Thesis (M.S.)--State University of New York at Binghamton, Department of Physics, Applied Physics and Astronomy, 2009. / Includes bibliographical references.

Thesis (M. Eng.)--Carleton University, 1992. / Also available in electronic format on the Internet.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 94-98).

Thesis (Ph.D.) - University of St Andrews, April 2009.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 169-180).

Thesis (Ph. D.)--University of Oregon, 2005. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 166-173). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 127-132).

Thesis (Ph. D.)--University of Oregon, 2006. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 128-137). Also available for download via the World Wide Web; free to University of Oregon users.

This thesis investigates the coherent phase modulation of ultrashort pulses using vibrating hydrogen as a molecular medium. Self-phase modulation in a gas-filled hollow core capillary allows the generation of highpower few-cycle pulses in the NIR. Such pulses can be used to drive high harmonic generation (HHG) to deliver attosecond duration pulses in the extreme ultraviolet and soft X-ray spectral region. While reaching unrivalled pulse durations (down to 67 as), these sources have characteristically low efficiencies. The pump-probe spectroscopy community would greatly benefit from brighter short wavelength sources with sub-5 fs duration. In this work I apply Amplified RamaN Impulsive Excitation for Molecular Phase Modulation (ARNIEMPM), a multiple pulse scheme, to coherently prepare vibrating hydrogen molecules and exploit them for the phase modulation of ultrashort pulses. The preparation of the molecular motion is performed via impulsive stimulated Raman scattering and transient stimulated Raman scattering. The generated in-phase motion of molecules creates an oscillating optical polarizability in the medium which can be exploited by a probe pulse propagating through it, acting as a 125THz frequency phase modulator, the fastest among molecular media. This technique has the potential to provide bright, isolated subfemtosecond duration ultra-violet (UV) pulses via spectral broadening of broadband pulses. I experimentally investigate the preparation of the molecular motion against multiple experimental parameters. I then demonstrate the molecular phase modulation of ultrashort broadband probes in the near-infrared (NIR) and UV via a degenerate interferometric scheme. I used a waveguide to increase the interaction length of the process and reduce the energy requirements for the medium preparation. This allowed the use of a single laser system to generate all the required pulses, which are largely diverse in terms of wavelength, duration and power. Additionally, I present a novel technique named Attosecond Resolved Interferometric Electric-field Sampling (ARIES), which is capable of directly measuring the waveform of arbitrary pulses with attosecond resolution. This technique is based on high-harmonic generation (HHG) acting as a temporal gate for an applied secondary field, and tracking its electric field amplitude as a shift in the HHG cut-off frequency. I present experimental demonstration of a pulse waveform measurement by accurately retrieving a know inserted variation in dispersion and carrier-envelope-phase. A theoretical calculation of the technique applicability over a wide spectral range is also presented.

Terahertz (THz) technology stands to solve a number of problems in everyday life, from next generation wireless communication to spectroscopic identification and imaging. However it is technically challenging to make a high power, compact source for terahertz radiation. The Quantum Cascade Laser (QCL), which produces gain at THz frequencies by exploiting inter-sub-band transitions in quantum wells, offers one solution to this problem. However controlling and detecting the emission from such sources remains a major challenge. This thesis investigates the theory and measurement of emission frequencies from aperiodic lattice THz QCLs. Crucially, realising both frequency control and detection provides a complete system for coherent THz characterisation of devices at precise, user defined frequencies. The author starts by studying the emission frequencies and threshold of discretely tuned aperiodic lattice lasers. This is achieved using a numerical transfer matrix method (TMM), which allows the calculation of the aperiodic lattice threshold spectrum for the first time. Calculations reveal that the low threshold modes of aperiodic lattice lasers form at peaks in the electromagnetic density of modes. This shows that lasing in aperiodic lattices arises from slow light propagation induced by multiple photonic band gaps, leading to both band edge and defect laser modes. Frequency selective lasing is maintained even under the influence of external facet feedback, albeit at the cost of precise knowledge of the mode frequency. Importantly this framework allows the understanding of essentially any aperiodic lattice laser system. Most significantly, the TMM is exploited in order to understand how graphene can be used to control a THz laser. Graphene interacts strongly with THz waves, and can be easily integrated with semiconductor structures such as lasers and waveguides. Here, numerical calculations reveal that graphene can be introduced into the waveguide of a THz QCL, generating electrically tunable THz surface plasmons. Such surface plasmons couple into an aperiodic lattice to change the scattering strength of each individual grating element. The TMM reveals that this change in scattering strength controls the modal selectivity of an aperiodic lattice THz QCL. This hypothesis successfully explains both earlier experiments and those performed by the author. Crucially, this model was central to a publication in the journal Science. Finally, this thesis demonstrates a novel coherent detection system for the characterisation of THz QCL emission. The technique exploits non-linear up-conversion of THz waves to a telecoms frequency side-band, a process shown to be sensitive to THz waveguide dispersion. By mixing the up-converted THz wave with a near infra-red local oscillator laser, coherent detection of QCL emission using all fibre coupled components is demonstrated for the first time. This measurement allows for the characterisation of laser emission with high frequency and temporal resolution. Specifically sub-microsecond pulses of THz emission and transients can be detected. When taken as a whole, the work of this thesis constitutes a major step towards realising cost effective THz characterisation and spectroscopy using QCLs.