Plasmonic Parametric Resonance (PPR) provides a novel method to excite plasmonic modes that are typically difficult to access by direct illumination due to linear or angular momentum mismatch between the modes and the incident field. By temporally modulating the permittivity near a plasmonic structure, PPR enables energy transfer into these modes, overcoming the constraints of energy and momentum conservation. This paper reviews the theory of PPR, explores its implementation via three-wave mixing interactions, and discusses applications in optical limiting through reverse saturable absorption processes. Additionally, we present a time-domain perturbation formalism to address pump saturation, depletion effects, and cascaded second-order nonlinear interactions, highlighting the potential for intermodal conversion.
KEYWORDS: Plasmonics, Physical coherence, Modulation, Energy transfer, Polarization density, Electric fields, Polarization, Particles, Modulation frequency
Dynamic electromagnetic structures, which vary in both space and time, enable unique operational regimes and effects unattainable in static systems due to modal orthogonality constraints. This paper presents a theoretical framework for intermodal energy transfer in time-varying plasmonic structures. By identifying a suitable mechanism for permittivity modulation, we develop a time-domain formalism to analyze the evolution of the dielectric polarization density in the system. Through a perturbative approach, we derive closed-form solutions that describe the energy transfer between a directly excited dipolar mode and a higher-order subradiant mode. We also demonstrate that the modal amplitudes reach a steady state under optimal modulation conditions, which maximize the amplitude of the high-order mode. Finally, we propose a coherent control strategy to enhance the conversion efficiency to higher-order modes.
We present the theory of parametrically resonant surface plasmon polaritons. We show that a temporal modulation of the dielectric properties of the medium adjacent to a metallic surface can lead to efficient energy injection into the surface plasmon polariton modes supported at the interface. When the permittivity modulation is induced by a pump field exceeding a certain threshold intensity, such field undergoes a reverse saturable absorption process. We introduce a time-domain formalism to account for pump saturation and depletion effects. Finally, we discuss the viability of these effects for optical limiting applications.
We present the theory of parametrically resonant surface plasmon polaritons. We show that a temporal modulation of the dielectric properties of the medium adjacent to a metallic surface can lead to efficient energy injection into the surface plasmon polariton modes supported at the interface. When the permittivity modulation is induced by a pump field exceeding a certain threshold intensity, such field undergoes a reverse saturable absorption process. We introduce a time-domain formalism to account for pump saturation and depletion effects. Finally, we discuss the viability of these effects for optical limiting applications. the abstract two lines below author names and addresses.
We discuss a new class of nonlinear absorbers termed Plasmonic Parametric Absorbers (PPA) relying on the recently introduced concept of Plasmonic Parametric Resonance (PPR). In contrast with conventional localized plasmonic resonances, whereby modes are excited directly by an external field of frequency and spatial profile matching those of a given mode of the plasmonic particle, PPR is a form of amplification in which a pump field transfers energy to a mode in an indirect fashion. In PPR in fact the modes of a plasmonic structure are amplified by means of a temporal permittivity modulation of the background medium interacting with an appropriate pump field. Such permittivity variation translates into a modulation of the modal resonant frequency, and under specific conditions amplification can occur. Among the unique characteristics of PPR is the possibility of accessing modes of arbitrarily high order with a simple spatially uniform pump, provided that such pump exceeds a certain intensity threshold. It is such threshold behavior that can lead to PPAs, a type of nonlinear metamaterial absorber with rather unique properties. PPAs exhibit a reverse saturable absorption behavior whereby an incident field that is parametrically resonant with one or more of the modes of a plasmonic particle experiences a strongly enhanced absorption whenever its intensity exceeds the relevant PPR threshold. Such effect makes PPAs very promising candidates for optical limiting applications, in addition of being of fundamental interest in the emerging field of nonlinear plasmonics.
Transparent conductive oxides (TCOs) have attracted a great deal of interest in the past few years as alternative materials for plasmonics in the near-infrared region. In contradistinction to noble metals, TCOs such as Indium Tin Oxide (ITO) display a vast tunability of their optical and electronic properties via doping and electric bias. The possibility of actively switching between a low-loss dielectric regime and a high-absorption plasmonic regime has been exploited for the design and realization of ultra-compact electro-absorption modulators, as well as for the proposal of novel multimode modulator architectures. At the heart of the applications outlined before is the electron accumulation layer that is created at the interface between a TCO layer and an insulator under appropriate electric bias. Here a rigorous study of the electromagnetic characteristics of these electron accumulation layers is presented. The unique modal properties of these systems that emerge as a consequence of the graded nature of their permittivity profiles are highlighted. The concept of Accumulation-layer Surface Plasmons is introduced and the conditions for the existence or for the suppression of surface-wave eigenmodes are analyzed.
