Analytical design of tunable THz refractive index sensor for TE and TM modes using graphene disks

Abstract

Novel metamaterial refractive index sensor based on impedance matching concept is proposed to achieve an ultra-narrowband absorption response in terahertz (THz) frequencies. To this end, the recently proposed circuit model of the periodic arrays of graphene disks has been exploited to model the graphene layer as circuit components while a developed transmission line method has been used to provide a circuit model for the whole structure. As a result, a perfect THz absorption response with absorptivity over 99.5% is achieved in desired resonance frequency. Two sensor structures at 3 and 6 THz have been designed as numerical examples, in which the frequency sensitivity of the structures is achieved as 0.834 and 1.57 THz per refractive index while the figure-of-merit of 11.75 and 24.5 are obtained, respectively. Its particular structure is polarization insensitive, further wide-angle absorptivity for both transverse electric and transverse magnetic waves is obtained. To verify the accuracy and validity of the presented circuit model approach, full-wave numerical modeling is performed.

Refractive Index-Based Terahertz Sensor Using Graphene for Material Characterization

“…It can be inferred from the data that are presented in this table that the proposed THz sensor showed improved sensitivity with maximized miniaturization. From Table 4 it can be inferred that the Q factor of the proposed sensor was higher compared to the Q factor(s) of [30,31] by 78.77%, 55%, 56.4% and 45.2%, respectively. The salient features of the periodic graphene-based THz sensor are as follows:…”

Highly tunable multi‐band THz absorber with circuit model representation using multi‐bias scheme

“…Graphene is embedded into polyethylene cyclic olefin copolymer (Topa's polymer with np = 1.53), which has very low losses in the THz band and is an appropriate bed substrate for utilization in THz absorbers. 8,9 Among dielectric properties, permittivity and thickness are important since they influence the input impedance. Also, a developed graphene pattern as periodic arrays of graphene Nanodisks is placed on top of the dielectric.…”

“…While we know that a single carbon atom has 0.34 nm thickness but due to fabrications limits and technology restrictions, we consider three carbon atom layers as graphene which is graphite for the accurate term. Graphene is embedded into polyethylene cyclic olefin copolymer (Topa's polymer with np = 1.53), which has very low losses in the THz band and is an appropriate bed substrate for utilization in THz absorbers 8,9 . Among dielectric properties, permittivity and thickness are important since they influence the input impedance.…”

“…Finally, a continuous graphene sheet is placed on top of the whole device to enhance total absorption. Compared to conventional designs in References 1‐12, two first layers benefit from an extra bias, which leads to more degree of freedom to adjust input impedance using external control parameters (gate biasing).…”

Analytical design and model analysis of dynamically tunable terahertz metal-graphene hybrid metamaterial

“…[15][16][17][18][19][20] The rational application of the equivalent model provides numerical substitution and theoretical support for the design and verification of metamaterial devices. The two-particle model for different metamaterials with the patterned metal unit, [21][22][23] the planar graphene unit, 24,25 the patterned graphene unit, 26,27 the metal-graphene hybrid unit; 28 and the equivalent circuit model for metamaterial devices with the patterned metal unit, 29 the planar graphene unit, [30][31][32][33] the patterned graphene unit, [34][35][36][37][38][39] the metal-graphene hybrid unit [40][41][42] have been successively studied.…”