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High harmonic generation

About: High harmonic generation is a research topic. Over the lifetime, 11694 publications have been published within this topic receiving 222650 citations. The topic is also known as: HHG.


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Journal ArticleDOI
21 Nov 2008-Science
TL;DR: Measurements of the HHG spectrum of N2 molecules aligned perpendicular to the laser polarization showed a maximum at the rotational half-revival, which indicates the influence of electrons occupying the orbital just below the N2 HOMO, referred to as the HomO-1.
Abstract: Molecular electronic states energetically below the highest occupied molecular orbital (HOMO) should contribute to laser-driven high harmonic generation (HHG), but this behavior has not been observed previously. Our measurements of the HHG spectrum of N2 molecules aligned perpendicular to the laser polarization showed a maximum at the rotational half-revival. This feature indicates the influence of electrons occupying the orbital just below the N2 HOMO, referred to as the HOMO-1. Such observations of lower-lying orbitals are essential to understanding subfemtosecond/subangstrom electronic motion in laser-excited molecules.

353 citations

Journal ArticleDOI
TL;DR: In this paper, the main experimental results on high-order harmonic generation in rare gases and their interpretation are reviewed and a review of the interpretation of the results can be found in Section 2.
Abstract: We briefly review the main experimental results on high—order harmonic generation in rare gases and their interpretation.

351 citations

Journal ArticleDOI
TL;DR: In this article, a single-mode nonlinear resonance acoustic spectroscopy (SIMONRAS) method was proposed to quantify the influence of mesoscopic features and damage in quasi-brittle materials.
Abstract: The presence of mesoscopic features and damage in quasi-brittle materials causes significant second-order and nonlinear effects on the acoustic wave propagation characteristics. In order to quantify the influence of such micro-inhomogeneities, a new and promising tool for nondestructive material testing has been developed and applied in the field of damage detection. The technique focuses on the acoustic nonlinear (i.e., amplitude-dependent) response of one of the material's resonance modes when driven at relatively small wave amplitudes. The method is termed single-mode nonlinear resonance acoustic spectroscopy (SIMONRAS). The behavior of damaged materials is manifested by amplitude dependent resonance frequency shifts, harmonic generation, and nonlinear attenuation. We illustrate the method by experiments on artificial slate tiles used in roofing construction. The sensitivity of this method to discern material damage is far greater than that of linear acoustic methods.

350 citations

Journal ArticleDOI
TL;DR: In this article, the authors studied absorption mechanisms for ultra-intense (I>10/sup 17/W/cm/sup 2/) laser pulses incident on solids and overdense plasma slabs.
Abstract: Absorption mechanisms for ultra-intense (I>10/sup 17/ W/cm/sup 2/) laser pulses incident on solids and overdense plasma slabs are discussed. We focus on the ultrashort pulse regime, i.e., where the laser pulse length is only a few to perhaps thousands of femtoseconds. Starting from well-known results at low intensity and long pulse length, we begin with absorption mechanisms such as inverse Bremstrahlung and classical resonance absorption and survey several additional absorption mechanisms significant for ultrashort, ultra-intense laser light interacting with overdense plasmas. Estimates for the fraction of laser energy absorbed by various mechanisms are given. It is found that the fraction of energy absorbed by the plasma, and the resulting electron temperatures, can depend considerably on the scale length of the plasma at the critical surface. It is also found that two-dimensional (2-D) effects greatly increase the amount of absorption into hot electrons, over the amount predicted using one-dimensional (1-D) theory. The inclusion of kinetic effects, collisionless absorption, and multidimensional effects are crucial to obtaining a complete picture of the interaction. We also review some of the experimental efforts to understand this complex process of absorption.

350 citations

Journal ArticleDOI
TL;DR: The rapidly decreasing microscopic single-atom yield, predicted for harmonics driven by longer-wavelength lasers, is compensated macroscopically by an increased optimal pressure for phase matching and a rapidly decreasing reabsorption of the generated X-rays, making tabletop, fully coherent, multi-keV X-ray sources feasible.
Abstract: We show how bright, tabletop, fully coherent hard X-ray beams can be generated through nonlinear upconversion of femtosecond laser light. By driving the high-order harmonic generation process using longer-wavelength midinfrared light, we show that, in theory, fully phase-matched frequency upconversion can extend into the hard X-ray region of the spectrum. We verify our scaling predictions experimentally by demonstrating phase matching in the soft X-ray region of the spectrum around 330 eV, using ultrafast driving laser pulses at 1.3-μm wavelength, in an extended, high-pressure, weakly ionized gas medium. We also show through calculations that scaling of the overall conversion efficiency is surprisingly favorable as the wavelength of the driving laser is increased, making tabletop, fully coherent, multi-keV X-ray sources feasible. The rapidly decreasing microscopic single-atom yield, predicted for harmonics driven by longer-wavelength lasers, is compensated macroscopically by an increased optimal pressure for phase matching and a rapidly decreasing reabsorption of the generated X-rays.

347 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023177
2022438
2021399
2020489
2019516
2018433