A novel technique for achieving high spectral resolution with a femtosecond laser system is presented. Transform-limited 800 nm, 90 femtosecond (fs) pulses pass off two gratings, stretching the pulse in time to a pulse width of several picoseconds due to an induced linear temporal chirp directly proportional to the grating separation. This chirped pulse is the degenerate pump (ω<sub>P</sub>) and probe (ω<sub>p</sub>) pulse for the CARS experiment. When overlapped in time with the 1050 nm, 90 fs transform-limited Stokes (ω<sub>S</sub>) pulse, only a fraction of the chirped ω<sub>p</sub> pulse generates the CARS signal, thereby creating a temporal slit that defines the spectral resolution of the technique. Spectra for liquid methanol and liquid isooctane are presented, with ~6 cm<sup>-1</sup> spectral resolution achieved for isooctane. Resonance enhancement and the mechanism of achieving high spectral resolution are shown by adjusting the ω<sub>S</sub> wavelength and ω<sub>p</sub> delay relative to the ω<sub>S</sub> pulse.
Quasi one-dimensional nanostructures are unique probes of cavity quantum electrodynamics because they are capable of exhibiting photonic and/or electronic confinement in two dimensions. The near-cylindrical geometry and sharp end facets of zinc oxide (ZnO) nanowires enable the realization of active nanoscale optical cavities that exhibit UV/blue photoluminescence (PL) waveguiding and lasing action at room temperature under appropriate optical pumping conditions. Study of individual nanostructures is crucial for isolating geometry-dependent effects, and here it is achieved through both near- and far-field microscopies. The polarization of the emitted PL or lasing from individual nanostructures characterizes the coupling of the spontaneous emission to cavity modes, depending both on the wavelength of the emitted light and the nature of the emitting species (i.e., excitons and intrinsic defects in various charge states). In addition, the spectral evolution of the lasing/PL as a function of the pump fluence indicates both exciton and electron-hole plasma dynamics. Variations of size, geometry, and material on the prototypical cylindrical ZnO nanowire lead to further observation of unique photonic and/or carrier confinement effects in novel nanostructures.