Design of off-axis double reflection freeform miniaturized antenna

Abstract

The asymmetrical divergence angle distribution of elliptical laser beam produced by a laser diode (LD) severely limits the application. In this paper, an off-axis double reflection freeform miniaturized antenna design method is proposed to collimate, shape, and transmit elliptical beams from LD. Based on the law of conservation of energy, reflection vector theory, and equal optical path principle, two freeform mirrors are constructed simultaneously by using the three-dimensional point-by-point construction iterative method. The simulation results show that the maximum divergence angle of the output light is compressed to 3.42 μrad, and the ratio of beam waist (RBW) of the output beam is reduced from 3.0000 to 1.0668 at the target plane (L=1 km). The volume of the antenna is 3229.99 cm 3 and the design realizes the miniaturization of the antenna. In addition, the effects of wavelength shift, astigmatism, and the offset of the light source on the collimation effect are analyzed. These research results will provide a practical method to collimate and shape the laser beam and increase the transmission efficiency of the optical communication system. Meanwhile, the proposed optimization method to obtain optimal parameters can be applied to design the initial structure of the freeform surface, and the method of constructing a line light source model in the design process can also provide a reference for the study of astigmatism of LD.