A team led by Jinyang Liang of the National Institute of Scientific Research (INRS) has developed an ultrafast camera capable of imaging photons in real time in the UV range. Until now, compressed ultrafast photography (CUP) techniques have been limited to the infrared and visible wavelengths, and therefore only applicable to a limited number of physical events. According to Liang, a professor in the Laboratory of Applied Computational Imaging at INRS, it is necessary to use shorter wavelengths to be able to image events that occur on short timescales, as they correspondingly often occur on a very small spatial scale. To be able to record in this range of wavelengths, the researchers designed a compact UV-CUP system with Christian-Yves Coté of Axis Photonique. The system features a patterned photocathode, which is used to simultaneously detect and encode “black light.” “Like a standard camera, our technology is passive. It does not produce light; it receives it,” Liang said. “Therefore our photocathode had to be sensitive to the photons emitted as UV light. This design makes our technique a stand-alone system that can be easily integrated into various experimental platforms.” Liang worked with fellow INRS professor François Légaré to generate and take images of UV pulses at the Advanced Laser Light Source (ALLS) laboratory. “Taking the picture is only the first half of the job,” said Liang. “It also has to be reconstructed.” To reconstruct the image, the researchers developed an algorithm through a collaboration with Boston University. Rather than solving the reconstruction problem as one piece, the algorithm divides the reconstruction into smaller problems that it tackles individually, Liang explained. The camera was able to achieve an imaging speed of 0.5 trillion frames per second. Even at that speed, the camera has room for improvement. The researchers plan to explore other types of materials for the photocathodes, and are looking to collaborate with Tiago Falk, also of INRS, to harness artificial intelligence to improve the device further. The system developed through this collaboration will be sent to the research laboratory SOLEIL Synchrotron in France to visualize physical phenomena. Examples include laser-plasma generation and UV fluorescence. The research was published in Laser & Photonics Reviews (www.doi.org/10.1002/lpor.202000122).