Part I. Optically induced, ferroelectric domain gratings in photorefractive crystals and applications to nonlinear optics. Part II. Self-focusing and self-trapping of optical beams upon photopolymerization and applications to microfabrication

Abstract

This thesis explores the application of two distinct nonlinear optical phenomena, the photorefractive effect and photopolymerization, to optically generate microstructures with feature sizes on the order of optical wavelengths. First, we have found that in certain photorefractive crystals, the photogenerated space charge field dynamically aligns ferroelectric domains. This is demonstrated by the observation of Barkhausen noise linked to the formation of domain gratings. Domain gratings are recorded with spatial periods on the order of optical wavelengths, which we use for quasi-phase matched second harmonic generation and holographic data storage. The second part of this thesis explores the nonlinear optical response accompanying photopolymerization. In some photopolymers, the crosslinking of polymer chains induces a significant increase in the index of refraction in the exposed region. This index perturbation acts as a lens which subsequently focuses down the input light wave. We observe self-focused and self-trapped optical beams upon photo-induced crosslinking of a liquid monomer. In the case of self-trapping, the inherent diffraction of the optical beam is exactly balanced by self-focusing, so the diameter of the beam does not change as it propagates through the medium. Most importantly, this waveguiding generates solid polymer microstructures in the illuminated region, which can be used to fabricate micro-electromechanical systems and optical interconnects