FLASH: Ultrafast Beam Quality Characterization via Spatial‐to‐Temporal Mapping

ABSTRACT Accurate and real‐time monitoring of spatial beam quality is the absolute prerequisite for intelligent optical field regulation and advanced laser applications. However, modern high‐power and multimode laser systems can exhibit rapid pulse‐to‐pulse fluctuations in their spatial beam profiles because of transverse‐mode competition, mode instability, nonlinear propagation, and external perturbations. Yet, capturing these ultrafast dynamics is bottlenecked by the kilohertz frame rates of conventional two‐dimensional image sensors. To break this dimensional and temporal barrier, we propose FLASH (Fiber‐based Laser Assessment via Spatial‐to‐temporal High‐speed‐mapping), an ultrafast non‐imaging beam quality monitoring technique. Utilizing a multimode fiber to encode spatial beam variations into high‐dimensional speckle fingerprints and a multicore fiber delay line array to serialize these features, we transform two‐dimensional spatial information into high‐speed one‐dimensional temporal pulse sequences. Empowered by a deep learning model to decipher serialized signals, FLASH supports spatial encoding and waveform acquisition at a rate of up to 100 MHz and achieves a minimum mean relative error of 0.32% on the offline‐processed testing data. Realizing a five‐order‐of‐magnitude speed improvement over standard camera‐based methods, this paradigm provides a transformative spatial oscilloscope. It unlocks new possibilities for real‐time intelligent adaptive control and the exploration of complex multimode nonlinear physics.