Master thesis defense by Mathias Jakob Rønne Staunstrup

Title: Measuring the quantum dot induced phase shift of light transmitted through a nanophotonic waveguide

Abstract: This thesis explores the transmission of light through a nanophotonic waveguide with an embedded single solid state quantum dot. The coupling between the quantum dot and the waveguide gives rise to giant nonlinerarites at the single photon or weak coherent limit of the transmitted light. Focus is here put on the phase shift that light obtains after transmission of the quantum dot and waveguide system. The theory of transmission is explored for both for an istotropic and chiral coupling of the quantum dot to the waveguide. These configurations give rise to respectively a π/2 and π phase shift. Theory shows that especially chiral coupling is shown to be more robust to physical dependent factors and supplies even larger nonlinearity than isotropic coupling. For the measurement of this phase shift, a Mach-Zehnder interferomter was constructed as a new tool for the lab. Methods have been developed to stabilize the interferometer, in order to compensate for large mechanical fluctuations in the interferometric signal. Using this interferometer, the spectral response of the phase shift induced by an isotropic coupled quantum dot is measured. For this first direct measurement of the phase shift, a maximum phase shift of 58.5^± 0.3 degrees is measured. The spectral response showed good agreement with theory. Finally, a measurement of the power dependence of the phase shift is performed, and show nonlinear behavior as predicted in the theory. 

Online at Zoom  - Zoom meeting ID 649 8239 4079 - password 4400