Cassegrain-based concentrator with a high uniformity and acceptance angle

In this study, we improved a Cassegrain concentrator [ Appl. Opt. 59 , 8603 [ 2020 ) APOPAI 0003-6935 10.1364/AO.400756 ] by redesigning the secondary optical element (SOE) with a freeform design, including geometrically mapped and tilted steps, to replace the design of the primary optical element (POE). This modification increased the acceptance angle and formed a more uniform irradiance distribution in the system without a homogenizer while maintaining the same level of efficiency. The result is a 1236× geometric concentration ratio, 1035× concentration ratio, 83.73% optical efficiency, ±0.40 ∘ acceptance angle, 8.96 uniformity, and 0.254 aspect ratio.