The optical response of noble-metal nanoparticles in the visible spectrum is characterized by the presence localized surface plasmon resonances. Localized surface plasmons are non-propagating coherent oscillations of free-carriers coupled to the electromagnetic field arising as a consequence of confinement effects in sub-wavelength nanoparticles. Plasmonic nanoparticles in general support an infinite discrete set of orthogonal localized surface plasmon modes, yet in the case of structures of deep-subwavelength dimensions only the lowest order resonances of dipolar nature can be effectively excited by an incident electromagnetic wave. By reciprocity such high-order modes tend to be subradiant and therefore difficult to observe in far-field. Here we discuss the novel localized surface plasmon dynamics that emerge when the electromagnetic properties of the plasmonic particle or of the background medium vary in time. We show in particular that such temporal permittivity variations lift the orthogonality of the localized surface plasmon modes and introduce coupling among different angular momentum states. Exploiting such dynamics we show how surface plasmon amplification of high order resonances can be achieved under the action of a spatially uniform optical pump of appropriate frequency.
Shannon Blunt, Christopher Allen, Emily Arnold, Richard Hale, Rongqing Hui, Shahriar Keshmiri, Carlton Leuschen, Jilu Li, John Paden, Fernando Rodriguez-Morales, Alessandro Salandrino, James Stiles
Radar research has been synonymous with the University of Kansas (KU) for over half a century. As part of this special session organized to highlight significant radar programs in academia, this paper surveys recent and ongoing work at KU. This work encompasses a wide breadth of sensing applications including the remote sensing of ice sheets, autonomous navigation methods for unmanned aerial vehicles (UAVs), novel laser radar capabilities, detection of highenergy cosmic rays using bistatic radar, different forms of waveform diversity such as MIMO radar and pulse agility, and various radar-embedded communication methods. The results of these efforts impact our understanding of the changing nature of the environment, address the proliferation of unmanned systems in the US airspace, realize new sensing modalities enabled by the joint consideration of electromagnetics and signal processing, and greater facilitate radar operation in an increasingly congested and contested spectrum.
Transformation optics provides a powerful tool for controlling electromagnetic fields and designing novel optical devices. In practice, devices designed by this method often require material optical properties that cannot be achieved at visible or near IR light wavelengths. The conformal transformation technique can relax this requirement to isotropic dielectrics with gradient refractive indices. However, there are few effective methods for achieving large arbitrary refractive index gradients at large scales, so the limitation for building transformation optical devices is still in fabrication. Here we present a photoelectrochemical (PEC) silicon etching technique that provides a simple and effective way to fully control the macro scale profiles of refractive indices by structuring porous silicon on the nanoscale. This work is, to our knowledge, the first demonstration of using light to control porosity in p-type silicon. We demonstrate continuous index variation from n = 1.1 to 2, a range sufficient for many transformation optical devices. These patterned porous layers can then be lifted off of the bulk silicon substrate and transferred to other substrates, including patterned or curved substrates, which allows for the fabrication of three dimensional or other more complicated device designs. We use this technique to demonstrate a gradient index parabolic lens with dimensions on the order of millimeters, which derives its properties from the distribution of nanoscale pores in silicon.
The optical excitation of high-order plasmonic resonant modes in nanostructures is important for the enhancement of light-matter interactions at the nanoscale. Due to the fast spatial variation of the electromagnetic field distribution associated with high-order modes, their excitation by conventional optical methods is extremely challenging. Here we describe a novel nonlinear scheme devised to access high-order plasmonic resonances. The proposed method is based on the temporal modulation of the permittivity of the medium surrounding a plasmonic nanoparticle. Analytical results are presented for the case of spherical nanoparticle demonstrating the effectiveness of the proposed method.
Metamaterials enable the control of electromagnetic fields over sub-wavelength scales. In addition to field enhancement effects, metamaterials offer an unprecedented control over the phase of electromagnetic fields, which is of paramount importance in coherent nonlinear optical processes. Here we explore frequency conversion effects in nanostructured media. The coherent interactions arising in ensembles of nanostructures lead to a very rich phenomenology and a unique set of degrees of freedom with which to engineer the overall nonlinear response of the system. In particular we here discuss novel phase-matching schemes in ensembles of discrete nonlinear scatterers. Keywords: Metamaterials, Plasmonics, Nonlinear Optics.
We provide a brief report on our recent work on dielectric and metallic colloidal nanosuspensions with negative polarizability where we observed robust propagation of self-trapped light over a long distance. Our results open up new opportunities in developing soft-matter systems with tunable optical nonlinearities.
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