  Microresonator-based degenerate optical parametric oscillation (DOPO) has
recently been explored as a compelling platform for all-optical computing and
quantum information applications, such as truly random number generation and
the production of squeezed states of light. Emerging research has highlighted
the potential of coupled microresonators, or photonic molecules, as a novel
avenue for spectral engineering, unlocking an extra degree of freedom for the
optimization of four-wave mixing interactions. Here, we demonstrate DOPO within
the coupled modes of a silicon nitride triple-state photonic molecule. Our
design introduces a distinctive mechanism for spectral engineering, using
microheaters to individually tune the resonance spectral positions, thus
enabling dynamic local dispersion control within the coupled modes. We
successfully generate a DOPO signal with active efficiency control and explore
the optical mode spacing in the tens of gigahertz range to use native
phase-locked optical pumps driven by a radio-frequency source.
