Self-referenced terahertz refractive index sensor based on a cavity resonance and Tamm plasmonic modes

Abstract

A self-referenced terahertz (THz) refractive index sensor is proposed. The structure consists of two opposite-facing, graphene-covered distributed Bragg reflectors (DBRs), with a cavity formed in between. The cavity is filled with the ambient medium, and its resonance frequency is sensitive to the changes of the ambient refractive index. On the other hand, Tamm-plasmonic modes, which are excited at the DBR-graphene boundaries, are insensitive to the ambient refractive index and thus provide a frequency reference. The proposed structure is studied using a semi-analytical transfer matrix method (TMM). The sensor, studied for gas sensing, achieves a sensitivity of 0.982 THz per refractive index unit (THz/RIU), and a figure of merit (FoM) of 142 R I U − 1 at the cavity resonance frequency of 1.1 THz. The effects of different parameters on the sensor’s performance are also investigated. Compared to the previous high-performance THz refractive index sensing approaches, the proposed structure is simpler because it requires no phase- or polarization-matching devices, such as polarizers, prisms, and gratings. Moreover, it provides a self-referenced operation, which was rarely achievable using previous methods.

Photonic and Plasmonic Metasensors

“…Confinement of the electromagnetic fields in such configurations is related to the negative dielectric constant of metallic layers and the photonic stop band of the Bragg mirror. Possessing a zero in-plane wavevector, polarization independency, and broadband tunability of the excited modes through varying the stop band of the distributed Bragg mirror, researchers exploited this technology for the development of a wide range of devices, [307] such as wavelength-selective thermal emitters, [308,309] refractive index sensors, [310] light sensing, [311,312] narrow-band color filters, [313] single-photon emission and enhancement of spontaneous emission. [314,315] Famous for having ultranarrow lineshapes, high-Q Tamm states have recently received growing attention to build sensi-tive biosensing tools.…”

Simulated Study of High-Sensitivity Gas Sensor with a Metal-PhC Nanocavity via Tamm Plasmon Polaritons

“…S (nm/RIU) FOM (/RIU) PhC-Au-Gas [31] 55 -Ag-Gas/Si PhC [4] 83.3 -Graphene-Gas-PhC [32] (in terahertz band) -142…”

Study of Terahertz Sensing Performance Based on Graphene-DBR Asymmetric Structure

“…But the conventional surface plasmon resonances (SPRs) can only be excited with TM polarization light [9], and need phase and polarization devices, such as prisms and gratings [10] [11]. Furthermore, TPPs can be excited no matter normal or oblique incident light, while the excitation of SPRs must require the matching angle of incident condition [12][13][14]. In addition, TPPs have strong field local characteristics [14] [15].…”

“…Furthermore, TPPs can be excited no matter normal or oblique incident light, while the excitation of SPRs must require the matching angle of incident condition [12][13][14]. In addition, TPPs have strong field local characteristics [14] [15]. In this paper, we design a novel double-dip terahertz sensor based on TPPs.…”