Femtosecond Temporal Pulse Shaping and Spectroscopy for Drilling and Inspecting Straight and Shaped Cooling Holes

Laser micromachining is being widely used in every industry, including aerospace, automobile, microelectronics and bio-technology. The recent advent of commercial turn-key, high power femtosecond lasers has prompted a great amount of interest in using femtosecond lasers for machining. It has been demonstrated that the femtosecond laser has potential for achieving high precision owing to its extremely confined heat-affected zone. The objective of the proposed research is to develop a novel femtosecond laser micromachining technology based on temporally-shaped femtosecond pulses for DoD and other applications, including drilling shaped film-cooling holes in turbine blades. In these femtosecond pulses, the temporal shape and energy of each pulse, and the pulse-to-pulse separation time are all designed and adjusted at a time scale from femtosecond to nanosecond to overcome common problems associated with laser machining and maximize the machining speed. We will also implement diagnostic techniques to provide a feedback for process monitoring and laser parameter control. This will be based on laser-plasma emission for identifying materials and machining rates. In this project, we will focus on optimizing the pulse shapes for machining of film-cooling holes in turbine blades. However, the technique to be developed is generally applicable for machining a wide variety of other materials. BENEFIT: The proposed technology will have large impact on DoD applications such as drilling shaped film-cooling holes in turbine blades and other areas require high precision micro-machining. The proposed technology will also have commercial applications where laser diagnostics and associated hardware and software are extensivey used (e.g. academic and research institutions).