashion, by using a pair of phase-conjugating mirrors is described. It is shown that a steady state exists where the overall diffraction efficiency is independent of the number of holographic exposures and the final holograms are exactly in phase with the initial ones. Both analytical and experimental results are presented

Frozen light in periodic stacks of anisotropic layers

We consider a plane electromagnetic wave incident on a periodic stack of dielectric layers. One of the alternating layers has an anisotropic refractive index with an oblique orientation of the principal axis relative to the normal to the layers. It was shown recently (A. Figotin and I. Vitebskiy, Phys. Rev. E68, 036609 2003) that an obliquely incident light, upon entering such a periodic stack, can be converted into an abnormal axially frozen mode with drastically enhanced amplitude and zero normal component of the group velocity. The stack reflectivity at this point can be very low, implying nearly total conversion of the incident light into the frozen mode with huge energy density, compared to that of the incident light. Supposedly, the frozen mode regime requires strong birefringence in the anisotropic layers - by an order of magnitude stronger than that available in common anisotropic dielectric materials. In this paper we show how to overcome the above problem by exploiting higher frequency bands of the photonic spectrum. We prove that a robust frozen mode regime at optical wavelengths can be realized in stacks composed of common anisotropic materials, such as YVO₄, LiNb, CaCO₃, and the like.Comment: to be submitted to Phys. Rev.

Proposal of an inspection methodology for pneumatic drills

In recent years the contribution of pneumatic drills to the dispersion in the environment of insecticides particles derived from the abrasion of dressed seeds has been studied and different devices aimed at reducing the dust drift have been proposed. The European Directive 128/09 on the sustainable use of pesticides aims to achieve a more sustainable use of pesticides and introduces the compulsory inspection of equipment for pesticide application.At the present time, an official methodology to inspect both new and in use drills and the effectiveness of drift reducing devices is still lacking. The aim of the paper is to present a simplified methodology that can be applied to periodical inspection of the above mentioned equipment. Such a methodology has been elaborated basing on the results of a three-year activity, carried out at CRA-ING within the APENET research project