All-Fiber Centralized Architecture for Parallel Terahertz Sensors

Abstract

ENSING instruments exploiting the THz band (0.3–10 THz) offer an attractive approach to nondestructive inspection of a wide range of materials with applications in an increasingly extensive variety of industries: in-line monitoring of plastics, compounds, glass, and paper; analytical sciences; biological, pharmaceutical, and medical sciences; quality control; and environmental monitoring; security [1], [2]. In many cases, these instruments sense features that are not accessible with sensors working in other spectral regions such as the optical, infrared or X-ray bands or complement the information obtained by these. Since THz radiation is located between the microwave and the optical regions of the electromagnetic spectrum, they exhibit merits of both bands: good penetration depth as well as submillimeter resolution. When exposed to terahertz radiation, neither scanned objects nor operators run considerable damage or health risk as opposed to X-ray-based inspection systems. Additionally, many materials that are opaque in the visible and near-infrared regime (such as plastics, paper, cardboard, and textiles) are transparent in the THz region, while many other materials present characteristic spectroscopic fingerprints in this band. Thus, the THz band allows the inspection of materials inside conventional packages. THz sources may be broadly classified depending on the generation technologiesas follows: up-conversion from microwave