Genetic optimization of attosecond-pulse generation in light-field synthesizers

Abstract

We demonstrate control over attosecond-pulse generation and shaping by numerically optimizing the synthesis of few-cycle to subcycle driver wave forms. The optical wave-form synthesis takes place in an ultrabroad spectral band covering the ultraviolet-infrared domain. These optimized driver waves are used for ultrashort singleand double-attosecond-pulse production (with tunable separation), revealing the potentials of the light wave synthesizer device demonstrated by A. Wirth et al. [Science 334, 195 (2011)]. The robustness of the results are also analyzed with respect to attosecond-pulse propagation phenomena.

Toward Waveform Nonlinear Optics Using Multimillijoule Sub-Cycle Waveform Synthesizers

“…The use of a sub-cycle optical waveform as a driving pulse for HHG would enable to naturally limit emission/recollision to a single event, greatly increasing the efficiency of IAP generation, as already demonstrated in first experiments [5], [6]. Additionally, a sub-cycle optical waveform would permit control of the tunnel ionization step [8] and enable to precisely manipulate the electron trajectory in the continuum, optimizing its kinetic energy and the corresponding energy cutoff of the HHG spectrum, realizing experimentally the theoretically predicted "perfect waveform" for HHG [9]- [14].…”

Macroscopic study and control of high-order harmonic and attosecond pulse generation in noble gases

“…The results to be presented here focus on the possibilities to increase the HHG cutoff, isolate single attosecond pulses from a pulse train while also minimizing its duration, increase harmonic yield at high photon energies, and in general to understand macroscopic processes in HHG. These are based on our theoretical papers about THz assisted attosecond pulse generation [2,3,4], quasi-phase matching of HOH radiation and its study for the special case of perpendicularly propagating IR and THz fields [5,6,7], optimization of attosecond pulse generation in light-field synthesizers [10], and an experimental study of attosecond GD dependence on generation gas pressure [8].…”

“…Thus the phase difference between the propagated and generated fields (ϕ q (z) − φ q (z)) is exactly half the value of the phase-difference between ϕ q (0) and ϕ q (z) (see Figure II.11.a). Due to this, the intensity of the radiation increases until z = π/∆k 10 Later it will be shown that this is equivalent to describing the process in a different coordinate frame, and does not affect the results discussed here.…”

“…These tools make use of a multi-parameter control over different colour ultrashort pulses, combined together to sculpt the electric field of a one-cycle pulse. I supervised the integration of a single-atom HHG model into the optimization algorithm and performed the macroscopic modelling of the process [10].…”

“…To illustrate the evolution of harmonics along the axis, the zk q part of Equation II.25 is discarded for the moment 10 , and the emission rate is taken to be unity. The field along the z axis is then given by…”