Real-time determination of focal position during laser fabrication with double-hole masks

Recently, ultrafast laser processing becomes increasingly significant in a broad field of academic research and engineering. A poor focusing condition can lead to permanent destruction of target sample, reduction of resolution, decrease in sensitivity of optic and electronic nano-devices, and low productivity[1,2]. Therefore, a precise, flexible, and rapid focus detection system is a considerable demand for increasing the productivity as well as accuracy of laser processing. In this paper, a new system of in situ real-time exploration of focal position during laser processing with double-hole mask is presented, possessing higher accuracy, higher reproducibility, and higher speed.