Topic
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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TL;DR: In this article, the results of a harmonic generation experiment in a simple gas (hydrogen) using 1-ps, 1- mu m laser pulses with a range of intensities extending from below to far above the laser ionization saturation threshold were reported.
Abstract: Reported are the results of a harmonic generation experiment in a simple gas (hydrogen) using 1-ps, 1- mu m laser pulses with a range of intensities extending from below to far above the laser ionization saturation threshold. The scaling with intensity above saturation of the third harmonic generated by a single laser-pulse in a filled gas cell is observed not to fit with a simple model that takes into consideration volume ionization effects alone. In another experiment, a pump-probe type, an upper limit on the conversion efficiency of third-harmonic generation in a preformed plasma is determined. It is found to be in agreement with the efficiency predicted by a relativistic harmonic generation theory. >
69 citations
TL;DR: In this article, the authors review the current state of tabletop extreme ultraviolet (XUV) sources based on high harmonic generation (HHG) in femtosecond enhancement cavities (fsEC), including current technical challenges to increasing the photon flux and maximum photon energy produced by this type of system.
Abstract: We review the current state of tabletop extreme ultraviolet (XUV) sources based on high harmonic generation (HHG) in femtosecond enhancement cavities (fsEC). Recent developments have enabled generation of high photon flux (1014 photons s?1) in the XUV, at high repetition rates (>50?MHz) and spanning the spectral region from 40 to 120?nm. This level of performance has enabled precision spectroscopy with XUV frequency combs and promises further applications in XUV spectroscopic and photoemission studies. We discuss the theory of operation and experimental details of the fsEC and XUV generation based on HHG, including current technical challenges to increasing the photon flux and maximum photon energy produced by this type of system. Current and future applications for these sources are also discussed.
69 citations
TL;DR: In this paper, a low-loss, indium-doped cadmium oxide thin film was used for high-harmonic generation from a thin film by leveraging the epsilon-near-zero (ENZ) effect, whereby the real part of the material permittivity in certain spectral ranges vanishes, as well as the associated large resonant enhancement of the driving laser field.
Abstract: High-harmonic generation (HHG) is a signature optical phenomenon of strongly driven, nonlinear optical systems. Specifically, the understanding of the HHG process in rare gases has played a key role in the development of attosecond science1. Recently, HHG has also been reported in solids, providing novel opportunities such as controlling strong-field and attosecond processes in dense optical media down to the nanoscale2. Here, we report HHG from a low-loss, indium-doped cadmium oxide thin film by leveraging the epsilon-near-zero (ENZ) effect3–8, whereby the real part of the material’s permittivity in certain spectral ranges vanishes, as well as the associated large resonant enhancement of the driving laser field. We find that ENZ-assisted harmonics exhibit a pronounced spectral redshift as well as linewidth broadening, resulting from the photo induced electron heating and the consequent time-dependent ENZ wavelength of the material. Our results provide a new platform to study strong-field and ultrafast electron dynamics in ENZ materials, reveal new degrees of freedom for spectral and temporal control of HHG, and open up the possibilities of compact solid-state attosecond light sources. High harmonics are generated from a thin film by leveraging the epsilon-near-zero effect. These kinds of harmonic are found to exhibit a pronounced spectral redshift as well as linewidth broadening caused by the time-dependency of this effect.
69 citations
TL;DR: In this article, an intuitive semiclassical model that makes use of the recently measured initial transverse momentum of tunneling ionization was developed to predict the dependence of the high-orderharmonic yield on driving laser ellipticity.
Abstract: High-order-harmonic-generation yield is remarkably sensitive to driving laser ellipticity, which is interesting from a fundamental point of view as well as for applications. The most well-known example is the generation of isolated attosecond pulses via polarization gating. We develop an intuitive semiclassical model that makes use of the recently measured initial transverse momentum of tunneling ionization. The model is able to predict the dependence of the high-order-harmonic yield on driving laser ellipticity and is in good agreement with experimental results and predictions from a numerically solved time-dependent Schr\"odinger equation.
69 citations
TL;DR: In this paper, a static cell at high pump energies, 5 m focal length, and up to 14 cm interaction length was studied for the generation of high-order harmonics in Xe.
Abstract: Generation of high-order harmonics in Xe was studied in a static cell at high pump energies, 5 m focal length, and up to 14 cm interaction lengths. Self-guided propagation of the pulse was observed experimentally and confirmed by a three-dimensional model. Phase-matched generation was demonstrated in the self-guided beam, and the high energy and low divergence of the harmonic radiation were explained. Harmonic field calculations, in good agreement with experimental results, allow for the explanation of the higher-order harmonic generation dynamics in the self-guided region.
69 citations