Embodiments of the invention describe substrates, used to form optical devices, which include high thermal conductivity intermediate layers. Said substrates comprise a bulk layer, an optical device layer comprising a first material, and an intermediate layer disposed between the bulk layer and the device layer comprising a second material having a higher thermal conductivity and a lower index of refraction than the first material.In the resulting devices, said intermediate layer functions as part of the device layer structure—i.e., provides optical or electrical power dissipation (i.e. thermal) functionality for the device formed from said substrate. Thus, optical devices do not necessarily need to utilize an add-on packaging solution for heat absorption when formed from substrate stacks according to embodiments of the invention. Moreover, in some embodiments, said intermediate layer is located at “zero-distance” from the source of the heat generation, thereby efficiently transferring heat out of that region.