"Considered one of the major fields of photonics of the beginning 21st century, plasmonics offers the potential to confine and guide light below the diffraction limit and promises a new generation of ...highly miniaturized photonic devices. Offering both a comprehensive introduction to the field and an extensive overview of the current state of the art,""Plasmonics Fundamentals and Applications""should be of great value to the newcomer and to the experienced researcher.The first part of the book describes the fundamentals of this research area, starting with a review of Maxwell s equations in a form suited to the description of metals. Subsequent chapters introduce the two major ingredients of plasmonics, surface plasmon polaritons at metallic interfaces and localized plasmons in nanostructures. The mathematics of their description, excitation and imaging of the modes are discussed. This part closes with a presentation of electromagnetic surface waves at lower frequencies in the THz and microwave regime, comprising both spoof or designer plasmons and surface phonon polaritons.Building on the fundamentals, the second part discusses some of the most prominent applications of plasmons: Plasmon waveguides, extraordinary transmission through aperturearrays, sensing and surface enhanced Raman scattering, spectroscopy as well as metamaterials. Exemplary studies in each of these fields taken from the original literature are presented."
Semiconducting two-dimensional (2D) crystals such as MoS2 and WSe2 exhibit unusual optical properties that can be exploited for novel optoelectronics ranging from flexible photovoltaic cells to ...harmonic generation and electro-optical modulation devices. Rapid progress of the field, particularly in the growth area, is beginning to enable ways to implement 2D crystals into devices with tailored functionalities. For practical device performance, a key challenge is to maximize light–matter interactions in the material, which is inherently weak due to its atomically thin nature. Light management around the 2D layers with the use of plasmonic nanostructures can provide a compelling solution.
Nanophotonic devices, which control light in subwavelength volumes and enhance light-matter interactions, have opened up exciting prospects for biosensing. Numerous nanophotonic biosensors have ...emerged to address the limitations of the current bioanalytical methods in terms of sensitivity, throughput, ease-of-use and miniaturization. In this Review, we provide an overview of the recent developments of label-free nanophotonic biosensors using evanescent-field-based sensing with plasmon resonances in metals and Mie resonances in dielectrics. We highlight the prospects of achieving an improved sensor performance and added functionalities by leveraging nanostructures and on-chip and optoelectronic integration, as well as microfluidics, biochemistry and data science toolkits. We also discuss open challenges in nanophotonic biosensing, such as reducing the overall cost and handling of complex biological samples, and provide an outlook for future opportunities to improve these technologies and thereby increase their impact in terms of improving health and safety.
Allowing subwavelength-scale-digitization of optical wavefronts to achieve complete control of light at interfaces, metasurfaces are particularly suited for the realization of planar phase-holograms ...that promise new applications in high-capacity information technologies. Similarly, the use of orbital angular momentum of light as a new degree of freedom for information processing can further improve the bandwidth of optical communications. However, due to the lack of orbital angular momentum selectivity in the design of conventional holograms, their utilization as an information carrier for holography has never been implemented. Here we demonstrate metasurface orbital angular momentum holography by utilizing strong orbital angular momentum selectivity offered by meta-holograms consisting of GaN nanopillars with discrete spatial frequency distributions. The reported orbital angular momentum-multiplexing allows lensless reconstruction of a range of distinctive orbital angular momentum-dependent holographic images. The results pave the way to the realization of ultrahigh-capacity holographic devices harnessing the previously inaccessible orbital angular momentum multiplexing.
High refractive index dielectric nanoantennas are expected to become key elements for nonlinear nano-optics applications due to their large nonlinearities, low energy losses, and ability to produce ...high electric field enhancements in relatively large nanoscale volumes. In this work, we show that the nonlinear response from a high-index dielectric nanoantenna can be significantly improved by adding a metallic component to build a metal–dielectric hybrid nanostructure. We demonstrate that the plasmonic resonance of a Au nanoring can boost the anapole mode supported by a Si nanodisk, strongly enhancing the electric field inside the large third-order susceptibility dielectric. As a result, a high third harmonic conversion efficiency, which reaches 0.007% at a third harmonic wavelength of 440 nm, is obtained. In addition, by suitably modifying geometrical parameters of the hybrid nanoantenna, we tune the enhanced third harmonic emission throughout the optical regime. Coupling metallic and dielectric nanoantennas to expand the potential of subwavelength structures opens new paths for efficient nonlinear optical effects in the visible range on the nanoscale.
