Browsing by Author "Chandan Singh Yadav"

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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.
Analysis of Bragg fiber waveguides having a defect layer for biosensing application
(Elsevier GmbH, 2020) Ritesh Kumar Chourasia; Chandan Singh Yadav; Abhishek Upadhyay; Nitesh Kumar Chourasia; Vivek Singh
A novel hollow core Bragg fiber waveguides having a defect layer are proposed and analyzed theoretically for sensing application. Matching the electric and magnetic fields at various interfaces, a relation between fields of first layer with final layer has been stabilized; hence, the equations for reflectance and transmittance of proposed structure are derived. Due to periodicity of concentric cylindrical structure, a perfect photonic band gap is observed in considered wavelength range. The presence of defect layer in cylindrical periodic structure shows a peak corresponding to defect mode in perfect photonic band gap region. The full width at half maxima of this peak depends on the periodicity of the cladding layers. Also, the spectral position and shift of peak of defect mode depend on the angle of incidence of light, refractive index of core material and design wavelength of structure. Therefore, it is more appropriate to consider this peak of defect mode as sensing signal instead of considering whole photonic band gap as sensing signal. © 2019 Elsevier GmbH
Bragg fiber with a doubly defect layer-based tunable multiband optical filter
(The Optical Society, 2022) Chandan Singh Yadav; Abhishek Upadhyay; Sushil Kumar; Vivek Singh
A Bragg fiber waveguide having double-defect layers in its periodic cladding region is investigated and optimized for inline tunable multi-bandpass filter applications. The proposed waveguide is classified in terms of a symmetric waveguide and an asymmetric waveguide depending upon the refractive index of the defect layers. The required reflectance and confinement loss equations are obtained using the boundary matching technique and the transfer matrix method. Due to the presence of the double-defect layer, two sharp passbands in the bandgap region are observed. The separation of the passbands and their intensities can be controlled by introducing the number of unit cells between the defect layers. Our analysis shows that the passband’s intensity, bandwidth, and central wavelength can also be tuned by changing the refractive index of the core material. In addition, the central wavelength for both defect modes are blue shifted with the increase of the core refractive index. In all of our considered cases, the higher tunability with a core refractive index variation in the right defect mode is 25.38 nm/RIU for the symmetric cases having defect layer refractive indices of 1.45. Similarly, the higher tunability with a core refractive index variation in the left defect mode is 16.9 nm/RIU for the asymmetric cases having a refractive index of 1.45 in the first defect layer and 3.42 in the second defect layer. Hence, our proposed waveguide can work as a tunable multi-bandpass inline filter with a narrow bandwidth. © 2022 Optica Publishing Group.
Common path interferometeric analysis of a planar polymer optical waveguide having adlayer of 2D materials for biosensing applications
(Springer, 2021) Abhishek Upadhyay; Chandan Singh Yadav; Gaurav Sharma; Sushil Kumar; Vivek Singh
Sensitivity of a planar polymer optical waveguide having adlayer of MoS2, WS2, MoSe2, WSe2 are estimated using common path Mach-Zehnder interferometer analyses. Dispersion relation and reflectivity equation of proposed waveguide is obtained by matching the electric and magnetic field at various boundaries. The obtained cutoff film thickness of the waveguide is approximately same in the presence of monolayer thickness of transition metal dichalcogenides materials. The cutoff film thickness 84.2 nm of this waveguide is approximately same for TE0, TM0 mode at wavelength 300 nm, these cutoff film thicknesses increases and become 304.6 nm at 1200 nm wavelength. In the proposed common path interferometer analysis, the superposition of TE0 and TM0 modes is considered as sensing signal. It is observed that the difference of their propagation constant is slightly decreased with increase of cover refractive index. Further the maximum phase change is obtained near the propagation constant maxima value hence around this value the output interference signal shows maximum shift with cover refractive index. In the considered wavelength range the maximum sensitivity 0.019 is obtained at wavelength 936nm, when a monolayer of WSe2 material is used as adlayer. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
Comparative study of defect mode intensity and wavelength modulation in Bragg fiber waveguide sensors
(Elsevier GmbH, 2020) Ritesh Kumar Chourasia; Chandan Singh Yadav; Abhishek Upadhyay; Nitesh K. Chourasia; Vivek Singh
Sensing parameters of Bragg fiber waveguides having a defect layer in the cladding region are studied theoretically for bio-sensing and thickness monitoring applications. A comparison between Bragg fiber waveguides consist of a liquid-core surrounded with alternate high refractive index (R.I.) contrast of claddings and low R.I. contrast of claddings is presented. In non-homogeneous multilayer cylindrical system, the transmittance of proposed waveguide-based sensors is formulated using transfer matrix method and Hankel formalism. Both considered structures show photonic bandgap with a narrow passband in the bandgap region. This narrow passband is treated as sensing signal because its position and intensity depends on the diameter and refractive index of core material. The high refractive index contrast cladding waveguide shows larger intensity shift than low refractive index contrast cladding waveguide. The presence of defect layer in both considered waveguides is able to increase the sensing parameters like detection accuracy and overall performance. © 2020 Elsevier GmbH
