Browsing by Author "Ankit Mishra"

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A novel tunable metal-clad planar waveguide with 0.62PMN-0.38PT material for detection of cancer cells
(John Wiley and Sons Inc, 2023) Rajiv Maurya; Ankit Mishra; Chandan Singh Yadav; Abhishek Upadhyay; Gaurav Sharma; Sushil Kumar; Vivek Singh
A dynamically tunable metal clad planar waveguide having 0.62PMN-0.38PT material is simulated and optimized for detection of cancer cells. Angular interrogation of the TE0 mode of waveguide shows that critical angle increases greater than the resonance angle with increasing of cover refractive index, which limits the detection range of waveguide. To overcome this limitation, proposed waveguide applies a potential on the PMN-PT adlayer. Although a sensitivity of 105.42 degree/RIU was achieved at 70 Volts in testing the proposed waveguide, it was found that the optimal performance parameters were obtained at 60 Volts. At this voltage, the waveguide demonstrated detection range 1.3330–1.5030, a detection accuracy 2393.33, and a figure of merit 2243.59 RIU−1, which enabled the detection of the entire range of the targeted cancer cells. Therefore, it is recommended to apply a potential of 60 Volts to achieve the best performance from the proposed waveguide. (Figure presented.). © 2023 Wiley-VCH GmbH.
Advancements in optical waveguide sensors through Fano resonance
(Elsevier Ltd, 2025) Ayushi Rawat; Rajiv Maurya; Ankit Mishra; Gaurav Singh; Aayush Dixit; Vivek B. Singh
Fano resonance, a unique interference phenomenon between a discrete state and a continuum, has shown great potential to enhance the performance of optical waveguide sensors. FR-based sensors exhibit sharp, asymmetric spectral features with a narrow full width at half maximum, offering high sensitivity and a high figure of merit. These characteristics make them promising candidates for refractive index sensing and various biochemical applications. While many waveguide configurations have been explored, this work focuses on planar and fiber optical waveguide platforms due to their practical advantages in integration, fabrication, and real-world applications. This review highlights recent advancements in FR-based optical waveguide sensors, their working principles, design strategies, and potential applications. Continued research in novel waveguide designs, material engineering, and resonance tuning will drive future innovations, ultimately paving the way for next-generation optical waveguide sensing technologies for diverse applications in biosensing, environmental monitoring, and more. © 2025 Elsevier Ltd
An Advanced PLL-less Control Scheme for LVRT Capability with Harmonics Current Mitigations in Grid-Tied PV System Under Weak and Distorted Grid
(Institute of Electrical and Electronics Engineers Inc., 2022) Manash Kumar Mishra; Ankit Mishra; V.N. Lal
This paper proposes an advanced phase-locked loop (PLL) less control scheme to mitigate the grid current harmonics along with enhanced low voltage ride-through (LVRT) capability of a grid-tied photovoltaic system (GTPVS) under the weak grid and distorted grid voltages. The enhanced LVRT operation of the GTPVS is achieved with the coordinated operation of the active power regulator (APR) and dynamic reactive power support (DRPS) controller. Moreover, an advanced phase compensated multiresonant (APCMR) current controller is utilized to mitigate the grid current harmonics under distorted grid voltages. The proposed control scheme is implemented in the αβ reference frame without park's transformation as well as a PLL unit. Thus, the computational burden of the proposed control scheme reduces. Further, the frequency adaptability of the GTPVS is improved during variations in grid frequency. To verify and evaluate the effectiveness of the proposed LVRTPLL-less control scheme (LPLCS) over the conventional LVRT PLL based control scheme (LPBCS), the experimental analysis is carried out using OPAL-RT OP 4510 real-time digital simulator. © 2022 IEEE.
Assessment of ground and surface water quality along the river Varuna, Varanasi, India
(Kluwer Academic Publishers, 2015) Pardeep Singh; R.K. Chaturvedi; Ankit Mishra; Lata Kumari; Rishikesh Singh; D.B. Pal; Deen Dayal Giri; Nand Lal Singh; Dhanesh Tiwary; Pradeep Kumar Mishra
Multivariate statistical techniques were employed for monitoring of ground-surface water interactions in rivers. The river Varuna is situated in the Indo-Gangetic plain and is a small tributary of river Ganga. The study area was monitored at seven sampling sites for 3 years (2010–12), and eight physio-chemical parameters were taken into account for this study. The data obtained were analysed by multivariate statistical techniques so as to reveal the underlying implicit information regarding proposed interactions for the relevant area. The principal component analysis (PCA) and cluster analysis (CA), and the results of correlations were also studied for all parameters monitored at every site. Methods used in this study are essentially multivariate statistical in nature and facilitate the interpretation of data so as to extract meaningful information from the datasets. The PCA technique was able to compress the data from eight to three parameters and captured about 78.5 % of the total variance by performing varimax rotation over the principal components. The varifactors, as yielded from PCA, were treated by CA which grouped them convincingly into three groups having similar characteristics and source of contamination. Moreover, the loading of variables on significant PCs showed correlations between various ground water and surface water (GW-SW) parameters. The correlation coefficients calculated for various physiochemical parameters for ground and surface water established the correlations between them. Thus, this study presents the utility of multivariate statistical techniques for evaluation of the proposed interactions and effective future monitoring of potential sites. © 2015, Springer International Publishing Switzerland.
