Decoupled Spectral Tuning and Polarization Locking in Twisted α -MoO₃ Polaritonic Crystals

Polaritonic crystals (PoCs), formed by integrating periodic lattices with two-dimensional polaritonic materials, provide a powerful platform for nanoscale light manipulation and far-field spectral engineering. However, far-field spectral engineering in existing PoCs is primarily achieved through geometric redesign, requiring structural reconfiguration to access different spectral responses. Here, we overcome this limitation by constructing a twisted bilayer $\alpha$ - ${\text{MoO}}_3$ PoC consisting of a patterned and a pristine layer, where interlayer twist enables spectral tuning without geometric modifications. Meanwhile, the principal crystal axis of the patterned layer deterministically governs the axes of polarization-selective resonances arising from lattice-assisted polariton excitation. This polarization-locking behavior remains robust against interlayer twisting, enabling independent control over the spectral response and the polarization direction. These findings provide a deterministic strategy for constructing deep-subwavelength PoCs for multidimensional infrared light manipulation, offering new opportunities for advanced flat optics and reconfigurable nanophotonic devices.