Faculty Publications
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Publications by NITK Faculty
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Item Magnetic-field tuning of whispering gallery mode lasing from ferromagnetic nematic liquid crystal microdroplets(OSA - The Optical Society info@osa.org, 2017) Mur, M.; Sofi, J.A.; Kvasi?, I.; Mertelj, A.; Lisjak, D.; Niranjan, V.; Mus?evic?, I.; Dhara, S.We report magnetic field tuning of the structure and Whispering Gallery Mode lasing from ferromagnetic nematic liquid crystal micro-droplets. Microlasers were prepared by dispersing a nematic liquid crystal, containing magnetic nanoparticles and fluorescent dye, in a glycerol-lecithin matrix. The droplets exhibit radial director structure, which shows elastic distortion at a very low external magnetic field. The fluorescent dye doped ferromagnetic nematic droplets show Whispering Gallery Mode lasing, which is tunable by the external magnetic field. The tuning of the WGM lasing modes is linear in magnetic field with a wavelength-shift of the order of 1 nm/100 mT. Depending on the lasing geometry, the WGMs are red- or blue-shifted. © 2017 Optical Society of America.Item A tri-band slot antenna loaded with split ring resonators(John Wiley and Sons Inc. P.O.Box 18667 Newark NJ 07191-8667, 2017) Paul, P.M.; Kandasamy, K.; Sharawi, M.S.A compact tri-band slot antenna with independent tuning capability of its resonant frequencies is proposed in this article. A microstrip line fed square slot is loaded with split ring resonators (SRR) to obtain multiband characteristics. The slot is designed to resonate at 2.6 GHz. Two SRRs with single and multiple splits are loaded with the slot, which provide additional resonances at 4.3 and 4.7 GHz, respectively. Parametric analysis of the antenna shows that its resonance frequencies are controlled independently. The proposed antenna is fabricated on an FR4 substrate with a size of 60 × 60 × 1.56 mm2. The proposed design offers stable omnidirectional patterns and >3.8 dBi at all the resonating frequency bands. © 2017 Wiley Periodicals, Inc.Item Compact triband circularly polarized planar slot antenna loaded with split ring resonators(John Wiley and Sons Inc. P.O.Box 18667 Newark NJ 07191-8667, 2019) Tharehalli Rajanna, P.K.T.; Rudramuni, K.; Kandasamy, K.In this article, a coplanar waveguide (CPW) fed triband circularly polarized (CP) planar slot antenna loaded with split ring resonators (SRRs) is presented. The truncated slot antenna resonates at 4.15 GHz, which gives two orthogonal degenerate modes to produce circular polarization at the first band. The second and third band resonances are achieved at 4.77 GHz and 5.1 GHz respectively due to the loading of SRRs on the slot antenna. The electric fields produced by the single and multiple split gaps in each ring of SRR1 and SRR2 produce CP at the second and third band. All three bands are tuned independently to achieve optimized axial ratio bandwidth. The antenna is fabricated and verified experimentally. The measured results give impedance bandwidth of 64.54% and axial ratio bandwidths of 11.76%, 1.9%, and 3.87% at first, second, and third band, respectively. © 2019 Wiley Periodicals, Inc.Item High Sensitivity Refractive Index Sensor Based on Indium Antimonide Terahertz Plasmonic Ring Resonator(Institute of Electrical and Electronics Engineers Inc., 2022) Thomas, S.; Singh, M.; Satyanarayan, M.N.A high sensitivity refractive index semiconductor-insulator-semiconductor (SIS) waveguide with a ring resonator sensor at THz frequency is proposed. The topological study of the proposed filter is numerically simulated using the finite element method. A maximum sensitivity of 0.509 THz/ Refractive index unit (RIU) is obtained by filling the air-filled ring resonator cavity with different refractive index materials. Besides that, the transmission characteristics are studied by varying the structural dimensions and observed that the system can be treated as a frequency selective device. The device gets modified by incorporating another concentric ring inside the single ring. From the transmission characteristics, the multiple modes of the concentric dual ring are studied, and concluded that the even TM1 mode shows a better response towards frequency tuning. © 2001-2012 IEEE.Item Characterization of a Pentagonal CSRR Bandpass Filter for Terahertz Applications(Springer, 2022) Elizabeth