|Ph.D Student||Cestier Isabelle|
|Subject||Nonlinear Photonic Crystal Devices|
|Department||Department of Electrical Engineering||Supervisor||Professor Emeritus Gad Eisenstein|
|Full Thesis text|
This thesis reports on nonlinear semiconductor photonic crystal (PhC) devices, waveguides and resonators, fabricated in GaInP and operating in the telecom range.
First, we explore Fabry-Perot resonators that enable a highly sensitive measurement of the nonlinear index of refraction by a direct observation of the phase shift experienced by the fringes. The observed nonlinearity is several orders of magnitude larger than any reported semiconductor PhC waveguide and is found to be due to a hybrid phenomenon of thermal and Kerr effects. It was exploited to perform a wavelength conversion experiment at 10 GHz, limited by the photonic structure. To investigate the exact nature of the nonlinearity we designed resonators with integrated mirrors that have a complex, wavelength dependent transfer function. Dynamical characterizations reveal that at low frequency the nonlinearity is due to a thermal contribution while at high frequency the nonlinear response is strictly due to the instantaneous Kerr effect. Kerr-induced all-optical switching and wavelength conversion experiments at rates up to 33 GHz were demonstrated using pulse energies of a few pJ. The switching process is dominated by the instantaneous Kerr effect and the device speed is determined by the resonator life time.
The second part of the thesis deals with parametric processes mainly four wave mixing (FWM). Different sets of waveguides having various dispersion functions were investigated. The enhancement due to slow light of the nonlinear interactions was studied. The experiments were accompanied by an analytical model that fits the data well. We demonstrated the first efficient FWM as well as the first ever observation of measurable parametric gain experienced by a CW probe together with pulse compression. Next we studied dispersion engineered structures with dispersion functions that have a wide spectral regime where the dispersion is almost wavelength independent. These waveguides enabled extremely wide bandwidth FWM as well as parametric gain. The dynamical FWM properties were used for wavelength conversion and time domain switching / demultiplexing of a PRBS signal at 10 Gbit/s. Finally, a last set of experiments provide the highlight of this thesis: the demonstration of a real usable chip scale parametric amplifier with 11dB gain in a nanoscale waveguide with a sub-Watt pump power. These observations were performed in a dispersion engineered waveguide where the nonlinear interactions were enhanced by the slow light effect. It enables, therefore, to incorporate the many advantages of parametric amplification within photonic chips for optical communication applications.