Fig. 1. Schematic diagrams of MZI filter. (a) Symmetric MZI; (b) asymmetric MZI; (c) flat-top filter based on traditional MRR assisted asymmetric MZI; (d) flat-top filter based on racetrack MRR assisted asymmetric MZI

Fig. 2. Schematic diagram of the on-chip flat-top filter. (a) 3D view; (b) top view and related structure parameters

Fig. 3. Spectra of the two output ports of the flat-top filter

Fig. 4. Spectra of the small flat-top filter. (a) Output spectra of out1 port under different g₁; (b) spectra of the two output ports when g₁=0.12 μm; (c) comparison of spectra of out1 ports between the two different size filters

Fig. 5. Performance of filter when there are deviations between l₂ and l_c. (a) Ripple factor; (b) shape factor; (c) sidelobe suppression ratio; (d) output spectra of out1 port when tuning heater1

Fig. 6. Performance of filter when there are deviations between r₁ and r₂. (a) Ripple factor; (b) shape factor; (c) sidelobe suppression ratio; (d) output spectra of out1 port when tuning heater2

Fig. 7. Spectra of the filter when there is deviation in the width of the MZI upper arm waveguide. (a) Output spectra of out1 port with different widths of waveguide; (b) output spectra of out1 port when tuning heater1

Fig. 8. Spectra of the filter when there is deviation in the width of the MZI lower arm waveguide. (a) Output spectra of out1 port with different widths of waveguide; (b) output spectra of out1 port when tuning heater1

Fig. 9. Spectra of the filter when there is deviation in the coupling gap g₁. (a) Output spectra of out1 port with different g₁; (b) output spectra of out1 port when tuning heater2

Fig. 10. Spectra of the filter when there is asymmetric loss in the arms of MZI. (a) Output spectra of out1 port with different transmission losses in the lower arm of MZI; (b) output spectra of out1 port with different internal transmission losses in MRR; (c) output spectra of out1 port with different coupling losses between MZI and MRR; (d) output spectra of out1 port when the variation of the loss coefficients are controlled within 10%