10.18453/rosdok_id00005659 Mandal, Santanu Santanu Mandal http://d-nb.info/gnd/1406944173 Universität Rostock 2025 530 Physics 2025 en https://purl.uni-rostock.de/rosdok/id00005659 urn:nbn:de:gbv:28-rosdok_id00005659-0 This thesis uses single-cycle and few-cycle femtosecond pulses to explore two major frontiers in condensed-matter and strong-field physics. First, single-cycle excitation clarifies the insulator-to-metal transition mechanism in M1-VO₂ by separating electronic and structural dynamics and revealing the anharmonic V–V bond oscillation central to the phase change. Second, it details the development of a solid-state high harmonic spectroscopy apparatus that enables precise study of the transition from perturbative to nonperturbative or extreme nonlinear optics in bulk crystals for the first time.