Table-top 50 W laser system for ultra-fast laser ablation

We have built a mode-locked Nd:YVO4 laser with a very long resonator which produces an average power of 50-W in 13-ps pulses at 1064nm and was designed for applications in micro-machining; the deposition of optical thin films; and the growth of nano-clusters in the laser-ablated plumes. By operating the laser at very low mode-locking repetition rates (1.5 MHz, 2.6 MHz, and 4.1 MHz), high pulse power is available in a near diffraction limited beam allowing focussed intensities to exceed 1012 W/cm2 and permitting efficient evaporation of difficult materials such as Si. The high power also allows conversion into the 2nd harmonic at 532nm with an efficiency exceeding 80%. Measurements of the ablation mass in experiments with metals show a 30-100 times increase in the ablated rate compared to the conventional low-repetition-rate ns-range lasers.