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Vertical Cavity surface Emission Lasers - indrajeet - 10-04-2017 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 ?o 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 = ?o/2 n1 , n2 refractive indices d1 , d2 thickness of layer ?o 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) |