The electromagnetic near field enables subwavelength applications such as near-field microscopy and nanoparticle manipulation. Present methods to structure the near field rely on optical antenna theory, involving nanostructures that locally convert propagating waves into confined near-field patterns. We developed a theory of remote rather than local near-field shaping, based on cascaded mode conversion and interference of counterpropagating guided waves with different propagation constants. We demonstrate how to structure at will the longitudinal and transverse variation of the near field, allowing for distributions beyond the conventional monotonic decay of the evanescent field. We provide an experimental realization that confirms our theory. Our method applies to fields with arbitrary polarization states and mode profiles, providing a path toward three-dimensional control of the near field.

电磁近场可实现亚波长应用，例如近场显微镜和纳米粒子处理。当前构造近场的方法依赖于光学天线理论，涉及纳米结构，该纳米结构将传播波局部地转换成受限的近场模式。我们基于级联模式转换和具有不同传播常数的反向传播导波的干扰，开发了一种远程而不是局部近场整形的理论。我们演示了如何随意构造近场的纵向和横向变化，从而允许分布超出beyond逝场的常规单调衰减。我们提供的实验实现证实了我们的理论。我们的方法适用于具有任意偏振态和模式轮廓的场，