US Patent 10120132 Photonic integrated circuit

A photonic integrated circuit having discrete optical components arranged on a top side of a substrate includes a first and second optical sources respectively configured to emit light beams, a first interferometer having a first and second input ports respectively coupled to the first and second optical sources via first waveguides, a second interferometer configured to receive signals from the first interferometer via second waveguides and combine the signals to transmit a combined signal via a third waveguide, and a submount configured to contact a back side of the substrate, wherein the submount includes a first thermal conductor having a first thermal conductivity and a second conductor having a second thermal conductivity, wherein the first thermal conductivity is greater than the second thermal conductivity, and the first and second optical sources are more proximity to the first thermal conductor than the second thermal conductor.