Polariton canalization is characterized by intrinsic collimation of energy flow along a single crystalline axis. This optical phenomenon has been experimentally demonstrated at the nanoscale by stacking and twisting van der Waals (vdW) layers of α-MoO₃, by combining α-MoO₃ and graphene, or by fabricating an h-BN metasurface. However, these material platforms have significant drawbacks, such as complex fabrication and high optical losses in the case of metasurfaces. Ideally, it would be possible to canalize polaritons “naturally” in a single pristine layer. Here, we theoretically predict and experimentally demonstrate naturally canalized phonon polaritons (PhPs) in a single thin layer of the vdW crystal LiV₂O₅. In addition to canalization, PhPs in LiV₂O₅ exhibit strong field confinement (\({{{{{{\boldsymbol{\lambda }}}}}}}_{{{{{{\bf{p}}}}}}} \sim \frac{{{{{{{\boldsymbol{\lambda }}}}}}}_{{{{{{\bf{0}}}}}}}}{{{{{{\bf{27}}}}}}}\)), slow group velocity (0.0015c), and ultra-low losses (lifetimes of 2 ps). Our findings are promising for the implementation of low-loss optical nanodevices where strongly directional light propagation is needed, such as waveguides or optical routers.

极化子管化的特征是能量流沿单晶轴的固有准直。这种光学现象已经通过堆叠和扭曲α-MoO ₃的范德华（vdW）层、通过将α-MoO ₃与石墨烯结合、或通过制造h-BN超表面在纳米尺度上得到实验证明。然而，这些材料平台具有显着的缺点，例如超表面的制造复杂和光学损耗高。理想情况下，可以在单个原始层中“自然”地引导极化激元。在这里，我们从理论上预测并通过实验证明了 vdW 晶体 LiV ₂ O ₅的单个薄层中的自然通道化声子极化激元 (PhP) 。除了管化之外，LiV ₂ O ₅中的 PhP还表现出强场限制（\({{{{{{\boldsymbol{\lambda }}}}}}}_{{{{{\bf{p}}} }}}} \sim \frac{{{{{{{\boldsymbol{\lambda }}}}}}}_{{{{{\bf{0}}}}}}}}{{{{ {{\bf{27}}}}}}}\)）、慢群速度 (0.0015c) 和超低损耗（2 ps 的寿命）。我们的研究结果有望用于需要强定向光传播的低损耗光学纳米器件，例如波导或光学路由器。