Terahertz (THz) radiation with frequencies between 100 GHz and 30 THz has developed into an important tool of science and technology, with numerous applications in materials characterization, imaging, sensor technologies, and telecommunications. Recent progress in THz generation has provided ultrashort THz pulses with electric field amplitudes of up to several megavolts/cm. This development opens the new research field of nonlinear THz spectroscopy in which strong light-matter interactions are exploited to induce quantum excitations and/or charge transport and follow their nonequilibrium dynamics in time-resolved experiments. This book introduces methods of THz generation and nonlinear THz spectroscopy in a tutorial way, discusses the relevant theoretical concepts, and presents prototypical, experimental, and theoretical results in condensed matter physics. The potential of nonlinear THz spectroscopy is illustrated by recent research, including an overview of the relevant literature.

Two-Dimensional Materials for Nonlinear Optics Comprehensive resource covering concepts, perspectives, and skills required to understand the preparation, nonlinear optics, and applications of two-dimensional (2D) materials Bringing together many interdisciplinary experts in the field of 2D materials with their applications in nonlinear optics, Two-Dimensional Materials for Nonlinear Optics covers preparation methods for various novel 2D materials, such as transition metal dichalcogenides (TMDs) and single elemental 2D materials, excited-state dynamics of 2D materials behind their outstanding performance in photonic devices, instrumentation for exploring the photoinduced excited-state dynamics of the 2D materials spanning a wide time scale from ultrafast to slow, and future trends of 2D materials on a series of issues like fabrications, dynamic investigations, and photonic/optoelectronic applications. Powerful nonlinear optical characterization techniques, such as Z-scan measurement, femtosecond transient absorption spectroscopy, and microscopy, are also introduced. Edited by two highly qualified academics with extensive experience in the field, Two-Dimensional Materials for Nonlinear Optics covers sample topics such as: Foundational knowledge on nonlinear optical properties, and fundamentals and preparation methods of 2D materials with nonlinear optical properties Modulation and enhancement of optical nonlinearity in 2D materials, and nonlinear optical characterization techniques for 2D materials and their applications in a specific field Novel nonlinear optical imaging systems, ultrafast time-resolved spectroscopy for investigating carrier dynamics in emerging 2D materials, and transient terahertz spectroscopy 2D materials for optical limiting, saturable absorber, second and third harmonic generation, nanolasers, and space use With collective insight from researchers in many different interdisciplinary fields, Two-Dimensional Materials for Nonlinear Optics is an essential resource for materials scientists, solid state chemists and physicists, photochemists, and professionals in the semiconductor industry who are interested in understanding the state of the art in the field.

Comprehensive resource covering concepts, perspectives, and skills required to understand the preparation, nonlinear optics, and applications of two-dimensional (2D) materials Bringing together many interdisciplinary experts in the field of 2D materials with their applications in nonlinear optics, Two-Dimensional Materials for Nonlinear Optics covers preparation methods for various novel 2D materials, such as transition metal dichalcogenides (TMDs) and single elemental 2D materials, excited-state dynamics of 2D materials behind their outstanding performance in photonic devices, instrumentation for exploring the photoinduced excited-state dynamics of the 2D materials spanning a wide time scale from ultrafast to slow, and future trends of 2D materials on a series of issues like fabrications, dynamic investigations, and photonic/optoelectronic applications. Powerful nonlinear optical characterization techniques, such as Z-scan measurement, femtosecond transient absorption spectroscopy, and microscopy are also introduced. Edited by two highly qualified academics with extensive experience in the field, Two-Dimensional Materials for Nonlinear Optics covers sample topics such as: Foundational knowledge on nonlinear optical properties, and fundamentals and preparation methods of 2D materials with nonlinear optical properties Modulation and enhancement of optical nonlinearity in 2D materials, and nonlinear optical characterization techniques for 2D materials and their applications in a specific field Novel nonlinear optical imaging systems, ultrafast time-resolved spectroscopy for investigating carrier dynamics in emerging 2D materials, and transient terahertz spectroscopy 2D materials for optical limiting, saturable absorber, second and third harmonic generation, nanolasers, and space use With collective insight from researchers in many different interdisciplinary fields, Two-Dimensional Materials for Nonlinear Optics is an essential resource for materials scientists, solid state chemists and physicists, photochemists, and professionals in the semiconductor industry who are interested in understanding the state of the art in the field.

