Dissertations, Theses, and Capstone Projects

Date of Degree

9-2025

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy

Program

Physics

Advisor

Robert Alfano

Committee Members

Godfrey Gumbs

Azriel Genack

Peter Delfyett

Roger Dorsinville

Sergey Vitkalov

Pouyan Ghaemi

Lingyan Shi

Subject Categories

Atomic, Molecular and Optical Physics | Condensed Matter Physics | Optics | Physics

Keywords

Nonlinear Optics, Femtosecond, Laser, SRS, SC, HHG

Abstract

This dissertation offers experimental and theoretical insights into nonlinear light-matter interactions induced by intense femtosecond (fs) laser pulses. It investigates key phenomena, including stimulated Raman scattering (SRS) from phonon and magnon quasiparticles, supercontinuum (SC) generation via self-phase modulation (SPM), conical emission (CE) arising from four-wave mixing (4WM), and modulation instability (MI) driven by cross-phase modulation (XPM) between SRS and SC processes. These effects are studied in diverse media using state-of-the-art femtosecond lasers.

The interplay among SRS, SC, 4WM, and MI is examined to probe vibrational modes and temperature-dependent magnetic excitations in condensed-matter systems. Experiments are conducted on anisotropic uniaxial calcite and antiferromagnetic perovskite KNiF3, with emphasis on quasiparticle dynamics and Kerr relaxation times across varying thermal regimes. Additionally, scattering effects on SC generation are characterized using aqueous media containing polyester beads of different sizes and concentrations, clarifying how scattering influences spectral broadening.

A universal model of high harmonic generation (HHG) and supercontinuum extension is presented, based on electromagnetic (EM) Kerr theory. This model, called electronic self-phase modulation (ESPM), explains the creation of harmonics and broadband spectra in all states of matter. It forecasts key HHG features such as harmonic intensity decay, plateau development, and cutoff frequency depending on laser pulse duration, propagation distance, nonlinear Kerr index, and medium response time. The model also expands the traditional supercontinuum (SC) into an extreme spectral region—referred to as the Ultra-Supercontinuum (USC)—which spans the EM spectrum from X-ray to DC regions.

This dissertation offers a comprehensive framework for understanding and controlling ultrafast nonlinear optical phenomena across various material systems, providing a new approach to developing ultrabroadband light sources, advancing attosecond science, and improving spectroscopic tools.

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