We generated single-cycle isolated attosecond pulses around ∼36 electron volts using phase-stabilized 5-femtosecond driving pulses with a modulated polarization state. Using a complete temporal characterization technique, we demonstrated the compression of the generated pulses for as low as 130 attoseconds, corresponding to less than 1.2 optical cycles. Numerical simulations of the generation process show that the carrier-envelope phase of the attosecond pulses is stable. The availability of single-cycle isolated attosecond pulses opens the way to a new regime in ultrafast physics, in which the strong-field electron dynamics in atoms and molecules is driven by the electric field of the attosecond pulses rather than by their intensity profile.

An optical compression technique which is particularly suitable for ultrashort pulses of high energy is presented. Spectral broadening is achieved by pulse propagation along a hollow-core fused silica waveguide filled with noble gases at high pressure. Pulse compression is then obtained in a prisms dispersive delay line. Experiments performed with pulses of 140 fs duration and 660 μJ energy from a Ti:sapphire laser demonstrate the generation of compressed pulses of 10 fs duration and 240 μJ energy.

In the past decade, attosecond technology has opened up the investigation of ultrafast electronic processes in atoms, simple molecules, and solids. Here, we report the application of isolated attosecond pulses to prompt ionization of the amino acid phenylalanine and the subsequent detection of ultrafast dynamics on a sub–4.5-femtosecond temporal scale, which is shorter than the vibrational response of the molecule. The ability to initiate and observe such electronic dynamics in polyatomic molecules represents a crucial step forward in attosecond science, which is progressively moving toward the investigation of more and more complex systems.

High-energy 20-fs pulses generated by a Ti:sapphire laser system were spectrally broadened to more than 250 nm by self-phase modulation in a hollow fiber filled with noble gases and subsequently compressed in a broadband high-throughput dispersive system. Pulses as short as 4.5 fs with energy up to 20-$\mathit{\mu }\mathrm{J}$ were obtained with krypton, while pulses as short as 5 fs with energy up to $70 \mathit{\mu }\mathrm{J}$ were obtained with argon. These pulses are, to our knowledge, the shortest generated to date at multigigawatt peak powers.