An optimized ultrafast transient absorption experiment from the visible to the near-infrared with the B matrix referencing technique

We present a transient absorption (TA) setup with a broadband white-light from 600 to 1700 nm without a detection gap. This TA setup differs from typical TA implementations in two distinct details. First, instead of seeding the 800 nm fundamental laser beam directly into the white-light generation (WLG) crystal, we pump our yttrium aluminum garnet WLG crystal with the 2080 nm idler of a home-built two-pass optical parametric amplifier pumped at 800 nm. Second, we implement the B matrix referencing scheme introduced by Feng et al. to suppress the white-light fluctuations down to the shot-noise limit of our detector. As such, our implementation of the B matrix leads to a reduction of the root mean square of about an order of magnitude in the 1200–1700 nm regime compared to the ratiometric referencing approach. Furthermore, we suppress baseline oscillations frequently encountered in TA by mitigating the effects of negative pixel correlation. To allow widespread implementation of the referencing scheme in the scientific community, we provide an introduction to the B matrix focusing specifically on data processing. The B matrix referencing scheme is easy to implement and is employed directly during data acquisition, thus maintaining similar alignment and measurement times compared to typical TA implementations. Finally, we show that the noise reduction provided by the B matrix referencing scheme allows for WLG schemes that would otherwise fluctuate too much to provide high-quality data in a reasonable amount of time, enabling the construction of more specialized TA experiments.