High Extinction Ratio Widely Tunable Low-Loss Integrated Si3N4 Third-Order Filter

Abstract: We demonstrate an integrated continuously tunable third-order ring filter with a measured extinction ratio of 80dB, a 100x improvement over previously demonstrated integrated 3rd or 6th order filters. Using integrated thermal tuning elements, the filter can be tuned over 100% of its 48 GHz free spectral range with 1.3 dB insertion loss. The filters are fabricated on a wafer-scale foundry compatible Si3N4 low-loss platform enabling integration with a wide variety of previously demonstrated passive and active elements. The high extinction ratio, low loss, flat passband and steep roll-off is desirable for a broad range of applications including pump-stokes separation for Brillouin scattering, idler separation in four-wave mixing and separation of entangled states for quantum communications that utilize nonlinear optics.