Surface polaritons display short wavelengths compared to propagating light, thus enabling large spatial concentration and enhancement of electromagnetic energy. However, this wavelength mismatch is generally accompanied by poor light-to-polariton coupling that limits potential applications in areas such as optical sensing and optoelectronics. Here, we address this problem by demonstrating that a small scatterer placed at a suitable distance from a planar surface can produce complete coupling of a focused light beam to surface polaritons. We present rigorous theoretical results for light coupling to plasmons in silver films and graphene, as well as phonon polaritons in hexagonal boron nitride films. We further formulate detailed general prescriptions on the beam profile and particle response that are required to achieve maximum coupling, which we supplement by analytical calculations for dipolar scatterers and finite-size particles. Our results open a practical route to circumvent the long-standing photon-polariton wavelength mismatch problem in nanophotonics.

中文翻译：

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聚焦光与表面极化子的完全耦合

与传播的光相比，表面极化子显示的波长短，因此可以实现较大的空间集中度并增强电磁能。然而，这种波长失配通常伴随着不良的光-极化耦合，从而限制了在光学传感和光电领域的潜在应用。在这里，我们通过展示一个小的散射体来解决这个问题，该散射体与平面的距离合适，可以使聚焦光束与表面极化子完全耦合。我们给出了光耦合到银膜和石墨烯中的等离激元以及六角形氮化硼膜中的声子极化子的严格理论结果。我们进一步针对光束轮廓和粒子响应制定了详细的一般处方，以实现最大程度的耦合，我们通过分析计算来补充偶极子散射体和有限尺寸的粒子。我们的结果为绕开纳米光子学中长期存在的光子-极化子波长失配问题开辟了一条可行的途径。