Engineering Photon Emission Statistics of Single Nanocrystals: From Quantum to Classical

Abstract

The development of stable and bright colloidal nanocrystals has long held promise for quantum photonics, optoelectronics, and bioimaging. Although isolated colloidal nanoparticle can be used for single-photon emission,these often suffer from blinking and reduced performance under high excitation fluences. To overcome these challenges, I designed a novel quantum dot architecture that achieves high-fidelity single-photon emission even in the absence of spectral filtering at a high excitation fluence by successfully rejecting the extra multiexcitons in the nanocrystal with the help of Auger recombination.

However, persistent blinking behaviour in these dots necessitated further investigation. To address this, I developed the non-blinking variety of the engineered quantum dots by achieving exquisite control over the surface chemistry. The strain profiles of these nanocrystals were determined and found to be exhibiting minimal surface strain. These new variants of the engineered nanocrystals show absence of fluorescence OFF state at both conditions of rapid re-excitation and variable power along with retaining its single-photon emission behaviour.

Furthermore, I have explored photon statistics in the case of conventional fluorescent markers used in laser microscopy. Because of the presence of exciton-exciton interactions, the luminosity is reduced by a substantial amount at high excitation fluences. To address this, I synthesized a distinct set of emitters capable of efficiently decreasing the interaction by achieving a net zero coulombic interaction between them. Optical studies on these emitters indicate significantly reduced excitonic interactions, favouring multiphoton emission events. Increase in luminosity and stability is observed in single particles and ensembles for this new class of nanocrystals. Together, these studies highlight the pathway toward high-performance, applicationspecific colloidal nanocrystals.