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single-photon (SPA) and two-photon laser absorption (TPA) techniques are established as reliable, effective methods to study specific single-event (SE) phenomena in advanced CMOS technologies. However, dense metal-fill in these nanoscale processes can prevent the use of top-side SPA in some cases. This paper demonstrates a novel methodology enabling top-side laser SPA single-event effects (SEEs) measurements in the presence of dense metal-fill for a test circuit fabricated in a commercial 90 nm CMOS process and validates it using unimpeded, through-wafer TPA approach. This is achieved by measuring and comparing the SEU thresholds for the sample circuit using both techniques.