Supercontinuum Generation Assisted by Wave Trapping in Dispersion-Managed Integrated Silicon Waveguides

Compact chip-scale comb sources are of significant interest for many practical applications. Here, we experimentally study the generation of supercontinuum (SC) in an axially varying integrated waveguide. We show that the local tuning of the dispersion enables the continuous blue shift of dispersive waves by more than 200 nm due to their trapping by the strongly compressed pump pulse. This mechanism provides an insight into supercontinuum generation in varying-dispersion integrated waveguides. Pumped close to 2.2 $\ensuremath{\mu}\mathrm{m}$ in the femtosecond regime and at a pulse energy of approximately 4 pJ, the output spectrum extends from 1.1 $\ensuremath{\mu}\mathrm{m}$ up to 2.76 $\ensuremath{\mu}\mathrm{m}$ and shows good coherence properties. Octave-spanning SC is also observed at an input energy as low as approximately 0.9 pJ. We show that the supercontinuum is more robust against variations of the input-pulse parameters and is also spectrally flatter in waveguides with an optimized dispersion profile than in dispersion-engineered ones. This research demonstrates the potential of varying-dispersion waveguides for coherent SC generation and paves the way for integrated low-power applications, such as chip-scale frequency-comb generation, precision spectroscopy, optical-frequency metrology, and wide-band wavelength division multiplexing in the near infrared.