CO2 Laser Ablation Impulse Generation with Polymer Propellants

The fluence dependence of the laser ablation of selected polymers including polytetrafluoroethylene, polycholorotrifluoroethylene, cellulose acetate, polyoxymethylene, and polyethylene was studied within the range 1-200 J/cm(2) in atmospheric air. A transversely excited atmospheric CO2 laser operating at 10.6 mu m with approximately 100 ns pulse length and about 3-20 J output pulse energy was used to ablate prepared polymer samples with single pulses of laser energy. Measurements of parameters such as ablated mass per spot area mu, momentum coupling coefficient C-m, specific impulse I-sp, and ablation efficiency eta(ab) were measured as functions of fluence and assessed based on an analytical vaporization model. Critical threshold effects are described in detail for the first time.