Abstract

Plasmonic Zero Waveguide Modes and Radiative Decay Engineering of Quantum

Emitters

by

David Cota Gonzalez

This paper documents an investigation of plasmonic behavior and the application of plasmonic phenomena with the intended purpose of fabricating and manufacturing a novel zero-mode waveguide (ZMW). The conventional ZMW can focus incident light to tiny volumes on the order of zeptoliters (zL) in magnitude. This ability to focus light beyond the diffraction limit is promising for single molecule detection (SMD) particularly when investigating a sample of µM concentrations or beyond.

While the prospect of having the excitation light intensity focused to zL volumes is desirable for SMD, the observer still requires that the intensity of light emissions from the molecule under investigation be sufficiently larger than the noise from the excitation light source, any fluorophores beyond the observation volume and other light emissions which may disrupt the sample study. The solutions under investigation may be susceptible to quenching; thus, the waveguide must be designed so as to apply a maximum intensity into a volume of minimal size all while detecting the enhanced emissions without damaging the sample.

A conventional ZMW consisting of a 50nm diameter cylindrical etch of a 100nm thick Aluminum (Al) metal film lying atop a glass substrate produces zL-effective observation volumes.[16] We proceeded to design and simulate ZMW structures consisting of two or more metallic columns standing in a rectangular etch of a heterogeneous stack — Gold and Aluminum — atop a glass substrate. The waveguide takes advantage of plasmonic devices’ capacity to both confine light and also enhance the fluorescence signal emanating from the confined volume.