title: Coupling of light from an LED into a thin light guide by diffractive gratings.
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.
authors.affiliation: Department of Physics, University of Joensuu, P.O. Box 111, Joensuu, Finland FIN-80101.
authors.forename: Samuli
authors.initials: S
authors.lastname: Siitonen
authors.forename: Pasi
authors.initials: P
authors.lastname: Laakkonen
authors.forename: Pasi
authors.initials: P
authors.lastname: Vahimaa
authors.forename: Konstantins
authors.initials: K
authors.lastname: Jefimovs
authors.forename: Markku
authors.initials: M
authors.lastname: Kuittinen
authors.forename: Marko
authors.initials: M
authors.lastname: Parikka
authors.forename: Kari
authors.initials: K
authors.lastname: Mönkkönen
authors.forename: Ahti
authors.initials: A
authors.lastname: Orpana