Contents I. Introduction
Integrated micro-ring resonators (MRRs) [1], [2], are cornerstone devices in contemporary Photonics, offering access to tailored dispersion, high accumulation of circulated power and great sensitivity to refractive index and loss variations, necessary for developing numerous switching/routing [3]–[5], slow [6] and topological [7] light devices, as well as, sensors [8]. Planar geometry is inherently attractive in robustly accommodating bus waveguides and complex MRR structures on a single substrate, including cross-coupled or concatenated MRR cavities [6]. MRRs have also been investigated, in knotted optical fibre tapers (OFTs) [9]; alternatively, whispering gallery mode (WGM) light resonating cavities have been infiltrated inside microstructured optical fibers [10], and exploited for nano-sensing applications [11]. While the above design approaches provide promising travelling wave light resonation functionalities, nonetheless, they rely on laborious fabrication protocols, which cannot be operated in a versatile prototyping fashion, for easily tuning the spectral response of the devices manufactured.
