Adiabatic Compression of Mid-IR Through THz Light in Diamond-Metal Campanile Probe for Ultrawide Spectral Range Nanospectroscopy

Developing methods for efficient nanoscale probing of light-matter interaction, especially in the Mid-IR and THz spectral range, is essential for studying fundamental physical phenomena as well as chemical properties at nanometer length scales. A highly efficient nanoscale focusing of visible and near-IR radiation light was reported recently using Au-SiO₂-Au tapered gap plasmon waveguide with an 830 nm wavelength that couples free space light into the nanoscale domain, enabling probing of materials in the visible and near-IR spectral range [1]. We expand this capability to the highly important mid-IR and THz range providing valuable information on local nanoscale chemistry and physical processes of materials and devices using a campanile shaped metal-insulator-metal (MIM) diamond tetragonal pyramid [2]. Our finite difference time domain (FDTD) simulation reveals that nanoscale focusing of mid-IR light is possible within the range of geometries and metal coatings including Au, Al and Cu. Here we report linked modeling and experimental results showing the confining efficiency of diamond pyramid in the mid-IR to THz range (3 – 150 µm). Furthermore, we will demonstrate the integration of the diamond light concentrator into a scanning probe microscope for performing the nanoscale optical spectroscopy of various materials in both reflection, scattering and transmission geometries.<br/>References:<br/>1) H. Choo <i>et al</i>., <i>Nature Photonics</i> <b>6</b>, 838 (2012).<br/>2) W. Bao <i>et al</i>., <i>Nature Commun.</i> <b>6, </b>7993 (2015).<br/>This work is supported by the EPSRC (EP/V00767X/1) HiWiN research grant and FELIX-Nijmegen, Radboud University.