  By providing an effective way to leverage nonlinear phenomena in chip-scale,
high-Q optical resonators have induced the recent advances of on-chip photonics
represented by micro-combs and ultra-narrow linewidth lasers. These
achievements mainly relying on Si, SiO$_{2}$, and Si$_{3}$N$_{4}$ are expected
to be further improved by introducing new materials having higher nonlinearity.
However, establishing fabrication processes to shape a new material into the
resonator geometries having extremely smooth surfaces on a chip has been a
challenging task. Here we describe a universal method to implement high-Q
resonators with any materials which can be deposited in high vacuum. This
approach, by which light-guiding cores having surface roughness in
molecular-scale is automatically defined along the prepatterned platform
structures during the deposition, is verified with As$_{2}$S$_{3}$, a typical
chalcogenide glass of high-nonlinearity. The Q-factor of the developed
resonator is 14.4 million approaching the loss of chalcogenide fibers, which is
measured in newly proposed tunable waveguide-to-resonator coupling scheme with
high ideality. Lasing by stimulated Brillouin process is demonstrated with
threshold power of 0.53 mW which is 100 times lower than the previous record
based on chalcogenide glasses. This approach paves the way for bringing various
materials of distinguished virtues to the on-chip domain while keeping the loss
performance comparable to that of bulk form.
