Acoustic wave monitoring of the excimer laser ablation of YBCO high-T-c superconductor

Monitoring the amplitude and the delay of arrival of the pressure waves gen erated during the interaction of laser pulses with YBCO in air, we can dete rmine the vaporization and the ablation thresholds, the etching rate, the c hange of the acoustic wave velocity and the effect of plasma shielding on t he etching rate. The steep increase of the amplitude and the order-of-magni tude increase of the etching rate above the ablation threshold, suggest tha t the laser-target coupling mechanism changes from (thermal) vaporization b elow threshold to a rapid solid-to-as phase transition. The dumping of the acoustic waves following the ablation with successive laser pulses correlat es with the evolution of the YBCO high-Tc superconductor surface morphology , which is known to relate to the deposition rate and the surface morpholog y of pulsed-laser-deposited high-T-c thin films.