Single-shot compressed ultrafast photography in the ultraviolet spectral range

Abstract

The conventional ultrafast optical imaging methods in the ultraviolet (UV) spectral range are based on pump-probe techniques, which cannot record non-repeatable and difficult-to-produce transient dynamics. Compressed ultrafast photography (CUP), as a single-shot ultrafast optical imaging technique, can capture an entire transient event with a single exposure. However, CUP has been experimentally demonstrated only in visible and near-infrared spectral ranges. Moreover, the requirement to tilt a digital mirror device (DMD) in the system and the limitation of controllable parameters in the reconstruction algorithm also hinder CUP’s performance. To overcome these limitations, we extended CUP to the UV spectrum by integrating a patterned palladium photocathode into a streak camera. This design also nullifies the previous restrictions in DMD-based spatial encoding, improves the system’s compactness, and offers good spectral adaptability. Meanwhile, by replacing the conventional TwIST algorithm with a plug-and-play alternating direction method of multipliers algorithm, the reconstruction process is split into three secondary optimization problems to precisely update the separated variables in different steps, which considerably enhances CUP’s reconstruction quality. The system exhibits a sequence depth of up to 1500 frames with a size of 1750×500 pixels at an imaging speed of 0.5 trillion frames per second. The system’s ability of ultrafast imaging was investigated by recording the process of UV pulses travel through various transmissive targets with a single exposure. We envision that our system will open up many new possibilities in imaging transient UV phenomena.