Faculty Publications

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Author: search.filters.author.Raghuwanshi, S.K.

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    Introduction tо Microwave Photonics
    (SPIE, 2025) Raghuwanshi, S.K.; Singh, M.; Kumar, R.; Kumar, S.
    Microwave photonics is a rapidly growing field that lies at the intersection of microwave engineering and optics. The integration of photonics and microwave engineering has opened up new possibilities for high-speed communication, radar and sensing systems, and signal processing applications. This book contains both the basic theory and the experimental techniques to demonstrate the interdisciplinary applications of microwave photonic systems. It discusses the underlying concepts, techniques, and devices used in microwave photonics, as well as the latest advances in the photonic generation, processing, and distribution of arbitrary microwave waveforms. The role of fiber Bragg grating in microwave photonic systems is described from a dispersion compensation point of view. The book also provides a deeper understanding of microwave photonic sensor systems, highly steerable beamforming systems, and photonic excitation of antenna—the process of exciting the antenna using light or photons instead of electrical signals—with applications in aerospace, defense, telecommunication, and biomedical sensing. Overall, microwave photonics is an interdisciplinary field that deals with the interaction between light and microwaves. Its unique features, including high-speed, low-power consumption and large bandwidth, make it an attractive technology for future applications. This book is intended for researchers, engineers, and students who are interested in this exciting and rapidly evolving field. © 2025 Society of Photo-Optical Instrumentation Engineers (SPIE). All rights reserved.
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    Highly steerable microwave beamforming system near Ku band based on the application of linearly CFBG
    (Institution of Engineering and Technology jbristow@theiet.org, 2020) Raghuwanshi, S.K.; Srivastava, N.K.; Singh, M.
    In this study, the authors present theoretical and experimental results of wideband beamforming networks steered by a single linear chirped fibre Bragg grating (CFBG). The standard single-sideband modulation technique is followed to validate the wideband (at 18 GHz) operation of the proposed system. CFBG has been fabricated by phase mask technology for the desired specification to be compatible with the antenna array. To the authors knowledge, the effect of dispersion slope feature of fabricated FBG on the performance of beam-steering capability of the antenna is reported for the first time in this study. Theoretically preceded by experimental testing, it was found that the scanning angle increased with the rise in the number of antenna elements and the frequency of modulating microwave signal. © 2019 The Institution of Engineering and Technology.
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    High-Resolution Fiber Optic Sensor based on Coated Linearly Chirped Bragg Grating
    (Elsevier GmbH, 2020) Singh, M.; Raghuwanshi, S.K.; Prakash, O.; Kumar, P.K.
    a fiber optic strain sensor is proposed and experimentally demonstrated using fiber Bragg grating (FBG) based interrogation scheme. Due to fast response time and better sensitivity of graphene oxide (GO) material, coated linearly chirped fiber Bragg grating (LCFBG) is used in this work. Interrogation scheme is used for the efficient strain sensing by placing LCFBG within the Sagnac loop (wavelength dependent receiver). The GO deposition is confirmed by ultraviolet–visible spectroscopy, atomic force microscopy (AFM), and field emission scanning electron micrograph (FESEM). Our proposed fiber optic strain sensor possesses better resolution, stable operation in the infra-red region. In addition, sensor demonstrates 5.25 ?? static strain and 0.645 ??/?Hz dynamic strain resolutions, respectively. © 2020 Elsevier GmbH
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    Real-time interrogation of fiber optic biosensor using TiO2coated etched long-period grating
    (American Institute of Physics Inc., 2020) Singh, M.; Raghuwanshi, S.K.
    In this work, a TiO2 coated etched long-period grating (e-LPG) fiber optic biosensor is developed for the detection of Escherichia coli (E. coli) bacteria in food items. Label-free Escherichia coli bacteria monitoring is done over the detection range of 0 cfu/ml-50 cfu/ml using an advanced spectral interrogation mechanism. The thin film deposition of 40 nm TiO2 over the e-LPG is confirmed by the microscopy method, such as scanning electron microscopy. In our proposed biosensor design, T4-bacteriophage is covalently immobilized over the TiO2 coated fiber surface. This biosensor system has reached sensitivity at 2.55 nm/RIU. Our experiments confirm the resolution and the limit of detection (3?/S) of 0.0039 RIU and 10.05 ppm, respectively. The proposed biosensor with enhanced sensitivity is suitable for monitoring harmful pathogens/infectious agents in various food products. © 2020 Author(s).
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    High sensitivity detection of chemicals based on sinusoidally apodized structured grating assisted liquid filled directional coupler
    (Springer, 2021) Raghuwanshi, S.K.; Singh, Y.; Singh, M.; Chack, D.; Kumar, R.; Prakash, O.
    The grating has a significant role in sensing applications. Similarly, the grating-assisted coupler has excellent potential in chemical sensing applications. The power coupling between two closely coupled waveguide couplers can be significantly tuned by incorporating grating between them. The grating has been taken of silica material with sinusoidal shape in variation. The grating layer is assumed to be embedded within the sensing layer while considering a changeable effective refractive index depending on the sensing layer substances. In the present paper, grating assisted directional coupler has been numerically analysed using its own developed MATLAB-based algorithm of finite difference method (FDM) scheme. FDM method has been applied to solve the Eigenvalue equation to obtain allowed Eigenvalues and corresponding Eigen vectors (TE and TM cases). In FDM, the analysis domain has been fine discretized into the mesh of 1-D equal spacing for reasonable accurate computation results. In experimental validation, Fibre Bragg grating (FBG) has been suspended between two high refractive index coupler regions, which act as a power coupling zone. Also, the coupling length has been changed from 5 to 20 ? m for tuning purposes and then optimized for grating parameters viz. length, period, etc. The whole structure is 2-Dimensional (x and y directions) with invariant in the y-direction. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.