  By self-injection-locking a 1560 nm distributed feedback semiconductor laser
to a high-$Q$ silicon nitride resonator, a high-coherence 780 nm second
harmonic signal is generated via the photogalvanic-induced second-order
nonlinearity. A record-low frequency noise floor of 4 Hz$^2$/Hz is achieved for
the 780 nm emission. The approach can be generalized for signal generation over
a wide range of visible and near-visible bands.
