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Since the development of chirped pulse amplification, there has been a significant increase in high peak intensity many-cycle laser pulses. Such pulses are of great interest for driving a variety of laser-plasma interactions, with many of these effects depending greatly on the driving intensity of the laser field. These effects include phenomena such as relativistic high harmonic generation with solid density targets and electron acceleration to relativistic speeds using laser wakefield acceleration. These interactions scale with the peak intensity of the laser pulse, meaning higher peak intensities are desired. Since the pulse duration for many of these systems are $\approx 10x$ longer than their single cycle limit, a factor of $10$ increase in peak intensity could be achieved by creating a pulse with identical energy but with a single cycle pulse duration.The current amplifier technologies makes the creation of high energy few-cycle laser pulses a very difficult task. Instead of focusing on maintaining a few-cycle laser pulse during amplification, one aspect of this thesis focuses on the application of self-phase modulation as a high efficiency method to compress a many-cycle laser pulse after amplification, enabling the creation of high energy few-cycle laser pulses. As the single-cycle limit is approached, the bandwidth required to support the pulse increases substantially. This can cause issues as a pulse propagates through material to an experiment, as material dispersion is able to substantially alter the temporal profile of the pulse, substantially reducing the peak intensity. In addition to material dispersion, there can be a nonlinear coupling between self-phase modulation and the material dispersion which can cause a substantially larger than expected change in the peak intensity of the pulse, which can not be pre-compensated for like material dispersion. In this thesis, I examine the effect of this coupling for a variety of laser intensities and discuss methods of mitigating the undesired decrease of the peak intensities. Since a few-cycle laser pulse is easily able to have the peak intensity reduced due to material propagation, proper temporal profile characterization is required to ensure the desired pulse duration is actually obtained. In this thesis, I discuss two machine learning based methods that utilize self-phase modulation to characterize the phase and temporal profile of the laser.

Like many problems in physics, the interaction between high intensity laser pulses and solid materials depends critically on the relative timescales of the drive (the laser pulse with finite duration) and the material response. This is especially true for Laser-Induced Damage and Ablation (LIDA) of solids, where femtosecond (1 fs = 10e−15 s) laser pulses can achieve extremely high energy densities since there isn’t enough time for energy to diffuse away during the laser pulse like there is for picosecond (10e−12 s) and nanoseond (10e−9 s) pulses,for example. The pulse duration dependence of fs-LIDA for Near-Infrared (NIR) pulses less than 100 fs is less well-understood, especially in the Few-Cycle Pulse (FCP) regime (

The following research was born out of the observation of a counter-propagating beam (CPB) originating from the interaction of a pump beam and a Fresnel reflection inside an organic liquid held inside a fused silica cuvette. The strong influence on overlap with the Fresnel reflection is evidence for degenerate frequency two-beam coupling (TBC) via a transient phase grating. It is well known that TBC requires a phase shift between the fields and the induced grating which is supplied by the finite temporal response of the nonlinearity. TBC also requires a frequency shift between the interacting fields. For degenerate frequencies to couple, this shift must arise from self or cross phase modulation in the medium. In this work, we present a strong, degenerate frequency TBC in two organic systems using a single nanosecond beam where the probe is generated from the Fresnel reflection of the cuvette and the necessary phase and frequency shifts are the result of the thermo-optic effect and population redistribution. Its effect on the analysis of nonlinear transmission experiments and its relationship with Stimulated Rayleigh Bragg Scattering (SRBS) is also presented.

The use of a saturated Semiconductor Optical Amplifier (SOA) as both a phase modulator and an amplifier for long range laser radar applications is explored. As will be discussed, this concept could reduce the hardware necessary to transmit high bandwidth pulses and allow for the transmission of shorter pulses that are less sensitive to the detrimental effects of target motion. After reviewing the concepts governing ranging, vibrometry, and synthetic aperture ladar, the nature of the phase and amplitude modulation from saturating an amplifier with a high peak power Gaussian pulse is explored. The key SOA parameters affecting the modulation of the output pulse are addressed and optimized, and their impact on the ideal pulse response of a laser radar system is explored. Proof of concept laboratory demonstrations using phase modulated pulses to interrogate stationary, vibrating, and translating targets are also presented. The concept of using a saturated SOA to enable short-pulse synthetic aperture ladar and vibrometry is also explored. This research will show that the range resolution of a ladar system can be optimized by saturating a SOA with a carrier lifetime that is one half the FWHM Gaussian input pulse duration, yielding a substantial improvement in range resolution that is highly insensitive to variations in the input pulse duration and energy.

The development of high power fiber laser and technologies are covered in this thesis. The first part of the thesis simulates the signal gain spectrum in an erbium-ytterbium fiber amplifier, which can be implemented in fiber laser systems to generate high power output. The second part proposes the use of gain-guided (GG) optical fibers to achieve high power mode-locked fiber lasers. The spatial-temporal pulse propagation in the GG fiber is simulated; self-focusing, and self-phase-modulation in this type of fiber is studied. The third part discusses phase-locked fiber laser designs. Self-imaging in optical fibers is simulated; the results provide a guide to the phase-locking fiber laser system design. The last part of the thesis investigates theoretically and experimentally cylindrical vector (CV) beams generation from fiber laser system using a birefringent crystal. Radial and azimuthal polarization output can be switched easily in this fiber cavity design. More interestingly, lasing with radial and azimuthal polarization can be achieved simultaneously. By introducing misalignment in the cavity, a beam with different polarization distributions is generated.