All-optical and active compressed ultrafast photography (AA-CUP)

Compressed ultrafast photography (CUP) has emerged as a powerful single-shot imaging technique capable of capturing dynamic scenes with ultrahigh frame rates and large sequence depths. While providing a proven implementation platform, arising from the passive-detection mechanism of streak cameras, conventional streak-camera-only (SCO) CUP systems encounter inherent limitations in further improvement of spatiotemporal resolution and reconstructing fidelity. In recent years, significant research efforts have been directed toward all-optical and active CUP (AA-CUP) frameworks. All-optical CUP realizes temporal shearing through purely optical means, circumventing electronic dispersion limitations. Active CUP employs controlled illumination to encode temporal or spatial information prior to acquisition. These approaches have achieved breakthroughs across several key performance metrics, including tens-of-femtoseconds temporal resolution, few-μm-scale spatial resolution, and sequence depths of approximately 1,000 frames. Aiming at solving several fundamental constraints in SCO CUP, this mini-review examines progress in AA-CUP, including the advances in temporal shearing mechanisms, compression ratio adjustments, data compression strategies, and the expansion of multi-functional imaging capabilities. The article concludes with perspectives on future research directions that aim to overcome existing limitations and expand the applicability of CUP across various scientific disciplines.