Title: Extraordinary optical transmission in nanopatterned ultrathin metal films without holes

Abstract

In this study, we experimentally and theoretically demonstrate that a continuous gold film on a periodically textured substrate exhibits extraordinary optical transmission, even though no holes were etched in the film. Our film synthesis started by nanoimprinting a periodic array of nanocups with a period of ~750 nm on a polystyrene film over a glass substrate. A thin non-conformal gold film was sputter-deposited on the polystyrene by angle-directed deposition. The gold film was continuous with spatial thickness variation, the film being thinnest at the bottom of the nanocup. Measurements revealed an extraordinary transmission peak at a wavelength just smaller than the period, with an enhancement of ~2.5 compared to the classically expected value. Scattering matrix simulations model well the transmission and reflectance measurements when an ultrathin gold layer (~5 nm), smaller than the skin depth is retained at the bottom of the nanocups. Electric field intensities are enhanced by >100 within the nanocup, and ~40 in the ultrathin gold layer causing transmission through it. We show a wavelength red-shift of ~30 nm in the extraordinary transmission peak when the nanocups are coated with a thin film of a few nanometers, which can be utilized for biosensing. The continuous corrugated metalmore » films are far simpler structures to observe extraordinary transmission, circumventing the difficult process of etching the metal film. Such continuous metal films with ultrathin regions are simple platforms for non-linear optics, plasmonics, and biological and chemical sensing.« less

Authors:

Peer, Akshit ^[1]; Biswas, Rana ^[1]

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+ Show Author Affiliations

1. Iowa State Univ., Ames, IA (United States); Ames Lab., Ames, IA (United States)

Publication Date:

Mon Feb 01 00:00:00 EST 2016

Research Org.:

Ames Laboratory (AMES), Ames, IA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1239840

Report Number(s):

IS-J-8934
Journal ID: ISSN 2040-3364; NANOHL

Grant/Contract Number:  

CMMI-1265844; AC02-05CH11231; AC02-07CH11358

Resource Type:

Accepted Manuscript

Journal Name:

Nanoscale

Additional Journal Information:

Journal Volume: 8; Journal Issue: 8; Journal ID: ISSN 2040-3364

Publisher:

Royal Society of Chemistry

Country of Publication:

United States

Language:

English

Subject:

77 NANOSCIENCE AND NANOTECHNOLOGY