Modelling and Design of Holographic Optical Elements for Beam-Coupling Applications for a Range of Incident Beam Angles
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1.3 PHYSICAL SCIENCES, Optics
Theoretical modelling has been used to calculate the holographic recording beam angles required in air (at any recording wavelength) to produce a Volume Holographic Optical Element (VHOE) for any defined input and output beam angles. The approach is used to facilitate the design and fabrication of diffractive coupling elements through a holographic process that avoids the use of coupling prisms during recording and will help in the design of recording arrangements that better suit the mass production of low-cost elements, especially those designed for non-normal incidence. In this study, the recording angles needed for a range of recording wavelengths were explored for VHOE couplers designed for input angles (in air) ranging from 0◦ to −55◦ . Then, in order to validate the model, holographic recording in Bayfol HX 200 photopolymer at 532 nm was used to fabricate photopolymer VHOE couplers for 633 nm light (−45◦ input angle in air). Bragg curves obtained experimentally for different probe wavelengths (403 nm, 532 nm and 633 nm) confirm the recording of the desired grating structures to a precision of ±1 ◦ , and coupling is demonstrated at 633 nm with a diffraction efficiency of up to 72%. Furthermore, the model is used to identify the origins of some weaker spurious gratings observed alongside the expected ones.
Chakraborty, D., Georgiev, R. & Aspell, S. (2022). Modelling and Design of Holographic Optical Elements for Beam-Coupling Applications for a Range of Incident Beam Angles. Photonics, vol. 9 no. 12. doi:10.3390/photonics9120936