Laser Peak Fluence, Peak Irradiance (Intensity) and Peak Power

Laser-Induced Damage Threshold (LIDT) is frequently expressed in units of laser peak fluence or laser peak power density. Let us take a closer look how it is evaluated.

Laser fluence describes the energy delivered per unit (or effective) area. Within the community of laser scientists and technicians, it is very common to define fluence in units of J/cm2. To calculate fluence use the following equation or download free app Lidaris Calc:

In the case of Gaussian beams, effective focal spot area is registered by CCDs. Then it is converted to the units of square centimeters at the I0/e level of maximal intensity. See figure below for more details. Sometimes (in community of nonlinear optics) intensity of peak irradiance is used instead of fluence:

While laser peak power is defined as:

It should be noted, that Laser-Induced Damage Threshold (LIDT) expressed as laser peak fluence is always quoted with the pulse duration used for the testing. Thus, laser peak power value can be always calculated, if necessary. Want to learn more on LIDT measurements and evaluation? Check out different testing regimes at Laser-Induced Damage Threshold (LIDT) Testing.