A method for fabricating a waveguide construction is described and has steps of: providing a layered structure by: forming a first-type InGaAsP layer on a substrate, forming a first-type InP layer on the first-type InGaAsP layer, forming an active layer containing gallium on the first-type InP layer, forming a second-type InP layer on the active layer, and forming a second-type InGaAsP layer on the second-type InP layer; forming an SiO.sub.2 patterned layer having SiO.sub.2 regions and at least one channel facing toward a desired direction and formed between the SiO.sub.2 regions on the second-type InGaAsP layer; and performing a rapid thermal annealing treatment on the layered structure formed with the SiO.sub.2 patterned layer. The rapid thermal annealing treatment has a treating temperature between 720 C. and 760 C. and a treating time between 60 and 240 seconds.

An array of monolithic wavelength division multiplexed (WDM) vertical cavity surface emitting lasers (VCSELs) is provided with quantum well intermixing. Each VCSEL includes a bottom distributed Bragg reflector (DBR), an upper distributed Bragg reflector, and a laser cavity therebetween. The laser cavity includes a multiple quantum well (MQW) layer sandwiched between a lower separate confinement heterostructure (SCH) and an upper SCH layer. Each MQW region experiences a different amount of quantum well intermixing and concomitantly a different lasing wavelength shift.

A device comprising a semiconductor layer including a plurality of compositional inhomogeneous regions is provided. The difference between an average band gap for the plurality of compositional inhomogeneous regions and an average band gap for a remaining portion of the semiconductor layer can be at least thermal energy. Additionally, a characteristic size of the plurality of compositional inhomogeneous regions can be smaller than an inverse of a dislocation density for the semiconductor layer.