Quantum interference in the presence of a resonant medium.

Interaction of light with media often occurs with a femtosecond response time. Its measurement by conventional techniques requires the use of femtosecond lasers and sophisticated time-gated optical detection. Here we demonstrate that by exploiting quantum interference of entangled photons it is possible to measure the dephasing time of a resonant media on the femtosecond time scale (down to 100 fs) using accessible continuous wave laser and single-photon counting.

Third-harmonic generation from Mie-type resonances of isolated all-dielectric nanoparticles.

Subwavelength silicon nanoparticles are known to support strongly localized Mie-type modes, including those with resonant electric and magnetic dipolar polarizabilities. Here we compare experimentally the efficiency of the third-harmonic generation from isolated silicon nanodiscs for resonant excitation at the two types of dipolar resonances. Using nonlinear spectroscopy, we observe that the magnetic dipolar mode yields more efficient third-harmonic radiation in contrast to the electric dipolar (ED) mode.

Multifold Enhancement of Third-Harmonic Generation in Dielectric Nanoparticles Driven by Magnetic Fano Resonances.

Strong Mie-type magnetic dipole resonances in all-dielectric nanostructures provide novel opportunities for enhancing nonlinear effects at the nanoscale due to the intense electric and magnetic fields trapped within the individual nanoparticles. Here we study third-harmonic generation from quadrumers of silicon nanodisks supporting high-quality collective modes associated with the magnetic Fano resonance. We observe nontrivial wavelength and angular dependencies of the generated harmonic signal featuring a multifold enhancement of the nonlinear response in oligomeric systems.

Enhanced third-harmonic generation in silicon nanoparticles driven by magnetic response.

We observe enhanced third-harmonic generation from silicon nanodisks exhibiting both electric and magnetic dipolar resonances. Experimental characterization of the nonlinear optical response through third-harmonic microscopy and spectroscopy reveals that the third-harmonic generation is significantly enhanced in the vicinity of the magnetic dipole resonances. The field localization at the magnetic resonance results in two orders of magnitude enhancement of the harmonic intensity with respect to unstructured bulk silicon with the conversion efficiency limited only by the two-photon absorption in the substrate.