Applications of dual pulsed neodymium:yttrium aluminum garnet laser to materials processing

Two dual pulse laser systems were developed for applications in materials processing. The output of each consists of the combination of two free-running pulses; pulse 1 is a high energy, long duration pulse and pulse 2 is a high peak power, short duration pulse. A tandem head laser was constructed by pairing two laser heads in a single cavity. Each head was driven by an independent power supply in order to produce the dual pulse. A single head dual pulse laser was also constructed. Two separate flashlamp drivers were integrated together in order to produce the dual pulse.; The performance of both the tandem head laser and the single head dual pulse laser were characterized. The dual pulse output of both lasers resembles the superposition of the two pulses. However, there were some effects observed due to the interaction of the two pulses in the cavity. The formation of pulse 2 was a function of the delay at which it was triggered relative to pulse 1. For the case of the tandem head laser, the energy of the dual pulse is greater than the sum of the independent pulses. A model for the output of the tandem head laser was developed and agrees well with the experimental results.; The so called dual pulse method was used to enhance the efficiency of material removal during laser drilling. Pulse 1 is used to produce a large molten pool of liquid which is expelled by the vapor recoil pressure generated by the interaction of the high intensity pulse 2 with the metal. The inherent improvement in efficiency through the removal of liquid allows for drilling at large laser-target standoff distances has been developed. A dual pulse laser was found to be capable of penetrating stainless steel targets with a thickness greater than 1/4" at standoff distances of 1 meter. The standoff distance is defined by the distance between the focusing lens and the target. The efficiency of the dual pulse method was optimized in terms of the energy and duration of each pulse at a standoff distance of 1 meter. It was found that increasing the energy of each pulse showed a corresponding improvement in efficiency. Increasing the duration of pulse 1 will decrease the drilling efficiency due to increased lateral thermal conduction losses. The dependence of shots for penetration as a function of target thickness was also carried out.; The dynamics of the interaction of each pulse with the target was also investigated. The high energy of pulse 1 enables it to produce a large pool of molten metal. Its dimensions is a function of the energy and pulse width of the pulse. The impulse produced by the recoil pressure generated by pulse 2 is responsible for the expulsion of the liquid produced by pulse 1. There is a minimum intensity necessary to overcome the surface tension for liquid expulsion to be initiated. For the free-running pulses used in this experiment, the total impulse delivered to the target will be sufficient for the complete expulsion of the molten pool.