An alternative referencing scheme that suppresses large noise contributions in ultrafast transient absorption spectroscopy with broadband Vis-NIR detection

We present a new referencing scheme for visible and near infrared ultrafast Transient Absorption (TA) measurements using a signal and a referencing beam. Instead of using the traditional ratiometric approach, where the absorption changes are referenced at each wavelength independently, we use a method used in the infrared range that fully utilized the spectral correlation between the reference and signal. We applied this method on a setup that produces an ultrabroad white light (WL) probe beam spanning the 600-1700nm range. This WL is noisy as it is generated from the Idler of an optical parametric amplifier in a YAG crystal. The new referencing scheme allowed to completely suppress the noise introduced by the WL generation. We will present the method, the setup and its application to some new organic semiconducting materials used or photovoltaic applications that benefited a lot from the broad spectral coverage and the low noise of our TA setup.