Laser pulse cascade

An illumination module of a wafer inspection system includes: an illumination source providing ultraviolet illumination having a wavelength less than 300 nm; a pulse cascade optically coupled to an illumination source to receive ultraviolet illumination, where the pulse cascade comprises a chain of a plurality of loops, each loop comprising: a loop input and a loop output, a first loop output optically coupled to a loop input of a subsequent loop in the chain; and a delay line having a delay line input optically coupled to the loop input, and a delay line output, the delay line configured to output a delay line light output from the delay line output after a time delay starting from a reception time of the light received at the delay line input, the delay line light output comprising an image of the light received at the delay line input; and an optical splitter configured to receive the light at the optical splitter input and to output a first portion of the light from the loop through the loop output and to