We demonstrate the fabrication of ultrahigh quality (Q) factor silica microdisk resonators on a silicon chip by inductively coupled plasma (ICP) etching. We achieve a dry-etched optical microresonator with an intrinsic Q factor as high as 1.94×108 from a 1-mm-diameter silica microdisk with a thickness of 4 μm. Our work provides a chip-based microresonator platform operating in the ultrahigh-Q region that will be useful in nonlinear photonics such as Brillouin lasers and Kerr microcombs.

A novel type of mid-IR microresonator, the chalcogenide glass (ChG) microfiber knot resonator (MKR), is demonstrated, showing easy fabrication, fiber-compatible features, resonance tunability, and high robustness. ChG microfibers with typical diameters around 3 μm are taper-drawn from As2S3 glass fibers and assembled into MKRs in liquid without surface damage. The measured Q factor of a typical 824 μm diameter ChG MKR is about 2.84×104 at the wavelength of 4469.14 nm. The free spectral range (FSR) of the MKR can be tuned from 2.0 nm (28.4 GHz) to 9.6 nm (135.9 GHz) by tightening the knot structure in liquid. Benefitting from the high thermal expansion coefficient of As2S3 glass, the MKR exhibits a thermal tuning rate of 110pm·°C?1 at the resonance peak. When embedded in polymethyl methacrylate (PMMA) film, a 551 μm diameter MKR retains a Q factor of 1.1×104. The ChG MKRs demonstrated here are highly promising for resonator-based optical technologies and applications in the mid-IR spectral range.

This paper describes the specially designed geometry of a dry-etched large-wedge-angle silica microdisk resonator that enables anomalous dispersion in the 780 nm wavelength regime. This anomalous dispersion occurs naturally without the use of a mode-hybridization technique to control the geometrical dispersion. By fabricating a 1-μm-thick silica microdisk with a wedge angle as large as 56° and an optical Q-factor larger than 107, we achieve a visible Kerr comb that covers the wavelength interval of 700–897 nm. The wide optical frequency range and the closeness to the clock transition at 698 nm of Sr87 atoms make our visible comb a potentially useful tool in optical atomic clock applications.

We demonstrate an ultra-low-threshold phonon laser using a coupled-microtoroid-cavity system by introducing a novel coupling approach. The scheme exhibits both high optical quality factors and high mechanical quality factors. We have experimentally obtained the mechanical quality factor up to 18,000 in vacuum for a radial-breathing mode of 59.2 MHz. The measured phonon lasing threshold is as low as 1.2 μW, which is ～5 times lower than the previous result.

By overcoming fabrication limitations, we have successfully fabricated silica toroid microcavities with both large diameter (of 1.88 mm) and ultra-high-Q factor (of 3.3×108) for the first time, to the best of our knowledge. By employing these resonators, we have further demonstrated low-threshold Kerr frequency combs on a silicon chip, which allow us to obtain a repetition rate as low as 36 GHz. Such a low repetition rate frequency comb can now be directly measured through a commercialized optical-electronic detector.