Lasers with a pulse width of picoseconds are referred to as picosecond lasers.
Diode-pumped Nd:YAG or Nd:YLF lasers using acousto-optic modulation mode-locking are now the standard light source for generating picosecond pulses. Since the energy of the individual pulses output from the oscillator is quite low, a regenerative amplifier is often required to amplify them. In commercially available lasers, the resonant cavity is typically folded several times to shorten the total length of the system. To get short pulses, a short resonant cavity and a high modulation frequency are required, and a single pulse needs to be separated by a bubbleglass box; the length of the cavity is a compromise between these two requirements.