Compressed spectral–temporal coherent modulation femtosecond imaging

Ultrafast complex-field imaging, which simultaneously records both intensity and phase evolutions, provides a robust methodology for elucidating the transient phenomena, but existing techniques face significant challenges in simultaneously achieving ultrahigh-frame-rate, large-sequence-depth, and high-fidelity imaging of the complex fields on the femtosecond timescale. CST-CMFI integrates three techniques, including time-spectrum mapping, compressive spectral and coherent modulation imaging, and inherits their respective advantages in high-temporal-resolution, large-sequence-depth, and complex-field imaging. By compressing the time-space-varying intensity and phase information into a single-frame intensity measurement and subsequently reconstructing the spatiotemporal intensity and phase evolutions by compressive sensing-based algorithm, CST-CMFI enables single-shot complex-field imaging at frame rates of up to 10 trillion Hz. To validate the powerful imaging performance of CST-CMFI, we successfully observed femtosecond laser-induced plasma dynamics in water with both intensity and phase variations and carrier dynamics in ZnSe with phase variation dominating. Given its femtosecond complex-field imaging capability, CST-CMFI emerges as a powerful tool for the real-time visualization of transient events, and therefore has significant applications in both basic and applied sciences.