Cavitation bubble dynamics for laser lithotripsy using ultrashort pulses in the near infrared

Laser lithotripsy typically relies on high water absorption at a laser wavelength of 2 µm using pulse durations > 1 µs and relatively high pulse energies of ~ 1 J. This may lead to large particle size and retropulsion. Ultrashort laser technology is on the other hand well-known for precise ablation at low pulse energy. Furthermore, thulium fiber laser technology at 1.9 µm has recently attracted considerable attention in both laser lithotripsy and ultrafast laser technology. In this study we investigate the ablation and bubble dynamics using femtosecond laser pulses in the NIR between 1 µm and 2 µm. Bubble dynamics in water is studied by pump-probe shadowgraphy and compared to numerical simulations. Results indicate an intermediate regime above ~ 1450 nm, for which linear and nonlinear absorption leads to a confined vapor bubble.