CW vs Pulsed Laser Wavelength

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)

Find below 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)