Simple and universal method in designs of high-efficiency diffractive optical elements for spectrum separation and beam concentration**Project supported by the National Basic Research Program of China (Grant No. 2013CBA01702), the National Natural Science Foundation of China (Grant Nos. 11474206, 91233202, 11374216, and 11404224), the Scientific Research Project of Beijing Education Commission, China (Grant No. KM201310028005), and the Scientific Research Base

Abstract

Diffractive optical elements (DOEs) with spectrum separation and beam concentration (SSBC) functions have important applications in solar cell systems. With the SSBC DOEs, the sunlight radiation is divided into several wave bands so as to be effectively absorbed by photovoltaic materials with different band gaps. A new method is proposed for designing high-efficiency SSBC DOEs, which is physically simple, numerically fast, and universally applicable. The SSBC DOEs are designed by the new design method, and their performances are analyzed by the Fresnel diffraction integral method. The new design method takes two advantages over the previous design method. Firstly, the optical focusing efficiency is heightened by up to 10%. Secondly, focal positions of all the designed wavelengths can be designated arbitrarily and independently. It is believed that the designed SSBC DOEs should have practical applications to solar cell systems.