Dynamical observation on laser ablation in bulk transparent materials

Abstract

Laser ablation of transparent materials is induced by non-linear absorption and some laser-induced damages are introduced in the bulk as well as on the surface. This process is used in laser marking and other applications such as refractive index modification of optical materials and 3-D data storage. We have observed the laser ablation dynamics in inside of bulk transparent materials by nanosecond time-resolved imaging technique. Output of fundamental radiation (1064nm) from a Q-switched Nd:YAG laser was focused at inside of bulk PMMA and soda glass. Second harmonic radiation (532nm) from the same laser was used as illuminating light and images were taken by a CCD camera with a band-pass filter at 532 nm. Series of images were taken at different intervals between the fundamental and the second harmonic light, which was controlled by optical delay line. In observation at longer intervals than 5Ons, another laser was used as illuminating source. When the laser was focused at inside of the bulk PMMA, damages occurred simultaneously at several independent points without the ablation at the surface. They located along laser incident axis. Propagation of shock waves, which started from these points, was clearly observed in the bulk. In the glass, absorbing point in the bulk formed a continuous line and its end-point moved from inside outward to the surface along the laser beam. Laser induced damages (cracks) continued to develop until some microseconds after laser pulse in PMMA.

Development of peeling tool for micro-EDM

“…The discharge current was set at 50-100 A and the discharge duration To investigate the removal process of the cladding layer in a single discharge, an ultrafast imaging system was used [6][7][8][9]. The basic concept of the system is similar to that used in our previous study on the laser ablation process [10]. In this system, a highspeed video camera was used as an imaging device and a highrepetition-rate, Q-switched Nd:YAG laser was used as an illuminating light source.…”