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
Original Manuscript: March 18, 2004
Revised Manuscript: July 15, 2004
Published: October 20, 2004
Samuli Siitonen, Pasi Laakkonen, Pasi Vahimaa, Konstantins Jefimovs, Markku Kuittinen, Marko Parikka, Kari Mönkkönen, and Ahti Orpana, "Coupling of light from an LED into a thin light guide by diffractive gratings," Appl. Opt. 43, 5631-5636 (2004)