Abstract: An optical switch includes a plurality of optical interferometric structures is serially connected between at least one optical input node and two optical output nodes. A primary waveguide directly connects an optical input node and a first optical output node. A complementary waveguide, which is directly connected to a second optical output node, is evanescently coupled with the primary waveguide in a pair of optically coupled sections provided in each optical interferometric structure. Each optical interferometric structure also includes a pair of decoupled sections, which includes a primary decoupled section embedding a portion of the primary waveguide and a complementary decoupled section which includes a portion of the complementary waveguide. The complementary decoupled section is embedded in a phase tuning structure that allows modulation of the phase of the optical signal passing through.

Abstract: A vertical stack of a first silicon germanium alloy layer, a second epitaxial silicon layer, a second silicon germanium layer, and a germanium layer are formed epitaxially on a top surface of a first epitaxial silicon layer. The second epitaxial silicon layer, the second silicon germanium layer, and the germanium layer are patterned and encapsulated by a dielectric cap portion, a dielectric spacer, and the first silicon germanium layer. The silicon germanium layer is removed between the first and second silicon layers to form a silicon germanium mesa structure that structurally support an overhanging structure comprising a stack of a silicon portion, a silicon germanium alloy portion, a germanium photodetector, and a dielectric cap portion. The germanium photodetector is suspended by the silicon germanium mesa structure and does not abut a silicon waveguide. Germanium diffusion into the silicon waveguide and defect density in the germanium detector are minimized.