Thesis Title: Ultrafast Electro-optical Time-resolved Spectroscopy of Nanomaterials on LAO/STO

Abstract: A comprehensive investigation of ultrafast electro-optical phenomena in LaAlO3/SrTiO3$ (LAO/STO) heterostructure nanojunctions and plasmonic gold nanorods coupled to (LAO/STO) nanojunctions using femtosecond time-resolved spectroscopy is presented. A single gold nanorod (AuNR) with longitudinal surface plasmon resonance absorption at 770nm was collocated with a nanodevice fabricated at the interface of LAO/STO by conductive AFM lithography. The experimental framework used to run experiments includes a carrier envelope phase stabilized, sub-7 femtosecond, broadband pulsed laser; GDD control; a Michelson interferometer providing femtosecond temporal resolution; and electronic measurements of the photocurrent across the LAO/STO nanodevice. Photocurrent measurements reveal nonlinear optical responses in LAO/STO and AuNR/LAO/STO devices including secondary oscillatory peaks in time-resolved measurements. These secondary peaks are GDD and time-delay dependent, indicating complex third-order nonlinear susceptibility of LAO/STO nanodevices and possible interactions between the field enhancement of AuNRs and the LAO/STO nanodevices. Sensitivity to pulse width and GDD was found in both LAO/STO and AuNR/LAO/STO devices across a wide range of temperatures (6K to 260K), showing promise for use as compact, room temperature ultrafast pulse characterization.