Optical Chirplet Transform for Observing Pulse Ultrafast Structures

The accurate measurement of ultrafast pulses is extremely important in both academic and industrial fields. Revealing fast- and slow-varying pulse information simultaneously still remains a considerable challenge in ultrafast science. We propose a novel ultrafast measurement method, termed the "optical chirplet transform for observing pulse ultrafast structures (OCTOPUS)", to measure the spectrotemporal transient information on pulses. This approach slices a measured pulse into a series of orthogonal chirplet bases and transforms it into the corresponding Fourier-transform-limited pulse (FTLP) through a phase editing process, in which a programmable waveshaper iteratively achieves the mirror image of the measured pulse's phase spectrum relative to the theoretical FTLP. As a result, the ultrafast pulse field is accurately reconstructed assisted by phase spectrum retrieval. This method can both reconstruct transient fast-varying pulse fields with higher resolution and accuracy and measure other pulse information such as phase distribution and slow-varying envelope, advancing progress in ultrafast measurement technology.