Technologies for focusing and aperturing terahertz radiation in the realization of terahertz spectroscopy on the subwavelength scale

Abstract

This work demonstrates the realization of terahertz (THz) spectroscopy on a subwavelength scale. We do so by using dielectric spheres as focusing elements and apertures as spatially constricting elements for THz radiation. Such a configuration forms intense, subwavelength-sized THz microjets. Two implementations are used to demonstrate the effectiveness of THz microjets, as follows: apertured THz plane waves and apertured THz microjets. Seven aperture diameters were chosen for each implementation to discern their capabilities at the subwavelength scale. We investigated the effectiveness of each implementation in mapping the material characteristics of the sample onto the THz beam. Such analyses show that apertured THz microjets were able to map material characteristics (via refractive index and extinction coefficient) onto the beam (via phase and amplitude) effectively and reliably. This is expected as the beam produced by apertured THz microjets has a small cross-sectional area (apertures) and high intensity (THz microjets). Here, we illustrate the capabilities of apertured THz microjets for a biological specimen, being lactose, to show the potential for biological applications. Overall, this work demonstrates the ability of apertured THz microjets to perform THz spectroscopy at a subwavelength scale. Such findings could bring about biological characterization with cellular-scale resolution.