Polaritons in Photonic Hypercrystals of van der Waals Materials

In‐plane Hyperbolic Phonon polaritons (HPhPs) are quasiparticles formed via coupling of photons and optical phonons in in‐plane hyperbolic materials and offer unique applications in sensing, thermal emitters and high‐resolution imaging. However, the large momentum mismatch between photons and these in‐plane HPhPs has restricted their technological potential as most experimental demonstrations rely on sophisticated and expensive near‐field detection schemes. In this work, using the example of α‐MoO3, it is demonstrated that by constructing photonic hypercrystals of this material, one can not only excite these in‐plane HPhPs in the far field but also tune the far field response via twisting the hypercrystal lattice with respect the lattice of α‐MoO3. The findings will pave the way for the development of practical in‐plane HPhP devices as well as provide access to new fundamental physics of such materials via conventional and well developed far‐field measurement techniques.