Edge emitter LED construction and working principle
Currently used, high radiance structure is the edge emitter LED. It have transparent guiding layers with a very thin active layer ( 50 to 100 un ) as shown in above figure.
The light produced in the active layer spreads into the transparent guiding layer, reducing self-absorption in the active layer. Most of the propagating light is emitted at one end face only due to a reflector on the other end faced and anti-reflection coating on the emitting end face. It is modified injection laser structure. It has very thick active region with significant different that a wave-guide around the active region channels radiation to the emitting face of the device. Here light is generated in the active layer and guided to emitting face. The light is coupled to the lowest. order guided mode parallel to the junction. Most of the light propagating in this mode is transmitted. to the end facets and emitted with a half power beam width of about 25-30* in plane of a junction. The beam emitted perpendicularly to the junction where there is no wave-guiding effect. Although the optical power obtained from such a structure is 2 to 6 times smaller than that of a SLED but more efficient copling due to narrow band width.
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| Diagram of Edge emitter LED construction |
Currently used, high radiance structure is the edge emitter LED. It have transparent guiding layers with a very thin active layer ( 50 to 100 un ) as shown in above figure.
The light produced in the active layer spreads into the transparent guiding layer, reducing self-absorption in the active layer. Most of the propagating light is emitted at one end face only due to a reflector on the other end faced and anti-reflection coating on the emitting end face. It is modified injection laser structure. It has very thick active region with significant different that a wave-guide around the active region channels radiation to the emitting face of the device. Here light is generated in the active layer and guided to emitting face. The light is coupled to the lowest. order guided mode parallel to the junction. Most of the light propagating in this mode is transmitted. to the end facets and emitted with a half power beam width of about 25-30* in plane of a junction. The beam emitted perpendicularly to the junction where there is no wave-guiding effect. Although the optical power obtained from such a structure is 2 to 6 times smaller than that of a SLED but more efficient copling due to narrow band width.
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