Intense femtosecond pulse interaction with transparent and absorbing medium
AuthorMlejnek, Michal, 1965-
AdvisorMoloney, Jerome V.
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractThe work reported in this dissertation represents an investigation into some aspects of resonant and nonresonant light-matter interaction as experienced by femtosecond optical pulses. We look at the role of plasma generation via multi-photon ionization in the arrest of the 2-D collapse of femtosecond pulses governed by the nonlinear Schrodinger equation. First we studied the exciting new area of anomalous long-distance propagation of femtosecond optical pulses in the atmosphere. Our simulations do not support the existence of a stable pulse propagating through the air, but rather a dynamical picture involving several collapse events emerges. This investigation led us to consider the question of the role of pressure on the pulse propagation in gases. The pressure dependence of the collapse in Argon is discussed next, and we make the connection between the results obtained in crystals on one hand, and low-density gases on the other. An interesting behavior is observed for pressures at which the Kerr nonlinearity and plasma-induced defocusing are of the same order. Next, we investigate second harmonic generation of femtosecond pulses at the boundary of a nonlinear medium using the full vector Maxwell equations and simple phenomenological constitutive relations. We observe the initial pulse to split in time into two ultrashort pulses in the case of phase-mismatch. This phenomenon should be readily measured experimentally. The effect of low-frequency material dispersion and a possibility of "one-hump" pulsed solution is discussed. Finally, in the last chapter we investigate the resonant coupling of light to a semiconductor which is sensitive to the field polarization, using a many-body model for electronic structure. Pump-probe type experiments with copropagating, cross-polarized beams are considered, and we demonstrate theoretically the existence of an oscillating signal at twice the optical frequency in the probe transmission measurements. Our results show that the change of the interaction among the carriers leads to a phase shift of the oscillation pattern. We also know that such interaction depends on the intensity of light: The Coulomb screening is changed. Thus the phase shift contains information about the microscopic interaction among the carriers.
Degree ProgramGraduate College