Ultrafast lasers have many important applications in engineering and science, where unique behavior is derived from the ultrashort nature of the pulse interacting with materials. The shape of the electric field of a laser pulse in time determines how the pulse will interact with an experimental system. Several techniques have been developed for shaping the electric field, and this Thesis expands upon the previous developments in pulse shaping to explore a novel process for manipulating the electric field of ultrashort laser pulses. Phase-sensitive optical parametric amplification as a method to directly manipulate the temporal phase of a signal pulse by amplifying the relative phase difference between signal and pump beams is explored in this work.

Numerical models are presented which are capable of describing phase-sensitive optical parametric amplification in both the spatial and temporal domains. Amplification of the phase of ultrashort laser pulses in the time domain is investigated as a method to directly affect the shape of ultrashort pulses. The models have been used to design an experiment to demonstrate temporal and spatial phase-sensitive optical parametric amplification. A novel pulse characterization instrument is presented, which was developed to measure the phase manipulation. The pulse characterization instrument is an implementation of the established technique spectral phase interferometry for direct electric-field reconstruction that is capable of simultaneously recovering the amplitude and phase of two laser pulses on a single shot. The instrument is used to make differential phase measurements of phase effects in the phase amplification experiment. Preliminary experimental evidence of phase amplification is presented.