Plasmonic Structure Integrated Single-Photon Detector Configurations to Improve Absorptance and Polarization Contrast

Configurations capable of maximizing both the absorption component of system detection efficiency and the achievable polarization contrast were determined for 1550 nm polarized light illumination of different plasmonic structure integrated superconducting nanowire single-photon detectors (SNSPDs) consisting of p = 264 nm and P = 792 nm periodic niobium nitride (NbN) patterns on silica substrate. Global effective NbN absorptance maxima appear in case of p/s-polarized light illumination in S/P-orientation (γ = 90°/0° azimuthal angle) and the highest polarization contrast is attained in S-orientation of all devices. Common nanophotonical origin of absorptance enhancement is collective resonance on nanocavity gratings with different profiles, which is promoted by coupling between localized modes in quarter-wavelength metal-insulator-metal nanocavities and laterally synchronized Brewster-Zenneck-type surface waves in integrated SNSPDs possessing a three-quarter-wavelength-scaled periodicity. The spectral sensitivity and dispersion characteristics reveal that device design specific optimal configurations exist

Active Individual Nanoresonators Optimized for Lasing and Spasing Operation

Plasmonic nanoresonators consisting of a gold nanorod and a spherical silica core and gold shell, both coated with a gain layer, were optimized to maximize the stimulated emission in the near‐field (NF‐c‐type) and the outcoupling into the far‐field (FF‐c‐type) and to enter into the spasing operation region (NF‐c*‐type). It was shown that in the case of a moderate dye concentra-tion, the nanorod has more advantages: smaller lasing threshold and larger slope efficiency and larger achieved intensities in the near‐field in addition to FF‐c‐type systems’ smaller gain and out-flow threshold, earlier dip‐to‐peak switching in the spectrum and slightly larger far‐field outcou-pling efficiency. However, the near‐field (far‐field) bandwidth is smaller for NF‐c‐type (FF‐c‐type) core–shell nanoresonators. In the case of a larger dye concentration (NF‐c*‐type), although the slope efficiency and near‐field intensity remain larger for the nanorod, the core–shell nanoresonator is more advantageous, considering the smaller lasing, outflow, absorption and extinction cross‐section thresholds and near‐field bandwidth as well as the significantly larger internal and external quantum efficiencies. It was also shown that the strong‐coupling of time‐competing plasmonic modes accompanies the transition from lasing to spasing occurring, when the extinction cross‐section crosses zero. As a result of the most efficient enhancement in the forward direction, the most uni-form far‐field distribution was achieved. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Plasmonic structure integrated single-photon detectors optimized to maximize polarization contrast

Numerical optimization was performed via COMSOL multiphysics to maximize the polarization contrast of superconducting nanowire single photon detectors (SNSPDs). SNSPDs were integrated with four different types of 1D periodic plasmonic structures capable of mediating p-polarized photon selectivity to the niobium-nitride superconducting nanowire pattern. Optimization with two different criteria regarding the maximal tilting resulted in wavelength-scaled periodic integrated structures, which have different geometrical parameters, and exhibit different polar angle dependent optical responses and dispersion characteristics, as well as accompanying near-field phenomena at the extrema. Polarization contrast of 6.4·10^2 and 3.3·10^2/6.9·10^11 and 1.4·10^11/1.8·10^13 and 7.9·10^12/1.9·10^3 and 1.2·10^5 can be achieved in nanocavity-/nanocavity-deflector-/nanocavity-double-deflector-/nanocavity-trench-array-integrated P-SNSPDs optimized with 85° and 80° criterion, regarding the maximal tilting

Improved emission of SiV diamond color centers embedded into concave plasmonic core-shell nanoresonators

Configuration of three different concave silver core-shell nanoresonators was numerically optimized to enhance the excitation and emission of embedded silicon vacancy (SiV) diamond color centers simultaneously. According to the tradeoff between the radiative rate enhancement and quantum efficiency (QE) conditional optimization was performed to ensure ~2-3-4 and 5-fold apparent cQE enhancement of SiV color centers with ~10% intrinsic QE. The enhancement spectra, as well as the near-field and charge distribution were inspected to uncover the physics underlying behind the optical responses. The conditionally optimized coupled systems were qualified by the product of the radiative rate enhancements at the excitation and emission, which is nominated as Px factor. The optimized spherical core-shell nanoresonator containing a centralized emitter is capable of enhancing considerably the emission via bonding dipolar resonance. The Px factor is 529-fold with 49.7% cQE at the emission. Decentralization of the emitter leads to appearance of higher order multipolar modes, which is not advantageous caused by their nonradiative nature. Transversal and longitudinal dipolar resonances of the optimized ellipsoidal core-shell resonator were tuned to the excitation and emission, respectively. The simultaneous enhancements result in 6.2∙10^5 Px factor with 50.6% cQE at the emission. Rod-shaped concave core-shell nanoresonators exploit similarly transversal and longitudinal dipolar resonances, moreover they enhance the fluorescence more significantly due to their antenna-like geometry. Px factor of 8.34∙10^5 enhancement is achievable while the cQE is 50.3% at the emission. The enhancement can result in 2.03∙10^6-fold Px factor, when the criterion regarding the minimum QE is set to 20%