Englische Version: This thesis exploits techniques of terahertz (THz) spectroscopy to investigate nonlinear low-frequency excitations of condensed matter. In particular, application of two-dimensional (2D) THz spectroscopy allows to disentangle different nonlinear signal contributions. The nonlinear polaronic response of solvated electrons and their surrounding solvent molecules in the polar liquid isopronal is studied. Solvated electrons are generated via multiphoton ionization. Longitudinal polaron oscillations with THz frequencies are impulsively excited during the ultrafast localization of the electrons. Perturbation of such polaron oscillations with an external THz pulse induces nonlinear changes of the transverse polaron polarizability, reflected in distinct modifications to the oscillation phase as mapped in 2D-THz experiments. Further, the generation of mono-cycle THz pulses from asymmetric semiconductor quantum wells upon resonant intersubband excitation in the mid-infrared (MIR) range is demonstrated. The temporal shape of the emitted THz electric field is modified by controlling pulse duration and peak electric field of the MIR driving pulses. Phase-resolved 2D-MIR experiments confirm that the THz emission is predominantly due to a nonlinear shift current generated upon femtosecond intersubband excitation. The influence of combined intra- and interband currents on symmetry properties, which opens novel quantum pathways for phonon excitation in narrow-band-gap materials, is demonstrated by 2D-THz experiments on bismuth. Nonperturbative long-wavelength excitation of charge carriers close to the L points leads to an anisotropic carrier distribution, reflected in a six-fold azimuthal angular dependence of the pump-induced change of THz transmission.[...].

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.

The Encyclopedia of Modern Optics, Second Edition, Five Volume Set provides a wide-ranging overview of the field, comprising authoritative reference articles for undergraduate and postgraduate students and those researching outside their area of expertise. Topics covered include classical and quantum optics, lasers, optical fibers and optical fiber systems, optical materials and light-emitting diodes (LEDs). Articles cover all subfields of optical physics and engineering, such as electro-optical design of modulators and detectors. This update contains contributions from international experts who discuss topics such as nano-photonics and plasmonics, optical interconnects, photonic crystals and 2D materials, such as graphene or holy fibers. Other topics of note include solar energy, high efficiency LED’s and their use in illumination, orbital angular momentum, quantum optics and information, metamaterials and transformation optics, high power fiber and UV fiber lasers, random lasers and bio-imaging. Addresses recent developments in the field and integrates concepts from fundamental physics with applications for manufacturing and engineering/design Provides a broad and interdisciplinary coverage of specialist areas Ensures that the material is appropriate for new researchers and those working in a new sub-field, as well as those in industry Thematically arranged and alphabetically indexed, with cross-references added to facilitate ease-of-use

Session 1 Elementary Excitations and Excitation Transport.- Picosecond Resolved Optically Driven Phonon Dynamics.- Relaxation and Propagation of High Frequency Phonons in Thin Crystalline Plates After Intense Laser Pumping.- Evolution in Real Time and Space of Short Polariton Pulses in Crystals.- Quasielastic Electronic Light Scattering in Semiconductors at Low Concentrations of Current Carriers.- Condensed Matter Science With Far Infra Red Free Electron Lasers (Abstract).- Nonequilibrium Terahertz Range Acoustic Phonons and Luminescence of Excitons in Semiconductors.- Session II Optical Properties of Surfaces and Interfaces.- Nonlinear Optical Studies of Molecular Adsorbates.- Enhancement of Exciton Transition Probabilities in Ultrathin Films of Cadmium Telluride.- Studies of Semiconductor Surfaces and Interfaces by Three Wave Mixing Spectroscopy (Abstract).- Time-Resolved Resonant Reflection of Light.- Femtosecond Photoemission Studies of Image Potential and Electron Dynamics in Metals.- High Intensity, Ultrashort Pulse Laser Heated Solids.- Session III Optical Studies of Growth, Instabilities and Pattern Formation.- Control of Transversal Interactions in Nonlinear Optics: New Spatio-Temporal Effects in Nonlinear Wave Dynamics (Abstract).- Synchronization of Atomic Quantum Transitions by Light Pulses.- Chaos in Nonlinear Optics.- Self-Organizaiton and Spatio-Temporal Chaos in Phase-Locked Semiconductor Laser Arrays (Abstract).- Competitive and Cooperative Dynamics in Optical Neural Networks (Abstract).- Transitions Between Ordered and Disordered Solid-Melt Patterns Formed on Silicon by Continuous Laser Beams: Competition Between Electrodynamics and Thermodynamics.- Session IV Elementary Excitations and Excitation Transport.- Light Scattering in Oxide Superconductors.- Raman Scattering in High-Tc Superconductors YBa2Cu3Ox With Different Oxygen Contents.- Raman Scattering from High Temperature Superconductors.- Decay of Exciton Gratings in Anthracene: Anisotropy of Lowest Exciton Bands and Coexistence of Longpath and Shortpath Waveguide Modes.- Excitation Transport in Polymeric Solids.- Vibron Lifetimes in Molecular Crystals.- Session V Optical Properties of Critical Phenomena Random Systems, and Coherent Phenomena.- Anomalies of the Elastic Light Scattering at Phase Transitions in Crystals with Point Defects.- Dynamical Fluctuations in a Dipolar Glass.- Localization of Light in Random Media (Abstract).- Quantum Optic and Transient Effects of Excitonic Polaritons, and Properties of Phonoritons.- Nonclassical Field Correlations in Quantum Optics (Abstract).- Phase-Conjugated Wave Enhanced by Weak Localization of Exciton-Polaritons.- Session VI Nonlinear Optical Properties of Semiconductors Organics and Fibers.- The Historical Relationship Between Nonlinear Optics and Condensed Matter (Abstract).- Optical Nonlinearities Enhanced by Carrier Transport.- Organic Nonlinear Optical Materials and Devices for Optoelectronics (Abstract).- Nonlinear Optical Susceptibilities of Surface Layers of Metals and Super- and Semiconductors Related to Electronic Structure and Crystal Symmetry.- Second Harmonic Generation in Optical Fibers.- Nonlinear Optical Probes of Glassy Polymers.- Session VII Quantum Wells.- Photoluminescence of Hot Electrons and Scattering Processes in Quantum-Well Structures.- High Resolution Nonlinear Laser Spectroscopy Measurements of Exciton Dynamics in GaAs Quantum Well Structures.- Optical Spectroscopy in the Regime of the Fractional Quantum Hall Effect.- Geminate Recombination in MQW Structures in a Magnetic Field.- Investigation of Two-Electron-Hole Pair Resonances in Semiconductor Quantum Dots.- Many Body Effects in Homogeneous Quasi 2D Electron-Hole Plasma in Undoped and Modulation Doped InGaAs Single Quantum Wells.- Session VIII Recent Significant Developments.- Pulsed Diffusing-Wave Spectroscopy in Dense Colloids.- Waves on Corrugated Surfaces: K-Gaps and Enhanced Backscattering.- Black Hole Radiation: Can Vir...

