EIT-based nanostructure detectors for detecting materials using terahertz waves

Different materials have different absorption spectra of the terahertz (THz) radiation. So, by detecting the absorption spectra of THz radiation of different materials we can assess material substances. We propose and analyze an efficient way to detect the THz radiation in a magnetized graphene system via electromagnetically induced transparency (EIT). In this paper an all-optical method for THz signal detection in graphene nanostructure in core of a detector is investigated. Such a scheme for THz signal detection mainly relies on the measurement of probe transmission spectra, in which the behaviors of a weak-probe transmission spectrum can be controlled by switching on/off the THz signal radiation. Taking into account the tunable optical transition frequency between the Landau levels in graphene, our analytical results demonstrate that a broad frequency bandwidth of the THz signal radiation can be inspected and modulated by means of an external magnetic field. This feature being useful for detection of explosives with width absorption spectra of the optical terahertz signal. Common explosives such as RDX, TEND and Ammonium Nitrate in the spectral range of THz signal are widely used in a variety of explosives. Effects of parameters such as intensity of the terahertz radiation and relative phase between the fields on the absorption anddispersion of probe field hase been studied. Also, Detector sensitivity and rapid response to fluctuations of terahertz radiation by measuring the switching time of group velocity of probe field from subluminal to superluminal and vice versa hase been studied. The estimated range of the switching time is between 5 ps to 8 ps for subluminal to superluminal light propagation.Such all optical detectors can be well used in a wide range of THz spectroscopy for (explosive or forbidden) material detection.