control atoms with light, and control light with atoms,

and to do this on the attosecond (1 as = 10^-18 s)  to femtosecond (1 fs = 10^-15 s)  timescales in the extreme ultraviolet (XUV) wavelength region.

Coherent light in the XUV region, with a pulse duration on the order of 100 attoseconds, can be produced when intense laser pulses interact with a gaseous target. It is our aim to control the properties of this light and use it to study and control electron motion.

The vision is to extend the possibility of controlling the properties of light from the visible region, where this is routinely done today, to the XUV region where the tools are currently lacking. Devices such as acousto-optical modulators are routinely used to control infrared (IR) and visible light. However, these devices are limited to long wavelengths, and therefore also long pulse durations, since a light pulse can never be shorter than one optical cycle. At a wavelength of 1300 nm, for instance, the pulse duration is restricted to 4.3 femtoseconds. For applications such as telecommunications this is more than sufficient, but in order to investigate the motion of electrons, which takes place on the attosecond timescale, pulses with a much shorter wavelength, in the XUV, have to be used and controlled.

Control will be achieved by tailoring the driving field generating the XUV light, and by further development of a novel opto-optical modulator that has the potential to modulate XUV light with very high precision, similar to the way in which acousto-optical modulators operate in the visible region.

This extended control is important for many reasons, and will, in particular:

-       improve our understanding of the world around us,

-       enable novel applications,

-       stimulate technological advances, and

-       make high-order harmonics both useful and applicable to various areas of research.

In addition, we hope to make high-order harmonics more accessible, thereby allowing new communities to use this light source.

We plan to achieve this vision through four closely related paths of research. We will:

1)    Continue to study and improve the HHG process.

2)    Control the generation process by shaping the generating laser field structure using controlled, multi-colored pulses.

3)    Tailor the light generated by extending the phenomenon of free induction decay (FID) to the XUV region, and develop a new method to control the phase of the FID.

4)    Demonstrate new applications of high-order harmonics and attosecond pulses in collaboration with various groups of users.