Replication Method for VHOEs

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Replication Method for Volume Holographic Optical Elements and Holographic Waveguide Couplers Tech ID: UA20-230 Invention: This invention is a replication method for volume holographic optical elements and waveguide couplers. It is a new configuration for fabricating transmission holograms using composite master holograms and reflection holograms using a pair of master holograms. It produces a method that is scalable and able to increase the type of waveguide holograms that can be fabricated. This invention has the potential for commercial application in augmented reality displays and solar energy systems. This method utilizes successful replication techniques from prism-coupled assemblies without the drawbacks of limited spatial frequencies in those systems. Background: Volume Holographic Optical Elements (VHOE) are a type of diffractive optical elements with applications in solar energy, display systems, security, and medical imaging. Holographic optical elements (HOE) can be classified into two main types, thin and volume. Historically, VHOEs have been used in customizable applications, but this application is becoming more commercially available as technology matures. Manufacturability still lags development so improvements to ease manufacturing are valuable to process efficiently an increased commercial demand. Currently, contact-copy is the main manufacturing process. It uses a master hologram that creates copies of itself through contact with a photopolymer. However, this process is not well suited to input beams that are non-planar or when apertures of the VHOE need to be well-defined. A prism-coupled technique used total internal reflection of beams to create replication holograms without these limitations, yet the technique required an air gap between the master hologram assembly and replication hologram, which prevented the production of waveguide holograms because the air gap limited spatial frequencies of the interference pattern created by the object and reference beams.