Photorefractive non-linear, electro-, and magneto-optics in II-IV and II-VI semiconductors
Abstract
This work presents the physics and applications of several nonlinear optical phenomena relying on charge transport nonlocal nonlinearity, and thermodynamic phase change that are studied in InP:Fe, GaAs:EL2, CdTe semiconductors and the transition-metal oxide vanadium dioxide. A systematic experimental and theoretical study has been performed using InP:Fe crystals to develop a nonlinear optical spectroscopy for semi-insulating semiconductors. Two-wave and four-wave mixing techniques are used to demonstrate that multiple deep level defects cause electron-hole competition. A multiple-defect model for charge transport is developed to explain experimentally observed behavior. The cross-sections and excitation energy associated with secondary defects are deduced. The influence of multiple defects on the temperature-intensity resonance mechanism for gain enhancement under an applied E-field is elucidated. A thin-film nonlinear interference filter of vanadium dioxide is designed to demonstrate an all-optical light switching and optical bistability at 1.06 micron with high contrast ratio using a thermal nonlinearity arising from a metal-semiconductor phase transition. A new class of photorefractive materials--magnetic semiconductors--are introduced, which has opened a new field of electro-magneto-optics. Crystallographic orientation and polarization dependence of dynamic holographic gratings have been studied in the presence of an applied magnetic field in a cadmium telluride crystal with 10% Mn$\sp{2+}$ concentration. Three magnetic-field configurations using transmission holographic gratings are identified: (1) the longitudinal Faraday geometry; (2) the transverse Faraday geometry; and (3) the Voigt geometry. Magnetic-field-induced circular and linear birefringence alter the polarization and phase of coupled modes propagating in the presence of electro-optic gratings generated by photo-induced space-charge. Experimental and theoretical behavior of two-beam coupling gain are presented for each configuration. The fundamental question of the effect of magnetic field on time reversal symmetry (optical phase conjugation) is experimentally and theoretically analyzed in a CdTe crystal. The longitudinal configuration is demonstrated to be analogous to a phase conjugate mirror with built-in Faraday isolator. Manifestations of the metastability of the EL2 defect in GaAs on the steady-state photorefractive gain and the transient diffraction efficiency are studied at low temperature.
Degree
Ph.D.
Advisors
Nolte, Purdue University.
Subject Area
Condensation|Optics|Electrical engineering
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