  Floquet topological photonic insulators, whose light transport properties are
dictated by the periodic drive sequence of the lattice, provide more
flexibility for controlling and trapping light than undriven topological
insulators, which can enable novel nonlinear optics applications in topological
photonics. Here, we employ a novel resonance effect called Floquet Defect Mode
Resonance in a 2D silicon Floquet microring lattice to demonstrate
resonance-enhanced frequency generation by four-wave mixing of Floquet bulk
modes in the presence of Kerr nonlinearity. The compact, cavity-less resonance
mode, induced through a periodic perturbation of the lattice drive sequence,
has the largest reported Q-factor for a topological resonator of ~10^5 with low
group velocity dispersion, which enables efficient broadband frequency
generation over several Floquet-Brillouin zones of the Floquet topological
insulator. We achieved wavelength conversion over 10.1 nm spectral range with
an average enhancement of 12.5 dB in the conversion efficiency due to the
Floquet Defect Mode Resonance. Our work could lead to robust light sources
generated directly on a topologically-protected photonic platform.
