Based on the computing fluid dynamics, the effects of the inhomogeneity of the flow filed at the nozzle entry on the flow characteristic at the gain region were investigated. The computing results indicate that the asymmetric -inhomogeneous conditions can induce the asymmetric influences and the boundary layer separation at the gain region. The symmetric - inhomogeneous conditions with different profiles have different effects. Along the nozzle spanwise direction, the incoming flow with the regular triangle pressure profile can increase the shock wave intensity. The flow structure is broken and the interaction position of boundary layer and shock waves move upstream in the condition with the regular triangle pressure profile. All results can provide information for study and design of the pipe at the COIL nozzle upstream.
Chemical oxygen iodine laser, or COIL, is an impressive type of chemical laser and is widely adopted in the past several decades. A novel approach for obtaining high power vortex beam is explored. A seed vortex beam is amplified by a chemical oxygen iodine amplifier. Numerical simulation is carried out to confirm the feasibility of obtaining high power vortex beam based on chemical oxygen iodine amplifiers. The behavior of the vortex beam is also revealed. As the beam is modulated by the gain media, the beam profile gets asymmetric, and the vortex center no longer locates at the midpoint between the upstream and downstream intensity maximum points. This study suggests a potential approach for developing chemical oxygen iodine lasers.
Chemical oxygen iodine laser, or COIL, is an impressive type of chemical laser that emits high power beam with good atmospheric transmissivity. Chemical oxygen iodine lasers with continuous-wave plane wave output are well-developed and are widely adopted in directed energy systems in the past several decades. Approaches of generating novel output beam based on chemical oxygen iodine lasers are explored in the current study. Since sophisticated physical processes including supersonic flowing of gaseous active media, chemical reacting of various species, optical power amplification, as well as thermal deformation and vibration of mirrors take place in the operation of COIL, a multi-disciplinary model is developed for tracing the interacting mechanisms and evaluating the performance of the proposed laser architectures. Pulsed output mode with repetition rate as high as hundreds of kHz, pulsed output mode with low repetition rate and high pulse energy, as well as novel beam with vector or vortex feature can be obtained. The results suggest potential approaches for expanding the applicability of chemical oxygen iodine lasers.
Unstable resonator with nonuniform magnification for improving the beam uniformity of chemical oxygen iodine lasers is explored for the first time. The magnification of the resonator is a function of the radial coordinate of the polar coordinate system on the front mirror surface. A resonator was designed to have a lower magnification at the center of the resonator than at the edge. The resonator consists of two aspherical mirrors. Method for designing the resonator is given. The energy conservation law and the aplanatic condition were used to derive the designing principle of the two aspherical mirrors. The design result was fitted to polynomial form which is suitable for manufacturing. Numerical experiment was carried out to evaluate the performance of the resonator. The computation was based on coupled simulation of wave optics model and computational fluid mechanics model. Results proved the effectiveness of the design method. The design tends to enhance the intensity near the center of the output beam and cripple that near the edge. Further analysis revealed that this effect is induced because rays of light are reflected more densely at the center of the pupil than at the edge. Therefore, this design affords for a potential approach for improving the near field uniformity of chemical oxygen iodine lasers.