Nonlinear Terahertz Spectroscopy in One and Two Dimensions PDF Download

Author: Wilhelm Kühn
Publisher:
ISBN:
Category :
Languages : en
Pages : 165

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Author: Thomas Elsaesser
Publisher: Morgan & Claypool Publishers
ISBN: 1643272160
Category : Science
Languages : en
Pages : 159

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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.

Author: Matthias Runge
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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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.[...].

Author: Sayyed Hadi Razavi-Pour
Publisher:
ISBN:
Category :
Languages : en
Pages :

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"Reducing the dimensionality of a material from 3D to 2D introduces new quantum effects that can be exploited to see new physics and produce new devices. Two examples of such materials are graphene, a single layer of carbon atoms, and quantum well heterostructures confining charges to a planar potential well. A powerful method for observing charge transport in these 2D materials is time-resolved terahertz (THz) spectroscopy, using picosecond pulses of far-infrared light to measure the complex valued ac conductivity. In this thesis, THz spectroscopy is used to study the linear and nonlinear electrodynamic response of two 2D systems: graphene and self-assembled metal halide perovskite quantum wells. In graphene, THz field-induced bleaching is studied, found to be well described by simple phenomenological reduction in intraband absorption using a free carrier Drude model that includes neutral and charged impurity scattering as well as optical phonon scattering. The Fermi level dependence of this nonlinearity is studied for the first time, which allows us to separate the contributions of long and short range momentum scattering and map their dependence on the field amplitude. We find, contrary to previous work, that the increase in scattering cannot be explained by an increase in the lattice temperature alone and that other mechanisms such as carrier-carrier scattering must be accounted for to explain the effect. Our results provide a deeper understanding of transport in graphene devices operating at THz frequencies and in modest kV/cm field strengths present in most devices. Second, time-resolved multi-THz spectroscopy was used to investigate carrier dynamics in 2D organic metallic halide perovskite (OMHP) systems. The 2D OMHPs are promising photovoltaic materials showing reduced sensitivity to environmental degradation, however their photoconductivity response has been unexplored on ultrafast time scales. We observed a rapid decay of injected photocarriers on a 10-100 ps time scale, indicating a significant trap/decay channel that limits device performance. Supporting hyperspectral photoluminescent imaging measurements confirm the band gap shift of the naturally formed quantum wells, however also show significant surface structural defects serving as monomolecular traps. We show how mono-molecular, bimolecular and Auger constants are sensitive to the changes in the electronic confinement of the quantum wells, of importance to devices attempting to exploit their tunable optical properties and environmental stability." --

Author: Qiang Wang
Publisher: John Wiley & Sons
ISBN: 3527838279
Category : Technology & Engineering
Languages : en
Pages : 373

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Book Description
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.

Author: Xian Li (Ph.D.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 210

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In this thesis, I describe work aimed at understanding nonlinear material responses initiated by strong terahertz (THz) field excitation. I discuss two aspects of nonlinear THz spectroscopy in condensed-matter materials: developments of experimental THz capabilities and spectroscopy methods and their applications in investigating ultrafast nonlinear dynamics in different classes of materials. I first describe the THz generation, detection and spectroscopy methods, which are the basis of all of our studies. We have generated strong single- and multi-cycle THz pulses covering several spectral ranges using inorganic and organic crystals and developed linear and nonlinear THz spectroscopy techniques to interrogate light-matter interactions based on different observables and/or symmetry criteria. We have demonstrated a new method for studying time-domain electron paramagnetic resonance that allows us to measure THz-frequency fine structures of spin energy levels on a tabletop and have developed nonlinear two-dimensional (2D) magnetic resonance spectroscopy to distinguish nonlinear THz-spin interaction pathways. We also show that THz-pump, optical-probe spectroscopy, including THz field-induced second-harmonic generation spectroscopy and THz Kerr effect spectroscopy, can be extended to study phase transitions in quantum paraelectric and topological materials. We have employed the THz methods to drive and detect nonlinear responses from several degrees of freedom in the materials. We have demonstrated collective coherent control over material structure by inducing a quantum paraelectric to ferroelectric phase transition using intense THz electric fields in strontium titanate. We show that a single-cycle THz field is able to drive ions along the microscopic pathway leading directly to their locations in a new crystalline phase on an ultrafast timescale. We have driven highly nonlinear lattice and electronic responses in a topological crystalline insulator by dynamically perturbing the protecting crystalline symmetry through THz phonon excitation. We have observed oscillations in optical reflectivity that may be associated with electronic gap opening and modulation in the topological surface states. Finally, we have demonstrated nonlinear manipulation of collective spin waves in a canted antiferromagnet using strong THz magnetic fields and we have observed full sets of the second- and third-order nonlinear responses in 2D THz magnetic resonance spectra, which are accurately reproduced in our numerical simulations.

