High-order parametric generation of coherent XUV radiation

Abstract

Extreme ultraviolet (XUV) radiation finds numerous applications in spectroscopy. When the XUV light is generated via high-order harmonic generation (HHG), it may be produced in the form of attosecond pulses, allowing access to unprecedented ultrafast phenomena. However, the HHG efficiency remains limited. Here we present an observation of a new regime of coherent XUV emission which has a potential to provide higher XUV intensity, vital for applications. We explain the process by high-order parametric generation, involving the combined emission of THz and XUV photons, where the phase matching is very robust against ionization. This introduces a way to use higher-energy driving pulses, thus generating more XUV photons.

Roles of the transition amplitude phases in photoelectron asymmetry of single strong attosecond pulse

“…23)) and LP (right column, equation ( 26)) pulses. Black dashed lines ('extracted') in panels (a) and (b) are calculated by equation (23) for CP pulse and calculated by equation (26) for LP pulse, but the amplitudes X i or X i (i = 0, 1, 2) and phase difference a 21 are extracted from TDSE, not calculated by PT or SFM. The laser intensity is I 0 = 5 × 10 15 W cm −2 , the photon energy is ω = 13.6 eV, and the CEP φ = 0.…”

“…Coherent and ultrashort pulse radiation is widely generated from x-ray free-electron lasers [22] and laser-driven XUV and x-ray sources [23]. Though these XUV pulses in the intensities of the order of 10 15 -10 16 W cm −2 is not available experimentally, they are expected to become reality by the high-order frequency mixing (HFM) [24,25] or high-order parametric generation process [26]. For the tunning of CEP of XUV pulses, reference [20] pointed out that the attosecond CEP could be finely tuned by using aluminum foils with variable thickness.…”

Generation of Attosecond Pulses with Controllable Carrier-Envelope Phase via High-order Frequency Mixing

“…Namely, the process is indissolubly connected to the photoionization of the medium, and the change in the refractive index due to the ionization leads to weaker phase matching [20]. This limitation can be significantly softened for the HFM process under a proper choice of frequencies of the generating fields [21][22][23][24][25], resulting in much longer propagation distances of the phase-matched generation (including the case when second field has much weaker intensity and much lower frequency than the fundamental) and thus to higher efficiency of the HFM [26,27]. This advantage defines the perspective of using the HFM process to design highly-effective attosecond pulse sources.…”

Shining the shortest flashes of light on the secret life of electrons

“…49,50 This possibility breaks many of the assumptions held during the construction of quantum mechanics in the 1920s and 1930s, similarly to the prospects offered by the manipulation of individual quantum systems. 51,52 The attosecond pulses produced via HHG have also been joined by pulses from additional sources, including other high-order parametric processes, 53 oscillating relativistic plasma mirrors, 54 and, most importantly, facility-scale X-ray free-electron lasers. 55 XFELs also offer attosecond capabilities, at high brightness, and with a nuanced set of trade-offs regarding coherence and timing precision.…”

“…The attosecond pulses produced via HHG have also been joined by pulses from additional sources, including other high-order parametric processes, 53 oscillating relativistic plasma mirrors, 54 and, most importantly, facility-scale X-ray free-electron lasers 55 . XFELs also offer at- tosecond capabilities, at high brightness, and with a nuanced set of trade-offs regarding coherence and timing precision.…”