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The CITIUS Laboratory was setup in 2014 at the University of Nova Gorica (Slovenia), as the result of the CITIUS project, funded by the Italy-Slovenia Cross-Border Cooperation Programme 2007-2013. The laboratory hosts an ultrafast light source capable of generating femtosecond pulses spanning the spectrum from the infrared (through the use of an optical parametric amplifier) to the x-ray spectral region (through high-harmonic generation in gas). Such pulses are used in a pump-probe configuration for time-resolved photoemission studies. Research focuses on ultrafast response of electrons in topological insulators, superconductors, and metal/organic interfaces, with potential use, e.g., in spintronics and energy harvesting, and on the development of novel schemes for generating short-wavelength light with exotic properties, such as optical vortices, i.e., light carrying orbital angular momentum.

Research highlights CITIUS: An infrared-extreme ultraviolet light source for fundamental and applied ultrafast science CITIUS generates intense, very short pulses from the infrared (IR) to the extreme ultraviolet (XUV). XUV pulses (14-80 eV) are produced using high-harmonic generation in gas. The systems includes an XUV monochromator that can either preserve the time structure of radiation or provide high wavelength resolution. The set-up allows combining IR, visible and ultraviolet laser pulses with XUV radiation in pump-probe experiments. C. Grazioli et al., dx.doi.org/10.1063/1.4864298 Read More Tunable orbital angular momentum in high-harmonic generation Using a two-color wave-mixing setup, we generate extreme-ultraviolet optical vortices with femtosecond duration carrying a controllable amount of orbital angular momentum (OAM). Such vortex beams will allow testing some of the recently proposed concepts such as OAM-induced dichroism, magnetic switching in organic molecules and violation of dipolar selection rules in atoms.  D. Gauthier et al.,dx.doi.org/10.1038/ncomms14971 Read More Double-configuration grating monochromator for extreme-ultraviolet ultrafast pulses We designed a double-configuration grating monochromator for the spectral selection of extreme-ultraviolet pulses produced by the CITIUS source. The system can work in two configurations: the offplane geometry which preserves the time structure of the pulse or the classical gemoetry which provides high wavelength resolution. L. Poletto et al., doi.org/10.1364/AO.53.005879   Read More Testing spin-flip scattering as a possible mechanism of ultrafast demagnetization in ordered magnetic alloys We use element-resolved IR-pump/extreme ultraviolet-probe experiments to disentangle the ultrafast interplay of the magnetic sublattices in the case of the FeRh alloy, which shows a delayed response for the different components.  S. Günther et al., doi.org/10.1103/PhysRevB.90.180407   Read More Observation of short-lived laser-dressed quantum states in the frequency plane We present a method for measuring a complete frequency map of laser-dressed states with femtosecond lifetimes. It is based on collecting decay products as a function of the frequency of the excitation pulse and its delay with respect to the linearly chirped laser pulse, centered at the resonant transition frequency. The method was tested for the case of laser-coupled 2s2p 1Po and 2p2 1Se autoionizing resonances in He and is applicable to other quantum systems with short-lived states. When the laser coupling effects are known, the excitation pulse properties can be extracted from the map.  M. Žitnik et al.,https://doi.org/10.1103/PhysRevA.99.053423   Read More 01234

The laboratory is equipped with an ultrafast Ti:Sa laser system, a high-harmonic generation beamline, an optical parametric amplifier, and two experimental chambers (one with a classical hemispherical analyzer and another one with an angle-resolved time-of-flight spectrometer) for time- and angle-resolved photoemission spectroscopy. One of the chambers is also equipped with an x-ray source for static, high-resolution x-ray photoemission spectroscopy. The ultrafast light source can be connected to an external experimental chamber provided by the user.

Being part of the University of Nova Gorica, the laboratory hosts undergraduate and graduate students (internal or external) working on their diploma, master or PhD theses.

The laboratory team performs two types of experiments:
- short-term measurements carried out as support for other laboratories or external users
- experiments related to long-term projects lead by the internal team.