Author: Byounghwak Lee
Publisher:
ISBN:
Category : Carbon nanotubes
Languages : en
Pages : 118

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This dissertation presents nonlinear terahertz (THz) properties of carbon nanomaterials investigated by time-resolved high-field THz spectroscopy. In order to determine THz characteristics of nanomaterials, we performed THz power spectrum measurement, THz raster imaging, THz time-domain spectroscopy (THz-TDS) and time-resolved pump-probe experiment on two different types of single layer graphene and a free standing multi-walled carbon nanotubes (MWCNTs), utilizing strong single-cycle THz pulses (central frequency, 0.9 THz; bandwidth, 1 THz; THz field amplitude, E_THz>1 MV/cm) generated by optical rectification (a second order nonlinear optical process) of femtosecond laser pulses (pulse energy, 1 mJ; pulse duration, 100 fs; repetition rate, 1 kHz) with titled pulse front for phase matching between optical and THz pulses in LiNbO3 crystal. Strong and broadband THz pulses induce transparency single layer graphene grown by catalytic chemical vapor deposition (CVD). A substrate-free homogeneous graphene becomes more transparent to the THz radiation than an inhomogeneous graphene on silicon as the peak strength of THz field increases over 50kV/cm considered as the threshold of the nonlinear transparency effect. The experimental results show that suspended graphene is more efficient to manipulate THz signal than one with a substrate. Free-standing MWCNTs drawn from a forest of MWCNTs synthesized by CVD exhibit highly anisotropic linear and nonlinear THz responses. There are no nonlinear effects for the polarization perpendicular to the MWCNT axis, whereas, in the parallel polarization configuration, intense THz pulses induce nonlinear absorption in the quasi-one-dimensional conducting media. That is, it is revealed via time-resolved measurements of transmitted THz pulses and a theoretical analysis of the data that strong THz fields enhance permittivity in carbon nanotubes by generating charge carriers. Optical-Pump/THz-probe (OPTP) spectroscopy shows that optical pump pulses induce interband transitions in MWCNTs: Its conductivity is increased by generating photo-excited hot-carriers as the optical pump energy increases. On the other hand, Optical-Pump/Intense THz-Pump spectroscopy (OPITP) exhibits three carrier dynamics phenomena which are optical pump-induced absorption, THz field-induced absorption and transparency in MWCNTs: Intense THz and optical pump energies (E_THz

Author: Nathaniel Curran Brandt
Publisher:
ISBN:
Category :
Languages : en
Pages : 176

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Book Description
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.

Author: Bob D. Guenther
Publisher: Academic Press
ISBN: 0128149825
Category : Technology & Engineering
Languages : en
Pages : 2253

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Book Description
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

Author: Federico Capasso
Publisher: Walter de Gruyter GmbH & Co KG
ISBN: 3110710684
Category : Technology & Engineering
Languages : en
Pages : 783

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Book Description
This book provides a cutting-edge research overview on the latest developments in the field of Optics and Photonics. All chapters are authored by the pioneers in their field and will cover the developments in Quantum Photonics, Optical properties of 2D Materials, Optical Sensors, Organic Opto-electronics, Nanophotonics, Metamaterials, Plasmonics, Quantum Cascade lasers, LEDs, Biophotonics and biomedical photonics and spectroscopy.