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.

Electrons emit light, carry electric current, and bind atoms together to form molecules. Insight into and control of their atomic-scale motion are the key to understanding the functioning of biological systems, developing efficient sources of x-ray light, and speeding up electronics. Capturing and steering this electron motion require attosecond resolution and control, respectively (1 attosecond = 10(-18) seconds). A recent revolution in technology has afforded these capabilities: Controlled light waves can steer electrons inside and around atoms, marking the birth of lightwave electronics. Isolated attosecond pulses, well reproduced and fully characterized, demonstrate the power of the new technology. Controlled few-cycle light waves and synchronized attosecond pulses constitute its key tools. We review the current state of lightwave electronics and highlight some future directions.

We present a two-stage noncollinear optical parametric chirped-pulse amplification system that generates 7.9 fs pulses containing 130 mJ of energy at an 805 nm central wavelength and 10 Hz repetition rate. These 16 TW light pulses are compressed to within 5% of their Fourier limit and are carefully characterized by the use of home-built pulse diagnostics. The contrast ratio before the main pulse has been measured as 10(-4), 10(-8), and 10(-11) at t=-3.3 ps, t=-5 ps, and t=-30 ps, respectively. This source allows for experiments in a regime of relativistic light-matter interactions and attosecond science.

We produce carrier-envelope-phase-stable 15.7-fs (2-cycle) 740-microJ pulses at the 2.1-microm carrier wavelength, from a three-stage optical parametric chirped-pulse amplifier system, pumped by an optically synchronized 49-ps 11-mJ Nd:YLF laser. A novel seed pulse spectral shaping method is used to ascertain the true amplified seed energy and the parametric superfluorescence levels.

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