31 research outputs found
Influence of generalized focusing of few-cycle Gaussian pulses in attosecond pulse generation
In contrast to the case of quasi-monochromatic waves, a focused optical pulse
in the few-cycle limit may exhibit two independent curved wavefronts,
associated with phase and group retardations, respectively. Focusing optical
elements will generally affect these two wavefronts differently, thus leading
to very different behavior of the pulse near focus. As limiting cases, we
consider an ideal diffractive lens introducing only phase retardations and a
perfect non-dispersive refractive lens (or a curved mirror) introducing equal
phase and group retardations. We study the resulting diffraction effects on the
pulse, finding both strong deformations of the pulse shape and shifts in the
spectrum. We then show how important these effects can be in highly nonlinear
optics, by studying their role in attosecond pulse generation. In particular,
the focusing effects are found to affect substantially the generation of
isolated attosecond pulses in gases from few-cycle fundamental optical fields.Comment: 8 pages and 6 figure
The effect of plasma-core induced self-guiding on phase matching of high-order harmonic generation in gases
In this work we numerically study a self-guiding process in which ionization
plays a dominant role and analyze its effect on high-order harmonic generation
(HHG) in gases. Although this type of self-guiding --- termed as plasma-core
induced self-guiding in previous works --- limits the achievable cut-off by
regulating the intensity of the laser beam, it provides favorable conditions
for phase matching, which is indispensable for high-flux gas high-harmonic
sources. To underline the role of self-guiding in efficient HHG, we investigate
the time-dependent phase matching conditions in the guided beam and show how
the spatio-temporally constant fundamental intensity contributes to the
constructive build-up of the harmonic field in a broad photon-energy range up
to the provided cut-off.Comment: 14 pages, 7 figure
Effect of plasma-core-induced self-guiding on phase matching of high-order harmonic generation in gases
In this work, we numerically study a self-guiding process in which ionization plays a dominant role and analyze its effect on high-order harmonic generation (HHG) in gases. Although this type of self-guiding-termed "plasma-core-induced self-guiding" in previous works-limits the achievable cutoff by regulating the intensity of the laser beam, it provides favorable conditions for phase matching, which is indispensable for high-flux-gas highharmonic sources. To underline the role of self-guiding in efficient HHG, we investigate the time-dependent phase-matching conditions in the guided beam and show how the spatiotemporally constant fundamental intensity contributes to the constructive buildup of the harmonic field in a broad photon energy range up to the provided cutoff. (c) 2019 Optical Society of Americ