Metasurfaces based on quasi‐bound states in the continuum (quasi‐BICs) constitute an emerging toolkit in nanophotonic sensing as they sustain high quality factor resonances and substantial near‐field ...enhancements. It is demonstrated that silicon metasurfaces composed of crescent shaped meta‐atoms provide tailored light‐matter interaction controlled by the crescent geometry. Significantly, this metasurface not only exhibits a fundamental quasi‐BIC resonance, but also supports a higher‐order resonance with tunable electromagnetic field enhancement and advantageous properties for sensing. The higher‐order resonance shows twice the sensitivity of the fundamental one for bulk refractive index sensing. It is further demonstrated that both the fundamental and higher‐order resonances can be exploited for sensing ultrathin layers of biomolecules in air and buffer solutions. Specifically, when measuring in buffer solution, the figure of merit of the sensor, defined as the change in the spectral position of the resonance normalized to its full width at half maximum, is a factor of 2.5 larger for the higher‐order resonance when compared to the fundamental one. Due to its high sensitivity and potential for straightforward microfluidic integration, the silicon crescent metasurface is ideally suited for real‐time and in situ biosensing, enabling compact sensing devices for a wide range of diagnostic applications.
An all‐dielectric crescent silicon metasurface serving as an efficient optical sensor is achieved. This sensing platform is driven by quasi‐bound states in the continuum with well‐tailored high quality factors of excited resonances and enhanced near‐fields, thus enabling refractive index sensing and ultrathin biomolecular detection both in air and buffer with high sensitivity and a low detection limit.
The ability to convert low-energy quanta into a quantum of higher energy is of great interest for a variety of applications, including bioimaging, drug delivery and photovoltaics. Although high ...conversion efficiencies can be achieved using macroscopic nonlinear crystals, upconverting light at the nanometre scale remains challenging because the subwavelength scale of materials prevents the exploitation of phase-matching processes. Light-plasmon interactions that occur in nanostructured noble metals have offered alternative opportunities for nonlinear upconversion of infrared light, but conversion efficiency rates remain extremely low due to the weak penetration of the exciting fields into the metal. Here, we show that third-harmonic generation from an individual semiconductor indium tin oxide nanoparticle is significantly enhanced when coupled within a plasmonic gold dimer. The plasmonic dimer acts as a receiving optical antenna, confining the incident far-field radiation into a near field localized at its gap; the indium tin oxide nanoparticle located at the plasmonic dimer gap acts as a localized nonlinear transmitter upconverting three incident photons at frequency ω into a photon at frequency 3ω. This hybrid nanodevice provides third-harmonic-generation enhancements of up to 10(6)-fold compared with an isolated indium tin oxide nanoparticle, with an effective third-order susceptibility up to 3.5 × 10(3) nm V(-2) and conversion efficiency of 0.0007%. We also show that the upconverted third-harmonic emission can be exploited to probe the near-field intensity at the plasmonic dimer gap.
Twisted light, an unbounded set of helical spatial modes carrying orbital angular momentum (OAM), offers not only fundamental new insights into structured light–matter interactions, but also a new ...degree of freedom to boost optical and quantum information capacity. However, current OAM experiments still rely on bulky, expensive, and slow‐response diffractive or refractive optical elements, hindering today's OAM systems to be largely deployed. In the last decade, nanophotonics has transformed the photonic design and unveiled a diverse range of compact and multifunctional nanophotonic devices harnessing the generation and detection of OAM modes. Recent metasurface devices developed for OAM generation in both real and momentum space, presenting design principle and exemplary devices, are summarized. Moreover, recent development of whispering‐gallery‐mode‐based passive and tunable microcavities, capable of extracting degenerate OAM modes for on‐chip vortex emission and lasing, is summarized. In addition, the design principle of different plasmonic devices and photodetectors recently developed for on‐chip OAM detection is discussed. Current challenges faced by the nanophotonic field for twisted‐light manipulation and future advances to meet these challenges are further discussed. It is believed that twisted‐light manipulation in nanophotonics will continue to make significant impact on future development of ultracompact, ultrahigh‐capacity, and ultrahigh‐speed OAM systems‐on‐a‐chip.
Twisted light, an unbounded set of helical spatial modes of electromagnetic light fields, offers both fundamental new insights into structured light–matter interactions and a new degree of freedom to boost optical and quantum information capacity. Recently, the nanophotonics field has transformed the photonic design and unveiled a diverse range of compact and multifunctional nanophotonic materials and devices for twisted‐light manipulation.
We present an all-dielectric germanium nanosystem exhibiting a strong third order nonlinear response and efficient third harmonic generation in the optical regime. A thin germanium nanodisk shows a ...pronounced valley in its scattering cross section at the dark anapole mode, while the electric field energy inside the disk is maximized due to high confinement within the dielectric. We investigate the dependence of the third harmonic signal on disk size and pump wavelength to reveal the nature of the anapole mode. Each germanium nanodisk generates a high effective third order susceptibility of χ(3) = 4.3 × 10–9 esu, corresponding to an associated third harmonic conversion efficiency of 0.0001% at an excitation wavelength of 1650 nm, which is 4 orders of magnitude greater than the case of an unstructured germanium reference film. Furthermore, the nonlinear conversion via the anapole mode outperforms that via the radiative dipolar resonances by about 1 order of magnitude, which is consistent with our numerical simulations. These findings open new possibilities for the optimization of upconversion processes on the nanoscale through the appropriate engineering of suitable dielectric materials.
PDF
