Nonlinear Anisotropic Dielectric Metasurfaces for Ultrafast Nanophotonics

137

123

Resonant dielectric nanoparticles made of materials with large positive dielectric permittivity, such as Si, GaP, GaAs, have become a powerful platform for modern light science, enabling various fascinating applications in nanophotonics and quantum optics. In addition to light localization at the nanoscale, dielectric nanostructures provide electric and magnetic resonant responses throughout the visible and infrared spectrum, low dissipative losses and optical heating, low doping effect, and absence of quenching, which are interesting for spectroscopy and biosensing applications. This review presents state‐of‐the‐art applications of optically resonant high‐index dielectric nanostructures as a multifunctional platform for light–matter interactions. Nanoscale control of quantum emitters and applications for enhanced spectroscopy including fluorescence spectroscopy, surface‐enhanced Raman scattering, biosensing, and lab‐on‐a‐chip technology are surveyed. The theoretical background underlying these effects is described, realizations of specific resonant dielectric nanostructures and hybrid excitonic systems are overviewed, and an outlook of the challenges in this field, which remain open to future research, is provided.

Section: Introductionmentioning

confidence: 99%

Spectroscopy and Biosensing with Optically Resonant Dielectric Nanostructures

Krasnok

Caldarola

Bonod

et al. 2018

137

123

“…The change of the permittivity due to the FC response can be described using the Drude model as

Δ ε_{FC} = - \frac{N_{e–h} e^{2}}{m_{opt}^{*} ε_{0} (ω^{2} + i ω τ_{normald}^{- 1})} = - \frac{ω_{normalp}^{2}}{ω^{2} + i ω τ_{normald}^{- 1}}

where ε 0 is the permittivity of vacuum; e is the electron charge; and ω is the angular frequency of THz waves.

ω_{normalp} = \sqrt{N_{e‐h} e^{2} / ε_{0} m_{opt}^{*}}

is the plasma frequency,

m_{opt}^{*} = 0.15 m_{normale}

and τ d = 80 fs are given above.…”

Section: Resultsmentioning

confidence: 99%

All‐Optical and Ultrafast Tuning of Terahertz Plasmonic Metasurfaces

Cai

Huang

et al. 2018

controlling, [3] metalens, [4] and so on. Among these metasurfaces, noble metals such as gold and silver are the most common candidates for electromagnetic resonance, such as split-ring resonators, [5,6] cut wire antennas, [7] and fishnet structures. [8] Nevertheless, the metallic structures suffer from not only intrinsic absorption losses that severely limit their efficiency, but also their permanent optical properties which are difficult to be tuned by external stimuli. A feasible way to solve these problems is to employ tunable metasurfaces consisting of active media. Many kinds of active metasurfaces have been reported, including graphene, [9][10][11] transparent conducting oxides, [12] as well as various semiconductors like Si, [13,14] InAs, [15] and GaAs. [16,17] With the rapid development of active metasurfaces, numerous studies have been focused on the modulation of terahertz (THz) waves. Considerable research efforts have been devoted to the dynamic tuning of THz waves using different stimuli, such as thermal heating, [18] electrical triggering, [19] and optical excitation. [20] While intensive amplitude, phase, and polarization control of the terahertz waves have been investigated by plenty of research, achieving ultrafast and efficient modulation remains an open challenge in the THz regime. Graphene has been widely used to form plasmonic metasurfaces, as it is capable of tuning THz waves by optical pumping and electrostatic gating. [21,22] Nonetheless, the electronic doping of graphene reduces the modulation speed, and the low absorption of light due to its monolayer feature limits the modulation depth. GaAs and Si have been demonstrated to control THz waves using all-optical-induced free carrier (FC) dynamics in the semiconductors, respectively. [16,23] But the delay of photoexcited FCs is relatively long (≈1 ns) in these intrinsic semiconductors, which is an essential limitation for ultrafast modulation. More recently, hybrid metasurfaces, by integrating an ultrathin layer of spin-coated solution-processed perovskite with metallic resonators, achieved ultrafast all-optical switching with a time constant of 500 ps. [24,25] However, the photoactivity of the solution-processed perovskite is weak as the differential transmission under femtosecond pulse excitation is only about 5%. A detailed analysis of the previous THz tunable metasurfaces can be found in Table S1 in the Supporting Information.As the backbone of modern technology, Si not only plays a dominant role in electronics, but also emerges as an excellent Metasurfaces have been widely used to manipulate terahertz waves due to their great potential for achieving unique electromagnetic responses. However, to realize ultrafast and efficient control of the light in active metasurfaces is still a critical challenge. Here, an ultrafast tunable metasurface which consists of ion-implanted and annealed silicon disk array is experimentally demonstrated in the terahertz range. By utilizing the optical-pump terahertz-probe spectroscopy, the absolute transmis...

“…This thermo‐optic effect of Si nanostructures has been utilized to realize spatial light modulation around the communication wavelengths at frequencies up to 10 kHz . On the other hand, optical carrier injection provides a more attractive approach for achieving response tuning of dielectric metasurfaces in an efficient manner by using femtosecond (fs) laser pulses that lead to ultrafast free carrier density change in semiconductors as well as other possible physical processes, such as two‐photon absorption (TPA) and lattice heating . Exploiting the ultrafast TPA process, Shcherbakov et al have identified a 65 fs long transmission switching effect in a hydrogenated amorphous silicon (a‐Si:H) metasurface around the magnetic Mie resonance of the nanodisk resonators.…”

Section: Tuning Dielectric Metasurfaces With Variable Constituent Promentioning

confidence: 99%

Recent Progress in Active Optical Metasurfaces

Kang

Jenkins

Werner

2019

154

Evolving from metamaterials, optical metasurfaces not only inherit their unprecedented flexibility in tailoring light–matter interaction but also the generally fixed response determined by the metaatoms' geometries—an undesirable property that hinders the development of practical metadevices. Consequently, novel optical metasurfaces that can be tuned in an active manner are intensively studied in recent years. Due to their optically thin structures, optical metasurfaces present unique characteristics in the realization of dynamic tuning. In this review, a detailed summary of the recent advances in active optical metasurfaces is provided including discussions reviewing a variety of active materials and approaches that enable faster, stronger, and more accurate tuning. Beyond facilitating practical metadevices, studies of active metasurfaces have, and will continue to deepen the understandings of the interaction between light and nanostructured photonic architectures and to promote the development of nanofabrication techniques involving high‐complexity.