Technical development of coherent two-dimensional and three-dimensional optical spectroscopy
Date of Issue2013
School of Physical and Mathematical Sciences
The work on this dissertation is focused on the technical development of multidimensional nonlinear optical spectroscopy. Using pulse shaping techniques, two-dimensional (2D) and three-dimensional (3D) optical spectroscopy are performed in the visible spectral region. Technical developments in generating and characterizing polarization-shaped ultraviolet (UV) pulses are explored as well, with the aim of implementing a polarization-based coherent multidimensional optical spectrometer. Polarization-shaped pulses in the ultraviolet (365 nm) are generated using two independent sum-frequency generation (SFG) processes in two orthogonally orientated β-barium borate crystals. The amplitudes, phases and the delays in the two sets of visible (650 nm) and near infrared (800 nm) pulses that contribute to the two SFG processes are controlled by a liquid crystal spatial light modulator pulse shaper (LC-SLM). The two orthogonally polarized shaped UV pulses are then temporally recombined via a birefringent crystal. The interferometric phase stability is well maintained in this common-path geometry setup. To characterize the amplitude, phase and polarization of the shaped UV pulses, we present a method referred to as “difference frequency generation cross-correlation tomographic ultrafast retrieval of transverse light E-fields” (DFG-XTURTLE) that combines the technique of tomographic ultrafast retrieval of transverse light E-fields (TURTLE) with the amplitude and phase retrieval algorithm of the cross-correlation frequency-resolved optical gating (XFROG). The handedness of the elliptically shaped pulses can also be retrieved with additional measurements with a quarter-wave retardation plate. 2D optical spectroscopy is performed in a pump-probe geometry via a pulse shaper assisted setup. An acousto-optic programmable dispersive filter (AOPDF) generates the first two interaction pump pulses with controllable delays and relative phases, while a white light continuum provides the third interaction probe pulse. Phase cycling schemes are prerequisite in order to isolate the desired signal. With additional data processing steps, we further retrieve the rephasing and non-rephasing 2D spectra with the same approach. A full discussion on the phase cycling schemes needed for coherent 3D optical spectroscopy is provided. The experimental demonstration used to measure purely absorptive fifth-order 3D electronic spectrum is based on the same experimental setup used in 2D spectroscopy. In the 3D electronic spectroscopy setup, four pulses are generated using a pulse shaper in 3D spectroscopy, and higher-order phase cycling schemes are needed to remove the unwanted signals. Through data processing, all pathways that contribute to the purely absorptive 3D spectrum are retrieved.