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In this paper, a multi-band metal-insulator-metal (MIM) perfect absorber with refractive index sensing capability has been investigated in near-infrared region. The proposed structure has been studied for biomedical applications such as detection of solution of glucose in water, diagnosis of different stages of malaria infection, bacillus bacteria and cancer cells. The MIM configuration improves the sensing parameters of the biosensor due to the good interaction with the analyte. The high sensitivity and figure of merit of 2000 nm/RIU and 100 RIU−1 have been achieved, respectively. Also, the Ag-air grating in the suggested plasmonic sensor helps the localized surface plasmons excitation and makes the structure sensitive to the incident lightwave polarization. Therefore, the presented biosensor behaves like a polarization switch with the high extinction ratio and fast response time of 25.15 dB and 100 fs, respectively. The methods of equivalent circuit model and transmission matrix have been utilized to verify the simulation results, as a new challenge in near-infrared region. The new idea of multi-application plasmonic devices, the feasibility of fabrication for the presented structure and utilizing mentioned analytical methods in near-infrared region could pave the way for the future of plasmonic structures.

In this paper a GST-based perfect absorber is investigated for sensing applications. The simulation results show the high sensitivity and figure of merit of 900 nm per refractive index unit (RIU) and 15 RIU−1, respectively. The sensing parameters are also studied for different biomedical applications such as detection of glucose in water, malaria infection, bacillus bacteria, and cancer cells. The phase change material GST makes the structure tunable and switchable by changing the phase through different annealing temperatures. By changing temperature, the optical characteristics of GST are altered and so the perfect absorption can be tuned at different near-infrared wavelengths. Moreover, the sweep between the amorphous and crystalline states of GST results in switching capability with the high extinction ratio of 13.97 dB at λ = 1724 nm. Therefore, the perfect tunable absorber supports our new idea of multi-application plasmonic devices with two capabilities of sensing and switching, simultaneously. Also, the E-field distributions and analytical method of equivalent circuit model are utilized to verify the simulation results and demonstrate a better insight of the proposed structure performance. The polarization independency of the proposed structure, tunability, good sensing and switching performances are some other benefits of our proposed structure, which can pave the way for development of new investigations about the phase change material applications in plasmonic studies.

In this paper, the simultaneous sensing and switching performance of a graphene-based plasmonic dual-band absorber in the terahertz region has been demonstrated and investigated. Due to the high confinement of graphene surface plasmons and the hydrophobic nature of graphene, the structure can be used as a refractive index sensor in biomedical applications such as detection of impurities of water, cancer cells, and STMV virus. The simulation results show an ultrahigh sensitivity of 360 THz/RIU and figure of merit of 654.54 R I U − 1 . Moreover, variation of the graphene chemical potential leads to a switching function between the perfect absorption and total reflection states, with the high extinction ratio of 12.15 dB and ultrafast response time of 1.5 ps. Two analytical methods of equivalent circuit model and transmission matrix have been used to validate the suggested idea of the proposed graphene-based structure. We have shown that there is a good agreement between the theoretical and simulation results. The specifications of our suggested structure are tunability, ultrahigh sensitivity, high extinction ratio, ultrafast response time, and simple design, which pave the ways for design and implementation of other multi-application terahertz plasmonic structures based on graphene in the future.

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