Cavity Induced Extraordinary Optical Transmission and Active Modulation with Graphene

TL;DR

This paper reports a novel cavity-induced extraordinary optical transmission phenomenon below the first order surface plasmon frequency, achieved by a gold-silicon-air cavity, with active modulation using graphene at terahertz frequencies.

Contribution

It introduces a new EOT mechanism via a bound surface state in a Fabry-Perot cavity, enabling broadband transmission and active modulation with low bias graphene.

Findings

EOT phenomenon extended into sub-wavelength region by 20%.

Achieved broadband EOT with a 10-fold bandwidth increase.

Demonstrated active modulation of transmittance from 0.5 to 0.25 at 500 GHz.

Abstract

Extraordinary optical transmission (EOT) is a phenomenon of exceptional light transmission through a metallic film with hole arrays enhanced by surface plasmon (SP) resonance, which stimulates renewed research hotspots in metamaterials, subwavelength optics, and plasmonics. Below the frequency of the first order SP mode, f_pl0, the metallic film typically shows strong reflection and no EOT. Here, we report an unusual EOT phenomenon below fpl0, i.e., beyond the long-held spectral boundary of classic EOTs. It is induced by a novel bound surface state in a Fabry-Perot(F-P) cavity comprising a holey gold film and a silicon-air interface. By tailoring the cavity length, EOT phenomenon has been pushed deep into the sub-wavelength region by a factor of as large as 20%, and EOT frequency comb with cavity function has been achieved. Due to the enhanced slow-wave effect as the frequency approaches fpl0, the cavity induced EOT gradually merges with the first order SP EOT. Distinguishing from the classic EOT phenomenon, no transmission zero is found between these two EOTs, which dramatically broadens the EOT bandwidth by a factor of 10 at terahertz (THz) frequencies. Furthermore, the EOT transmittance is actively modulated with graphene, achieving a large modulation range from 0.5 to 0.25 under a sub-volt bias from -0.3 to 0.5 V at 500 GHz. To the best of the authors' knowledge, both the modulation range and the low bias are among the best for active EOT devices with graphene to date. Such a structure provides a new strategy for miniaturizing sensing devices, high-power sources, and broadband photonics as well as their active control in the THz regime.