Toy model of harmonic and sum frequency generation in 2D dielectric nanostructures

Optical nonlinearities of matter are often associated with the response of individual atoms. Here, using a toy oscillator model, we show that in the confined geometry of a two-dimensional dielectric nanoparticle a collective nonlinear response of the atomic array can arise from the Coulomb interactions of the bound optical electrons, even if the individual atoms exhibit no nonlinearity. We determine the multipole contributions to the nonlinear response of nanoparticles and demonstrate that the odd order and even order nonlinear electric dipole moments scale with the area and perimeter of the nanoparticle, respectively.

Broadband Active Control of Transverse Scattering from All-Dielectric Nanoparticle

Steering electromagnetic scattering by subwavelength objects is usually accompanied by the excitation of electric and magnetic modes. The Kerker effect, which relies on the precise overlapping between electric and magnetic multipoles, is a potential approach to address this challenge. However, fundamental limitations on the reconfigurability and tunability challenge their future implementation in practical applications. Here, we demonstrate a design approach by applying coherent control to a silicon nanodisk. By utilizing an experimentally feasible two-wave excitation, this coherent light-by-light control enables a highly reconfigurable, broadband, and tunable transverse scattering, extending the feasibility of unidirectional scattering in various practical scenarios, including on-chip integrations and optical communications.

Third-harmonic generation in optical nanoantennas: efficiency enhancement

Optical nanoantennas have attracted a lot of research interest over the last decade owing to their unique characteristics in concentrating far-field radiation into the sub-wavelength dimensions. Also, they have been recently utilized to enhance the functionality of nonlinear optical devices. By inserting a dielectric nanoparticle within the gap of a dipole nanoantenna, the third-harmonic generation (THG) emission can be boosted. In this study, we simulate dipole and bowtie nanoantennas and compare their THG output spectra with and without the presence of indium tin oxide (ITO) nanocrystal in the nanoantennas gap. The results show that with proper design of the nanoantenna and changing the geometry from the dipole to the bowtie shape as well as inserting the ITO nanocrystal, the THG efficiency can be enhanced by a factor of three, which is higher than the dipole counterpart reported in recent established works. Our work opens a new window to generate more efficient nonlinear phenomena at nanoscale devices.

Mathematical Model of a Nanosensor Based on Optical Tweezers

The paper considers the conditions for capturing a dielectric nanoparticle in a liquid by an optical tweezers trap. It is shown that the displacement of a nanoparticle from the equilibrium position under the action of a local physical field not associated with a laser trap shaper can be used to create a nanosensor for fields of physical or chemical origin.