Electronic pulsing of laser driving circuit for producing a pulsed output (1 to 100,000 Herz), of which the peak power must be at least one order of magnitude higher than the highest attainable average power. This process is often used in some CO2 surgical lasers and GaAs laser diodes.

To better understand this, we can start from a continuous light source. The output power is then constant. Regularly switching it on and off makes the output light pulsed. This can also be done by periodically block the light with a mechanical shutter. The duty cycle can be chosen between 100% and 0%. The most common value is 50% and then the average output power is 50% of the non switched output. Pulse frequency can be any. For high duty cycle values, the average output power is close to the output power of the non switched situation.

In pulsing in general it is not always possible for a light source to run in continuous mode. A good example of this is the very first semiconductor laser - the Gallium-Arsenide laser. In order to achieve lasing (inverted population), the current density in the crystal had to be in the order of 10,000 amperes per square centimeter. This causes, however a very fast temperature raise, which could only be handled by using a very short on-time, i.e. a very low duty cycle, typically in the order of 0.1%. The advantage was that the momentary peak power could be made very high. Typical values of these parameters in todays applications is 100 - 200 ns pulse duration and peak power of 1 to 1000 watts and pulse repetition rates of 1 - 100 kHz. The wavelength is typically 904, 905 or 890 nm. This semiconductor laser is today primarily used in some brands of therapeutic laser devices (LLLT) and in speed measuring cameras.

Finally, a similar type of extreme pulsing is Q-switching, when both peak power and pulse energy can be extremely high, but with low pulse repetion rate. Typical parameter values can be: pulse duration 100 ps, 100 - 10,000 megawatts in peakpower and pulse repetition rates of 1 to 10 Hz. Q-switched lasers are today often used in cataract surgery and bleaching of tattoo pigment.