In this paper, a high-resolution refractive index sensor is proposed based on a novel metal–insulator–metal plasmonic topology. The structure is based on a Si nano-ring located inside a circular cavity. It acts as an optical notch filter with a quality factor equal to 269. The proposed filter topology is numerically simulated using the finite difference time domain method. It is shown that the proposed filter can also act as a refractive index sensor with a sensitivity of 636 nm/RIU and a fairly high figure of merit (FoM) equal to 211.3 RIU−1. It is shown that the sensor can easily detect a refractive index change of ± 0.001 for dielectrics whose refractive index is between 1 and 1.2. For the refractive index range of 1.33 to 1.52, the maximum FoM of the sensor is 191 RIU−1. The simplicity of the design and its high resolution are the two main features of the proposed sensor which make it a good candidate for biomedical applications.
相似文献In this article, a surface plasmon resonance (SPR) biosensor based on D-typed optical fiber coated by Al2O3/Ag/Al2O3 film is investigated numerically. Resonance in near infrared with an optimized architecture is achieved. Refractive index sensitivity of 6558 nm/RIU (refractive index unit) and detection limit of 1.5 × 10−6 RIU, corresponding to 0.4357 nm/μM and detection limit of 23 nM in BSA (bovine serum albumin) concentration sensing, are obtained. The analysis of the performance of the sensor in gaseous sensing indicates that this proposed SPR sensor is much suitable for label-free biosensing in aqueous media.
相似文献In this report, a novel D-shaped long-range surface plasmon resonance (LRSPR) fiber base sensor has been introduced. The demonstration of proposed sensor involves two D-shaped silver-coated models to study the sensitivity responses. The entire study with the constructed models is based on a single-mode fiber. The models are multilayered consisting of metal, dielectric, and analyte as separate layers. Silver (Ag) and magnesium fluoride (MgF2) strips are used as metal and dielectric layers respectively. The constituency of analyte as an interface excellently standardized the models for sensitivity detection. In this report, a large range of analyte refractive indices (RI) which varies from 1.33 to 1.38 is appraised for the proposed models to characterize the sensitivity. The entire context is encompassed by the wavelength region from 450 to 850 nm with an interval of 20 nm. Sensitivities in this report are measured based on the analyte position from the core and metal for both models. For each of the two models, the analyte is placed as the top layer. RIs of the applied metal (Ag) are measured using the Drude-Lorentz formula. The simulated sensitivities for model-1 and model-2 vary from 6.3?×?103 nm/RIU to 8.7?×?103 nm/RIU.
相似文献A dual-core and dual D-shaped photonic crystal fiber (PCF)-based surface plasmon resonance (SPR) sensor with silver and aluminum nitride (AlN) films is designed. The distribution characteristics of the electromagnetic fields of core and plasmon modes, as well as the sensing properties, are numerically studied by finite element method (FEM). The structure parameters of the designed sensor are optimized by the optical loss spectrum. The results show the resonance wavelength variation of 489 nm for the refractive index (RI) range of 1.36?~?1.42. In addition, a maximum wavelength sensitivity of 13,400 nm/RIU with the corresponding RI resolution of 7.46?×?10?6 RIU is obtained in the RI range of 1.41?~?1.42. The proposed sensor with the merits of high sensitivity, low cost, and simple structure has a wide application in the fields of RI sensing, such as hazardous gas detection, environmental monitoring, and biochemical analysis.
相似文献In this paper, a plasmonic perfect absorber (PPA) based on metal-insulator-metal-insulator-metal (MIMIM) structure has been designed for refractive index sensing of glucose solutions (analyte) and then a new method has been proposed for fast, low-cost, and easy measurement of sensor’s sensitivity. Simulation results show that the absorption spectrum of the proposed sensor has two resonance peaks that with an increase in analyte refractive index, both of them are red-shifted. In our proposed measurement technique, two conventional single-wavelength lasers (with wavelengths of 1050 nm and 1750 nm) are used for vertical plane wave light illumination on the structure. Then, the absorbed powers at 1750 nm (A2) and 1050 nm (A1) wavelengths are calculated and variation of the absorption ratio (A2/A1) due to change of analyte refractive index would be introduced as the sensitivity of sensor (S = Δ(A2/A1)/Δn). Obtained results show that the increase of analyte refractive index from n = 1.312 to n = 1.384 will result in an increase of sensor’s sensitivity from 9.3/RIU to 33.475/RIU.
相似文献Platinum diselenide (PtSe2), an emerging two-dimensional transition metal dichalcogenide, exhibits thickness-dependent refractive index, and hence, intriguing optical properties. Here, we employ it as a plasmonic sensing substrate to achieve significant enhancement in Goos-Hänchen shift sensitivity. Through systematic optimization of all parameters, four optimum sensing configurations have been achieved at different wavelengths ranging from visible to near-infrared region, where the Goos-Hänchen shift sensitivity receives four times enhancement in comparison with the conventional bare gold sensing substrate. There is a linear range of Goos-Hänchen shift with the tiny change of refractive index for each optimal configuration. The detection limit of the refractive index change can be as low as 5 × 10−7 RIU which is estimated to be lower by 2 orders of magnitude, and the corresponding sensitivity of biomolecules has a 1000-fold increment compared with that of bare gold-based sensors.
