Color separation gratings for diverting the unconverted light away from the NIF target

Most of the glass laser based inertial confinement fusion systems around the world today employ non-linear frequency conversion for converting the 1.053 pm light at the fundamental frequency (referred to as 1o light) to either its second harmonic (called 2o) at 527 nm or to its third harmonic (called 3w) at 351 nm. Shorter wavelengths are preferred for laser fusion because of the improved coupling of the laser light to the fusion targets due to reduced fast electron production at shorter wavelengths. The frequency conversion process, however, is only about 60-70% efficient and the residual 30-40% of the energy remains at la) and 2w frequencies.