Diffraction efficiency

Diffraction efficiency is the performance of diffractive optical elements – especially diffraction gratings – in terms of power throughput. It's a measure of how much optical power is diffracted into a designated direction compared to the power incident onto the diffractive element of grating.

If the diffracted power is designated with ${\displaystyle P}$ and the incident power with ${\displaystyle P_{0}}$ the efficiency ${\displaystyle \eta }$ reads

${\displaystyle \eta ={\frac {P}{P_{0}}}\ .}$