This dissertation focus on the use of sub-ten femtosecond pulses applied to coherent anti-Stokes Raman scattering spectroscopy. The use of such a broadbandwidth pulse coupled with adaptive pulse shaping has provided a method to impulsively excite all vibrational modes within the bandwidth of the pulse. Furthermore, this method using only a single beam eliminates many of the experimental difficulties associated with the typical multi-beam CARS methods. The generation of supercontinuum has allowed for high energy, amplified pulses to reach the same time duration/bandwidth as lower energy femtosecond oscillators. This significant increase in pulse energy has allowed the single-beam CARS method to be extended beyond microspectrocopy, which requires the tight focusing conditions afforded by a microscope objective in order to reach the necessary pulse energy. This extension has opened single-beam CARS to fields such as remote sensing and combustion diagnostics. This dissertation presents the evolution of single-beam CARS in the context of these fields. Remote sensing is demonstrated at distances of 12 m for solids, liquids, and gases in a retro reflective set-up with signal to noise levels high enough for molecular identification. Single shot measurements are also made, along with direct backscatter measurements. CARS gas phase measurements are made on several atmospheric gases, as well as mixtures of gases. Mode-selective CARS excitation is used to excite a single Raman mode, creating a contrast mechanism that allows for direct visualization of a CO2 jet. Several gases were also measured in various pressure regimes to determine the number density relationship.Lastly, the group velocity dispersion of several combustion gases was measured to illustrate the temporal broadening that occurs when femtosecond pulses propagate in combustion environments. The ability to manipulate the axial resolution of a nonlinear optical process when using adaptive pulse shaping is also discussed
Read
