Optical attosecond pulses and tracking the nonlinear response of bound electrons

Abstract

The time it takes a bound electron to respond to the electromagnetic force of light sets a fundamental speed limit on the dynamic control of matter and electromagnetic signal processing. Time-integrated measurements of the nonlinear refractive index of matter indicate that the nonlinear response of bound electrons to optical fields is not instantaneous; however, a complete spectral characterization of the nonlinear susceptibility tensors--which is essential to deduce the temporal response of a medium to arbitrary driving forces using spectral measurements--has not yet been achieved. With the establishment of attosecond chronoscopy, the impulsive response of positive-energy electrons to electromagnetic fields has been explored through ionization of atoms and solids by an extreme-ultraviolet attosecond pulse or by strong near-infrared fields. However, none of the attosecond studies carried out so far have provided direct access to the nonlinear response of bound electrons. Here we demonstrate that intense optical attosecond pulses synthesized in the visible and nearby spectral ranges allow sub-femtosecond control and metrology of bound-electron dynamics. Vacuum ultraviolet spectra emanating from krypton atoms, exposed to intense waveform-controlled optical attosecond pulses, reveal a finite nonlinear response time of bound electrons of up to 115 attoseconds, which is sensitive to and controllable by the super-octave optical field. Our study could enable new spectroscopies of bound electrons in atomic, molecular or lattice potentials of solids, as well as light-based electronics operating on sub-femtosecond timescales and at petahertz rates.

Efficient broadband highly dispersive HfO_2/SiO_2 multilayer mirror for pulse compression in near ultraviolet

“…A customized set of UV DMs was produced. Their implementation allowed post compression down to 6.5 fs [22] corresponding well to the theoretical estimation of 6.9 fs, shown in Fig. 3, for initial design.…”

“…Here we present broadband highly dispersive mirrors designed for the central wavelength of 325 nm, that were successfully implemented for post compression of the UV pulse down to ∼7 fs [22]. By tuning the structure of the multilayer stack, we managed to significantly suppress the linear and nonlinear absorbance [23] and reach the overall reflectance of 94% and the total compressor efficiency of ≥ 50% in straight forward set up.…”

Nonlinear optical polarization response and plasma generation in noble gases: Comparison of metastable-electronic-state-approach models to experiments

“…The polarization, as a function of time, becomes ever slightly retarded with respect to the driving wave, with a delay given by a textbook argument based on the ionization potential. This was only recently verified in an experiment [26], showing a delay on the order of a hundred attoseconds. Such a small value is negligible for the present purposes.…”

The Application of Coherent Local Time for Optical Time Transfer and the Quantification of Systematic Errors in Satellite Laser Ranging

“…Over 5 orders of magnitude of variation of the input intensity caused a non-linear change in detector timing delay of more than 500 ps between the various components of the ranging system, the optical echo detection process also contributes to the error budget. The response of a bound electron to the electromagnetic force of light is fast but not instantaneous (Hassan et al 2016). While the resultant delay is on the sub-fs timescale in the interaction of electrons to light, the macroscopic response, namely the time delay between the arrival of a short light pulse and the appearance of the electrical output voltage on a fast linear detector is already of the order of 211 ps and for a high bandwidth photon counting device this builds up to about 1.745 ns ), leading to a large gap with significant uncertainty between the moment of arrival of an optical signal at the detector and the actual electrical timing output response.…”