Full-optical tunable add/drop filter based on nonlinear photonic crystal ring resonators

• Based on Kerr-like nonlinear effect in a photonic crystal ring resonators (PCRRs) scheme, a full-optical tunable Add/Drop filter is realized.
• For nonlinear tuning of the single ring (SR) configuration, the minimum power required to 1 nm redshift the center operating wavelength (λ0 = 1550 nm) for inner PCRR scenario and outer scenario is 125 mW/μm2 (refractive index change of ΔnNL = 0.005).
• For nonlinear tuning of the dual ring (SR) configuration, the minimum power required to 1 nm redshift the center operating wavelength (λ0 = 1550 nm) for inner PCRR scenario and outer scenario is as low as 8 mW/μm2 (refractive index change of ΔnNL = 0.005).
• The optical power required to switch the state of SR PCRR from turn on to turn off, for the nonlinearity applied is at least 2000 mW/μm2, and for DR PCRR is as low as 150 mW/μm2.

Here, we propose a full-optical tunable Add/Drop filter based on single (SR) and double-vertically (DR) aligned Kerr-like nonlinear photonic crystal ring resonators (PCRRs). Silicon (Si) nano-crystal is used as the nonlinear material inside and outside of PCRRs. The minimum optical power required to turn–on/turn–off the SR and DR filters are 2000 mW/μm2, and 150 mW/μm2, respectively. We believe since the DR filter has a higher Q-factor rather than SR and also since the optical power reads more nonlinear rods with a longer time to pass the structure, thus the optical power required is much lower (10 folds). In addition, the minimum power required to 1 nm redshift the center operating wavelength of SR filter is 125 mW/μm2 (i.e. ΔnNL = 0.005) and for DR is as low as 8 mW/μm2. Performance of the Add/Drop filter structure is simulated by means of finite difference time domain (FDTD) method, in which the simulations showed an ultra-compact size structure with promising ultrafast tune-ability speeds.