Modeling Study of a cw HF Resonance Transfer Laser Medium

Abstract : A nonreactive kinetics model of the flowing gaseous medium of a cw HF optical resonance transfer laser (ORTL) has been developed and used to examine the prospects of this type of laser for efficient performance. Model development has required the generation of HF(v1, J1) + HF(v2, J2) V-V, R-R, T, and V-R cross section by classical trajectory calculations and by surprisal methods. These cross section packages have been validated using non-ORTL HF kinetics experiments, and the entire ORTL medium model has been validated by modeling the reported experimental results of past ORTL experiments without any adjustment of the kinetics packages. The subsequent study observing the effect on small signal gain by varying controllable parameters, such as pumping laser radiative flux and flux distribution, flow velocity, flow density, and HF mole fractions, has suggested a regime for most efficient ORTL operation, in which overall efficiency could reach 0.50. For this regime., pumping laser fluxes should exceed 5000 W/per sq cm with a spectral pattern in which most of the power is in P1(5), p1(6), p2(5), and p2(6). The medium should be operated at slightly elevated temperatures to enhance kinetic-pumping rates with characteristic velocities allowing any ORTL fluid element to remain in the pump beam no longer than 200 microsec.