Abstract

Optical nonlinear properties of cusps formed at the junction between two circular apertures in a metal film have been studied by scanning confocal microscopy. For gold, both second harmonic and broadband emission are enhanced when the pump polarization is directed across the gap between cusps, similar to the behavior of the recently studied bowtie antennas and apertures. However, field enhancements are also present when the polarization is perpendicular to the gap direction. A quantitative explanation of the observed relative signal intensities requires considering both field concentration near cusps and shape resonances of the entire structure. The occurrence of broadband emission from the cusp region when Al is used instead of Au indicates that broadband emission is the result of additional mechanisms besides pure two-photon luminescence.

Latest Publications

Dragnea Research is at the forefront of multidisciplinary innovation, exploring the intersection of nanoscale optics, quantum photonics, physical virology, and bio-architected hybrid materials with 3D nanoscale order. Their latest publications highlight groundbreaking advancements in fields such as self-assembly, optics and spectroscopy, and the physical manipulation of virus-like particles (VLPs) for chemical imaging and surface modifications. Drawing from their expertise in using near-field scanning techniques and laser-induced effects, these works showcase how nanoscale phenomena can be harnessed for applications in material science, virology, and beyond. The accompanying visual mosaic underscores the diverse range of their research, from probing molecular dynamics to the development of 3D-ordered structures, all united by a commitment to pushing the boundaries of applied and theoretical science.