Enhancement and broadening of extreme-ultraviolet supercontinuum in a relative phase controlled two-color laser field

Abstract

We experimentally demonstrate the generation of an extreme-ultraviolet (XUV) supercontinuum in argon with a two-color laser field consisting of an intense 7 fs pulse at 800 nm and a relatively weak 37 fs pulse at 400 nm. By controlling the relative time delay between the two laser pulses, we observe enhanced high-order harmonic generation as well as spectral broadening of the supercontinuum. A method to produce isolated attosecond pulses with variable width and intensity is proposed.

Generating elliptically polarized isolated attosecond pulses from the 2 p 0 state of He + with a linearly polarized two-color field

“…During the recombination process, a photon with energy equaling to the ionization potential plus the kinetic energy is emitted. Various gating schemes have been proposed to produce isolated attosecond pulses according to the model, such as using a few-cycle laser [5,6], polarization gating [7][8][9][10][11][12], ionization gating [13,14] and two-color or multi-color field [15][16][17][18][19][20][21][22][23][24][25][26], and so on.…”

“…Therefore, it is urgently desired to produceelliptically polarized isolated attosecond pulses with broader bandwidth and shorter duration. Because the twocolor scheme can significantly enlarge the difference between the highest and the second highest half-cycle photon energies, and generate a broadband supercontinuum near the cutoff [26], we theoretically investigate the He þ prepared in an initial 2p 0 irradiated by a linearly polarized two-color field by numerically solving the three-dimensional Schrodinger equation in this work. It is shown that the two-color field can produce the elliptically polarized supercontinuum with broader bandwidth by controlling the acceleration step of high-order harmonic generation.…”

Extension of harmonic cut-off in a waveform controlled laser field by prolonging the recombining period

“…High-order harmonic generation (HHG) has shown itself to be the most promising method for the production of attosecond pulses, by interaction between an intense laser pulse and atomic or molecular system (Dombi et al, 2009;Dromey et al, 2009;Gupta et al, 2007;Hafeez et al, 2008;Ozaki et al, 2007;Verma & Sharma, 2009;Zeng et al, 2007, Zheng et al, 2008Zhang et al, 2009;Hong et al, 2009). Although HHG from ions (Teubner & Gibbon, 2009;Krausz & Ivanov, 2009) can be more efficient due to the higher laser intensity (above 10 15 -10 16 W/cm 2 ) being applicable, the phase matching condition of harmonic generation is difficult to achieve due to the presence of strong plasma.…”

Tunable phase-stabilized infrared optical parametric amplifier for high-order harmonic generation

“…The generation of these pulses is based on the nonlinear interactions between laser and atoms: high-order harmonic generation (HHG) or stimulated Raman scattering. The stability of the carrierenvelope phase (CEP) of driven pulses is extremely important in the HHG for the generation and measurement of an isolated attosecond pulse [1,2].The single-atom dipole response enhances as the central wavelength of driven pulses increases; therefore, the longer pump laser wavelength leads to the higher cutoff energy in the spectrum of highharmonic radiation. However, for the longer carrier wavelength, the electron wave packet experiences a longer propagation distance before recombining with the parent ion and thus a higher quantummechanical diffusion, which leads to the decrease in the HHG conversion efficiency.…”

“…The generation of these pulses is based on the nonlinear interactions between laser and atoms: high-order harmonic generation (HHG) or stimulated Raman scattering. The stability of the carrierenvelope phase (CEP) of driven pulses is extremely important in the HHG for the generation and measurement of an isolated attosecond pulse [1,2].…”