Niladri S. Karan

Quantum Optical Signature of Plasmonically Coupled Nanocrystal Quantum Dots

Small clusters of two to three silica-coated nanocrystals coupled to plasmonic gap-bar antennas can exhibit photon antibunching, a characteristic of single quantum emitters. Through a detailed analysis of their photoluminescence emissions characteristics, it is shown that the observed photon antibunching is the evidence of coupled quantum dot formation resulting from the plasmonic enhancement of dipole-dipole interaction.

Coupling single giant nanocrystal quantum dots to the fundamental mode of patch nanoantennas through fringe field

Through single dot spectroscopy and numerical simulation studies, we demonstrate that the fundamental mode of gold patch nanoantennas have fringe-field resonance capable of enhancing the nano-emitters coupled around the edge of the patch antenna. This fringe-field coupling is used to enhance the radiative rates of core/thick-shell nanocrystal quantum dots (g-NQDs) that cannot be embedded into the ultra-thin dielectric gap of patch nanoantennas due to their large sizes. We attain 14 and 3 times enhancements in single exciton radiative decay rate and bi-exciton emission efficiencies of g-NQDs respectively, with no detectable metal quenching. Our numerical studies confirmed our experimental results and further reveal that patch nanoantennas can provide strong emission enhancement for dipoles lying not only in radial direction of the circular patches but also in the direction normal to the antennas surface. This provides a distinct advantage over the parallel gap-bar antennas that can provide enhancement only for the dipoles oriented across the gap.

Plasmonic giant semiconductor nanocrystals with enhanced light output and suppressed blinking for biomedical applications

Hybrid semiconductor-metal nanoparticles are of both fundamental and practical interest. CdSe semiconductor nanocrystal quantum dots (NQDs) are emissive following direct absorption of photons, while nanosized metal structures exhibit plasmonic absorption and light scattering. In a hybrid nanoscale architecture, both optical phenomena can be integrated as metal-semiconductor coupling via non-radiative energy transfer and modifications of the radiative decay rates through Purcell effect, alter the emission mechanism resulting in a range of effects from photoluminescence (PL) quenching to enhancement.