Abstract
Areal-time monitoring method that simultaneously measures hole depth during femtosecond laser processing has been developed. It measures and analyzes the interference between reflected pulses from sample material and prepared reference pulses in a Mach-Zehnder interferometer. Since femtosecond laser light has broad spectrum, measurement depth resolution achieves accuracy as high as 5.5 micrometers. We applied the method to acrylic resin microdrilling and succeeded in real-time depth measurement. It was also proved experimentally that this new method measured hole depth having high aspect ratio because it was in a situ measurement. This real-time hole depth measurement is expected to be a powerful and useful tool for femtosecond laser material processing.
