Patent ID: 8842942

Claim:
A modulator, comprising: a bulk-silicon substrate having an upper surface, and a trench extending downwardly form the upper surface, wherein the trench has a width less than that of the substrate and a depth less than a thickness of the substrate; a bottom cladding layer occupying at least a portion of the trench in the bulk-silicon substrate; a plurality of waveguides each extending on the bottom cladding layer; a phase modulation unit comprising one of the waveguides, a first electrode, and a second electrode, and said phase modulation unit being configured to modulate a phase of an optical signal propagating along said one of the waveguide by modulating a refractive index of the waveguide, wherein said one of the waveguides has a slab and a core, the slab comprises silicon and is disposed on the bottom cladding layer, and the slab has first and second opposite sides, a first P-type carrier region in the first side and electrically connected to the first electrode, and a first N-type carrier region in the second side and electrically connected to the second electrode; the core is disposed on the slab and spans only a portion of the slab in a direction parallel to an upper surface of the bulk-silicon substrate such that the core projects upwardly relative to an upper surface of the slab, and the core has a P-type carrier region contiguous with the first P-type carrier region, and an N-type carrier region contiguous with the first N-type carrier region, the P-type carrier region and the N-type carrier region of the core being located in opposite sides of the core, respectively and each extending to the top of the core; and a top cladding layer on the plurality of waveguides.