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Rainbow-free guided-mode resonance metasurfaces for optical eye-tracking with near-unity transmission (Conference Presentation)
Author(s): Jung-Hwan Song; Soo Jin Kim; Jorik van de Groep; Mark L. Brongersma
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Paper Abstract

Eye tracking has been an indispensable analysis method in a wide range of research fields, including Psychology, Neurology, and ophthalmology. Recent developments in augmented reality are pushing for more compact, transparent eye trackers compatible with head-mounted display or heads-up display. Oblique half-mirror and holographic waveguide satisfy these criteria and now widely used in eye-controlled displays, auto-driving, and near-to-eye displays. However, these still require bulky supplementary optics, are poorly transparent, and produce rainbow images due to non-zero diffraction in the visible spectrum. Here, we demonstrate ultra-thin, rainbow-free eye tracking diffractive optical elements based on guided mode resonance that exhibits near-unity transmission. It consists of a 200-nm-thick Si3N4 slab waveguide sandwiched between a quartz substrate and a 100-nm-thick SiO2 capping layer designed for high transmission (>90%) over the whole visible spectrum. The insertion of 3-nm-thick Si grating layer at the interface between the slab waveguide and capping layer launches high-quality (Q~2,000), leaky guided modes in the slab waveguide at specific wavelengths for a fixed incident angle and polarization, which enables us to efficiently (13%) characterize resonant light diffraction at 870 nm. In the visible, on the other hand, the guided mode resonance becomes weak due to Si absorption, resulting in strongly suppressed rainbow-producing diffractions below 0.1% efficiency. By locating a single webcam at near-grazing angle, corresponding to the output diffracted order at 870 nm, the full anterior images of an artificial eyes are obtained. Our device opens a promising route toward ultra-compact, transparent, and non-obtrusive imaging for displays and optical switching applications.

Paper Details

Date Published: 8 March 2019
Proc. SPIE 10928, High Contrast Metastructures VIII, 1092810 (8 March 2019); doi: 10.1117/12.2507273
Show Author Affiliations
Jung-Hwan Song, Stanford Univ. (United States)
Soo Jin Kim, Korea Univ. (Korea, Republic of)
Jorik van de Groep, Stanford Univ. (United States)
Mark L. Brongersma, Stanford Univ. (United States)

Published in SPIE Proceedings Vol. 10928:
High Contrast Metastructures VIII
Connie J. Chang-Hasnain; Andrei Faraon; Weimin Zhou, Editor(s)

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