Double-Foci Beamline for Attosecond Transient Reflection Spectroscopy

Although attosecond transient absorption spectroscopy (ATAS) is a powerful experimental technique, it suffers from important limitations. The high absorption coefficient of solid state samples in the extreme-ultraviolet (XUV) spectral range and the relatively low photon flux of standard attosecond sources force the thickness of the samples to be below a few tens of nanometres. It is possible to overcome these drawbacks obtaining equivalent information by using a reflection geometry in the investigation of ultrafast carrier dynamics in solids [1] , [2] . Attosecond transient reflection spectroscopy (ATRS) investigates pump-induced variations in the reflectivity of a sample in the XUV spectral region on an attosecond timescale. We present a novel beamline suitable for performing ATRS experiments with attosecond temporal resolution [3] . Its double-foci configuration allows for a simultaneous characterization of the pump and probe pulses and for a precise calibration of the delay axis of the transient reflectivity measurement.