Wavelength-shifted holographic recording of multiplexed volume holographic optical couplers for solar collection

Recent research towards using slanted Volume Gratings as coupling elements for solar collection applications is outlined, in particular the development of coupling films intended for collection of solar energy from vertical glass surfaces and windows. The design, fabrication and testing process is presented for holographic recording of such couplers, with an emphasis on those designed for the typical angles of incidence for vertically oriented surfaces such as windows and glass building facades. By using a combination of transmission and reflection recording arrangements, it is shown that wavelength-shifted prism-free holographic recording can produce couplers that trap sunlight in the red, green and blue regions of the spectrum. Holographic recording without prims is important for low cost mass production through contact-copying methods. High diffraction efficiencies are shown for couplers operating at red green and blue wavelengths using commercially available photopolymer (Bayfol HX200) and Multiplexing of reflection and transmission holograms is demonstrated.