Conventional optical components are limited to size scales much larger than the wavelength of light, as changes to the amplitude, phase and polarization of the electromagnetic fields are accrued gradually along an optical path. However, advances in nanophotonics have produced ultrathin, so-called ‘flat’ optical components that beget abrupt changes in these properties over distances significantly shorter than the free-space wavelength^{1,2,3,4,5,6,7,8}. Although high optical losses still plague many approaches⁹, phonon polariton (PhP) materials have demonstrated long lifetimes for sub-diffractional modes^10,11,12,13 in comparison to plasmon-polariton-based nanophotonics. We experimentally observe a threefold improvement in polariton lifetime through isotopic enrichment of hexagonal boron nitride (hBN). Commensurate increases in the polariton propagation length are demonstrated via direct imaging of polaritonic standing waves by means of infrared nano-optics. Our results provide the foundation for a materials-growth-directed approach aimed at realizing the loss control necessary for the development of PhP-based nanophotonic devices.

常规的光学组件被限制在远大于光波长的尺寸范围内，因为沿着光路逐渐累积了电磁场的幅度，相位和极化。然而，纳米光子学的进步已经产生了超薄的所谓“扁平”光学组件，这些组件在远小于自由空间波长^{1,2,3,4,5,6,7,8的}距离上会突然改变这些特性。尽管高的光损耗仍然困扰着许多方法⁹，但是声子极化子（PhP）材料已经证明了亚衍射模^{10、11、12、13的}使用寿命长。与基于等离激元极化的纳米光子学相比。我们实验观察到通过六方氮化硼（hBN）的同位素富集，极化子寿命提高了三倍。通过利用红外纳米光学技术对极化子驻波进行直接成像，可以证明极化子传播长度的相应增加。我们的结果为旨在实现基于PhP的纳米光子器件开发所必需的损耗控制的材料生长定向方法奠定了基础。