Photonics2015, 2(2), 568-593; doi:10.3390/photonics2020568 (registering DOI) - published 22 May 2015 Show/Hide Abstract
Abstract: Hybridized decaying oscillations in a nanosystem of two coupled elements—a quantum emitter and a plasmonic nanoantenna—are considered as a classical effect. The circuit model of the nanosystem extends beyond the assumption of inductive or elastic coupling and implies the near-field dipole-dipole interaction. Its results fit those of the previously developed classical model of Rabi splitting, however going much farther. Using this model, we show that the hybridized oscillations depending on the relationships between design parameters of the nanosystem correspond to several characteristic regimes of spontaneous emission. These regimes were previously revealed in the literature and explained involving semiclassical theory. Our original classical model is much simpler: it results in a closed-form solution for the emission spectra. It allows fast prediction of the regime for different distances and locations of the emitter with respect to the nanoantenna (of a given geometry) if the dipole moment of the emitter optical transition and its field coupling constant are known.
Photonics2015, 2(2), 553-567; doi:10.3390/photonics2020553 (registering DOI) - published 22 May 2015 Show/Hide Abstract
Abstract: Nanoscale light fields near nanoplasmonic objects can be highly structured and can contain highly-subwavelength features. Here, we present the results of our search for the simplest plasmonic system that contains, and can be used to control, the smallest such optical feature: an optical singularity. Specifically, we study the field around subwavelength holes in a metal film and look for polarization singularities. These can be circular (C)-points, at which the polarization is circular, or linear (L)-lines, where the polarization is linear. We find that, depending on the polarization of the incident light, two or three holes are sufficient to create a wealth of these singularities. Moreover, we find for the two-hole system that C-points are created in multiples of eight. This can be explained using symmetry arguments and conservation laws. We are able to predict where these singularities are created, their index and the topology of the field surrounding them. These results demonstrate the promise of this plasmonic platform as a tool for studying and controlling fundamental properties of light fields and may be important to applications where control over these properties is required at the nanoscale.
Abstract: In this contribution, we review and discuss our recent results on the design of optical scattering cancellation devices based on an array of plasmonic nanoparticles. Starting from two different analytical models available to describe its electromagnetic behavior, we show that a properly designed array of plasmonic nanoparticles behaves both as an epsilon-near-zero metamaterial and as a reactive metasurface and, therefore, can be successfully used to reduce the optical scattering of a subwavelength object. Three different typologies of nanoparticle arrays are analyzed: spherical, core-shell, and ellipsoidal nanoparticles. We prove, both theoretically and through full-wave simulations, that such nanostructures can be successfully used as a cloaking device at ultraviolet and optical frequencies.
Abstract: We investigate and compare the performance of wavelength conversion for two different non-return-to-zero (NRZ) modulation formats at 40 Gb/s: on off keying (OOK) and differential phase-shift keying (DPSK). To achieve wide wavelength coverage and integrability, we use a dual pump scheme exploiting four-wave mixing in semiconductor optical amplifiers. For phase stability, we use a quantum-dash mode-locked laser (QD-MLL) as a multi-wavelength source for the dual pumps, with tunability provided by the output filter. The significant sidelobes of the DPSK spectrum (relative to OOK) require the balancing of the pump proximity to the original signal (facilitating high conversion efficiency) with the signal degradation from the pump spectrum overlapping the converted DPSK signal. We achieve a conversion efficiency near –3.6 dB for OOK and –5.4 dB for DPSK across a 12 nm tuning range with low input powers (1 dBm). We measure bit error rate (BER) and obtain error free transmission (BER < 10−9) with a power penalty less than 2 dB for OOK and 3 dB for DPSK.
Abstract: This paper studies constructing advanced effective materials using arrays of circular radially-anisotropic (RA) cylinders. Homogenization of such cylinders is considered in an electrodynamic case based on Mie scattering theory. The homogenization procedure consists of two steps. First, we present an effectively isotropic model for individual cylinders, and second, we discuss the modeling of a lattice of RA cylinders. Radial anisotropy brings us extra parameters, which makes it possible to adjust the desired effective response for a fixed frequency. The analysis still remains simple enough, enabling a derivation of analytical design equations. The considered applications include generating artificial magnetism using all-dielectric cylinders, which is currently a very sought-after phenomenon in optical frequencies. We also study how negative refraction is achieved using magnetodielectric RA cylinders.
Abstract: On-chip nonreciprocal light transport holds a great impact on optical information processing and communications based upon integrated photonic devices. By harvesting gain-saturation nonlinearity, we recently demonstrated on-chip optical asymmetric transmission at telecommunication bands with superior nonreciprocal performances using only one active whispering-gallery-mode microtoroid resonator, beyond the commonly adopted magneto-optical (Faraday) effect. Here, detailed theoretical analysis is presented with respect to the reported scheme. Despite the fact that our model is simply the standard coupled-mode theory, it agrees well with the experiment and describes the essential one-way light transport in this nonreciprocal device. Further discussions, including the connection with the second law of thermodynamics and Fano resonance, are also briefly made in the end.