Picosecond

A picosecond (symbol ps) is a unit of time equal to 10^-12 seconds, or one trillionth of a second. It lies between the femtosecond (10^-15 s) and the nanosecond (10^-9 s) on the time scale. One picosecond is equal to 1,000 femtoseconds or 0.001 nanoseconds. Light travels about 0.3 millimeters in vacuum during a single picosecond.

Picoseconds are commonly used to describe ultrafast events and laser pulses. Light sources such as mode-locked lasers can emit pulses with durations ranging from a few picoseconds to several hundred femtoseconds. Measurement and characterization of picosecond pulses rely on techniques including optical autocorrelation, frequency-resolved optical gating, and streak cameras.

In research and industry, picosecond-scale timing enables time-resolved studies of fast phenomena. Applications include ultrafast spectroscopy and pump-probe experiments to observe chemical reaction dynamics, carrier and exciton lifetimes in semiconductors, and fast processes in materials science. Picosecond pulses are also used in some high-speed optical communication systems and in laser micromachining where precise, short energy delivery is required.

Related time scales include the femtosecond (10^-15 s) and nanosecond (10^-9 s). Understanding picoseconds helps characterize processes such as molecular vibrations, electronic relaxation, and light–matter interactions that occur on ultrafast time frames.