Plasmonics for solid-state lighting: enhanced excitation and directional emission of highly efficient light sources

Light sources based on reliable and energy-efficient light-emitting diodes (LEDs) are instrumental in the development of solid-state lighting (SSL). Most research efforts in SSL have focused on improving both the intrinsic quantum efficiency (QE) and the stability of light emitters. For this reason, it is broadly accepted that with the advent of highly efficient (QE close to 1) and stable emitters, the fundamental research phase of SSL is coming to an end. In this study, we demonstrate a very large improvement in SSL emission (above 70-fold directional enhancement for p-polarized emission and 60-fold enhancement for unpolarized emission) using nanophotonic structures. This is attained by coupling emitters with very high QE to collective plasmonic resonances in periodic arrays of aluminum nanoantennas. Our results open a new path for fundamental and applied research in SSL in which plasmonic nanostructures are able to mold the spectral and angular distribution of the emission with unprecedented precision. Photonics: LEDs showing their bright side The emission efficiency of a light-emitting diode (LED) can be boosted by metallic nanostructures that enhance the directionality of the emitted light. Gabriel Lozano and Jaime Gómez Rivas from the FOM Institute AMOLF and collaborators have designed small aluminium cylinders whose electronic resonances at the surface—known as surface plasmon resonances—modify the light emitted from a white LED such that it is preferably emitted straight from the surface, rather than toward the side. The overall efficiency of emission in this direction was enhanced by more than a factor of 60 for a specific color. Although the emitters in white LEDs are already very efficient with little room for improvement, this enhancement approach based in a more directional extraction of light out of the LED promises positive implications for lighting technologies.