An ultrashort pulse laser is a laser

Laser

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...

 that emits ultrashort pulse

Ultrashort pulse

In optics, an ultrashort pulse of light is an electromagnetic pulse whose time duration is of the order of a femtosecond . Such pulses have a broadband optical spectrum, and can be created by mode-locked oscillators...

s of light, generally of the order of femtoseconds to ten picosecond

Picosecond

A picosecond is 10−12 of a second. That is one trillionth, or one millionth of one millionth of a second, or 0.000 000 000 001 seconds. A picosecond is to one second as one second is to 31,700 years....

s. Thus they are also known as ultrafast lasers. But "ultrafast laser" is a misnomer, since the speed of light is constant in a given medium.
Common current ultrashort pulse laser technologies include Ti-sapphire laser

Ti-sapphire laser

Ti:sapphire lasers are tunable lasers which emit red and near-infrared light in the range from 650 to 1100 nanometers. These lasers are mainly used in scientific research because of their tunability and their ability to generate ultrashort pulses...

s and dye laser

Dye laser

A dye laser is a laser which uses an organic dye as the lasing medium, usually as a liquid solution. Compared to gases and most solid state lasing media, a dye can usually be used for a much wider range of wavelengths. The wide bandwidth makes them particularly suitable for tunable lasers and...

s. High output peak power usually requires chirped pulse amplification of a seed pulse from a modelocked laser

Modelocking

Mode-locking is a technique in optics by which a laser can be made to produce pulses of light of extremely short duration, on the order of picoseconds or femtoseconds ....

. Dealing with high optical powers also needs the nonlinear optical phenomena to be taken in account.