Structured Light for Ultrafast Videography

Abstract: Monitoring natural events at ultrafast timescales is a prerequisite for our continued understanding of physical, chemical and biological processes. Due to exponential advancements in knowledge and optical technology, the field of ultrafast videography has seen a sudden uptick in activity beginning in the mid-2010s. Today, the field has matured past its infancy and is slowly becoming a standard tool used to solve both fundamental and applied scientific questions. However, there are constant improvements to be made in terms of speed, video lengths and spatial resolution in order to reach full accessibility.This thesis work presents, discusses and puts the applied method for ultrafast videography, Frequency Recognition Algorithm for Multiple Exposures (FRAME), into a larger context of videography as a whole and ultrafast videography in particular. FRAME is then both stress-tested in terms of illumination, video length and speed and furthermore, applied to novel scientific questions such as plasma diagnostics and light matter interactions. In addition, the underlying principle, structured light, was applied to alleviate the electro-optical problems of passive ultrafast detection seen most prominently in streak cameras.In short we have shown and pinpointed the whens and wheres that the FRAME technique is most advantageous for ultrafast videography. Firstly, the technique is quite insensitive to illumination source, which, being an active technique, is key for its accessibility. Secondly, since the method of encoding involves the use of spatial frequency modulations, FRAME can be made sensitive to e.g., spectroscopic information alongside its temporal sensitivity, unlocking potential utilisation in fields that are dependent on the detection of other photon degrees of freedom. Finally, new ways of approaching the optical setup (e.g., with diffractive optical elements) and the post-processing (e.g., with a phase sensitive algorithm,), have shown that FRAME is a robust and versatile way of observing natural events with ultrafast temporal resolutions.With that, I believe that the work presented herein will contribute to the bank of knowledge that will help propel FRAME as an ultrafast videography method to the far reaches of monitoring nature at its limits.