petawatt

Petawatt is a unit of power equal to 10^15 watts (W). It denotes peak power, typically realized in laser systems that deliver ultrashort pulses with extreme intensity. The term sits above the terawatt (10^12 W) and below the exawatt (10^18 W) in the SI prefix hierarchy. Petawatt-scale lasers achieve their power through ultrafast pulses and energy concentration rather than continuous operation.

Petawatt-class lasers reach their peak power by compressing and amplifying laser pulses, often using chirped-pulse amplification. The pulses are usually in the femtosecond range (one quadrillionth of a second). Because power is energy per unit time, the energy per pulse equals the peak power multiplied by the pulse duration. For example, a 1 PW pulse lasting 1 femtosecond carries about 1 joule of energy; a 100-femtosecond pulse would carry about 100 joules. Repetition rates are typically low, so the average power remains modest despite the very high instantaneous power.

Applications of petawatt-scale lasers are primarily in high-energy density physics and related fields. They enable intense laser–plasma interactions, acceleration of electrons and ions, generation of high-energy photons, and studies of extreme states of matter. They also support research in attosecond science and, in some facilities, inertial confinement fusion research.

Notable facilities and efforts include large research centers pursuing PW lasers, such as the National Ignition Facility in the United States and multi-PW projects under the Extreme Light Infrastructure initiative in Europe. Ongoing development aims to push to higher peak powers, shorter pulse durations, and higher repetition rates while managing associated technical challenges.