Single-Shot Real-Time Ultrafast Imaging of Femtosecond Laser Fabrication

Femtosecond laser fabrication outperforms the traditional fabrication techniques with high precision, high efficiency, low collateral damage and wide applicability, which has shown to be a powerful tool in precision machining. Imaging the ultrafast dynamics of femtosecond laser fabrication is necessary for understanding the processing mechanism and for establishing the corresponding physical models. Up to now, ultrafast measurement techniques based on the pump-probe strategy are the most used methods. However, they are limited by laser energy stability and materials surface uniformity, which have a heavy impact on the dynamic measurement precision of femtosecond laser fabrication. To overcome this limitation of the traditional pump-probe techniques, we developed chirped spectral mapping ultrafast photography (CSMUP), which can achieve single-shot real-time ultrafast imaging with a frame rate of about 250 billion frames per second (temporal frame interval of 4 ps) and a spatial resolution of less than 833 nm. We experimentally imaged the dynamics of femtosecond laser ablation in silicon under a 400 nm femtosecond laser exposure with CSMUP, and the experimental result agreed well with previous theoretical models. CSMUP provides a new strategy to improve the efficiency and accuracy of femtosecond laser fabrication by a single-shot dynamic measurement of the interaction between the femtosecond laser and materials, and it is expected to work as a real-time detection method for various ultrafast phenomena.