Edge Emitting LED structure, working, advantages, disadvantages
This page covers structure, working operation, advantages and disadvantages of Edge Emitting LED. It mentions Edge Emitting LED advantages or benefits and Edge Emitting LED disadvantages or drawbacks.
Edge Emitting LED structure | Edge Emitting LED working operation
• It is widely used in optical fiber communication system.
Here collimated light from LED is required to be fed into the fiber with
high coupling efficiency.
• The figure-1 depicts multilayer structure of InP based edge emitting LED. It is used for long wavelength optical communication approx. between 1.33 to 1.55 µm.
• Modern epitaxial growth techniques such as MBE, MOCVD etc. are used in order to
design such complex LED structures.
• Central active layer is made using InGaAs having narrow bandgap. It is bounded by wide bandgap layers such as p+ InGaAsP and n+ InP cladding layers.
• These two cladding layers help in confining injected electrons and holes into the middle layer. It also helps emitted photons to travel along LED axis as per optical properties.
• Due to above, light is emitted from the edge of the LED. Hence it is known by the name edge emitting LED.
Benefits or advantages of Edge Emitting LED
Following are the benefits or advantages of Edge Emitting LED:
➨It has superior beam collimation property which offers greater coupling efficiency with fiber optic cable compare to surface emitting LED.
➨It offers higher efficiency with low to high radiance. It fulfills high brightness LED requirements of the lighting industry.
➨It radiates less power to the air compare to surface emitting LED due to reabsorption and interfacial recombination.
➨It offers better modulation bandwidth and more directional emission pattern.
➨It offers 5-6 times more coupled power into NA (Numerical Aperture) of step/graded index fibers. This is due to small beam divergence.
➨It offers high data rates (> 20 Mbps) than surface emitting LED.
Drawbacks or disadvantages of Edge Emitting LED
Following are the drawbacks or disadvantages of Edge Emitting LED:
➨Its structure is complex.
➨It is difficult to design heat sink.
➨It is expensive compare to other LED types.
➨There are many issues to be handled during mechanical mounting and installation.