Numerical simulation of stimulated radiation on reacting flowfield in DF supersonic chemical laser

Abstract

A DF chemical laser can transfer chemical energy into high-power laser beam in the megawatt range, which may be used for industrial manufacturing or military purposes. Reacting flowfield and optical field always interact in the process of optical energy extraction from the chemical laser cavity. On the one hand, nonuniform distribution of gain medium may affect the transmission of light beams, may lead to light deflection and phase deviation furtherly. On the other, power extraction may cause the variation of species and energy distribution in the flowfield. Therefore a numerical simulation is presented for investigating the interaction of chemical reaction flowfield and optical field. An 11-species (including DF molecules in various excited states of energies), 23-step chemistry model is adopted for the chemical reaction of the DF chemical laser system. Meanwhile, laser oscillating in the optical cavity is solved by geometric optical models. Variations of flow and optical fields from the establishment to the stabilization status in the optical cavity are simulated. Major results reveal that stimulated radiation has dominant effects only on the concentrations of the lasing species (DF excited molecules), and it has relatively minor influence on the basic fluid dynamic variables. For the case without lasing, the complete population inversion phenomena could be found in wider range, which does not occur for lasing. The lasing output is based on the partial population inversion of the vibration-rotation transition in DF molecules.