The ability to control light with light at ultralow powers has been a major avenue of research in photonics with applications to optical communications, computation, and signal processing. Such light-by-light scattering is achieved in a medium with a strong light-matter interaction, and for the development of quantum information networks it is important to demonstrate such effects near the single-photon level. Alkali-metal vapors such as rubidium (Rb) enable strong light-matter interactions due to the large cross section per atom and well-defined energy level structure, while the use of optical fibers offers the advantage of possible integration with modern optical communication systems. Hollow-core photonic band-gap fibers (PBGFs) can combine both these technologies such that both the atoms and the optical fields are transversely confined to a region that is a few wavelengths in size, which offers the prospect of exploring few-photon nonlinear interactions. We generate large optical depths in such a Rb-PBGF system, and the tight light confinement, high vapor density and long interaction length allow us to perform nonlinear optics at ultralow power. We demonstrate large signal amplification (>100) and frequency conversion using a four-wave mixing process with only microwatts of pump power. This is, to our knowledge, the largest gain observed at such low power. We perturb the coherence of this four-wave mixing to demonstrate all-optical modulation at unprecedented bandwidths (~300 MHz) for an atomic-vapor system, with an energy density of only tens of pho- tons per atomic cross-section, comparable to that achieved in more elaborate setups based on cold-atomic clouds. We then demonstrate an enhancement of several orders of magnitude in degenerate two-photon absorption in our RbPBGF system over that achieved in bulk vapor cells in a focused beam geometry. This allows us to directly measure two-photon absorption from a beam by detecting its intensity on a photodiode. Further, employing a near-resonant, non-degenerate two-photon transition in Rb, we demonstrate all-optical intensity modulation with just a few photons (

Photonic structures such as photonic bandgap fibers and high confinement nanowaveguides have proven to be excellent platforms for studying nonlinear optical interactions tailored towards applications in spectroscopy, quantum communication, quantum computation protocols, optical clockwork and precision frequency metrology. This thesis discusses our approach towards exploiting these high confinement media for demonstrating novel few photon nonlinear optical interactions such as two-photon absorption and cross-phase modulation in hot atomic vapors (Rubidium) confined inside hollow-core photonic bandgap fibers (PBGF), generating ultra-broadband optical frequency combs that utilize cascaded parametric four-wave mixing and mode-locked femtosecond pulses in silicon nitride nanowaveguides. We generate large optical depths in such a Rb-PBGF system, and the tight light confinement, high vapor density and long interaction length allow us to perform nonlinear optics at ultralow power. We observe 25% all-optical modulation with

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.

This book reviews techniques used to characterize non-linear optical constants of chalcogenide glasses in bulk or thin films, and presents the properties of many chalcogenide systems. A range of applications of these glasses are surveyed, including ultra-fast switching, optical limiting, second harmonic generation and electro-optic effects. Also addressed are suitability of chalcogenide films in all-optical integrated circuits, fabrication of rib as well as ridge waveguides and of fiber gratings.

