Method and structure to incorporate multiple low loss photonic circuit components

A method comprising:

• fabricating a first wafer that includes:
• a first substrate;
• a first plurality of oxide layers on the first substrate;
• a first silicon nitride (SiN) waveguide in the first plurality of oxide layers, the first SiN waveguide characterized by a first thickness and a first optical loss;
• a second SiN waveguide in the first plurality of oxide layers, the second SiN waveguide characterized by a second thickness different from the first thickness and a second optical loss different than the first optical loss, the first SiN waveguide being subjected to a high-temperature annealing to which the second SiN waveguide is not subjected to;
• and
• a superconductive nanowire single photon detector (SNSPD) in the first plurality of oxide layers;
• fabricating a second wafer that includes:
• a second substrate;
• a second plurality of oxide layers on the second substrate;
• and
• a Pockels effect optical phase shifter in the second plurality of oxide layers;
• bonding the first plurality of oxide layers to the second plurality of oxide layers;
• removing the second substrate;
• forming electrical connectors in the second plurality of oxide layers and the first plurality of oxide layers;
• and
• forming, on the second plurality of oxide layers,
• a third plurality of oxide layers;
• and
• one or more metal layers in the third plurality of oxide layers, the one or more metal layers in electrical connection with the electrical connectors.