The breakdown of superconductivity in current-carrying devices is governed by the nucleation and spatial propagation of dissipation from localized regions, shaped by geometry, defects, and material inhomogeneity. Accessing this behavior requires probes with significant spatial resolution under operating conditions. In Bi2Sr2CaCu2O8+x (BSCCO-2212), low-temperature laser scanning microscopy has revealed spatially varying photoresponse across a range of devices, with contributions ranging from bolometric, thermoelectric, and vortex-assisted mechanisms.

In this study, we perform photovoltage (PV) and photoconductivity mapping on ultrathin BSCCO-2212 devices using 532 nm excitation (~1 µm resolution), focusing on the emergence of criticality through both thermal and current-driven transitions. In both cases, we observe the formation and evolution of a criticality front separating weakly and strongly dissipative regions before the device transitions into a more homogeneous resistive state. Under current bias, photoconductivity hotspots also emerge at notches introduced in the flake. These results provide a spatially resolved view of superconducting breakdown in BSCCO-2212 and shed light on the role of local inhomogeneity in seeding criticality in the bulk.