Terahertz Microjets as Realizations of Subwavelength Focusing in the Terahertz Spectrum

Abstract

In this article, we recognize the growing interest to realize terahertz (THz) spectroscopy on the submillimetre scale and target its fundamental challenge - in the need for subwavelength focusing. The challenge is addressed here by way of the THz microjet. We show that THz microjets can be formed as intense focal spots with subwavelength sizes by focusing THz radiation through engineered dielectric spheres. The dielectric spheres are analyzed via the electromagnetic (Mie) theory and effective medium (Bruggeman) theory, and then implemented out of microcomposite material with the requisite (optimal) refractive indices and (minimal) extinction coefficients for the targeted 0.3-0.7-THz spectrum. Ultimately, the dielectric spheres are tested and found to realize THz microjets as intense focal spots with the desired subwavelength sizes.