Research Progress of Spatio-Temporal Couplings in Ultrashort Laser Pulses

The research progress of spatio-temporal couplings in ultrashort laser pulse is summarized. The spatio-temporal couplings are classified into two categories, first order spatio-temporal couplings and high-order spatio-temporal couplings. The history and the recent situation of the study on the two types of spatio-temporal couplings are introduced. Comparing with high-order spatio-temporal couplings, the first order spatio-temporal couplings are relatively simple, and the theoretical and experimental research about them are comparatively abundant. Comparing with first order spatio-temporal couplings, the high-order spatio-temporal couplings have broader origin, more rich species and more complex space-time structure. At present, the research on the high-order spatio-temporal couplings is just in a fledging period. Finally, the research trend in this field is forecasted.