相似文献A surface plasmon resonance (SPR) sensor based on a photonic crystal fiber (PCF) is proposed for low refractive index (RI) detection. The core of PCF is formed by two-layer air walls and either layer is composed of six identical sector rings with negative curvature. Plasmonic material gold (Au) is coated on the external cladding surface. Finite element method (FEM) is applied to investigate the performance of the SPR sensor. Results show that the sensor is independent of polarization due to the coincident coupling properties of the two polarized modes. Additionally, in low RI ranging from 1.20 to 1.33, the sensor keeps a high spectral sensitivity with an average value of 7738 nm/RIU. When RI varies from 1.32 to 1.33, the resolution reaches to its maximum of 8.3 × 10−6. The proposed sensor shows much significance in low RI detection, which is promising in real-time measurement for medical, water pollution, and humidity.
相似文献In this paper, individual split Au square nanorings were numerically proposed as novel substrates for surface-enhanced Raman and hyper-Raman scattering (SERS and SEHRS) simultaneously. The peak wavelengths of their localized surface plasmon resonance (LSPR) fall in the near-infrared and visible light regions, respectively, which are able to be finely tuned to match well with the wavelengths of the incident laser and hyper-Raman scattered light beams. Their SEHRS and SERS performances along with electromagnetic (EM) field distributions are numerically investigated by finite element method. With the enhancement of near electric-fields generated by LSPRs, the maximum SEHRS and SERS enhancement factors are demonstrated to reach 1.22?×?1012 and 108, respectively. Meanwhile, the corresponding SERS-based refractive index (RI) sensitivity factor reaches as high as 258 nm/RIU and 893 nm/RIU, at visible and near-infrared wavelengths, respectively. The proposed structure holds great promise both for developing SEHRS- and SERS-based RI sensing substrates, which shows strong potential applications in nanosensing and enhanced Raman scattering.
相似文献In this study, we demonstrate the design of a photonic crystal fiber (PCF)-based plasmonic sensor to measure the glucose level of urine. The sensor is designed by placing a small segment of PCF between a lead-in and a lead-out single-mode fiber. We utilize the finite element method to simulate the proposed plasmonic sensor for the measurement of glucose level in urine. To offer external sensing, the cladding layer of the PCF was coated by a thin layer of gold where the gold-coated PCF was immersed in the urine sample. As a result, the urine can easily interact with the plasmonic layer of the sensor. In the outermost laser of the PCF, we considered a perfectly matched layer as a boundary condition. The simulation results confirm excellent wavelength and amplitude sensitivities where the maximum wavelength sensitivity was 2500 nm/RIU and amplitude sensitivity was 152 RIU?1 with a sensing resolution of 4?×?10?6. For optimization of the plasmonic sensor, we varied the physical parameters of the cladding air holes and the thickness of the gold layer during the simulation. We strongly believe that the proposed plasmonic sensor will play a significant role to pave the way for achieving a simple but effective PCF-based glucose sensor.
相似文献A speckle-free fast angular interrogation surface plasmon resonance imaging (SPRi) sensor based on a diode-pumped all-solid-state laser and galvanometer is reported in this work. A bidirectional scan using a galvanometer realizes the fast scanning of the incidence angle. The experimental results showed that the time needed for completing an SPR dip measurement was decreased to 0.5 s. And through cascading an immovable diffuser and two diffusers rotating in opposite directions, laser speckle was eliminated. The dynamic detection range and the sensitivity reached 4.6 × 10−2 and 1.52 × 10−6 refractive index unit (RIU), respectively, in a 2D array sensor when the angle scanning range was set as 7.5°. More importantly, the results demonstrated that the angular interrogation SPR imaging sensor scheme had the capability to perform fast and high-throughput detection of biomolecular interactions at 2D sensor arrays.
相似文献We theoretically propose a surface plasmon resonance (SPR)-based fiber optic refractive index (RI) sensor. A surface plasmon exciting metallic grating formed with the alternation of indium tin oxide (ITO) and silver (Ag) stripes is considered on the core of the fiber. A thin film of silicon is used as an overlay. Silicon film not only protects the metallic grating from oxidation but also enhances the field to improve the device sensitivity. The sensor is characterized in terms of sensitivity, detection accuracy (DA), figure of merit (FoM), and quality factor (QF). The maximum sensitivity in the RI range 1.33 to 1.38 refractive index unit (RIU) is reported to be?~25 µm/RIU in infra-red region of investigation.
相似文献A self-referencing plasmonic platform is proposed and analyzed. By introducing a thin gold layer below a periodic two-dimensional nano-grating, the structure supports multiple modes including localized surface plasmon resonance (LSPR), surface plasmon resonance (SPR), and Fabry-Perot resonances. These modes get coupled to each other creating multiple Fano resonances. A coupled mode between the LSPR and SPR responses is spatially separated from the sensor surface and is not sensitive to refractive index changes in the surrounding materials or surface attachments. This mode can be used for self-referencing the measurements. In contrast, the LSPR dominant mode shifts in wavelength when the refractive index of the surrounding medium is changed. The proposed structure is easy to fabricate using conventional lithography and electron beam deposition methods. A bulk sensitivity of 429 nm/RIU is achieved. The sensor also has the ability to detect nanometer thick surface attachments on the top of the grating.
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