Abstract Short wavelength probing (SWP) uses wavelengths of light shorter than 1100 nm or energies higher than silicon bandgap for laser probing applications. While SWP allows a significant improvement to spatial resolution, there are aberrations to the collected laser probing waveforms which result in difficulties in signal interpretations. In this work, we assess the signals collected through SWP (785 nm) and introduce a photodiode model to explain the observations. We also present a successful case study using 785 nm for failure analysis in sub-20 nm FinFET technology.