Light does not interact with itself in linear optical materials. Such interactions occur only in non-linear optical (NLO) materials and typically require high intensity optical beams to be signifi-cant. The ever-increasing role of NLO, where intense light may change the properties of the me-dium, has created a pressing demand to invent materials for achieving more efficient light-light and light-matter interaction due to their potential capacity to augment and possibly replace cur-rent technologies with more efficient devices. There are numerous applications of NLO devices in fundamental science, technology, health, and defense such as all-optical computation and sig-nal processing, ultrashort laser technology, photodynamic cancer therapy, and quantum commu-nication and information. The main objective of my Ph.D. dissertation is to investigate the interaction of laser puls-es with an exciting class of material that has the dielectric constant close to zero, so-called epsilon-near-zero (ENZ). The ENZ materials and their scientific development have become a topic of interest owing to their fascinating nonlinear optical properties particularly in frequency ranges that the material is transitioning from dielectric to metal. The goal of my dissertation is the theo-retical and experimental study of transparent conducting oxides such as Indium Tin Oxide (ITO) as a candidate material exhibiting the ENZ condition and utilizing this effect for nonlinear opti-cal devices. The NLO effects in TCOs are dominated by carrier related nonlinearities. Additionally, this dissertation studies instantaneous third-order and non-instantaneous carrier nonlinearities in semiconductors such as GaAs and Silicon and fifth-order nonlinear absorption (three-photon absorption) in direct gap semiconductors. In this work, we first introduce the development of NLO spectroscopy systems for the characterization of the NLO properties. In particular, the Beam-Deflection (BD) technique, which allows us to simultaneously characterize the nonlinear refraction and absorption of the ma-terial. This technique enables us to characterize the sign, magnitude, temporal and polarization dependence of the nonlinearities, which all are of paramount importance in understanding the underlying physics of the material. We also extend BD to a cross-propagating geometry to measure off-diagonal nonlinear susceptibility matrix elements. Moreover, we employ BD to measure ultrafast and carrier-induced nonlinear absorption and refraction of common semiconductor materials and transparent conducting oxides. The ability of BD to measure the time-dynamics and polarization-dependence of the nonlinear phase shift becomes apparent in both subjects presented in this dissertation.
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Doctor of Philosophy (Ph.D.)
College of Optics and Photonics
Optics and Photonics
Optics and Photonics
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Ahmadzadeh Benis, Sepehr, "Nonlinear Optical Mechanisms in Semiconductors and Enhanced Nonlinearities at Epsilon-Near-Zero" (2020). Electronic Theses and Dissertations, 2020-. 167.