Pulsed DF and DF-CO2 laser performance

Abstract

A comprehensive set of pulsed DF and DF-CO2 laser performance measurements is presented as a function of gas mixture composition (F2, O2, D2, diluent, and CO2), laser threshold gain, and reaction initiation strength. All the data were collected on a 47-l device using flash photodissociation of F2 to initiate the D2/F2 chain reaction. For helium buffered mixtures, maximum DF laser energy was found to occur at the highest pressures investigated (760 Torr), where the least amount of O2 is required for stabilization of the D2-F2 mixture prior to initiation. The addition of N2 or NF3 is deleterious to DF laser performance. However, at low partial pressures (∼100 Torr) the performance of N2 or NF3 diluted mixtures is comparable to that of He mixtures, suggesting that N2 or NF3 may be acceptable alternatives to He diluent in some laser system designs. The maximum DF-CO2 transfer laser energy was found to be 40% higher than the corresponding DF laser energy for comparable gas mixtures without any CO2. As with DF, the DF-CO2 laser energy was found to scale with the pump rate parameter, PF2(F/F2)1/2, provided the partial pressure of CO2 was adjusted to maintain a constant ratio of PCO2/(PF2(F/F2)1/2)2. The presence of NF3 caused a strong decline in DF-CO2 laser output, which is believed to be due to the ν1, symmetric stretch absorption band of NF3 at 10.3 μm.