Nanophotonic octave-spanning supercontinuum generation with flat dispersive waves via near-zero integrated dispersion engineering

Nanophotonic supercontinuum generation (SCG) offers a compact, power-efficient approach for broadening femtosecond laser pulses. However, achieving octave-spanning operation typically relies on anomalous-dispersion waveguides and often suffers from degraded spectral flatness. To overcome this limitation, we demonstrate dispersion engineered lithium niobate nanophotonic waveguides, specifically designed to lower the integrated dispersion barrier for dispersive wave emission. Under 1560 nm pumping in either normal- or anomalous-dispersion regimes, we achieve octave-spanning SCG featuring spectrally flat short-wavelength dispersive waves with a 3 dB bandwidth exceeding 70 THz. These experimental observations are corroborated by numerical predictions, validating the proposed design strategy. Our work provides a viable pathway toward on-chip SCG spectral shaping for applications in precision spectroscopy and biomedical imaging.