Biomedical material ablation by flexible-hollow-fiber-delivered double pulses

In this study, we demonstrate a high quality beam delivery using a flexible small-core hollow fiber and the ablation processing of hydroxyapatite (HAp) and collagen with fs double pulses through a bending hollow fiber. HAp is a main component of bones and teeth. We adopted two new methods: One is the use of a hollow fiber with a 320-mum core diameter in order to improve the output beam intensity profile by eliminating the high order modes. The other one is an fs double pulse laser transmission scheme with a tailored ps-order delay time, which is earlier than the ablation onset. Since the optical damage threshold of the hollow fiber depends on the peak intensity of the incident laser pulse, therefore, the double pulse transmission enabled us to deliver higher pulse energies than the single pulse even by keeping the fs laser ablation characteristics. By adopting these two new methods of flexible hollow fiber, double pulse transmission and ablation processing, we delivered high energy enough to ablate HAp and collagen. We demonstrated the delivery of a near Gaussian output beam profile, and high ablation rates