Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain
the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in
Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles
and JavaScript.
When a medium is irradiated with a laser pulse so intense that it forces the medium's electrons to move in synchrony with the laser's electric field, the exact phase of this field with respect to the pulse envelope — known as the carrier-envelope hase (CEP) — plays an important role in determining how the medium responds. Measuring the value of this phase is challenging, and usually requires averaging over many pulses. In this issue, Charles Haworth and colleagues show that by analysing the high harmonics generated by the interaction of an intense femtosecond laser pulse with a gaseous medium, they can determine the CEP of a single pulse. Moreover, they suggest that such an approach could soon enable individual attosecond pulses emitted during a particular optical half-cycle of the driving field to be isolated.
How shock waves travel through a superfluid provides clues to understanding the deeper nature of Bose–Einstein condensation. An optical analogue that behaves as a pure superfluid could tell us what these clues mean.
Experimental evidence for discontinuous behaviour of the magnetization suggests that ferromagnetic transitions at very low temperatures are different from their high-temperature brethren, for which the phase transitions are usually continuous.
The ability to distinguish the high-harmonic emission generated by individual half-cycles of a driving laser leads to a simpler approach to characterizing the laser pulse and isolating a single attosecond pulse.
Traditionally, complex networks are classified on the basis of their global properties. But taking into account the modular structure of the network leads to a better understanding of how the underlying systems work.