On the Optical Concentration Achievable by a Non-imaging Microprism Array Combined to an Image Photodetector

An array of non-imaging micro-prisms can offer a substantial recovery of the sensitivity loss due to area fill-factor in photodetectors. This is especially true for device in which complex circuit functions are required, that consume a large fraction of pixel area, like e.g., CMOS sensors, image rengefinders, SPAD arrays, fluorescence analysers, etc. In this paper, after a general introduction, we evaluate the achievable concentration at asymptotically low NA (input/output area ratio) and high NA (inverse square of the input NA). Then, we present the results of a ray-tracing method for the fast and efficient calculation of the optical parameters of several types of prism concentrators, i.e., truncated cone, parabolic and compound parabolic, both reflective and refractive. Parameters considered are: power efficiency, effective concentration, channel crosstalk and power penalty for output gap.