A custom phase plate for a light beam of wavelength "»" includes a sheet of plastic material having a base refractive index "n o ". Formed onto a surface of the sheet is a plurality of contiguous spots having different refractive indices. Together, the spots establish a diffraction pattern in a light beam that removes optical aberrations from the beam. Specifically, each spot has a selected Optical Path Difference (OPD) relative to the base index (n o ) that is equal to k»/10 (for k = 1 to 10). Further, the OPD for each spot in the pattern is individually established by heating the plastic material with a laser beam of ultra-short pulses.
