In 1994 the High Intensity Laser Research Group was founded at the Department of Experimental Physics (DEP). A high intensity short pulse hybrid dye/excimer laser system was built capable of the generation of I>10¹⁹ W/cm² focused intensities at the UV range. Several research projects were initiated in solid-state and plasma physics involving researchers of the department and other research institutes.

       In the High Intensity Laser Laboratory (HILL) the research and development of high-intensity excimer lasers are carried out which makes possible generation of high energy, high focused intensity and short pulses.
       The experimental work at HILL is based on a KrF high-intensity excimer laser system. The short (248 nm) wavelength of this gas laser gives better focusability compared to solid-state systems, which compensates the relatively moderate power level. Significant part of the research activity is concentrated on the development of the laser system, which includes discharge physics and ultrafast laser phenomenon as well. Presently the laser produces pulses of 20 mJ energy and 100-600 fs duration which can be focused to a diffraction-limited spot, resulting in intensities of 10¹⁸ W/cm². Another important activity targets the compression of the laser pulse below 100 fs.

       Research in the field of laser-plasma interactions is carried out in strong cooperation with the Plasma Physics Department of KFKI Research Institute of Particle and Nuclear Physics (PPD).
       Short-wavelength high-intensity laser plasma interactions are not driven strongly because of the Iλ² scaling. An exception is high-harmonics generation which can be efficient even for short wavelength pumping. On the other hand the energy of fast electrons generated in laser plasma interactions is expected to be significantly lower for short-wavelength lasers. Experiments are planned to clear the electron acceleration mechanism (which might be better defined under these conditions) and to compare the results obtained with infrared lasers. These experiments can also answer which wavelength is most appropriate for fast ignitor. X-ray spectroscopy of the plasma is carried out with VUV holographic and transmission gratings. Raman scattering in neutral gas and in plasma is studied using a gas jet. This arrangement can also be used for high-harmonics generation in gases. The fs laser systems are also used to perform material processing experiments.

       The interaction of solids with laser pulses plays an important role in many fields of applications, such as laser processing and pulsed laser deposition, etc.
       The discipline of laser-solid interaction has passed over a huge development with the advent of higher laser intensities and shorter pulses. The pump-and-probe measurement is a well known technique for fast process investigation, such as a solid state and ultra-short laser pulse interactions.
       We have studied the optical behavior of vanadium-pentoxide (V₂O₅) under the influence of ultra-short laser pulses from an UV excimer laser (500 fs). Femtosecond laser pulses can excite vibrations in materials if the duration of the laser pulse is less than the vibrational period. By measuring small changes in the probe light reflected from the sample as a function of the time delay between the pump and probe pulses, we can extract information about the vibrational dynamics of the sample. The dynamic reflectivity yields not only the vibrational frequencies, but also how the amplitudes of the vibrations change with time. We report on dynamic reflectivity measurements of TeO₂ crystals.