Holographic waveguide display with a combined-grating in-coupler.

Area of Science:

• Optics and Photonics
• Display Technology
• Nanophotonics

Background:

• Volume holographic gratings are essential for waveguide display systems.
• Existing gratings exhibit lower TM polarized energy efficiency compared to TE.
• This limitation impacts overall display performance.

Purpose of the Study:

• To propose and theoretically evaluate a novel in-coupler design for holographic waveguide displays.
• To enhance the diffraction efficiency and luminance efficiency of coupling gratings.
• To address the polarization-dependent efficiency issue in current systems.

Main Methods:

• Design of a combined-grating in-coupler integrating a subwavelength metal grating onto a volume holographic grating.
• Theoretical calculations to determine diffraction efficiency for TM, TE, and unpolarized light.
• Analysis of luminance efficiency improvements for the proposed design.

Main Results:

• The combined-grating design increases diffraction efficiency by 16.4% (TM), 4.3% (TE), and 10.0% (unpolarized).
• Luminance efficiency is enhanced by 26.8% (TM), 9.0% (TE), and 15.6% (unpolarized).
• Significant improvements over single volume holographic gratings were demonstrated.

Conclusions:

• The novel combined-grating design effectively enhances coupling efficiency in holographic waveguide displays.
• This approach offers a viable solution to improve performance for various polarization states.
• The findings pave the way for more efficient and brighter waveguide display systems.