The aim of this project is to generate ultra-short pulses of X-rays, ranging in wavelength from 1 nm to 100 nm, for dynamical studies of matter and studies of non-linear optics under extreme conditions. For this purpose high-harmonic generation is employed based on focusing fully phase controlled few cycle (< 10 fs) terawatt infrared laser pulses in a noble gas. The development of the
required laser system is an important part of the project.
The starting point of the system is a frequency comb laser (11 fs pulses at 800 nm) which is carrier-envelope phase controlled. Pulses from this laser are amplified in a non-collinear chirped-pulse parametric amplifier system (running at 1 kHz and at 30 Hz repetition rate). It consists of a synchronized and frequency doubled Nd:YAG picosecond laser system which acts as a pump laser for the parametric amplification process in two 5 mm long BBO crystals. Pulses of the frequency comb are amplified from ~1 nJ to 25 mJ with a spectral bandwidth that greatly surpasses the capabilities of traditional Ti:sapphire amplifier systems. As a result, 10 fs pulses can be generated with terawatt peak power (about 10 mJ after compression) at 30 Hz.
Spectral phase control is achieved by a 640 element LCD 4f-shaping device just before the parametric amplifier. This means that full computer control over the electromagnetic field of the amplified pulse is available. Such control can be used for the optimisation of the pulse length (dispersion compensation), but also for optimisation of nonlinear optical processes driven by the laser pulses. This laser system is used in combination with a X-ray monochromator to study and apply the short wavelength radiation obtained from high harmonic generation.
Contact: Kjeld Eikema, email: email@example.com
Atomic, Molecular and Laser Physics
On the left the result is shown of multiple filament continuum generation by loosely
focusing the terawatt laser beam in air. The right side shows a part of the terawatt
chirped pulse parametric amplifier system.