Nonlinear optics is a field of study resulting from laser beam interactions with materials which started with the advent of lasers in the early 60 s. This field of study is maturing dramatically while playing a major role in newly emerging photonic technologies. Nonlinear optics has spawned the development of numerous optical devices that have become indispensable in our daily lives. This exciting field has played a major role in the development of optical applications such as optical signal processing, optical computers, ultrafast switches, ultra-short pulsed lasers, sensors, laser amplifiers, and many others. This special review volume on Nonlinear Optics and Applications is intended for those who want to become more aware of some of the most recent developments in photonics and to provide a glimpse of the role of nonlinear optics in modern photonic technologies. It is also important to note that the vast quantity of research in nonlinear optics, optical materials, and nonlinear optical devices in the last five years alone is enormous, the totality of which is well beyond the scope of a single volume. This fact along with other constraints, such as communication and time, has made our efforts toward fair and comprehensive discussion of the most representative of modern advances in this vast field extremely difficult, and no doubt futile. Consequently, we apologize in advance to those whose high quality and equally significant work has been unavoidably left out. We are hopeful that similar volumes will follow, and that this dialogue will continue to expand. In this book, we give a survey on the recent advances of nonlinear optical applications. Emphasis will be on novel devices and materials, switching technology, optical computing, and important experimental results. We also include the recent developments in topics which are of historical interest to many researchers, and, at the same time, of potential use in the fields of all-optical communication and computing technologies. In addition, we enclosed a few new and unconventional related topics which might provoke new thinking and discussion. This review volume is designed to be of interest to a broad range of research scientists, engineers, and graduate students engaged in multidiscipline research areas such as optics, material science, chemistry, physics, lasers, fibers, semiconductors, computer and electrical engineering. The book is organized as follows: Chapter 1 provides an introduction and update to nonlinear optics and applications particularly as related to organic p-electron materials and devices fabricated from such materials. This chapter provides insight into the fundamental concepts and guiding principles leading to improved materials and devices. Chapter 2 gives a brief review of the nonlinear Schrodinger and associated equations that model spatio-temporal propagation in one and higher dimensions in nonlinear dispersive media. Fast adaptive numerical techniques were used to solve these equations. A unique variational approach is also outlined that helps in determining the ranges of nonlinearity and dispersion parameters. Chapter 3 is an update of the supercontinuum light source by professor Alfano, who observed the phenomenon for the first time in 1970. The phase change induced by an intense ultrashort laser pulse propagating through a medium causes a frequency sweep within the pulse envelope, resulting in a well-defined temporal chirp. A look into the nonlinear mechanisms involved in producing such a system and its potential applications are presented. Chapter 4 demonstrates wideband ultrashort pulse fiber laser sources using optical fibers and ultrashort pulse fiber lasers and a wavelength tuning range from 0.78 to 2.0 mm. The generation process and characteristics have been analyzed both experimentally and numerically. Chapter 5 provides an overview of experimental demonstrations and theoretical understanding of lattice fabrication (including 1D lattices, 2D square lattices and ring lattices, and lattices with structured defects), as well as their linear and nonlinear light guiding properties. Discrete diffraction and self-trapping are demonstrated in a variety of settings, including fundamental discrete solitons, discrete vector solitons, discrete dipole solitons, discrete vortex solitons, and necklace-like solitons. In addition, the formation of 1D and 2D lattices with single-site negative defects, and linear bandgap guidance in these structures are demonstrated. Chapter 6 discusses the second-order EO (Pockels) effect, the third-order (Kerr) and thermo-optical effects in optical waveguides and their applications in optical communication. Chapter 7 presents a theoretical study and experimental data of beam combination using Stimulated Brillouin Scattering for improving upon beam quality in optical fibers. The study includes both coherent and incoherent combination as well as two-beam phasing using the unique polarization characteristics of stimulated Brillouin scattering. Chapter 8 demonstrates theoretical and experimental results of a double-functional interferometer, using holographic recording of a dynamic grating in CdTe:V crystal. The mechanisms involved were attributed to a slow electro-optical effect and a fast free-carrier grating. Chapter 9 represents the poling process of optical polymers to induce second and third order nonlinear optical effects. The chapter attributes the electro-optic effect in polymers to the presence of chromophore in the polymer matrix and explains the different approaches for incorporating the chromophore into the polymer matrix. This chapter also describes the different poling methods, and explains accompanying mechanisms. Chapter 10 treats the effects of a magnetic field on materials, and its role in nonlinear optics. The chapter presents a set of experimental results, which prompts reconsideration of the role of magnetization in optics and predictions of optical magnetic resonance, negative permeability, and magnetic birefringence at optical frequencies. Chapter 11 describes observations of Stokes and anti-Stokes emissions of gold nano-particles as a three step process involving single-photon or three-photon excitation of electron-hole pairs, relaxation of excited electrons and holes, and emission from electron-hole recombination. This chapter also presents quantitative analyses of the experimental data. Chapter 12 explores the use of linear optics and the reliance on detection to design a number of optical logic gates that perform operations in the complex domain of linear optics and are converted to Boolean operations by the act of detection. These logic gates have no energy cost and the bandwidth is strictly limited by the electronic modulation and demodulation rate and can be integrated on chips with the electronics. Chapter 13 presents an answer to the important question: Can the electric field of a light wave be assigned a definite polarity? In other words, can an optical field vector be more up than down? It also describes physical experiments and devices where this polar asymmetry is generated and detected and also connects the answer to the independently developed, Nobel Prize-winning technique of generating stabilized combs of mode-locked frequency components of light. Chapter 14 presents an excellent review of chalcopyrite materials and their potential as compact highly sensitive nonlinear optical sensors, of potential for many remote sensing devices. The chapter also touches on the integration of miniaturized photonic nonlinear bandgap structures, which enhances the nonlinearity and minimizes problems associated with walk-off effects, and outlines a theoretical analysis of nonlinear propagation in these structures. Chapter 15 presents the status of the ultimate device, the development of which can be achieved within the time-frame of this 21st century through photonic technologies: optical computing. This chapter lists the different components of which the optical computer might consist of and lists the most recent advances in their development to date, along with a substantial list of the recent literature on each component. The chapter concludes with a discussion of obstacles yet to be overcome to enable building of such a system.

The efficient generation of single photon and entangled photon states is of considerable interest both for fundamental studies of quantum mechanics and practical applications, such as quantum communications and computation. It is now well known that correlated pairs of photons suitable for such applications can be generated directly in a guided mode of an optical fiber through the nonlinear process of spontaneous four-wave mixing. Detection of one photon of the pair can be used to herald the presence of the other, in order to realise a probabilistic heralded single photon source. Alternatively, both photons can be used directly as an entangled photon pair if the source is designed such that the two photons are correlated in one or more of their degrees of freedom. This chapter provides an overview of the progress that has been made into the development of photon sources based on four-wave mixing in optical fibers. A theoretical model of four-wave mixing is described in Section 12.2, which demonstrates how the dispersion characteristics of an optical fiber influence the properties of the photon pair state that is generated. Section 12.3 focusses on heralded single photon sources operating in both the anomalous and normal dispersion regimes of optical fiber, and highlights several experimental demonstrations of this type of source. Section 12.4 discusses the concept of non-classical interference and the parameters of the generated photons that can influence the interference visibility. Section 12.5 expands upon this discussion to consider two different approaches for preparing photons in pure states that have been used to demonstrate high visibility two-photon interference. Section 12.6 describes several different experimental implementations of entangled photon pair sources. Finally, two practical applications using fiber-based photon sources are presented, with an all-fiber, quantum controlled-NOT gate discussed in Section 12.7, and the potential to use photonic fusion to build up large photonic cluster states outlined in Section 12.8.

The XIX International Conference on Laser Spectroscopy, one of the leading conferences in the very diverse and still growing field of laser spectroscopy, was held in Hokkaido, Japan, on June 7-12, 2009. This volume, comprising a collection of invited contributions presented at the conference, will report on the latest developments in the area of laser spectroscopy and related fields: cold atoms and molecules, degenerate quantum gases, quantum optics, quantum information processing, precision measurements, atomic clock, ultra-fast lasers and strong field phenomena, and novel spectroscopic applications.