Improvements in Light Emitters by Controlling Spontaneous Emission: From LEDs to Biochips
Ecole Polytechnique, 91120 Palaiseau, France andMaterials Department, UC–Santa Barbara, Santa Barbara, CA 93106, U.S.A.
Materials Department, UC–Santa Barbara, Santa Barbara, CA 93106, U.S.A.
Genewave, bât. XTEC, Ecole Polytechnique, 91128 Palaiseau Cedex, France
Labo. Charles Fabry de l’Institut d’Optique, CNRS, 91127 Palaiseau, France
The need to control electron and photon motion in solids, which would in particular enable better optoelectronic devices, has driven the field of light–matter interactions for the past thirty years.
Semiconductors, although uniquely useful for electrically pumped light emission, are hampered in this application by their high n ≥ 2.5 refractive index. At a planar face of a standard light-emitting diode (LED), extraction efficiency is limited to only η = 2−4% by the small fraction of internal emission that impinges at angles smaller than the critical angle, while substrate absorption usually consumes the remaining 96−98% of the internally reflected photons.1,2 One possible solution to this drawback is to have light make multiple attempts to escape by impinging on the semiconductor-air interface at different angles. This is the solution offered by geometrical or ray optics, relying on shaped devices or ...