This thesis investigates the detection efficiency of field-resolved measurements of ultrashort mid-infrared waves via electro-optic sampling for the first time. Employing high-power gate pulses and phase-matched upconversion in thick nonlinear crystals, unprecedented efficiencies are achieved for octave-spanning fields in this wavelength range. In combination with state-of-the art, high-power, ultrashort mid-infrared sources, this allows to demonstrate a new regime of linear detection dynamic range for field strengths from mV/cm to MV/cm-levels. These results crucially contribute to the...

This thesis reports the discovery of relativistic stellar explosions outside of the gamma ray band, using optical time domain surveys. It is well known that some massive stars end their lives with the formation of a compact object (a neutron star or black hole) that launches a relativistic jet detectable from earth as a burst of gamma rays. It has long been suspected, however, that gamma ray bursts are only the tip of the iceberg in a broad landscape of relativistic explosions, and so the results presented in this thesis represent a major breakthrough. Highlights of this thesis...

This book characterizes the kinematic and chemical structures of disk-forming regions around low-mass protostellar sources and their interplay based on Atacama Large Millimeter/submillimeter Array (ALMA) observations. It describes the chemical evolution of molecules formed in an interstellar gas using the ALMA observations of 5 Sun-like protostars at a spatial resolution of a few tens au scale, which unveils the physical mechanism of star and planetary formation.

The book reviews the author’s successful works, focusing on two key findings: (i) A drastic change in the chemical...

This book highlights the doctoral research of the author on electronic band structure engineering and ultrafast dynamics of Dirac semimetals. Dirac semimetals exhibit unique electronic band structure and novel physical properties with rich light-matter interaction, which inspires a wide range of potential applications. Enabling band engineering and revealing ultrafast dynamics of Dirac semimetals is therefore important. In the research work covered by the book, the first ultrafast time- and angle-resolved photoemission spectroscopy with tunable probe photon energy is developed, providing...

This thesis presents significant advances in the use of neural networks to study the properties of neutrinos. Machine learning tools like neural networks (NN) can be used to identify the particle types or determine their energies in detectors such as those used in the NOvA neutrino experiment, which studies changes in a beam of neutrinos as it propagates approximately 800 km through the earth. NOvA relies heavily on simulations of the physics processes and the detector response; these simulations work well, but do not match the real experiment perfectly. Thus, neural networks trained...

This book clears up some confusion in the field of star formation and proposes a solution to a problem that remains unsolved for more than a decade. Observations of molecular clouds show that dense filaments are the sites of present-day star formation, and it is thus necessary to understand the filament formation process because the filament is an initial condition in a star formation process. Theoretical studies suggest that shock waves in molecular clouds trigger filament formation. Several different mechanisms have been proposed, and the formation mechanism of the observed star-forming...