Tridimensional ablation region in femtosecond laser micromachining with diffractive lenses

Abstract

Increment of the axial region of ablation in a micromachining process is demonstrated when a refractive lens (RL) is replaced by a diffractive lens (DL). The depth of focus of a DL and a RL with the same numerical aperture are compared. For ultrashort pulses, the broadband spectrum of the laser together with the chromatic aberrations associated to the DL made its ablation region greater than the one corresponding to a RL. We measure experimentally the tridimensional ablation region for both types of lenses with 100 fs and 30 fs pulses. This study is expected to be promising to alleviate the mechanical tolerances in femtosecond micromachining with diffractive optical elements (DOEs).