A new LED structure with a self-aligned sphere lens for efficient coupling to optical fibers

1 July 1977

journal article
Published by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Transactions on Electron Devices

Vol. 24 (7) , 986-990
https://doi.org/10.1109/T-ED.1977.18866

Abstract

A practical new structure of the high radiance GaAs-GaAlAs LED with a self-aligned sphere lens has been developed for efficient coupling to low-less optical fibers as a light source for fiber optic communications. In this new configuration, the sphere lens is automatically settled into the center of the light-emitting surface by an etched hole containing clear epoxy resin. When applied to a low-loss optical fiber ( NA = 0.14 , core diameter: 80 µm), a coupling efficiency in excess of 9 percent has been reproducibly achieved for an LED structure with an emitting-area diameter of 35 µm and with a lens having a diameter of 100 µm and a refractive index of 2.0. Using an LED with a light-emitting-layer carrier concentration of 3 × 10 18 /cm 3 , an optical power of 150 to 200 µW coupled into the fiber and a cut-off frequency (optical power down to ½) of about 90 MHz have been reproducibly obtained.

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