Volume hologram replication system for photovoltaic applications

A replication system and method for fabricating volume hologram arrays is reviewed in this paper. The replication system can be used to fabricate high-efficiency transmission volume holographic lens arrays that are well-suited for spectrum-splitting photovoltaic applications. As in the well-known contact-copy replication technique, the new technique uses a master hologram to generate the desired holographic exposure, however no contact is required with the copy hologram. The object and reference beams for the holographic exposure are generated by discrete "coupling elements" on the master hologram and coupled through a prism to form an interference pattern on the copy hologram. The system can be implemented using relatively inexpensive lab equipment, but also has potential for large-scale production of holographic elements. A prototype system was developed and used to fabricate an experimental holographic lens array with a large aperture (9.6cm X 6cm) and high median diffraction efficiency (95.6%).