We present a novel method for measuring the spectral phase of laser mirrors, where fringe free spectrally resolved interferograms are recorded, and a simple arcus cosine transformation is used to retrieve the spectral phase from the normalized interferograms. The method does not require time delay correction during the evaluation of the interferograms. Group-delay dispersion of a silver and a high reflection mirror is measured to test the precision of the method and it is compared with the precision provided by the cosine function fit and the Fourier-transform method.
The Attosecond Light Pulse Source (ALPS) facility of the pan-European Extreme Light Infrastructure (ELI) project was designed as a laser-based research infrastructure in which light pulses of few optical cycles in the infrared or mid-infrared spectral range are used for basic and applied research. In particular, these pulses will be used as the driving source for generating even shorter extreme ultraviolet (XUV) pulses with durations as short as a few tens of attoseconds.
All the six major laser systems available at ELI-ALPS were designed for stable and reliable operation, while featuring unique pulse parameters, such as unprecedented photon flux and extreme bandwidths. Each laser will run synchronized to the central facility clock, while femtosecond synchronization on target will be ensured by a dedicated timing system. Experimental beam time will be provided with uninterrupted operation of the primary driving lasers and associated secondary sources for at least eight hours per day.
The primary focus of ELI-ALPS is the generation of the best quality attosecond XUV pulses in terms of pulse energy, repetition rate and photon energy. This goal is only achievable using the highest quality primary sources and expertly designed, innovative high-harmonic beamlines. The generation of high flux attosecond pulse trains and isolated attosecond pulses is targeted using Gas-based or Surface Plasma-based High Harmonic Generation. These secondary sources will feature dedicated target end stations (e.g. Reaction Microscope, Condensed matter end station, Velocity Map Imaging Spectrometer and Magnetic Bottle Electron Spectrometer) enabling users to perform state-of-the-art experiments.
Experimental activities in the building complex started in 2018 with the installation of two 100 kHz repetition rate laser systems: the mid-infrared laser (MIR) and the first High Repetition Rate laser (HR1). They successfully served almost ten commissioning user experiments with external collaborators, for the investigation of phenomena such as electron migration in water, electron rescattering induced K-shell fluorescence, photoionization of droplets, photon statistics in harmonic generation in band gap materials etc., altogether for 51 operational weeks in 2018. In 2019 we expect to extend commissioning experiments to the SYLOS laser as well as to, at least, two attosecond and THz beamlines. The first attosecond beamline, driven by HR1 and dedicated to the investigation of ultrafast pheonemena in gas targets, is to be inaugurated mid 2019. In addition, the operation of the THz laboratory, as well as nanoplasmonic experiments are planned for 2019.
The major research equipment of the Attosecond Light Pulse Source of the Extreme Light Infrastructure (ELI-ALPS) are driven by laser pulses of few cycle duration operating in the 100 W average power regime. The peak power and the repetition rate span from 1 TW at 100 kHz up to PW at 10 Hz. The systems are designed for stable and reliable operation, yet to deliver pulses with unique parameters, especially with unmatched fluxes and extreme bandwidths. This exceptional performance will enable the generation of secondary sources with exceptional characteristics, including light sources ranging from the THz to the X-ray spectral ranges, and particle sources.
The experimental activities in the building complex to be inaugurated early 2017 will start with the installation of the two 100 kHz repetition rate, CEP stabilized lasers in May 2017. The MIR laser produces 0.15mJ, shorter than 4-optical-cylce pulses tunable between 2.5-3.9 µm. The first stage of the HR laser will provide pulses around 1 µm with 1 mJ energy and pulse duration less than 6.2 fs. The systems will be optically synchronized to each other with a temporal jitter below 1 fs.
Along with the installation of the lasers, we will also start the assembly of the high harmonic beamlines and the THz laboratory, as well as nanoplasmonic experiments. The XUV bursts of light with attosecond duration are expected to be generated by the end of 2017.
In this work we have measured the group-delay dispersion of an empty Michelson interferometer for s- and p-polarized
light beams applying two different non-polarizing beam splitter cubes. The interference pattern appearing at the output of
the interferometer was resolved with two different spectrometers. It was found that the group-delay dispersion of the empty
interferometer depended on the polarization directions in case of both beam splitter cubes. The results were checked by
inserting a glass plate in the sample arm of the interferometer and similar difference was obtained for the two polarization
directions. These results show that to reach high precision, linearly polarized white light beam should be used and the
residual dispersion of the empty interferometer should be measured at both polarization directions.