Si3N4 micro-ring resonators for frequency comb generation

Waveguide micro-ring resonators are of high importance for frequency comb generation on a chip such as for precision spectroscopy, frequency metrology, and optical clocks. Essential properties for the resonator are a high quality factor and small mode volume to yield a low threshold, a dispersion engineered cross section to fulfill phase matching conditions, and appropriate optical laser excitation. We investigate micro-rings resonators fabricated from stoichiometric silicon nitride (Si3N4) with various ring diameters and coupling parameters in terms of quality factor and input coupling [1]. We will discuss the options for intra-cavity pumping with Erbium fiber lasers and excitation with ultra-narrow band diode lasers. [1] C.G.H. Roeloffzen et al., "Low-loss Si3N4 TriPleX optical waveguides: technology and applications overview", IEEE J. Sel.Top. Quant. Electron. 24, 4400321 (2018).