title: Nonlinear chiro-optical amplification by plasmonic nanolens arrays formed via directed assembly of gold nanoparticles.
abstract: Metal nanoparticle assemblies are promising materials for nanophotonic applications due to novel linear and nonlinear optical properties arising from their plasmon modes. However, scalable fabrication approaches that provide both precision nano- and macroarchitectures, and performance commensurate with design and model predictions, have been limiting. Herein, we demonstrate controlled and efficient nanofocusing of the fundamental and second harmonic frequencies of incident linearly and circularly polarized light using reduced symmetry gold nanoparticle dimers formed by surface-directed assembly of colloidal nanoparticles. Large ordered arrays (>100) of these C∞v heterodimers (ratio of radii R1/R2 = 150 nm/50 nm = 3; gap distance l = 1 ± 0.5 nm) exhibit second harmonic generation and structure-dependent chiro-optic activity with the circular dichroism ratio of individual heterodimers varying less than 20% across the array, demonstrating precision and uniformity at a large scale. These nonlinear optical properties were mediated by interparticle plasmon coupling. Additionally, the versatility of the fabrication is demonstrated on a variety of substrates including flexible polymers. Numerical simulations guide architecture design as well as validating the experimental results, thus confirming the ability to optimize second harmonic yield and induce chiro-optical responses for compact sensors, optical modulators, and tunable light sources by rational design and fabrication of the nanostructures.
authors: Air Force Research Laboratory , 2941 Hobson Way, Wright Patterson Air Force Base, Ohio 45433, United States.
authors: Sushmita
authors: S
authors: Biswas
authors: Xiaoying
authors: X
authors: Liu
authors: Jeremy W
authors: JW
authors: Jarrett
authors: Dean
authors: D
authors: Brown
authors: Vitaliy
authors: V
authors: Pustovit
authors: Augustine
authors: A
authors: Urbas
authors: Kenneth L
authors: KL
authors: Knappenberger
authors: Paul F
authors: PF
authors: Nealey
authors: Richard A
authors: RA
authors: Vaia
keywords: Directed assembly; circular dichroism; gold heterodimers; nanolens; second harmonic generation