edgeemitting

Edgeemitting refers to optoelectronic devices that emit light from the edge or plane of a semiconductor chip, rather than from its top surface. The term is most commonly applied to edge-emitting semiconductor lasers and light-emitting diodes in which the active region lies in the plane of a waveguide and light is extracted from the cleaved edge of the chip.

In operation, the device relies on a planar or ridge waveguide formed by epitaxial layers that confine light laterally. A cavity is created by reflectors at the ends, often cleaved facets with anti-reflection or high-reflection coatings, or by distributed feedback structures. The optical mode propagates along the junction and exits through the edge, producing a line-shaped beam that is well suited for coupling into optical fibers.

Materials and wavelength ranges vary by technology. GaAs-based edge emitters typically cover shorter near-infrared wavelengths, while InP-based devices target the 1.3 to 1.55 micrometer range for telecommunications. Device variants include Fabry-Pérot edge emitters, ridge-waveguide lasers, and single-frequency sources using distributed Bragg reflectors (DBRs) or distributed feedback (DFB) gratings. Facet coatings and precise facet machining are used to control threshold, efficiency, and spectral characteristics.

Compared with surface-emitting devices such as VCSELs, edge emitters generally offer higher power and favorable coupling to single-mode fibers, but may require more complex packaging and alignment and can exhibit ezact beam astigmatism. Applications span telecommunications, data communications, optical sensing, laser printing, and disc-reading technologies, where a high-power, high-beam-quality source is advantageous.