Estimation of cover sensitivity of a planar polymer waveguide through double path broadband difference interferometeric analysis
(Elsevier GmbH, 2020) Abhishek Upadhyay; Chandan Singh Yadav; Gaurav Sharma; Vivek Singh
Broadband difference interferometeric analysis of a double path planar polymer optical waveguide is presented for bio-sensing applications. Mathematical formulation of intensity of output signal is obtained using interferometeric analysis. Further, the dispersion equation is obtained by matching the field at core cladding interface that gives the cutoff film thickness for TE0 and TM0 modes in considered spectral range. The waveguide is analyzed by propagating either same polarized (TE[sbnd]TE or TM[sbnd]TM) modes or unlike polarized (TE[sbnd]TM) modes in the reference arm and sensing arm. It is observed that difference of propagation constant for same polarized mode increases with increase of wavelength while for unlike polarized modes it first increases up to a maximum value and then decreases in the considered wavelength range. The maxima of output interference signal shifted prominently with the cover refractive index for the wavelength range near the maximum value of propagation constant difference. The obtained sensitivity 9.226 for unlike polarized modes in arms is much larger than the sensitivity 0.071 of same polarized modes in arms. © 2020 Elsevier GmbH
Estimation of power loss spectra in slightly flattened distorted Bragg fiber waveguide
(Elsevier GmbH, 2020) Chandan Singh Yadav; Abhishek Upadhyay; Vivek Singh
Dispersion characteristic and fiber loss spectra of a Bragg fiber waveguide having slightly flattened distortion are estimated for sensing applications. The characteristic and optical power loss equations of waveguide are obtained by matching the fields at various boundaries under quarter wave stack conditions. It is found that the optimum power loss is inversely proportional to the ninth power of distortion coefficient. The obtained results show that optimum fiber loss decreases with decrease of refractive index of cladding layer 'b' (low refractive index layer) and increase of refractive index of cladding layer 'a' (high refractive index layer). Also, fiber losses are estimated with increase of the high and low refractive index cladding layer losses. This loss spectrum of fiber can be considered as sensing signal. Since obtained fiber losses in distorted Bragg fiber are higher than standard Bragg fiber therefore, the sensitivity of proposed structure is higher than the standard Bragg fiber. Also, the sensitivity increases with the increase of refractive index of core medium. These results would be helpful to design a novel highly sensitive sensor based on hollow core distorted Bragg fiber. © 2020 Elsevier GmbH
Experimental detection of chlorpyrifos by MoS2 coated planar polymer waveguide sensor utilizing common path interferometric principle
(Elsevier GmbH, 2023) Abhishek Upadhyay; Chandan Singh Yadav; Rajiv Maurya; Gaurav Sharma; T. Sonamani Singh; Sushil Kumar; Vivek Singh
A common path Mach-Zehnder interferometer is fabricated using a planer polymer waveguide having MoS2 as an adlayer for chlorpyrifos detection. The dispersion characteristic and cutoff condition of proposed waveguide are obtained theoretically and hence the cutoff film thickness is optimized to get TE0 and TM0 propagating modes. Variations between the phase shift of propagating modes with the concentration of pure chlorpyrifos and its commercial sample are obtained. A good linear variation between phase shift and concentration of chlorpyrifos is obtained in our fabricated waveguide for all considered temperatures. The obtained maximum sensitivity, minimum limit of detection, and limit of quantification of chlorpyrifos are 5.66 degree/μM, 1.57 μM, and 5.24 μM respectively, at 45° C. The capability of the fabricated sensor to generate distinct response for a pure and commercial sample of chlorpyrifos at different concentration and temperature were confirmed by principal component analysis. Since the response of sensor is better for commercial samples at a lower temperature, therefore it is recommended that the concentration of chlorpyrifos in commercial samples should be measured at low temperatures. © 2023 Elsevier GmbH
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.
Mach-Zehnder interferometric analysis of planar polymer waveguide having an adlayer of WS2for biosensing applications
(Walter de Gruyter GmbH, 2023) Abhishek Upadhyay; Chandan Singh Yadav; Vivek Singh
To enhance the sensing performance of a four-layer planar polymer optical waveguide, an adlayer of tungsten disulfide material is introduced. Also, the proposed waveguide is used to demonstrate theoretically the detection of uric acid concentration in blood or urine. The heterostructure of two-dimensional WS2 offers excellent dry lubricity with respect to any other 2D substance, such as graphite or molybdenum disulfide. The proposed waveguide is analyzed using the common path Mach-Zehnder interferometric method. The dispersion characteristic i.e., the effective refractive indices and thickness of proposed waveguide is plotted for a particular wavelength range to optimize the thickness of film layer. The difference in propagation constant and output interference signal for changing the cover medium is calculated. Using the output interference signal, the phase sensitivity 213degree/RIU is obtained in the proposed waveguide. The maximum obtained sensitivity, limit of detection and limit of quantification for uric acid concentration in the proposed waveguide structure is 6.86 × 10-2degree mM-1, 0.061mM and 0.203mM, respectively. © 2023 Walter de Gruyter GmbH, Berlin/Boston.
