Dipolar resonances in conductive carbon micro-fibers probed by near-field terahertz spectroscopy

We observe dipole resonances in thin conductive carbon micro-fibers by detecting an enhanced electric field in the near-field of a single fiber at terahertz (THz) frequencies. Time-domain analysis of the electric field shows that each fiber sustains resonant current oscillations at the frequency defined by the fiber’s length. Strong dependence of the observed resonance frequency and degree of field enhancement on the fibers’ conductive properties enable direct non-contact probing of the THz conductivity in single carbon micro-fibers. We find the conductivity of the fibers to be within the range of 1–5 10 4 S/m. This approach is suitable for experimental characterization of individual doped semiconductor resonators for THz metamaterials and devices.