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

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 single- and 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.

Figure 1

Spectral channels of the driving wave from 1040 to 272 nm. The boundary wavelengths are 698, 501, and 347 nm. We extended the three experimentally demonstrated channels with a fourth super-Gaussian in the UV range.

Figure 2

Flow sheet of the genetic optimization process of a light-field synthesizer for the generation of tailored attosecond pulses.

Figure 3

Generation of short, isolated attosecond pulses. (a) Driver electric field (black solid line) and instantaneous half-cycle period (red dashed line). (b) The time-frequency map of the generated dipole radiation from the full Lewenstein integral shows the presence of the two trajectory components, (c) which results in the two pulses in the single-atom calculations. (d) Macroscopic effects, however, eliminate the second pulse, and spatial filtering also makes the remaining one shorter. Harmonics between 118 and 195 eV are used here for the synthesis of the attosecond pulse.

Figure 4

Double pulse, with 900-as separation. (a) The electric field (black solid line) and instantaneous half period (red dashed line) calculated from the phase derivative shows the complex structure of the driving field. (b) Time-frequency analysis showing the two pulses created in different half-cycles. Suppressing harmonics below 81 eV produces the two pulses which are present in both (c) single-atom and (d) macroscopic results.

Figure 5

Double pulse, with 700-as separation. (a) Generating electric field (black solid line) and instantaneous half period (red dashed line). (b) Time-frequency analysis showing the two pulses created in different half cycles. Spectral selection from 108 to 170 eV produces the two pulses which are present in both (c) single-atom and (d) macroscopic results.

Figure 6

Double pulse, with 300-as separation. (a) Generating electric field (black solid line) and instantaneous half period (red dashed line). (b) Time-frequency analysis showing the two pulses created in the same half cycle by short and long trajectories. (c) Spectral selection (from 130 to 166 eV) produces the two pulses in the single-atom calculations. (d) These merge in the near field but are again separated by spatial filtering of the harmonic beam.