Generation of 2nd harmonic light from noncentrosymmetric material

Abstract

Over the past few years significant progress has been made ininvestigations into the synthesis of nanowires of various materials andtheir applications to nanoscale electronics, optical devices and sensingsystems; nevertheless, a major hurdle facing the developers of theintegrated nanowire systems is organizing, manipulating, or controllingthe placement of large numbers of nanowires. These problems can besolved by using a shadow deposition method for fabrication ofpolycrystalline metallic nanowires. This technique uses topographicalfeatures of ridge-to-valley to expose specific areas of the alkali halidesubstrates in order to grow the nanowire arrays. Nanowires of large areasshow a preference for formation along exposed steps in the atomicstructure of the substrate. The minimum widths of the obtained nanowiresare less than 40 nm.The strongly geometrical shape, high aspect ratios, and nanoscalecross-section of metallic nanowires can be expected to affect opticalproperties through confinement effects. Optical properties of the obtainedmetallic nanowires are then investigated by studies of linear reflectivityspectra, linear absorption spectra, and second harmonic generationspectra. Theoretical calculation by Maxwell-Garnett model and finitedifferencetime-domain method are also represented for predicting thereflectivity, absorption and the electric field distributions close to thewires. With experimental and theoretical studies, it is discovered thatthere are differences of optical properties among these metallicnanowires. These will be one of the most important issues whenconsidering the types of materials used in current applications anddevelopment of new applications.