Document Type

Theses, Ph.D

Abstract

The main purpose of this research is to explore volume holographic optical couplers and investigate their potential for use as solar collectors in glass building structures. Such couplers are from the family of volume holographic optical elements (VHOEs) and their primary function is to re-direct the incident light so that it is trapped by Total Internal Reflection (TIR). They have been proposed for different waveguiding applications such as solar collection, head-up displays, and optical communication. Since the Sun is a non-stationary light source, often at a high altitude, couplers designed for non-normal incidence are crucial.

Ultimately, this work will address three challenges: (1) developing designs and fabrications of VHOE couplers without using prisms for mass production, (2) fabrication of such couplers to cover a range of angles and wavelengths, and (3) investigating the limitations of such couplers for large area solar collection. This report outlines the work done for the completion of the PhD work. Initially, a theoretical model was developed, which enabled the identification of the appropriate recording conditions (incident beam angles, spatial frequency, slant angle) so that the couplers could be holographically recorded without the use of any prisms. Then using the results from the model, holographic couplers were experimentally fabricated and characterised demonstrating that it is possible to record at a different wavelength than the target operating wavelength and achieve the expected diffraction behaviour. Different coupler configurations for collection were then explored, and it was found that using reflection geometry, the range of operative wavelengths could be extended into the blue region without the need for UV recording wavelengths. All the couplers were recorded in commercially available material known as Bayfol HX 200. The transmission regime couplers were demonstrated to in-couple 633 nm light, having been recorded using a 532nm laser. The reflection-type couplers recorded at 532 nm were demonstrated to in-couple blue (450 nm) light. In the next phase of the work, one transmission-type and one reflection-type coupler were multiplexed to cover the entire visible iii spectrum in the same photopolymer layer. The multiplexed couplers were subjected to both angular and spectral characterization.

Finally, the limitations of such couplers, including identifying dominant loss mechanisms for large area solar collection, have been systematically investigated and demonstrated both qualitatively and quantitatively, and solutions were proposed to mitigate these losses

DOI

https://doi.org/10.21427/326b-5f37

Creative Commons License

Creative Commons Attribution-Share Alike 4.0 International License
This work is licensed under a Creative Commons Attribution-Share Alike 4.0 International License.

Download


Share

COinS