Optical resonator with nonuniform magnification for improving beam uniformity 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.