High Convergence Efficiency Design of Flat Fresnel Lens with Large Aperture

As a part of the solar pumped laser project, this paper optimized a circle-shaped Fresnel lens with large aperture. It was a simulation design of light tracing conducted in Matlab. This paper analyzed parameters of light spot size, light intensity distribution and optical efficiency under four conditions-monochromatic parallel light, parallel spectrum light, divergent monochromatic light and sunlight. The size of optimized Fresnel lenses was 1000mmx1000mm. It was made of polymethyl methacrylate ( PMMA). Beams of 550nm wavelength was used and Fresnel reflection was considered. When the coaxial annular rings have the same width of 0.3mm with focus length of 1200mm, the result indicated that the optimized lens could converge sunlight to a 78.7% optical efficiency within diffraction limit of 11.8mm. However, under the same condition, the Fresnel lens that based on spherical lens cutting could only obtain a 30.4% optical efficiency. This result showed that by optimization, Fresnel lens could obtain higher optical efficiency and light intensity.