Stanford University , 476 Lomita Mall, Stanford, California 94305, United States.
Nano Lett. 2015 Jan 14;15(1):120-6. doi: 10.1021/nl503179j. Epub 2014 Dec 29.
The resonant properties of a plasmonic cavity are determined by the size of the cavity, the surface plasmon polariton (SPP) dispersion relationship, and the complex reflection coefficients of the cavity boundaries. In small wavelength-scale cavities, the phase propagation due to reflections from the cavity walls is of a similar magnitude to propagation due to traversing the cavity. Until now, this reflection phase has been inferred from measurements of the resonant frequencies of a cavity of known dispersion and length. In this work, we present a method for measuring the complex reflection coefficients of a truncation in a 1D surface plasmon waveguide using electron energy loss spectroscopy in the scanning transmission electron microscope (STEM EELS) and show that this insight can be used to engineer custom cavities with engineered reflecting boundaries, whose resonant wavelengths and internal mode density profiles can be analytically predicted given knowledge of the cavity dimensions and complex reflection coefficients of the boundaries.
等离子体腔的共振特性由腔的大小、表面等离激元（SPP）色散关系以及腔边界的复反射系数决定。在小波长尺度的腔中，由于腔壁反射引起的相位传播与由于穿过腔引起的相位传播具有相似的大小。到目前为止，这种反射相位是从具有已知色散和长度的腔的共振频率的测量中推断出来的。在这项工作中，我们提出了一种使用扫描透射电子显微镜（STEM EELS）中的电子能量损失光谱来测量一维表面等离激子波导中的截断的复反射系数的方法，并表明可以利用这种方法来设计具有工程反射边界的定制腔，其共振波长和内部模式密度分布可以根据腔尺寸和边界的复反射系数进行分析预测。
