| dc.description.abstract | The integration of short laser pulses with crystals and photonic crystal structures offers a versatile platform for exploring fundamental light-matter interactions and discovering novel techniques in ultrashort pulse generation and shaping, as well as spectroscopy. In this thesis, I will first discuss the coherent generation of a broad spectrum in Raman-active crystals such as lead tungstate (PbWO4) and single-crystal diamond, which enables us to study the transfer of orbital angular momentum (OAM) of light in ultrashort shaped pulses through coherent Raman processes as well as near-single-cycle pulse generation with pulses as short as 4.8 femtoseconds (fs) and ability to be shaped temporally and spatially. We characterize these pulses through a nonlinear technique called interferometric cross-correlated frequency-resolved optical gating (ix-FROG). Multi-photon ionization is another reliable technique to characterize our synthesized near-single-cycle pulse. As proof of principle, we perform mass spectroscopy on xenon ionized by our ultrashort pulses. In this thesis, we study another nonlinear interaction in Raman media in the form of picosecond (ps) coherent anti-stokes Raman scattering (CARS) spectroscopy in hollow-core photonic crystal fibers (HC-PCFs) and hollow-core fibers (HCFs). CARS spectroscopy is a reliable nonlinear technique that probes the vibrational and rotational modes of a target molecule, enabling chemical-selective microscopy and spectroscopy. We take advantage of hollow-core optical fibers to enhance the CARS signal in gaseous media up to two orders of magnitude. We also conduct a similar study on biological analytes such as Immunoglobulin G (IgG) antibody samples. I will introduce a type of HCF called anti-resonance HCF (AR-HCF), which provides low-loss broadband light guidance for relatively large core diameters. AR-HCF also reduces the pulse energies required for strong nonlinear interactions from the millijoule to the microjoule level, thus, allowing scaling from kHz to MHz repetition rates. I will discuss the results that illustrate the absence of a substantial non-resonant background (NRB), an unavoidable by-product of the CARS spectroscopy, using an AR-HCF. | |
