Arbitrary‐Orientation High‐Performance AWGs on X‐Cut Thin‐Film Lithium Niobate Enabled by Phase‐Accurate Compensation

ABSTRACT Integrated photonics offers a promising route to overcome the limitations of electronic interconnects, but its implementation on birefringent platforms such as X‐cut thin‐film lithium niobate (TFLN) faces a fundamental challenge: the intrinsic refractive‐index anisotropy induces significant phase errors in phase‐sensitive devices, including arrayed waveguide gratings (AWGs), traditionally restricting device placement to specific orientations. Here, we demonstrate a generalizable phase‐accurate compensation strategy that overcomes this limitation, enabling high‐performance AWGs to be realized at arbitrary orientations on X‐cut TFLN. By quantitatively linking birefringence‐induced phase mismatch to device geometry, we perform direction‐dependent refractive‐index modeling and structural optimization to align the optical phase across all arrayed waveguides. The approach is validated experimentally through a 16 × 400 GHz AWG with insertion loss below 6.2 dB and adjacent‐channel crosstalk suppression better than −16.8 dB, as well as an 8 × 200 GHz AWG with insertion loss below 4.8 dB and crosstalk below −13.5 dB. These results establish that phase‐accurate compensation eliminates orientation constraints, providing a scalable route to multifunctional, high‐fidelity spectral devices on birefringent photonic platforms.