A novel apparatus for bonding of two polished substrates includes a plasma source in a ultra-high vacuum (UHV) chamber and a wafer-guiding element to control and guide wafers in the UHV chamber, where after a plasma activation process the wafers are guided and pressed against each other to form a covalent bond between wafer surfaces. The plasma activation process involves deposition of mono-layer or sub-monolayer metallic atom on the surface of substrates. After deposition of metallic layers, a high-force actuation presses the wafers and forms a covalent bond between the wafers. Then, the bonded wafer pair is ion-sliced or thinned to form single crystalline optical thin film. An annealing process oxidizes the deposited metallic layers and produces optically-transparent single crystalline thin film. An optical waveguide may be fabricated by this thin film while utilizing an electro-optic effect to produce optical modulators and other photonic devices.

A novel apparatus for bonding of two polished substrates includes a plasma source in a ultra-high vacuum (UHV) chamber and a wafer-guiding element to control and guide wafers in the UHV chamber, where after a plasma activation process the wafers are guided and pressed against each other to form a covalent bond between wafer surfaces. The plasma activation process involves deposition of mono-layer or sub-monolayer metallic atom on the surface of substrates. After deposition of metallic layers, a high-force actuation presses the wafers and forms a covalent bond between the wafers. Then, the bonded wafer pair is ion-sliced or thinned to form single crystalline optical thin film. An annealing process oxidizes the deposited metallic layers and produces optically-transparent single crystalline thin film. An optical waveguide may be fabricated by this thin film while utilizing an electro-optic effect to produce optical modulators and other photonic devices.

A manufacturing system for fabricating optical waveguides includes a diffusion channel with a plurality of inlets at a first end and an outlet at a second end opposite to the first end and separated from the inlets by a channel length. Each of the plurality of inlets includes a central inlet flowing a first resin into the diffusion channel such that the first resin flows along the channel length of the diffusion channel toward the outlet, and an outer inlet flowing a second resin along a periphery of the first resin. The second resin may have an index of refraction different than the first resin. The diffusion may occur between portions of the first resin and portions of the second resin over the channel length to form a composite resin having a profile with a plurality of indices of refraction in at least one dimension.