THz-Micro-Spectroscopy

We compare different near-field methods operating in the frequency range between 50 GHz and 1.5 THz with respect to their application potential for terahertz-micro-spectroscopy. Scanning near-field optical microscopes (SNOMs) can be divided into two basic principles: aperture SNOMs using a small pinhole and apertureless SNOMs, where a small scatterer acts as a near-field probe. As an alternative method, we include in our comparison a microscope based on a solid immersion lens. Most of these techniques are well known in the visible and infrared range, where they are mainly utilized to reach a high spatial resolution. In real samples, the physics behind the observed image contrast is often unclear, and therefore, additional spectroscopic information on a subwavelength spot size is desired. In this paper, we discuss different microscopic techniques in respect of their micro-spectroscopic potential in the THz range.