Detection of aqueous nitro explosives using SPR sensors integrated with D-shaped optical fibers
(Springer, 2025) Abhishek Upadhyay; Gaurav Sharma; Rajiv Maurya; Ankit Mishra; Vivek B. Singh
This study presents an optimization and simulation of a surface plasmon resonance-based optical fiber sensor with a D-shaped configuration, for the precise detection of aqueous nitro explosive. The proposed sensor undergoes simulation and analysis using finite element techniques. Optimization of the Au layer thickness, with a 30 nm layer identified for maximum SPR curve reflection, Subsequently, a polyaniline layer was applied to enable selective detection. Varying sample concentrations interact uniquely with the polyaniline sensing surface, as concentration increases, the SPR dip shifts toward longer wavelengths like red-shift in the spectra. Simulating sensor lengths ranging from 1 to 5 mm provides valuable insights into sensor responses, showing improved detection accuracy and figure of merit as the sensor length decreases. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.
Fano resonance-enhanced planar waveguide sensor utilizing MoS2 for high-performance sensing application
(Institute of Physics, 2024) Rajiv Maurya; Ankit Mishra; Chandan Singh Yadav; Abhishek Upadhyay; Vivek Singh
Sensing performance of a Fano resonance waveguide based sensor having a MoS2 material assisted with low refractive index coupling prism BK7 is analyzed. Position of MoS2 is optimized by considering two six-layer structural configurations i.e. PAMCFS and PMACFS and their results are compared at particular guiding layer thickness 500 nm and coupling layer thickness 700 nm. The reflectance formula of proposed six-layer waveguide is obtained using Fresnel’s equations. Our analysis shows that the PAMCFS waveguide gives better sensing performance than PMACFS. Further, sensing parameters is analyzed for different thickness of coupling layer and guiding layer. The maximum obtained sensitivity for zero order Fano resonance mode in intensity interrogation of the proposed PAMCFS waveguide structure is 6.847 × 106 a.u.-RIU-1 at guiding layer thickness 800 nm and coupling layer thickness 1000 nm. Also, at these thicknesses, FWHM is obtained in order of ∼10−6 while the achieved detection accuracy and figure of merit in order of ∼107 and ∼106 respectively. © 2024 IOP Publishing Ltd.
LMR and SPR induced Fano resonance in a planar waveguide-coupled D-shaped optical fiber for enhanced refractive index sensing in the Vis–NIR region
(Optica Publishing Group (formerly OSA), 2025) Rajiv Maurya; Ankit Mishra; Chandan Singh Yadav; Abhishek Upadhyay; Gaurav Sharma; Vivek B. Singh
This study examines the performance of an indium tin oxide coated D-shaped optical fiber (ITO-DOF) sensor and a planar waveguide-coupled indium tin oxide coated D-shaped optical fiber (PWG-DOF) sensor for inline refractive index sensing applications. The ITO-DOF sensor enables lossy mode resonance in the visible region and surface plasmon resonance in the near-infrared region. The PWG-DOF sensor enables the simultaneous generation of Fano resonance in both regions by utilizing lossy mode resonance and surface plasmon resonance effects across the visible and near-infrared regions. It is observed that the PWG-DOF sensor achieves a higher figure of merit than the ITO-DOF sensor due to its narrower full-width at half-maximum. Also, the penetration depth of the Fano resonance mode is recorded at 127.99 nm in the visible region and 500.81 nm in the near-infrared region, surpassing lossy mode resonance (126.75 nm) and surface plasmon resonance (499.91 nm). These values increase with film thickness, highlighting the Fano resonance as a superior sensing signal. Given its improved figure of merit and penetration depth, this study suggests that Fano resonance can enhance the sensitivity and performance of refractive index sensors beyond conventional lossy mode resonance and surface plasmon resonance techniques. © 2025 Optica Publishing Group.
