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Nonlinear Optics || Quantum-Mechanical Theory of the Nonlinear Optical Susceptibility
摘要： In this chapter, we use the laws of quantum mechanics to derive explicit expressions for the nonlinear optical susceptibility. The motivation for obtaining these expressions is at least three-fold: (1) these expressions display the functional form of the nonlinear optical susceptibility and hence show how the susceptibility depends on material parameters such as dipole transition moments and atomic energy levels, (2) these expressions display the internal symmetries of the susceptibility, and (3) these expressions can be used to make predictions of the numerical values of the nonlinear susceptibilities. These numerical predictions are particularly reliable for the case of atomic vapors, because the atomic parameters (such as atomic energy levels and dipole transition moments) that appear in the quantum-mechanical expressions are often known with high accuracy. In addition, since the energy levels of free atoms are very sharp (as opposed to the case of most solids, where allowed energies have the form of broad bands), it is possible to obtain very large values of the nonlinear susceptibility through the technique of resonance enhancement. The idea behind resonance enhancement of the nonlinear optical susceptibility is shown schematically in Fig. 3.1.1 for the case of third-harmonic generation. In part (a) of this figure, we show the process of third-harmonic generation in terms of the virtual levels introduced in Chapter 1. In part (b) we also show real atomic levels, indicated by solid horizontal lines. If one of the real atomic levels is nearly coincident with one of the virtual levels of the indicated process, the coupling between the radiation and the atom becomes particularly strong and the nonlinear optical susceptibility becomes large.
关键词： resonance enhancement,quantum mechanics,nonlinear optical susceptibility,third-harmonic generation,dipole transition moments,atomic energy levels
更新于2025-09-23 15:21:01
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Resonance Enhancement in Laser-Produced Plasmas (Concepts and Applications) || Front Matter
摘要： The motivation in writing this book is to show the most recent findings of newly emerged field of resonance-enhanced high-order harmonic generation (HHG) using the laser pulses propagating through the narrow and extended laser-produced plasma plumes. It becomes obvious that the developments in this field are aimed for improvement of harmonic yield through precise study of resonance effects during fine-tuning of driving pulses to the resonances. The purpose of writing this book is to acquaint the readers with the most advanced, recently developed methods of plasma harmonics generation at the conditions of coincidence of some harmonics, autoionizing states, and some ionic transitions possessing strong oscillator strengths. This book demonstrates how one can improve the plasma harmonic technique using this approach.
关键词： extreme ultraviolet,plasma harmonics,laser-produced plasmas,high-order harmonic generation,resonance enhancement,XUV,nonlinear optics,HHG
更新于2025-09-19 17:13:59
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Resonance Enhancement in Laser-Produced Plasmas (Concepts and Applications) || Resonance Enhancement of Harmonics in Metal-Ablated Plasmas: Early Studies
摘要： In this subsection, the first observation of an exceptionally strong resonance enhancement of a single harmonic in a plateau region is described. This phenomenon was observed during investigations of harmonic generation from femtosecond pulse interacting with indium plasma. A very strong 13th harmonic generation (λ = 61.2 nm), almost 2 orders of magnitude, exceeding the intensities of neighboring harmonics in the plateau range was observed in those studies [1].
关键词： harmonics,femtosecond pulse,extreme ultraviolet,indium plasma,resonance enhancement
更新于2025-09-11 14:15:04
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Resonance Enhancement in Laser-Produced Plasmas (Concepts and Applications) || Resonance Processes at Different Conditions of Harmonic Generation in Laser-Produced Plasmas
摘要： Resonance Processes at Different Conditions of Harmonic Generation in Laser-Produced Plasmas
关键词： resonance enhancement,laser-produced plasmas,picosecond pulses,high-order harmonic generation,harmonic generation
更新于2025-09-11 14:15:04