Visually clear diffusive light panel with embedded semi-reflective rough-surface planar outcouplers

• Published in: Journal of micromechanics and microengineering 2023-06, Vol.33 (6), p.65003
• Main Authors: Park, Hongbae, Stoeber, Boris
• Format: Article
• Language: English
• Subjects: diffuser; light guide; photolithography; transparent
• ISSN: 0960-1317; 1361-6439
• DOI: 10.1088/1361-6439/accc3b

We present a visually transparent light-diffusing panel in the form of a light guide, which has semi-reflective, thin-film blades buried within it acting as diffusive outcouplers. The semi-reflective blades can be tilted relative to the length of the light guide and are textured to partially scatter the light incident upon them in the reflection domain, while transmitting the rest. We show that the texturization of the outcouplers can be achieved following a simple molding process using a mold with well-defined roughness regions to subsequently create light-scattering surfaces. The mold is either based on frosted glass or on a photolithographic process using a polymer photomask. We demonstrate with a prototype that the view through the textured outcouplers is visually clear. Also, we demonstrate that by varying the angular difference between the incidence of the propagating light rays and the outcoupler angle, the ratio of the amount of diffused light emanating from the two surfaces of the light guide can be biased from ∼1:2 to ∼1:20. The proposed device can be used as a transparent light source that provides an occlusion-free and undistorted see-through view.