Theory and experiments of Bragg cavity modes in passive and active metallic nanoslit array devices

Abstract

Metallic nanoslit arrays exhibit several unique, surprising, and useful properties, such as resonant enhanced transmission and resonant local field enhancements. Here we present both a theoretical study of these static properties, as well as experiments showing the utilization of these features combined with active optical media. We develop an approximated, simple closed-form model for predicting and explaining the general emergence of enhanced transmission resonances through metallic gratings, in various configurations and polarizations. This model is based on an effective index approximation and it unifies in a simple way the underlying mechanism of all forms of enhanced transmission in such structures as emerging from standing wave resonances of the different diffraction orders of periodic structures. The known excitation of surface plasmon polaritons or slit cavity modes emerges as a limiting case of a more general condition. We also use this understanding of the resonant behavior of nanoslit arrays to design and fabricate such structures with embedded nanocrystal quantum dots, and show beaming of nonclassical light to a narrow angle of less than 4 deg, as well as an enhancement of the two-photon upconversion fluorescence process by a factor of ∼400.

Photoconductive Terahertz Near-Field Detector with a Hybrid Nanoantenna Array Cavity

“…Within the photonic structure, the gate pulse photons first encounter the array of sparse nanoantennas, which scatter the incident photons (38)(39)(40)(41). The fundamental antenna resonance (along the antenna length) is designed to match the optical excitation wavelength  .…”

“…Within the photonic structure, the gate pulse photons first encounter the array of sparse nanoantennas, which scatter the incident photons. − The fundamental antenna resonance (along the antenna length) is designed to match the optical excitation wavelength λ o . Photons scattered into angles larger than the critical angle become trapped in the high-index LT GaAs layer due to total internal reflection (Figure d), whereas photons that experience small-angle or no scattering are reflected by the DBR stack (Figure d).…”