Dual-directional interferometric control for post-fabrication wavelength alignment in a silicon photonic bidirectional arrayed waveguide grating

Precise wavelength alignment is essential for dense wavelength-division multiplexing (DWDM) systems, where fabrication-induced deviations can lead to channel mismatch and degraded performance. Arrayed waveguide gratings (AWGs) are widely used in silicon photonics DWDM systems; however, their passive nature limits post-fabrication spectral correction, while conventional thermo-optic tuning predominantly produces unidirectional wavelength shifts. Here, we demonstrate a dual-arm interferometric approach for post-fabrication wavelength alignment using a silicon photonic asymmetric Mach–Zehnder interferometer (AMZI)–bidirectional arrayed waveguide grating (BiAWG) device. Independently addressable thermo-optic phase shifters integrated into both AMZI arms enable dual-directional interferometric control through selective actuation of the long or short interferometer arm. In the fabricated device, an initial wavelength offset of approximately +0.17 nm from the design wavelength of 1527.99 nm is observed. At 1.8 V (29 mW), thermo-optic actuation improves the spectral overlap between the AMZI transfer function and the BiAWG passbands, resulting in a cascaded peak-transmission enhancement of approximately 3–4 dB. Under short-arm actuation at 2.1 V, the measured peak associated with the nominal central channel is observed at 1527.98 nm, bringing the measured wavelength into agreement with the design wavelength of 1527.99 nm within the experimental wavelength-sampling resolution (0.01 nm). The demonstrated dual-directional interferometric control provides a compact post-fabrication calibration approach for compensating fabrication-induced wavelength offsets while enhancing the cascaded transmission through improved spectral overlap between the AMZI transfer function and the BiAWG passbands.