NONLINEAR OPTICAL TECHNOLOGY Comprehensive resources describing today’s Nonlinear Optics (NLO) technology, its applications, and concepts behind the technology Taking shape at the unique interdisciplinary engineering school at Dartmouth College, Nonlinear Optical Technology explores the importance of NLO in terms of how it permeates a vast number of applications such as fiber optics, biomedicine, sensors (especially Internet of Things), microscopy, spectroscopy, and machining, under the assumption engineers of all stripes may end up working in technical areas impacted by Nonlinear Optics (NLO) and would benefit from learning about the field. Each section follows a set format, beginning by describing some exciting new technology made possible by NLO. This part is followed by a description of the background information necessary for students to understand the basic NLO concepts for that application. The author occasionally includes personal experiences as a pioneer in this field where it provides additional understanding and motivation. Each section ends with a description of other developments in technology that use the same NLO concept. Bringing together disparate topics in NLO under a straight-forward rubric based on applications, Nonlinear Optical Technology includes information on: Extending lasers (with NLO technology), covering new colors (harmonic generation, stimulated raman, and stimulated brillouin) and pulsed lasers (saturable absorption and ultra-high harmonic generation) Information technology, covering telecommunications (fiber optics NLO and photonic NLO) and data storage (NLO in nanostructures and photonic crystals) Sensors, covering distributed sensing (brillouin scattering in fibers) and localized sensors (NLO in photonics) Materials interaction, covering machining (nonlinear absorption), spectroscopy (four-wave mixing), and microscopy (two-photon absorption) Serving as a comprehensive standalone resource on the subject for engineers and students without requiring pre-knowledge of advanced concepts, Nonlinear Optical Technology is an essential resource for those in fields that intersect with NLO applications and integration, as well as anyone who wishes to self-teach NLO concepts in general.

Nonlinear terahertz (THz) spectroscopy is a rapidly developing field, which is concerned with driving and observing nonlinear material responses in the THz range of the electromagnetic spectrum. In this thesis, I present several advances in nonlinear THz spectroscopy that expand the range of systems in which responses may be driven, the types of responses that may be initiated, and the way in which these responses may be observed. Sufficiently strong THz pulses are generated using the tilted-pulse-front technique, and are collected, focused, and detected using a THz spectrometer specifically designed for maximum peak THz electric field strength and maximum flexibility, allowing for a wide range of experimental geometries to be implemented. Further enhancement in the peak THz electric field strength is obtained through the use of metamaterial structures, which concentrate free-space THz fields in their antenna gaps. Impact ionization was observed in high-resistivity silicon, a material in which no nonlinear THz response had been previously seen, using metamaterial structures to enhance free space THz electric fields. Using three-dimensional metamaterial structures, the THz magnetic field is shown to also be capable of driving ionization processes both in high-resistivity silicon as well as air. Using metamaterial structures with open gaps, the THz electric field is shown to induce breakdown in air at both high and low pressures due to field ionization processes involving the gold metamaterial antennas. Furthermore, THz-driven electromigration of the gold metamaterial antennas is observed. Probing of THz-driven structural changes in both vanadium dioxide and perovskite ferroelectrics is demonstrated using femtosecond Xray pulses from the LCLS facility at the SLAC National Accelerator Laboratory. Finally, ongoing results involving energetic materials, stimulated Raman measurements, and Stark effect measurements are discussed. This work, coupled with the ongoing expansion of nonlinear THz techniques and potential applications demonstrates the continued development of nonlinear THz spectroscopy into a robust and valuable method for investigating fundamental processes in a multitude of systems.