Ultrafast optical spectroscopy using collinear phase-coherent pulses

Nuclear Magnetic Resonance (NMR) is an extremely useful tool for structure determination. However, because of the inherent timescales in NMR, only time-averaged structures can be determined. Much information is contained in the dynamics of such structures. Ultrafast optical analogs of NMR could enhance our understanding in this area, since such experiments have a temporal resolution of picoseconds or less. With the recent developments in ultrafast laser technology, such experiments are now becoming feasible, and analogs of NMR COSY and NOESY experiments employing non-collinear pulse geometries have started to emerge.; This dissertation focuses on a different approach to optical analogs of NMR, employing a sequence of phase coherent collinear pulses that is created using an acousto-optic pulse shaper. It was shown that selection of coherence transfer pathways—which in the non-collinear experiments is achieved through phase matching—can be achieved by phase cycling: co-adding a series of experiments with different inter-pulse phase differences.; By using an acousto-optic pulse shaper to create the pulse sequences, this phase cycling can be done automatically at a very high rate. Automatic phase cycling and coherence transfer pathway selection were demonstrated by detecting the one- and two-photon optical free induction decays (OFIDs) of the model system rubidium. In addition to a step by step method, where the OFID signal for each point in time is measured in a separate experiment, a multiplexed method was developed where the entire OFID can be measured at once.; Using an amplified laser system and a 16-step phase cycling scheme, an optical analog of a 2D COSY NMR experiment—a two-dimensional photon echo—was demonstrated on the same model system.; The one-dimensional demonstration experiments were done at very high optical densities, so that propagation effects needed to be taken into account to fully explain the experimental observations. These theoretical calculations were extended to the two-dimensional experiments. It was shown that propagation effects can be observed at surprisingly low optical densities, and that such effects need to be taken into account when interpreting these experiments.