Ultrafast optics is the part of optics dealing with ultrafast phenomena, i.e., phenomena which occur on a time scale of picoseconds or less. Typically, ultrafast optics experiments involve ultrashort Pulses as generated with mode-locked lasers.

As ultrafast phenomena are too FAST to be directly monitored with electronics, optical techniques, such as e.g. pump-probe measurements, are required. With such techniques, phenomena occurring on time scales of picoseconds or femtoseconds can be monitored. Examples for such phenomena are femtosecond dynamics of electrons (particularly in solids, e.g. in Semiconductor devices such as SESAMs), light-induced phase changes (e.g. melting or vaporization of metals), chemical reactions, and processes in plasmas.