Fig. 1. Top-down view of the proposed notch filter. The filter is composed of two wavelength-selective 50/50 power splitters/combiners in MZI configuration. A heater is placed above one of the MZI arms for phase tuning. Unillustrated are heaters used to tune each individual Bragg filter.

Fig. 2. (a) Top-down view of an apodized four-port Bragg add/drop filter. The structure’s simulated spectral response in (b) shows the transmission to the through-port and drop-port with the fabricated device’s parameters of Gmin=0.6  μm, H=0.5  μm, a=2.5, and L=775  μm.

Fig. 3. (a) Top-down view of four concatenated Bragg add/drop filters. The through-port and each drop-port are experimentally measured in (b).

Fig. 4. Simulated performance of the notch filter. (a) For simplicity, the combiner Bragg filter is replaced with an ideal Y-junction. (b) Two Bragg add/drop filters are used for power splitting/combining.

Fig. 5. (a) Spectral measurement of a single notch filter where the thermal phase shifter is tuned to demonstrate extinction ratio tuning. The magnitude of the extinction ratio is shown in (b) as it varies with heater power. Optical microscope image of the fabricated device is shown in (c).

Fig. 6. Measured spectral performance of four concatenated notch filters. Each filter is tuned through full extinction using the integrated thermal phase shifter.

Fig. 7. Measured spectra of a single notch filter where heaters above the Bragg filters are tuned to redshift the center wavelength of the notch filter.