Abstract: The present invention provides an optical device and a method of manufacture thereof. In one embodiment, the method of manufacturing the optical device may include isolating an end of a first layer from a cladding layer located over a mesa structure that has been formed from a substrate. The end of the first layer may be isolated from the cladding layer by encapsulating the end between second and third layers located adjacent the mesa structure.

Abstract: Disclosed are strained layer heteroepitaxial structures (e.g., GeSi/Si) that can have low threading dislocation density as well as a substantially planar surface. Furthermore, a large fraction (e.g., >90%) of the total surface are of the structure can be available for device processing. These advantageous features are achieved through utilization of novel "dislocation sinks" on or in the substrate whose height parameter h is less than or about equal to the thickness of the strained heteroepitaxial layer on the substrate. Exemplarily, h.gtoreq.h.sub.c, where h.sub.c is the critical thickness associated with misfit dislocation generation in the substrate/overlayer combination.