Single emitters coupled to bow-tie nano-antennas

Abstract

Approaching a metallic tip to a single quantum emitter quenches the photolumi- nescence by opening non-radiative decay channels for the excited-state. This is one of the main problems in nano-optics research which prohibits optical studies on single emitters in contact with the tip with high resolution and high sensitivity. In this thesis I have shown that a bowtie nanoantenna can be used to overcome the quenching problem at the single chromophore level. Bowtie antenna tip in- teracts with the dipole of the single emitter. This is most probably the ¯rst study on this type of measurements which opens new pathways for many disciplines. Semiconductor nanocrystals were selected as a single emitter system due to their relatively high photo-stability. Based on °uorescence confocal studies, satura- tion behavior of single CdSefZnSg nanocrystal (NC) is studied under one- and two-photon excitation. In one-photon excitation (1PE) laser wavelength of 532 nm and in two-photon excitation (2PE) laser wavelength of 830 nm were used to excite the °uorophore. Due to the broad distribution in photoluminescence (PL) intensity of nanocrystals, power dependence studies were done based on an average over » 90 nanocrystals. Using focused ion beam, bowtie antennas are sculptured at the apices of silicon nitride AFM tips, which were fully-coated with a homogeneous layer of 40 nm of aluminum ¯lm. Details of structuring procedures used to fabricate well-de¯ned bowtie antennas with smallest possible feedgaps are described. Interaction of bowtie nanoantennas with single semicon-