Modeling Gold:Vanadium Dioxide Plasmon Nanomodulators

Modeling Gold-Vanadium Dioxide Plasmon Nanomodulators

 Autumn Douthitt, Christina McGahan and Richard Haglund

        On-chip communication is currently the principal limiting factor in computer speed.  Optical modulators could replace electronic switches and interconnects on computer chips, carrying data by light pulses instead of electrical signals.  This would greatly increase speed while reducing electrical resistance and heat generation. Plasmonic devices built from metal nanostructures can be used to transmit and manipulate light on a sub-wavelength scale, reducing the modulator footprint. In this research project, the goal is to improve upon signal processing using optical modulators by simulating electromagnetic waves propagating through a gold:vanadium dioxide (Au:VO₂) dimer placed on a glass substrate using a finite-difference, time-domain (FDTD) modeling software (Lumerical^® Solutions). Such dimers have recently been described as efficient photon modulators.¹ Normalized data after repeating the Au: VO₂ computations reproduced those results. We hypothesized that dimers comprising gold nanorods and VO₂ nanodisks would produce narrower resonances than the nanodisk dimer, resulting in higher contrast and optimized signal switching. FDTD simulations assessed the ideal aspect ratios for nanorods placed on a glass substrate. The results harvested from rod and disk simulations compared favorably with experimental observations.² Working towards combining these studies, we have found that small (4nm) gaps between VO₂ disks and Au particles with higher aspect ratios affect the plasmon resonance shift as the VO₂ switches, seen previously for disk dimers.¹

1. Appavoo, K. and Haglund, R. F., “Polarization selective phase-change nanomodulator,” Scientific Reports 4, 6771 (2014).
2. Sönnichsen C, Franzl T, Wilk T, von Plessen G, Feldmann J. “ Drastic reduction of plasmon damping in gold nanorods,” Phys Rev Lett 2002, 88:077402.

Research partially supported by the Office of Science, United States Department of Energy (DE-FG02-01ER45916)