Continuous Wave ("CW") Laser vs a Pulsed Laser

Continuous Wave ("CW") Laser vs a Pulsed Laser

Published by The Laser Safety Experts on Feb 21st 2021

Purchasing laser safety protection is impacted by if the laser is continuous or pulsed.  Below, we illustrate generally how although the average power of a laser may be the same, a pulsed laser has peaks that require more protection (as it becomes necessary to protect from the peaks).  

Continuous Wave Lasers are defined as having a pulsed length > 0.25s.  The calculation is relatively simple, and all that is needed is the average power of the laser.

Repetitive Pulse Lasers – Have higher peak energies and therefore are more complicated to calculate a Maximum Permissible Exposure (“MPE”). To determine the MPE with a repetitive pulse laser, you must have the following:

  • Wavelength (measured in nm, µm)
  • Pulse repetition frequency (F – measured in Hertz or Hz)
  • Duration of a single pulse or pulse width (time – measured in seconds or s)
  • Energy per Pulse (J)

Included are the four types of lasers (defined by pulse frequency) mentioned in EN guidance.  


Continuous Wave (cw) with constant average power.

Pulsed Length: > 0.25 seconds


I: Pulsed: short single or periodic energy emission

> 1µs to 0.25s

R: Giant Pulsed: very short single or periodic energy mission

1 µs to 1ns


M: Mode locked. 

< 1 ns (pico and femtosecond)