Efficient, high-speed ablation of soft tissue with few-microjoule, femtosecond pulse bursts

Femtosecond pulses hold great promise for high-precision tissue removal. However, ablation rates are severely limited by the need to keep average laser power low to avoid collateral damage due to heat accumulation. Furthermore, previously reported pulse energies preclude delivery in flexible fibers, hindering in vivo operation. Both of these problems can be addressed through use of groups of high-repetition-rate pulses, or bursts. Here, we report a novel fiber laser and demonstrate ultrafast burst-mode ablation of brain tissue at rates approaching 1 mm$^3$/min, an order of magnitude improvement over previous reports. Burst mode operation is shown to be superior in terms of energy required and avoidance of thermal effects, compared to uniform repetition rates. These results can pave the way to in vivo operation at medically relevant speeds, delivered via flexible fibers to surgically hard-to-reach targets, or with simultaneous magnetic resonance imaging.