Multiplexed holographic lenses: Realization and optical characterization

Solar panels in both space (satellites) and earth applications have a fundamental problem related to their pointing with a right angle towards the sun. In fact, a correct pointing of the sun could improve energy efficiency produced by the panels. In this paper, with the aim to obtain a solar concentrator, we present the realization of Volume Holographic Optical Elements (V-HOEs), such as holographic lenses, by means of an interferometric recording set-up (Michelson type), and their characterization. The recording material was a photopolymer sensitive to light at wavelength of 532 nm. In particular, using multiplexed holographic lenses, the mechanical unit for the correct pointing of the solar panels can be eliminated. As a result, there are less problems related both to the wear of moving parts and possible vibrations due to movements. This is possible if, during the writing process, the photosensitive support is used to record different holograms by changing the angle of incidence of the object and reference wavefronts. In this way, a V-HOE that addresses the solar radiation incident with different angles, on a single photovoltaic cell, can be realized.