Ph.D Thesis


Ph.D StudentUdi Mizrahi
SubjectTime Resolved Correlation Spectroscopy of Single Photons
from Semiconductor Quantum Dots
DepartmentDepartment of Physics
Supervisors Professor Emeritus Ehrenfreund Eitan
Full Professors Gershoni David


Abstract

Quantum dots (QDs) are nanometer size semiconductor structures that confine charge carriers in three dimensions. Their discrete energy spectrum and sharp lines in photoluminescence, distinguish QDs from other solid-state semiconducting heterostructures. QDs are an excellent tool for probing basic concepts of light and matter interactions. They are currently the subject of forefront research efforts, motivated by future technologies like quantum information processing and quantum cryptography.


This thesis is concerned with the optical studies of single self assembled In(Ga)As QDs. Low temperature diffraction limited scanning confocal microscope was utilized in order to spatially isolate single QDs. The QDs were excited non-resonantly above the GaAs matrix bandgap. The photogenerated charge carriers diffuse to the QD, where they recombine radiatively. The photon emission of the single QDs was resolved spectroscopically and temporally and its statistical properties were studied, in order to obtain information about the dynamics of photoexcited carriers within these dots. We have significantly increased the extraction efficiency by studying the emission of single QDs embedded within planar resonant electromagnetic microcavity.


We demonstrated that under optical pulsed excitation, a single QD emits a series of consecutive single photons after each excitation pulse. Under continuous wave excitation, we showed that a QD is a source of non-classically correlated monochromatic photons with tunable statistics. We found that the emitted photon statistics can be varied by the excitation power from a sub-Poissonian one, where the photons are temporally antibunched at low power, to super-Poissonian, where they are temporally bunched at higher power.