A graphene based tunable terahertz sensor with double Fano resonances

Abstract

We propose an ultrasensitive terahertz (THz) sensor consisting of a subwavelength graphene disk and an annular gold ring within a unit cell. The interference between the resonances arising from the graphene disk and the gold ring gives rise to Fano type resonances and enables ultrasensitive sensing. Our full wave electromagnetic simulations show frequency sensitivity as high as 1.9082 THz per refractive index unit (RIU) and a figure of merit (FOM) of 6.5662. Furthermore, the sensing range can be actively tuned by adjusting the Fermi level of graphene.

Ultrasensitive terahertz metamaterial sensor based on spoof surface plasmon

“…The extremely sharp resonance with narrow linewidth and high Q factor can be utilized for refractive index and thickness sensing. Under certain conditions, the MMs sensor can realize much superior performance in the THz regime, such as sensitivity and FOM, which are higher than previously reported works based on planar MMs structures 28, 30, 32 . Furthermore, we find that the metal thickness has an important effect on the sensor performance.…”

“…Both resonance frequencies of the broad and the sharp are gradually red shifting with refractive index increasing from 1.0 to 1.8 in steps of 0.2, arising from the dynamic-capacitance changes with the analyte layer. The range of refractive indices represents a series of important materials for THz sensing application and it also covers biomolecules varied from 1.4 to 1.6 in DNA and 1.6 to 2.0 in RNA 30, 32 . From Fig.…”

“…For terahertz-time domain spectroscopy, if the frequency domain resolution is D f , then the film thickness resolution D t of the MMs sensor can be calculated as D t  =  D f / S ( t ), indicating that even a very small changes of the film thickness can be also detected since the sensitivity is highly increased with the film thickness decreasing. Furthermore, to quantitatively describe the sensing performance, we calculated the FOM, defined as the ratio of sensitivity to full width at half maxima (FWHM) of the transmission spectrum, and the FWHM is inversely proportional to the Q factor 30 . Figure 4(d) plotted the variation of Q factor and the corresponding FOM as a function of the analyte refractive index, with the analyte thickness fixed as 11 μm.…”

“…The tightly confined SSPs mode 25 indicates that they could be very sensitive to surrounding dielectric environment, offering another important sensing technique in THz frequencies. Many THz MMs sensors have been proposed as metal-dielectric-metal configurations 26, 27 , planar structures based on breaking symmetry 28, 29 and graphene based structures 30, 31 , but the planar THz MMs structures with the SSPs-based sensing are rarely investigated.…”

Artificial high birefringence in all-dielectric gradient grating for broadband terahertz waves

“…It shows great application prospect in communication1, imaging2, and spectroscopy3. To realize these applications, THz functional devices such as modulator4, filter5, absorber6 and sensor7 are indispensable. Phase and polarization are two basic properties of EM waves.…”