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Vertical Cavity surface Emission Lasers

Vertical Cavity surface Emission Lasers (VCSEL) are lasers that emit light from their surface in contrast with regular ‘edge emitters’. Also they have got a vertical cavity , as the name suggests, which enables surface emission.”Vixels” , as they are commonly called ,have several superior characteristics compared to their edge emitting counter parts.

VCSEL – Semiconductor micro laser diodes which emit light perpendicular to their PN junction in a cylindrical beam vertically from the surface of a fabricated wafer and feature circular low divergence beam

Earliest reported in 1965 by Melngailis
VCSEL was first demonstrated in 1979 at Tokyo Institute of Technology
Epitaxial mirrors for GaAs/ AlGaAs VCSELs
pioneered in 1983

Distributed Bragg Reflection
If layers of alternating semiconductors are stacked periodically , each layer having a thickness
λo n , the reflections from each of the boundaries will be added in phase to produce a large reflectivity
Brag reflection condition
Periodicity of cladding layer is chosen so that
n1d1 + n2d2 = λo/2
n1 , n2 refractive indices
d1 , d2 thickness of layer
λo free space wavelength of the optical beam
Epitaxial growth of VCSEL
There are two methods
1 . Molecular beam epitaxy ( MBE )
2 . Metal Organic Vapour Phase Epitaxy (MOVPE)

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