Femtosecond beam transformation effects in water, enabling increased throughput micromachining in transparent materials

Abstract

Femtosecond lasers are widely applied in scientific and industrial fields. Recent trends in the laser market show decreasing prices for femtosecond units, which will ultimately lead to the opening of new markets that were inaccessible in the past due to the high costs of such systems. To this end, new techniques that enable micromachining of materials with increased effciency are interesting. In this article, we demonstrate a technique that may be used for cutting and drilling various materials. By placing a layer of water on top of the samples and loosely focusing laser light on the surface, it was found that the micromachining throughput is increased by up to 10-fold as compared with micromachining without the water layer (conventional focusing in air), however, the main reasons for the increase in fabrication effciency have not been fully understood until now. By modelling the propagation of the femtosecond pulses by means of the nonlinear modified Schrodinger equation through the water layer, we show that the increased throughput is attributed to the changing of the Gaussian intensity profile. In addition, we confirm these findings by numerically modelling the ablated crater formation.