Numerical Optimization of Refractive Index Sensors Based on Diffraction Gratings with High Aspect Ratio in Terahertz Range

Kameshkov, Oleg E.; Gerasimov, V. V.; Knyazev, B. A.

doi:10.3390/s22010172

Cited by 11 publications

(6 citation statements)

References 36 publications

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“…We shall evaluate this absorber’s performance in terms of sensitivity (S) and quality factor (FOM). The formulas for these two metrics are as follows [ 59 , 60 , 61 ]:

where

is the amount of change in the resonance wavelength of the absorption peak with respect to the change in the ambient refractive index. FWHM is the half-height width of the absorption peak.…”

Section: Resultsmentioning

confidence: 99%

Tunable High-Sensitivity Four-Frequency Refractive Index Sensor Based on Graphene Metamaterial

Bao,

Yu,

et al. 2024

Sensors

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As graphene-related technology advances, the benefits of graphene metamaterials become more apparent. In this study, a surface-isolated exciton-based absorber is built by running relevant simulations on graphene, which can achieve more than 98% perfect absorption at multiple frequencies in the MWIR (MediumWavelength Infra-Red (MWIR) band as compared to the typical absorber. The absorber consists of three layers: the bottom layer is gold, the middle layer is dielectric, and the top layer is patterned with graphene. Tunability was achieved by electrically altering graphene’s Fermi energy, hence the position of the absorption peak. The influence of graphene’s relaxation time on the sensor is discussed. Due to the symmetry of its structure, different angles of light source incidence have little effect on the absorption rate, leading to polarization insensitivity, especially for TE waves, and this absorber has polarization insensitivity at ultra-wide-angle degrees. The sensor is characterized by its tunability, polarisation insensitivity, and high sensitivity, with a sensitivity of up to 21.60 THz/refractive index unit (RIU). This paper demonstrates the feasibility of the multi-frequency sensor and provides a theoretical basis for the realization of the multi-frequency sensor. This makes it possible to apply it to high-sensitivity sensors.

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“…We shall evaluate this absorber’s performance in terms of sensitivity (S) and quality factor (FOM). The formulas for these two metrics are as follows [ 59 , 60 , 61 ]:

where

is the amount of change in the resonance wavelength of the absorption peak with respect to the change in the ambient refractive index. FWHM is the half-height width of the absorption peak.…”

Section: Resultsmentioning

confidence: 99%

Tunable High-Sensitivity Four-Frequency Refractive Index Sensor Based on Graphene Metamaterial

Bao,

Yu,

et al. 2024

Sensors

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show abstract

“…Terahertz radiation has recently become the focus of researchers thanks to its special properties [1][2][3][4][5][6][7][8][9][10][11] . The considerable energy transmitted by photons in the infrared, visible and ultraviolet frequency ranges can damage biological cells and pose a risk to highly ammable sample materials.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, there is still a room to create new unit cells with these conditions [36][37][38] . On the other hand, the possibility of realization of the structure has become a double motivation for researcher to design their THz sensors at frequencies below 3 THz 1,4,5,39 .…”

Section: Introductionmentioning

confidence: 99%

Terahertz Spoof Surface Plasmon Polariton Structure for High-precision Gas Sensor Technology

NAJAFY,

ABBASI-ARAND,

HESARI-SHERMEH

2024

Preprint

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In the realm of sensor technology, it is a significant challenge to accurately identify and differentiate sample materials in the gas phase, especially when they have closely similar refractive indices. A promising solution in the THz range is the use of plasmonic spoof surface structures configured in an Otto arrangement. This configuration increases sensitivity by amplifying the trapped fields within the periodic structure and the sample material. This represents a remarkable improvement over the conventional binary-grating structure (CBGS) model with the proposed multilevel meta-grating structure (MMGS) sensor. An in-depth analysis of gas samples shows a remarkable increase in sensitivity to a small refractive index change up to by 11.4 (TH/RIU). The refractive index of gas sample is more sensitive to both pressure and molecular density. The proposed setup has been meticulously designed to maximize reflectance within the sensor's reflectance spectrum. This has been achieved by precisely adjusting the air gap distance, effectively minimizing the impact of sample material density. The new proposed design proves to be particularly suitable for effectively detecting different gas with closely spaced refractive indices. An investigation of four common and well-known gas shows a minimum resolution of 5 GHz for resonance peak positions. The results are validated by simulating the reflection spectrum using the semi analytical rigorous coupled wave analysis (RCWA) method. Moreover, the eigenmode solver in the CST-Studio software is used to generate dispersion curves. The proposed structure is very useful for high precision sensors with a small refractive index change.

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“…It is noted that the terahertz sensing based on SSPPs of PGMS has been well discussed in the published literatures [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. For example, Ng et al experimentally analyzed the relationship between spectral shift of SSPPs excitation on PGMS and refractive index filling in 1D periodic grooves [22,23].…”

Section: Introductionmentioning

confidence: 99%

“…Li et al have used the PGMS to achieved a high sensitivity of 335 GHz RIU −1 [34]. Recently, such sensors were further studied in the works of other authors [37][38][39], who parametrically analyzed the optimal parameters for surface plasmon resonance (SPR) and obtained the maximum sensitivity to be as high as 3.57 THz RIU −1 . In addition to spectral shift-based sensing of one-sided grooved metal surface, other terahertz sensing schemes based on excitation angle of SSPPs [25,29], phase jump signal of SSPPs [33] and the new type of doublecorrugated sensor [30] have also been introduced and studied.…”

Section: Introductionmentioning

confidence: 99%

Resolved terahertz spectroscopy of tiny molecules employing tunable spoof plasmons in an otto prism configuration

Yao¹,

Zhang²,

Liu³

et al. 2022

J. Opt.

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Sensitive detection of terahertz fingerprint absorption spectrum for tiny molecules is essential for bioanalysis. However, it is extremely challenging for traditional terahertz spectroscopy measurement because of the weak spectral response caused by the large mismatch between terahertz wavelengths and biomolecular dimensions. Here, we proposed a wideband-tunable metal plasmonic terahertz biosensor to detect tiny biomolecules, employing attenuated total reflection in an Otto prism configuration and tightly confined spoof surface plasmons on the grooved metal surface. Benefitting from the plasmonic electric field enhancement, such a biosensor is able to identify the molecular terahertz fingerprints. As a proof of concept, a hypothetical molecule modeled by the Lorentz model with two vibrational modes is used as the sensing analytes. Simulation results show that the absorption of two vibrational modes of analytes can be selectively enhanced up to ten times by plasmonic resonance, and their fingerprints can be resolved by sweeping incident angle in a wide waveband. Our work provides an effective approach for the highly sensitive identification of molecular fingerprints in fields of biochemical sensing for tiny analytes.

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Numerical Optimization of Refractive Index Sensors Based on Diffraction Gratings with High Aspect Ratio in Terahertz Range

Cited by 11 publications

References 36 publications

Tunable High-Sensitivity Four-Frequency Refractive Index Sensor Based on Graphene Metamaterial

Tunable High-Sensitivity Four-Frequency Refractive Index Sensor Based on Graphene Metamaterial

Terahertz Spoof Surface Plasmon Polariton Structure for High-precision Gas Sensor Technology

Resolved terahertz spectroscopy of tiny molecules employing tunable spoof plasmons in an otto prism configuration

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