Vertical-cavity surface emitting lasers (VCSELs) are now key optical source
s in optical communications, Their main application is currently in local a
rea networks using multimode optical fibers. VCSELs are also being rapidly
commercialized for single-mode fiber metropolitan area and nide area networ
k applications, The advantages of VCSEL include simpler fiber coupling, eas
ier packaging and testing, and the ability to be fabricated in arrays. In a
ddition, VCSELs have an inherent single-wavelength structure that is well s
uited for wavelength engineering. All these advantages promise to lead to c
ost-effective wavelength-tunable lasers, which are essential for the future
intelligent, all-optical networks.
In this paper, I will review the advances on wavelength-tunable VCSELs. I w
ill summarize some of the early breakthroughs in wavelength engineering of
VCSELs and then concentrate on the designs and properties of micromechanica
l tunable VCSEL.