ultrafastpulse

An ultrafast pulse, or ultrafast pulse, is a light pulse with a duration on the order of femtoseconds to picoseconds. These pulses achieve extremely high peak powers with relatively low pulse energies and enable temporal resolution sufficient to observe electronic and molecular processes on their natural timescales.

Most ultrafast pulses are produced by mode-locked solid-state or fiber lasers. Common light sources include Ti:sapphire lasers, which commonly deliver pulses in the 20 to 100 femtoseconds range around 800 nanometers, and ytterbium-doped fiber systems that operate near 1 micron with sub-picosecond durations. To reach higher pulse energies without damaging the gain medium, chirped-pulse amplification is often used: a short pulse is stretched in time, amplified, and then recompressed to its short duration.

The duration of a pulse is linked to its spectral content by the time-bandwidth product; shorter pulses require broader spectral bandwidths. In practice, pulses are often stretched and then compressed using dispersive optics such as gratings or prism pairs, and spectra can be further broadened through nonlinear effects in fibers or crystals.

Characterization of ultrafast pulses typically employs autocorrelation, frequency-resolved optical gating (FROG), or SPIDER techniques to reconstruct the electric field in time and the spectral phase.

Applications of ultrafast pulses span time-resolved spectroscopy, pump–probe experiments, nonlinear optics, microfabrication, and the generation of attosecond pulses via high-harmonic generation. The field continues to advance toward shorter durations, higher peak powers, and broader tunability across the visible and infrared regions.