Source noise suppression in attosecond transient absorption spectroscopy by edge-pixel referencing

TL;DR

This paper introduces edge-pixel referencing techniques to suppress noise in attosecond transient absorption spectroscopy, significantly enhancing sensitivity and enabling more precise observation of photoexcited dynamics.

Contribution

It presents two novel edge-pixel referencing methods, correlation analysis and singular value decomposition, to improve ATAS sensitivity by fivefold.

Findings

Edge-pixel referencing reduces noise in ATAS measurements.

The methods increase sensitivity close to the detector noise floor.

Both techniques can be applied to live data and existing datasets.

Abstract

Attosecond transient absorption spectroscopy (ATAS) is used to observe photoexcited dynamics with outstanding time resolution. The main experimental challenge of this technique is that high-harmonic generation sources show significant instabilities, resulting in sub-par sensitivity when compared to other techniques. This paper proposes edge-pixel referencing as a means to suppress this noise. Two approaches are introduced: the first is deterministic and uses a correlation analysis, while the second relies on singular value decomposition. Each methods is demonstrated and quantified on a noisy measurement taken on $\text{WS}_2$ and results in a fivefold increase in sensitivity. The combination of the two methods ensures the fidelity of the procedure and can be implemented on live data collection but also on existing datasets. The results show that edge-referencing methods bring the sensitivity of ATAS near the detector noise floor. An implementation of the post-processing code is provided to the reader.