Siday Thomas, Natrella Michele, Wu Jiang, Liu Huiyun, Mitrofanov Oleg
Opt Express. 2017 Oct 30;25(22):27874-27885. doi: 10.1364/OE.25.027874.
We propose and characterize a scattering probe for terahertz (THz) near-field microscopy, fabricated from indium, where the scattering efficiency is enhanced by the dipolar resonance supported by the indium probe. The scattering properties of the probe were evaluated experimentally using THz time-domain spectroscopy (TDS), and numerically using the finite-difference time-domain (FDTD) method in order to identify resonant enhancement. Numerical measurements show that the indium probes exhibit enhanced scattering across the THz frequency range due to dipolar resonance, with a fractional bandwidth of 0.65 at 1.24 THz. We experimentally observe the resonant enhancement of the scattered field with a peak at 0.3 THz. To enable practical THz microscopy applications of these resonant probes, we also demonstrate a simple excitation scheme utilizing a THz source with radial polarization, which excites a radial mode along the length of the tip. Strong field confinement at the apex of the tip, as required for THz near-field microscopy, was observed experimentally.
我们提出并表征了一种用于太赫兹（THz）近场显微镜的散射探针，该探针由铟制成，其中铟探针所支持的偶极共振增强了散射效率。使用太赫兹时域光谱（TDS）对探针的散射特性进行了实验评估，并使用时域有限差分（FDTD）方法进行了数值评估，以识别共振增强。数值测量表明，由于偶极共振，铟探针在太赫兹频率范围内呈现出增强的散射，在1.24太赫兹处的分数带宽为0.65。我们通过实验观察到散射场的共振增强，其峰值在0.3太赫兹处。为了使这些共振探针能够应用于实际的太赫兹显微镜，我们还展示了一种简单的激发方案，该方案利用具有径向极化的太赫兹源，沿尖端长度激发径向模式。实验观察到了太赫兹近场显微镜所需的尖端顶点处的强场限制。
