Phase-shifting point-diffraction interferometry at 193 nm.

Phase-shifting point-diffraction interferometry at the 193-nm wavelength suitable for highly accurate measurement of wave-front aberration is introduced. The interferometer preserves the advantages of the previously described extreme-ultraviolet phase-shifting point-diffraction interferometer but offers higher relative efficiency. Wave-front measurement of an imaging system, operating at the 193-nm wavelength, is reported. Direct measurement of the refractive-index change in a deep-ultraviolet radiation-damaged fused-silica sample is also presented as an application.