| In this dissertation work, a reliable and reproducible area-selective Zn diffusion technique utilizing a semi-sealed graphite box diffusion system and thin Si3N4 layers as a diffusion mask was characterized and implemented in the fabrication of Mach-Zehnder electro-optic switching devices. The Zn concentration profile measured by secondary ion mass spectroscopy (SIMS) showed that the zinc concentration exceeded 1018 cm −3 throughout the top layer of diffused samples that were initially doped with donor impurities at a concentration of 1017 cm −3 and then abruptly dropped down to the background level of the measuring instrument, resulting in p-n junctions that had good I-V characteristics with a breakdown voltage of around 12 V.; In the second part of this dissertation work, an ultrafast all-optical Mach-Zehnder interferometric switching device, integrated by using a silica capped impurity free vacancy diffusion disordering (IFVD) technique, is reported. Ultrafast all-optical switching with adjustable switching widows that were as short as 2 ps and a switching contrast ratio of 10 dB was measured for the device. A computer model was developed to calculate the differential phase shift between two arms of the Mach-Zehnder interferometer that is responsible for optical switching of the device. The nonlinearity is due to photogenerated carrier-induced excitonic nonlinearities in multiple quantum well structures. The model showed that the energy for each control pulse needed for switching operation was around 8 pJ. |
