Near-visible integrated soliton microcombs with detectable repetition rates.

Integrated soliton microcombs benefit a wide range of conventional comb applications through their compactness and scalability. And applications such as optical clocks and biosensing have driven interest in their operation at wavelengths approaching the visible band. However, increasing normal dispersion and optical loss at shorter wavelengths make short pulse operation at low pumping power challenging, especially for detectable-rate microcombs. Here, low-pump-power, detectable-rate soliton microcombs are demonstrated from telecom to visible bands using ultra-low-loss silicon nitride waveguides. Wavelength-multiplexed operation spanning 2/3 octave is also demonstrated in a single device. The results fill a gap needed for realization of integrated self-referenced visible microcombs.