Characterization of optothermal transition dynamics in Ge ₂ Sb ₂ Te ₅ and Sb ₂ Te ₃ via spatial light modulation microscopy

We present a confocal microscopy-based method for constructing power-dependent optothermal transition (OTT) diagrams of phase-change chalcogenide (PCC) thin films via spatial light modulation, without diffraction-limited optics, pulse shaping, or temporal modulation. Optical dosage is engineered through controlled scanning dynamics to systematically map amorphous, crystalline, semi-crystalline, and failure regimes in Ge 2 Sb 2 Te 5 and Sb 2 Te 3 on silicon and silicon-on-insulator substrates. Substrate-dependent transition setpoints and cycling behavior are identified and supported by optothermal simulations, while failure mechanisms, including delamination and dewetting, are experimentally resolved through spatially mapped optical measurements. Reproducible intermediate optical states are achieved through controlled variations in incident power and exposure count. Integration of two-photon excitation fluorescence and second-harmonic generation probes enable single-step discrimination between phase transitions and degradation, while revealing dynamic nonlinear behavior within the crystalline phase. This scalable optical platform advances PCC materials characterization and programming for photonic memory and reconfigurable integrated photonics.