Session 1 Elementary Excitations and Excitation Transport.- Picosecond Resolved Optically Driven Phonon Dynamics.- Relaxation and Propagation of High Frequency Phonons in Thin Crystalline Plates After Intense Laser Pumping.- Evolution in Real Time and Space of Short Polariton Pulses in Crystals.- Quasielastic Electronic Light Scattering in Semiconductors at Low Concentrations of Current Carriers.- Condensed Matter Science With Far Infra Red Free Electron Lasers (Abstract).- Nonequilibrium Terahertz Range Acoustic Phonons and Luminescence of Excitons in Semiconductors.- Session II Optical Properties of Surfaces and Interfaces.- Nonlinear Optical Studies of Molecular Adsorbates.- Enhancement of Exciton Transition Probabilities in Ultrathin Films of Cadmium Telluride.- Studies of Semiconductor Surfaces and Interfaces by Three Wave Mixing Spectroscopy (Abstract).- Time-Resolved Resonant Reflection of Light.- Femtosecond Photoemission Studies of Image Potential and Electron Dynamics in Metals.- High Intensity, Ultrashort Pulse Laser Heated Solids.- Session III Optical Studies of Growth, Instabilities and Pattern Formation.- Control of Transversal Interactions in Nonlinear Optics: New Spatio-Temporal Effects in Nonlinear Wave Dynamics (Abstract).- Synchronization of Atomic Quantum Transitions by Light Pulses.- Chaos in Nonlinear Optics.- Self-Organizaiton and Spatio-Temporal Chaos in Phase-Locked Semiconductor Laser Arrays (Abstract).- Competitive and Cooperative Dynamics in Optical Neural Networks (Abstract).- Transitions Between Ordered and Disordered Solid-Melt Patterns Formed on Silicon by Continuous Laser Beams: Competition Between Electrodynamics and Thermodynamics.- Session IV Elementary Excitations and Excitation Transport.- Light Scattering in Oxide Superconductors.- Raman Scattering in High-Tc Superconductors YBa2Cu3Ox With Different Oxygen Contents.- Raman Scattering from High Temperature Superconductors.- Decay of Exciton Gratings in Anthracene: Anisotropy of Lowest Exciton Bands and Coexistence of Longpath and Shortpath Waveguide Modes.- Excitation Transport in Polymeric Solids.- Vibron Lifetimes in Molecular Crystals.- Session V Optical Properties of Critical Phenomena Random Systems, and Coherent Phenomena.- Anomalies of the Elastic Light Scattering at Phase Transitions in Crystals with Point Defects.- Dynamical Fluctuations in a Dipolar Glass.- Localization of Light in Random Media (Abstract).- Quantum Optic and Transient Effects of Excitonic Polaritons, and Properties of Phonoritons.- Nonclassical Field Correlations in Quantum Optics (Abstract).- Phase-Conjugated Wave Enhanced by Weak Localization of Exciton-Polaritons.- Session VI Nonlinear Optical Properties of Semiconductors Organics and Fibers.- The Historical Relationship Between Nonlinear Optics and Condensed Matter (Abstract).- Optical Nonlinearities Enhanced by Carrier Transport.- Organic Nonlinear Optical Materials and Devices for Optoelectronics (Abstract).- Nonlinear Optical Susceptibilities of Surface Layers of Metals and Super- and Semiconductors Related to Electronic Structure and Crystal Symmetry.- Second Harmonic Generation in Optical Fibers.- Nonlinear Optical Probes of Glassy Polymers.- Session VII Quantum Wells.- Photoluminescence of Hot Electrons and Scattering Processes in Quantum-Well Structures.- High Resolution Nonlinear Laser Spectroscopy Measurements of Exciton Dynamics in GaAs Quantum Well Structures.- Optical Spectroscopy in the Regime of the Fractional Quantum Hall Effect.- Geminate Recombination in MQW Structures in a Magnetic Field.- Investigation of Two-Electron-Hole Pair Resonances in Semiconductor Quantum Dots.- Many Body Effects in Homogeneous Quasi 2D Electron-Hole Plasma in Undoped and Modulation Doped InGaAs Single Quantum Wells.- Session VIII Recent Significant Developments.- Pulsed Diffusing-Wave Spectroscopy in Dense Colloids.- Waves on Corrugated Surfaces: K-Gaps and Enhanced Backscattering.- Black Hole Radiation: Can Vir...