Integrated photonic devices enabled by silicon traveling wave-like Fabry–Perot resonators

Integrated photonic devices play a key role in modern optical communications, of which optical resonators are important fundamental structures. This work proposes and experimentally demonstrates compact integrated photonic devices based on a traveling wave-like Fabry–Perot (TW-like FP) resonator(s) coupled with waveguides. Add-drop filters based on a single TW-like FP resonator have been realized with a high drop efficiency and the same output direction for the through and drop ports. Particularly, their transmission response can be either symmetric Lorentzian or asymmetric Fano line shape, through adjusting the shift between the two bus waveguides and the waveguide widths. Fano resonance has been demonstrated in a TW-like FP resonator with a very high extinction ratio and large slope rate. The second-order optical filter exhibits low-loss flat-top passbands with small ripples. Owing to the compact size, easy scalability, and large flexibility, TW-like FP cavity-based devices using Fano and Lorentzian resonances will provide new potential applications in integrated photonics.