The research activities aim at a deeper understanding of controlled nonlinear energy deposition for surgery and material processing in optically transparent materials. The processes of nonlinear energy deposition are investigated by means of optical breakdown in liquid media in which a cavitation bubble is formed abruptly after energy deposition. The optical breakdown can be generated by focusing ultra short pulsed laser radiation into an optically transparent material. The irradiance is so high that energy can be deposited in the focus volume by nonlinear absorption. The process of plasma formation by multiphoton absorption, inverse bremsstrahlung absorption, impact ionization, cascade ionization and thermal ionization is extremely complex and depends strongly on the pulse duration and wavelength of the laser as well as the type of focusing. Together with the team of AG Vogel, a method was developed which allows the exact size of the laser-induced cavitation bubble to be determined using a scattered light method. The size of the cavitation bubble provides a measure for the deposited energy. The smaller the cavitation bubble, the smaller the thermo-mechanical side effects and the finer the laser-induced effect.

Linz N, Freidank S, Liang XX, Vogel A (2016) Wavelength dependence of femtosecond laser-induced breakdown in water, and implications for laser surgery. Phys. Rev. B 94:024113, 1-19

Linz N, Freidank S, Liang X.-X., Vogelmann H, Trickl T, Vogel A (2015) Wavelength dependence of nanosecond IR laser-induced breakdown in water: Evidence for multiphoton initiation via an intermediate state. Phys. Rev. B 91:134114, 1-10