Dielectric sphere-coupled THz super-resolution imaging

A straightforward terahertz (THz) imaging method, analogous to microsphere optical nanoscope, is proposed and developed with spatial resolution beyond the diffraction limit. By attaching a 3 mm Teflon sphere directly onto a free-standing silicon grating, a subwavelength spatial resolution better than the Rayleigh limit is demonstrated. Furthermore, the dielectric sphere-coupled THz microscope not only enables far-field, large-area measurement, but also characterizes high-throughput and broad-bandwidth imaging properties. In addition, a numerical study of the THz pulse propagation through a dielectric sphere agrees well with the experimental results, showing frequency-dependent magnification and focal length.