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.
Modal Analysis and Cutoff Condition of Bragg Fibers
(Springer Science and Business Media Deutschland GmbH, 2021) Chandan Singh Yadav; Abhishek Upadhyay; Vivek Singh
In this paper, the dispersion characteristics and cutoff conditions of Bragg fiber having different core refractive index are analysed and compared, theoretically. Using transfer matrix method the required characteristic equation of these waveguides is derived. The TE and TM mode analysis of these waveguides show that the cut off radius decreases with increase of core refractive index. The obtained respective TE01andTM01 modes cut-off radius is 0.633μm and 0.398μm at core refractive index nc= 1.49. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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.
Quasi-periodic layering of linear/nonlinear materials in hollow core Bragg fiber for all-optical diode action
(Elsevier B.V., 2023) Chandan Singh Yadav; Abhishek Upadhyay; Sushil Kumar; Gaurav Sharma; Vivek Singh
A novel approach to achieving an inline all-optical diode action is presented using a quasi-periodic arrangement of titanium dioxide and polydiacetylene 9-BCMU in cladding region of hollow core Bragg fiber structure. The proposed quasi-periodicity is based on Fibonacci sequences. The reflectance formula and power transmission are derived using the transfer matrix method, and their spectra are plotted for two different Fibonacci sequences. The quasi-periodicity of the structures enables the formation of multiple photonic bandgaps. An optical asymmetry is introduced at both ends of the fiber by splicing two combinations of Bragg fibers. The all-optical diode action is investigated and simulated under two conditions: both spliced Bragg fibers have identical Fibonacci sequences (symmetric combination) and different Fibonacci sequences (asymmetric combination). In the symmetric structure, light propagation is reciprocal for both ends, while the asymmetric structure exhibits non-reciprocal propagation with significantly reduced backward light 92 % less at the output compared to forward propagation. The proposed structure demonstrates a high transmitted contrast over 97 % and exhibits a nonlinear response with increasing incident light intensity at a specific wavelength (λ = 1735 nm). Furthermore, by adjusting the refractive index of the fiber core, the all-optical diode action remains nearly constant. This suggests that the proposed structure can serve as a stable inline all-optical diode in higher wavelength regions with a variable core index. © 2023 Elsevier B.V.
Sensing performance of Bragg fibers having a defect layer utilizing confinement loss analysis for brain cancer cells detection
(Elsevier B.V., 2022) Chandan Singh Yadav; Abhishek Upadhyay; Vivek Singh
The sensing performance of the Bragg fiber having a defect layer in the cladding region is optimized for brain cancer cell detection using the refractive index of brain lesions fluids. The optimization is achieved by comparing the confinement loss of low contrast and a high contrast defected Bragg fiber with similar standard Bragg fiber. Using the transfer matrix method and matching the fields at various interfaces equation of confinement loss is obtained in presence of a defect layer. It is observed that the sensing performance of low contrast waveguide is better than high contrast waveguide in the absence of the defect layer but the situation become reversed in presence of a defect layer. Wavelength interrogation shows high sensing performance with the variation of defect layer refractive index while intensity interrogation shows high sensing performance with the variation of core refractive index. Here wavelength interrogation of high contrast defected Bragg fiber is demonstrated to detect normal and abnormal brain tissues due to its feasibility. Our analysis shows that the respective maximum sensitivity, detection accuracy, and quality parameters are 12.1519 nm/RIU, 4365.7235, and 41.6161 RIU−1 in the benign stage corresponding to the wall of brain and 11.0233 nm/RIU, 4242.7191 and 38.8281 RIU−1 in the malignant stage corresponding to low-grade glioma. © 2022
Sensitivity Estimation of Bragg Fibers having Double Defect Layers
(Institute of Electrical and Electronics Engineers Inc., 2022) Chandan Singh Yadav; Abhishek Upadhyay; Vivek Singh
The sensitivity of two Bragg fibers having symmetric and asymmetric double defect layers are studied, optimized, and compared. The thicknesses of symmetric defects are 267.24 nm and asymmetric defects are 113.30 nm and 267.24 nm. Two sharp defect modes arise due to the resonance of core and defect modes. The sensitivity of proposed waveguides depends on the separation between defect layers. Right defect mode of symmetric defected Bragg fiber shows maximum sensitivity. © 2022 IEEE.