  Photonic integrated microcombs have enabled advanced applications in optical
communication, microwave synthesis, and optical metrology, which in nature
unveil an optical dissipative soliton pattern under cavity-enhanced nonlinear
processes. The most decisive factor of microcombs lies in the photonic material
platforms, where materials with high nonlinearity and in capacity of
high-quality chip integration are highly demanded. In this work, we present a
home-developed chalcogenide glasses-Ge25Sb10S65 (GeSbS) for the nonlinear
photonic integration and for the dissipative soliton microcomb generation.
Compared with the current integrated nonlinear platforms, the GeSbS features
wider transparency from the visible to 11 um region, stronger nonlinearity, and
lower thermo-refractive coefficient, and is CMOS compatible in fabrication. In
this platform, we achieve chip-integrated optical microresonators with a
quality (Q) factor above 2 x 10^6, and carry out lithographically controlled
dispersion engineering. In particular, we demonstrate that both a bright
soliton-based microcomb and a dark-pulsed comb are generated in a single
microresonator, in its separated fundamental polarized mode families under
different dispersion regimes. The overall pumping power is on the ten-milliwatt
level, determined by both the high Q-factor and the high material nonlinearity
of the microresonator. Our results may contribute to the field of nonlinear
photonics with an alternative material platform for highly compact and
high-intensity nonlinear interactions, while on the application aspect,
contribute to the development of soliton microcombs at low operation power,
which is potentially required for monolithically integrated optical frequency
combs.
