Gadi Eisenstein – QD Laser Dynamics on Ultrashort Time Scales: The Quantum Coherent Regime

Gadi Eisenstein – QD Laser Dynamics on Ultrashort Time Scales: The Quantum Coherent Regime

Prof. Gadi Eisenstein, ECE Department and Russell Berrie nanotechnology Institute, Technion – Haifa Israel

Library, A.2.500, Staudtstr. 2
Location Details

Abstract
Excitation of short resonance pulses in a room temperature quantum dot optical gain medium induces a variety of quantum coherent phenomena including Rabi oscillations, Ramsey fringes, and coherent revival. The high quality InAs / InP quantum dots exhibit a very long room temperature dephasing time of 5.2 ps which is responsible to the eJicient coherent interaction when using 100 fs wide excitation pulses.
This talk describes the principle of those quantum coherent interactions. We discuss a semiclassical model and a series of experiments that employ the cross-correlation frequency resolved optical gating (X-FROG) technique.
The optical pulses emerging from the quantum dot gain medium are naturally accompanied by noise. Using homodyne characterization, we demonstrate that the noise properties are cyclical with the excitation pulse energy. While undergoing Rabi oscillations, the quantum dots oscillate between gain, transparency and loss. During the part of the Rabi cycle when the quantum dots exhibit gain, the noise is squeezed. Moreover, the squeezing repeats itself for every fourfold increase in energy which amounts to a full cycle around the Bloch sphere. For a particular level of excitation energy, the system generates non-Gaussian states resulting from a superposition of the gain and absorption conditions occurring at transparency. This non-Gaussian state resembles a CAT-like state whose Wigner negativity is not observable due to a large optical output loss.