Antenna Coupled Photoemission From Single Quantum Emitters

Download or read book Antenna-coupled Photoemission from Single Quantum Emitters written by Palash Bharadwaj and published by . This book was released on 2012 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Optical antennas are analogs of their radiowave and microwave counterparts, and can be defined as devices that serve to efficiently convert free-propagating optical radiation to localized energy, and vice-versa. Colloidal metal nanoparticles with their strong plasmonic optical response offer a convenient realization of optical antennas. Such nanoparticle antennas serve to spatially enhance and localize fields, and modify the excitation rate and the radiative decay rate when placed close to single emitters (molecules, quantum dots, etc.). In addition, they can also cause undesirable losses, leading to an increase in the non-radiative decay rates of these emitters. This interplay of rates can lead to a strong modification of the emission characteristics over the intrinsic behavior. We study photoemission from single emitters coupled to antennas of different geometries made from colloidal metal nanoparticles. We demonstrate enhancements of fluorescence from single quantum emitters by a factor 10 to 100, with the highest enhancements resulting for molecules with very low intrinsic quantum yields. Such enhancements afford an improvement in resolution for fluorescence imaging down to [lambda]/40. We also investigate changes to fluorescence blinking of a colloidal quantum dots (QD) coupled to an antenna, as a function of antenna-QD distance. We find that power-law blinking is preserved unaltered even as the antenna drastically modifies the excitonic decay rate in the QD, and reduces the blinking probability. This resilience of the power-law to change provides evidence that blinking statistics are not swayed by environment-induced variations in kinetics, and offers clues towards identifying the as-yet unknown mechanism behind universal fluorescence intermittency. Finally, in analogy with traditional electromagnetic antennas, we excite prototypical optical antennas using electrons (current) instead of photons (fields). We excite localized plasmons using low energy tunneling electrons, which are then converted to propagating far-field photons. We demonstrate electrically excited photon emission from a smooth gold film, an extended gold nanowire and from isolated gold nanoparticles. We thus show that electron tunneling provides a non-optical, voltage-controlled and low-energy pathway for photoemission on the nanoscale"--Page vi-vii.