Abstract

Ring-shaped and radial diffractive gratings are designed with rigorous diffraction theory to couple light of a nearly monochromatic LED into a thin planar light guide on the bottom side. The theoretical coupling efficiencies for ring-shaped and radial gratings are 41% and 66%, respectively. Optimized diffractive elements are manufactured with direct electron-beam lithography and reactive-ion-etching into SiO₂ substrates. Good agreement between experimental and theoretical results for selected radial gratings is reached. Furthermore, the mass production tests using injection molding are carried out with good replicability.

© 2004 Optical Society of America

White LED light coupling into light guides with diffraction gratings

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