Small Holes, Drilled in Hard Materials, Using Ultrasort Laser Pulses.

"Ultrashort laser pulses are able to deposit nearly all of their energy before thetarget material responds significanly. As a result, they avoid the losses/scatteringwhich typically accompany other forms of laser processing. Another benefit isthe absence of the melt-phase with its associated slag and thermal trauma/cracking.The amount of material ablated by each pulse can be controlled by adjustingthe pulse energy and spot size. For very small pulse energies, incremeentalamounts of material can be removed. If the spot size is gradually reduced frompulse to pulse, the hole can be very smoothly tapered/contoured.Small pulse energies enable fine control, but also necessitate highpulse repetition rates in order to be useful. One of the main concerns involvedin rapid pulsesuccession is the interaction of a given pulse with the ablation plume of itspreceding pulse. This problem can be mitigated by machining in a vacuum, howeverwhen multiple holes are drilled, the pulses can be alternated among many holes,allowing sufficient time between pulses at any given hole.We propose the application of ultrashort laser pulses to drill arrays of small holesin hard and/or coated materials. lower cost, finer control, drill through coatings, etc The anticipated benefits ofthis technology are much lower cost and time requirements over conventional drillingmethods in the ABL program. The method will also allow higher precision thanconventional methods