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