Machine learning-enhanced detection of chlorpyrifos using molecularly imprinted polymer-coated optical fibers
(Elsevier B.V., 2025) Ankit Mishra; Rajiv Maurya; Suraj Prakash; Chandan Singh Yadav; Abhishek Upadhyay; Ritu Singh; Meenakshi K. Singh; Vivek B. Singh
This paper explores the use of large core declad optical fibers coated with molecularly imprinted polymers for chlorpyrifos detection, a key marker of organophosphate pesticides. The performance of sensor is evaluated using artificial neural networks and principal component analysis. By varying the declad length, the performance of molecularly imprinted polymer-coated fibers is compared to uncoated fibers, and both are used to identify commercial and pure samples of chlorpyrifos pesticides. Molecularly imprinted polymer-coated declad fiber sensors particularly those with longer declad lengths, exhibit significantly lower detection limits and higher sensitivity. The obtained maximum sensitivity, and minimum detection limit at 4 cm declad fiber length are 0.0027 mV/nM and 60.70 nM respectively. The results obtained also demonstrate that the artificial neural network can make an accurate prediction and the principal component analysis validates the efficacy of our molecularly imprinted polymer-coated fibers in chlorpyrifos detection. © 2025 Elsevier B.V.
Novel Planar Waveguide-Coupled D-Shaped Optical Fiber Sensor to Generate Fano Resonance for Enhanced Refractive Index Sensing Applications
(Institute of Electrical and Electronics Engineers Inc., 2025) Rajiv Maurya; Ankit Mishra; Chandan Singh Yadav; Abhishek Upadhyay; Gaurav Sharma; Vivek B. Singh
In this article, the generation of Fano resonance (FR) in a novel optical fiber platform, which addresses a significant challenge within the scientific community, is theoretically investigated. The proposed sensor is designed with a D-shaped surface plasmon resonance (SPR) fiber coupled with a three-layer planar waveguide (PWG) structure for inline and enhanced refractive index (RI) sensing applications. Our analysis demonstrates that an optimum thickness of low index dielectric material, i.e., cytop fluoropolymer, as a coupling layer is required to generate FR in association with SPR. It is observed that the FR demonstrates a significant enhancement in the figure of merit (FOM), achieving 6383 RIU-1 for wavelength interrogation and 13 195 a.u./RIU for intensity interrogation at df = 520 nm and dc = 700 nm. These values greatly surpass the FOM of conventional SPR-based sensors, which are 34.90 RIU-1 and 39.96 a.u./RIU. Also, the FOM increases by increasing the thickness of coupling layer. Furthermore, FWHM of the FR is consistent with the length of D-shaped region, whereas FWHM of SPR increases as the length of D-shaped region increases. The penetration depth of FR mode's evanescent field in the sensing region also increases with the film layer thickness, consistently exceeding the penetration depth of SPR (122.47 nm). Hence, the FR mode is proposed as the sensing signal instead of conventional SPR mode because it offers superior performance compared in terms of FOM and penetration depth. © 2025 IEEE.
Optimization and Analysis of a Palladium-Coated Tapered Optical Fiber-Based Hydrogen Sensor
(Institute of Electrical and Electronics Engineers Inc., 2023) Ankit Mishra; Rajiv Maurya; Vivek Singh
This study presents a hydrogen sensor design and simulation using optical fiber and COMSOL Multiphysics. The sensor consists of a palladium-coated tapered optical fiber that transforms upon detecting hydrogen, altering optical properties linked to hydrogen concentration. Simulations show the sensor's response varies with light wavelength, adjustable via parameters like taper diameter and interaction length. Notably, the sensor is highly sensitive, detecting even low hydrogen levels (<4%) with noticeable transmission shifts. It's easily evaluated using LED and photodetector, highlighting its potential for hydrogen detection in energy storage contexts. © 2023 IEEE.
Optimization and performance analysis of a D-shaped polymer optical fiber SPR sensor for selective detection of cadmium ions
(Elsevier GmbH, 2025) Ankit Mishra; Rajiv Maurya; Abhishek Upadhyay; Gaurav Sharma; Pushpender Kumar Gangwar; Dr Vivekanand Mishra; Vivek B. Singh
This article explores the theoretical optimization and performance analysis of a surface plasmon resonance sensor utilizing a single-mode D-shaped polymer optical fiber for the detection of cadmium ions. In this structure, a sensing layer made of polyvinylpyrrolidone is employed over metal to protect it from environmental chemical reactions and selective sensing application of cadmium ions. Numerical investigations of the proposed structure have been carried out employing the finite element method. By optimizing the thickness of the metal, residual cladding, and sensing layer, the sensitivity and detection accuracy of the surface plasmon resonance sensor are estimated. The proposed sensor can detect the cadmium ions of concentration ranging from 0.5 ppm to 1000 ppm. The highest sensitivity (1500 nm/RIU), detection accuracy (29.6921), and figure of merit (64.4640 /RIU) of proposed sensors is observed at 1 ppm concentration of cadmium ions. Despite some variation, the detection accuracy and figure of merit remain high across all considered concentrations of cadmium ions, indicating the reliable performance of the sensor. Its optimal performance at lower concentrations is particularly beneficial for early detection and continuous monitoring of cadmium contamination. © 2024 Elsevier GmbH