Time-resolved complex optical-field imaging for revealing physical processes in laser processing

We present time-resolved holographic imaging that captures the complex optical-field over the ten-orders temporal range, from sub-picoseconds to milliseconds. Two probe branches are integrated into an ultra-stable digital holographic interferometer: a mechanically scanned branch covering 100 fs–ns and an electronically scanned branch spanning ns–ms. This approach visualizes the cascade of laser-induced phenomena—carrier excitation, lattice heating, plume dynamics, and energy dissipation through thermal diffusion—with milliradian phase precision. In deep-UV femtosecond processing of BK7 glass, the method resolves subtle phase shifts from crater-rim formation and thermal diffusion that are normally masked by material ablation. Nanosecond-pulse experiments expose remarkable differences in structuring dynamics. Our imaging platform furnishes full-time-domain coverage for comprehensive laser–matter interaction studies.