21-09-2008, 11:30 PM
Vertical Cavity surface Emission Lasers (VCSEL) are lasers that emit light from their surface in contrast with regular ???edge emittersâ„¢. 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)
