Attosecond beamline with actively stabilized and spatially separated beam paths

Abstract

We describe a versatile and compact beamline for attosecond spectroscopy. The setup consists of a high-order harmonic source followed by a delay line that spatially separates and then recombines the extreme-ultraviolet (XUV) and residual infrared (IR) pulses. The beamline introduces a controlled and actively stabilized delay between the XUV and IR pulses on the attosecond time scale. A new active-stabilization scheme combining a helium-neon-laser and a white-light interferometer minimizes fluctuations and allows to control delays accurately (26 as rms during 1.5 h) over long time scales. The high-order-harmonic-generation region is imaged via optical systems, independently for XUV and IR, into an interaction volume to perform pump-probe experiments. As a consequence of the spatial separation, the pulses can be independently manipulated in intensity, polarization, and frequency content. The beamline can be combined with a variety of detectors for measuring attosecond dynamics in gases, liquids, and solids.

Collinear setup for delay control in two-color attosecond measurements

“…Such a setup requires both passive and active stabilization in order to minimize the temporal jitter due to the change in the optical path in each arm originating from airflow, thermal expansion of the mirrors, mechanical vibrations and beam pointing instability. By using active stabilization, in combination with beam pointing stabilization, a residual jitter of~30 as has been obtained [18,19]. Figure 1.…”

Photoionization delays in xenon using single-shot referencing in the collinear back-focusing geometry

“…It is to be noted that the implementation of our chopper wheel is different compared to those that have been reported till now. Since the XUV and IR beams are co-propagating, and there are no separate pathways for the beams [17], the chopper has to be prepared such that the XUV stays unaffected, while the IR signal is alternated between consecutive shots. The IR is therefore filtered out at half the repetition rate of the laser.…”

Photoelectron spectrometer for attosecond spectroscopy of liquids and gases

“…9, it is evident that electrons below 0.5 eV kinetic energy are still collected. In another publication using the same spectrometer 35 , we demonstrate that the useful energy range extends to above 60 eV kinetic energy.…”

“…The actively-stabilized beamline part is shown in Fig. 3 and will be described in more detail elsewhere 35 . Briefly, the output of an amplified Ti:Sa femtosecond laser centered at 800 nm is focused by an offaxis parabolic mirror into a gas cell consisting of three differential pumping stages.…”