Temporal pulse manipulation and consequences for ultrafast laser processing of materials

Following advances in ultrafast laser technology as a reliable tool for material probing and processing, we discuss various options for control and optimization. The possibility to tailor the temporal shape of ultrashort laser pulses enables extended opportunities for material processing. The concept of optimizing laser interactions is based on the possibility to regulate the energy delivery so that control of laser-induced phenomena can be achieved and quality structures can be realized. An experimental demonstration of the possibility to design excitation sequences tailored with respect to the material response is described, laying the groundwork for adaptive optimization in materials structuring. We show that under particular irradiation conditions involving modulated excitation, the energy flow can be controlled and the material response can be guided to improve processing results. This is particularly important for processing brittle materials. Further examples are given to illuminate the possibility to optimize the kinetic properties of ions emitted from laser-irradiated semiconductors, using excitation sequences synchronized with the solid-to-liquid transformation time. Versatile sub-kilo-electron-volt ion beams are obtained, exploiting transitions to supercritical fluid states with minimal energetic expenses. Temporally selective irradiation can thus open up efficient thermodynamic paths, unfolding interesting perspectives for "intelligent," feedback-assisted processing of materials. (c) 2005 Society of Photo-Optical Instrumentation Engineers.