Two-dimensional differential null interferometry of transmission wavefront of axicon lens

Abstract

Axicon lenses are critical in the beam transforming, such as the Bessel beam and hollow beam generation, and its manufacturing accuracy directly affects the quality of the output beam. Aiming at the versatility and high accuracy, we propose a two-dimensional differential null interferometry for measuring transmission wavefront of axicon lens. The method uses a pair of axicon lens to construct a null interferometric setup, with one as the compensator. The two-dimensional difference separates the wavefront information introduced by the compensator and achieves the orthogonal difference of the measured wavefront. Finally, the measured wavefront is reconstructed from the differential wavefront based on the Hudgin slope method. The experiments proved that this method achieves a measurement accuracy of ±0.125 µm with a repeatability of 0.759 nm.