By providing an effective way to leverage nonlinear phenomena in integrated devices, high-Q optical resonators have led to recent advances in on-chip photonics. However, developing fabrication processes to shape any new material into a resonator with extremely smooth surfaces on a chip has been an exceptionally challenging task. Here, we describe a universal method to implement ultra-high-Q resonators with any new material having desirable properties that can be deposited by physical vapor deposition. Using this method light-guiding cores with surface roughness on the molecular-scale are created automatically on pre-patterned substrates. Its efficacy has been verified using As2S3, a chalcogenide glass that has high-nonlinearity. The Q-factor of the As2S3 resonator so-developed approached the propagation loss record achieved in chalcogenide fibers which were limited by material losses. Owing to the boosted Q-factor, lasing by stimulated Brillouin scattering has been demonstrated with 100 times lower threshold power than the previous record.

We report a supercontinuum generation (SCG) in a waveguide that spontaneously forms without an etching process during the deposition of a core material on a preformed S i O 2 substructure. The mechanism of dispersion control for this new, to the best of our knowledge, type of waveguide is analyzed by numerical simulation, which results in a design rule to achieve a target dispersion profile by adjusting the substructure geometry. SCG is experimentally demonstrated with a waveguide made of A s 2 S 3 , chalcogenide glass, which has low material absorption over the mid-IR range. A dispersion-controlled waveguide with a length of 10 mm pumped with 77 pJ pulses at a telecommunication wavelength of 1560 nm resulted in a supercontinuum that extends by more than 1.5 octaves.

We present a new device platform which defines on-chip chalcogenide waveguide/resonators without directly etching chalcogenide. Using our platform, we have demonstrated chalcogenide ring resonators with record high Q-factor exceeding 1.1x10 7 which is 10 times larger than previous record on on-chip chalcogenide resonators. A ring cavity is designed and fabricated for Stimulated Brillouin lasing on our platform. Thanks to the high-Q factor, Brillouin lasing with threshold power of 1 mW is demonstrated. This value is more than an order of magnitude improvement than previous world record for on-chip chalcogenide Brillouin lasers. We also developed an efficient and flexible method for resonatorwaveguide coupling with our device platform. Coupling between a resonator and a waveguide can be varied from undercoupled region to over-coupled region.

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 1 and ultra-narrow linewidth lasers 2 . 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 3 , 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 4 . 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.High-Q optical resonators, which had long been used for scientific researches such as cavity quantum electrodynamics 5 and optomechanics 6 , have become an irreplaceable core of on-chip photonics with huge practical impacts. With dedicated efforts over a past decade, now, resonators can be fabricated on a chip with high Q-factor 1,7,8 . Their geometry can be precisely designed and shaped to control the major properties such as free spectral range (FSR) and dispersion to

We show a two-point resonator-waveguide coupling method which allows optimizing coupling independently at distinct wavelengths. An intuitive equation is provided to predict the coupling behavior of the method and the equation is verified by experiments.