In the last decade, solid-state nanopores have been intensively investigated as label-free detectors of for single biological entities, such as protein chains or DNA molecules. With this approach, single entities are typically driven through a nanopore by applying an external electrical potential. However, this method cannot enable control over the speed of translocation, thus limiting the signal integration time. The most explored approach to introduce control of the translocation speed is based on trapping. In particular, a long acquisition time can be obtained by trapping a nanoparticle tagged with molecules close to a nanopore. The trapping phenomena can be generated by means of external stimuli such as light excitation and magnetic field application, obtaining respectively the so-called optical and magnetic trapping. Magnetic trapping, in particular, has been less explored but can be a useful approach to obtain very large trapping forces without interfering with other optical exitations that can be used for spectroscopic purposes. Here, we will briefly summarize the major examples of magnetic trapping approaches reported so far in solid-state nanopore technology.
Hyperbolic nanoparticles provide a versatile platform to widely tune light-matter interactions. Active nanophotonics can be realized by controlling the optical properties of materials with external magnetic fields. Here, we explore the influence of optical anisotropy on the magneto-optical response of hyperbolic nanoparticles across the visible and near infrared spectral range. By using a perturbative approach, we establish a model where the magneto-optical activity of the system is described in terms of the coupling of fundamental electric and magnetic dipole modes, which are induced by the hyperbolic dispersion, with a static magnetic field. Finally, an analytical model is established in the framework of Mie theory to describe the magneto-optical response and identify the contribution of electric and magnetic modes to the total spectrum.
In the framework of magneto-photonics, the optical properties of a material can controlled by an external magnetic field, providing active functionalities for applications, such as sensing and nonreciprocal optical isolation. For noble metals in particular, the inherently weak magnetooptical coupling of the bulk material can be greatly enhanced via excitation of localized surface plasmons (LSP) in nanostructured samples. Hyperbolic metamaterials therein provide the ideal platform to tune the plasmonic properties via careful design of the effective permittivity tensor. Here, we report on the magnetic circular dichroism of electric and magnetic dipole modes of a type II hyperbolic metasurface. Disk-shaped nanoparticles consist in stacks of alternating dielectric and metallic layers. Using an effective medium theory, we show that the optical properties of the system can be perfectly described by an anisotropic homogenized permittivity. Magnetic circular dichroism spectroscopy experiments are compared with plain gold disk samples and reveal a broadband magneto-optical response across the visible and near infrared spectral range. In particular, derivative-like spectral signatures at the resonances of the nanoparticles prove the induced dichroism for the two modes of the system. Results are interpreted in terms of magnetically induced spatial confinement/broadening of circular currents in the nanoparticles and are compared with a comprehensive numerical model based on the finite elements method using the real dimensions of the nanostructure. Spherical particles are employed as an analytical model system, allowing to generalize the contribution of electric and magnetic modes to the total magneto-optical response. More in detail, interaction cross sections are calculated as a weighted sum of the corresponding Mie coefficients. Utilizing a perturbative approach, we describe the magneto-optical effect in terms of linear changes in the cyclotron frequency of free charge carriers in the metal. By comparing our analytical model with full-wave numerical results, we can identify the contribution of electric and magnetic dipole modes to the spectrum and reproduce the spectral line shape we observe in the experiments for the hyperbolic nanoparticles.
We report on ultrafast opto-acoustic modulation of light reflectance in artificial epsilon-near-zero metamaterials made of two layers of Ag separated by an Al2O3 layer. By means of non-degenerate two color pump-probe experiments we demonstrate an optically induced acoustic modulation of the reflectance up to 20% via generation of acoustic waves inside the cavity upon mechanical expansion of the metal due to hot electron-phonon coupling nonlinearity in the Ag layers. The presented architecture opens the pathway towards novel routes to exploit light-matter interactions for opto-acoustic modulation at GHz frequencies. Moreover, our system can be designed to work in transmission geometry and is very versatile in terms of shifting the presented properties along a broad range of wavelengths, from UV to mid-IR. Our approach, beyond light-driven information processing, might impact also opto-mechanics, light-driven phonon induced up conversion mechanisms, non-linear optical and acoustic properties of materials, energy harvesting, and heat-assisted ultrafast magneto-optical recording.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.