Design and Construction of Linear and Nonlinear Optical Systems for Measurements of Nanomaterials: Towards Chemistry at the Space-Time Limit

Both linear and nonlinear optical methods were utilized to carry out measurements of Chemistry at the Space-Time Limit (CaSTL). Two ultrafast synchronously pumped Noncollinear Optical Parametric Amplifiers (NOPAs) were designed and constructed for use in Four Wave Mixing (FWM) experiments. The NOPAs were able to reproducibly generate ultrafast, ultrashort transform limited pulses from a 250 kHz amplified Ti:Sapph laser. The NOPAs were used to measure time-resolved Coherent anti-Stokes Raman Scattering (tr-CARS) of neat styrene and neat thiophenol. These measurements were calibrated by using forward simulations of their Raman spectra, and correlating them with Gaussian representations of the laser fields. These measurements were successfully executed and simulated to 10 ps time delay, showing a very long decay of the two solutions.;Surface Enhanced Raman Scattering (SERS) active molecules were successfully created utilizing a novel synthesis to chemically bond di-thiolated molecules to the surface of two metal spheres to form dimer antennae. The dimer geometry was found to give a Raman enhancement of 6 orders of magnitude, and led to the detection of single molecule SERS spectra. The dimer geometry decomposed into clusters and monomer spheres after several months of storage, and three different spectrum types were observed: clusters (3 or more spheres), dimers (2 spheres), and most surprisingly, monomers (one sphere). It was also found that due the gradient field effect, the appearance of non-Raman active vibrational modes were evident in the monomer spectrum. An ultrafast tr-CARS microscope was designed and constructed for measurement of surface plasmon polaritons on gold film, and fs coherent anti-Stokes scattering (CAS) of both multi-walled and single-walled carbon nanotubes (CNTs). Preliminary measurements were made to determine the polarization dependence of the CNTs using both CAS and TA. Time-resolved transient absorption (TA) microscopy measurements were also carried out on carbon nanotubes (CNTs) to obtain background free electronic absorption dynamics.;A novel optical scheme for the implementation of ultrafast laser-induced Scanning Tunneling Microscopy (STM) was carried out. Utilizing polarization manipulation, two time-delayed Ti:Sapph laser pulses were coupled into a STM in such a manner as to avoid thermal oscillations of the STM tip that would normally hinder any time-resolved optical measurements. By applying a bias voltage on the STM junction equal to the energy of two photons, the interaction of two photons with the tip induced electron tunneling. Laser-induced atomic imaging was carried out for silver atoms on a silver surface.