Numerical study of Self-Detection Near Field Optical Microscopy in the Terahertz range

We numerically study the self-detection scattering type near field optical microscopy (SD s-SNOM), a detectorless and high resolution technique exploited for the retrieval of the dielectric properties of a resonant material sample in the terahertz (THz) range. We derive an approximated method for the reconstruction of the dielectric function in the weak feedback regime, where the signal to noise ratio is expected to be higher than in the commonly used very weak feedback regime, reporting reasonable accuracy in the estimation of the phonon resonances for a supposed Cesium Bromide (CsBr) sample.