  Dissipative Kerr solitons (DKS) in optical microresonators provide a highly
miniaturized, chip-scale frequency comb source with unprecedentedly high
repetition rates and spectral bandwidth. To date, such soliton frequency comb
sources have been successfully applied in the optical telecommunication band
for dual comb spectroscopy, coherent telecommunications, counting of optical
frequencies and distance measurements. Yet the range of applications could be
significantly extended by operating in the near-infrared spectral domain, a
prerequisite for biomedical and Raman imaging applications, and a part of the
spectrum which hosts commonly used optical atomic transitions. Here we
demonstrate the operation of photonic chip-based soliton Kerr combs pumped with
1 micron laser light. By engineering the dispersion properties of a $\rm
Si_3N_4$ microring resonator, octave-spanning soliton Kerr combs extending to
776 nm are attained, thereby covering the optical biological imaging window.
Moreover, we demonstrate that soliton states can be generated in normal group
velocity dispersion regions, when exploiting mode hybridization with other mode
families. The reported near-infrared soliton Kerr combs are suitable for a
range of studies, including frequency-comb-based optical coherence tomography,
coherent anti-Stokes Raman spectro-imaging, and they spectrally overlap with
optical atomic transitions in Alkali vapors.
