Recent results have shown unprecedented control over separation distances between two metallic elements hundreds of nanometers in size, underlying the effects of free-electron nonlocal response also at mid-infrared wavelengths. Most of metallic systems, however, still suffer from some degree of inhomogeneity due to fabrication-induced surface roughness. Nanoscale roughness in such systems might hinder the understanding of the role of microscopic interactions. Here we investigate the effect of surface roughness in coaxial nanoapertures resonating at mid-infrared frequencies. We show that, although random roughness shifts the resonances in an unpredictable way, the impact of nonlocal effects can still be clearly observed. Roughness-induced perturbation on the peak resonance of the system shows a strong correlation with the effective gap size of the individual samples. Fluctuations due to fabrication imperfections then can be suppressed by performing measurements on structure ensembles in which averaging over a large number of samples provides a precise measure of the ideal system's optical properties.
|Original language||English (US)|
|Number of pages||6|
|State||Published - Apr 15 2020|
Bibliographical noteFunding Information:
F.V.-C. and J.P. acknowledge support from the AFOSR Grant No. FA9550-19-1-0240. D.Y. and S.-H.O. acknowledge support from the National Science Foundation (NSF ECCS 1809723 and ECCS 1809240) and Sanford P. Bordeau Endowed Chair at the University of Minnesota. D.R.S. acknowledges funding from AFOSR (Grant No. FA9550-18-1-0187).
© 2020 American Chemical Society.
- coaxial aperture
- epsilon-near-zero mode
- hydrodynamic model
- nonlocal response
- surface roughness