Caroline, E.C.; Sagadevan, K.; Danasegaran, S.K.; Kumar, S.With the fast magnification of terahertz (THz) technology, it becomes necessary to regulate the terahertz wave transmittance resourcefully. THz filters are crucial for managing devices in THz communication. A metamaterial-based THz bandpass filter (BPF) using a complementary split-ring resonator (CSRR) is proposed with the structure of a square in pentagon (SP). The proposed filter provides high tunability over resonant frequency and bandwidth. The result shows that the resonant frequency of the designed filter is 7 THz, a maximum 3 dB bandwidth of 1.6 THz, return loss of − 28.66 dB, low insertion loss of − 0.001 dB, and the transmittance is almost 100%. The proposed THz filters are used in security screening and biomedical imaging. © 2022, The Minerals, Metals & Materials Society.Item Aperture-Coupled Plasmonic Ring Resonator-Based Temperature Sensor: 3-D FEM Modeling(Institute of Electrical and Electronics Engineers Inc., 2024) Thayaba Nausheen, A.; Nakul Nayak, B.V.; Khanna, A.; Singh, M.Nanophotonic ring resonators have emerged as promising candidates for sensing applications due to their high sensitivity and compact footprint. In this study, we investigated a 3-D aperture-coupled plasmonic microring resonator (AC-PMRR)-cum-plasmonic spectral shaper as a temperature sensor using finite-element method (FEM). The sensor operates based on the principle of the temperature-dependent refractive index change of the surrounding medium, which modulates the resonance characteristics of the microring. The aperture coupling technique enhances the sensitivity and allows efficient excitation of localized surface plasmon resonances. We analyzed the sensing performance of the proposed device through rigorous numerical simulations. The effects of various design parameters, such as ring radius, aperture size, and coupling distance, on the sensor's performance are systematically examined. Furthermore, we explore the influence of material properties and temperature range on the sensor's sensitivity and resolution. The proposed refractive index sensor demonstrates a high sensitivity of ~0.065 nm/K, the figure of merit of ~102 RIU1, and detection accuracy of ~0.32 nm1, making it suitable for various temperature sensing applications in fields such as environmental monitoring, biomedical diagnostics, and industrial process control. © 2024 IEEE.Item Engineering Porous Silicon-Based Plasmonic Microdisk Resonator for Highly Sensitive Methanol Sensing(Institute of Electrical and Electronics Engineers Inc., 2024) Mehta, S.; Nakul Nayak, V.B.; Singh, M.This study introduces a novel application of a plasmonic microdisk resonator as a highly sensitive sensor for detecting methanol vapor. Leveraging the inherent advantages of plasmonic nanostructures, the microdisk resonator demonstrates a remarkable capability to detect minute concentrations of methanol. In this work, we modeled a novel 3-D porous-silicon (p-Si)-based hybrid plasmonic aperture-coupled microdisk resonator (HPACMR) with specific dimensions and porosity to optimize the sensitivity toward methanol vapor detection. The resonator's design incorporates a thin layer of copper on a dielectric microdisk, creating a plasmonic cavity that supports localized surface plasmon resonances. Finite element method-based simulations predict strong interactions between the resonator's plasmonic field and methanol molecules, leading to detectable shifts in the resonant frequency. By tuning the layout dimensions and p-Si properties, we achieved an altitudinous sensitivity of 569.52 nm/RIU and a Q-factor of nearly 370. The sensors' miniature footprint and potential for integration into portable devices make it an attractive candidate for field-deployable applications. © 2001-2012 IEEE.Item High-Q Plasmonic Resonator for Volatile Organic Compound Detection(Institute of Electrical and Electronics Engineers Inc., 2025) Mehta, S.; Shivaputra, S.; Ramesh, S.; Mandi, M.V.; Singh, M.A hybrid plasmonic waveguide (HPWG)-based resonator designs are studied for on-chip detection of volatile organic compounds (VOCs). The HPWG, which combines dielectric and metallic layers, significantly enhances the confinement of electromagnetic field, leading to increased interaction between the guided light and the surrounding analytes. The system achieves high spectral sensitivity and narrow linewidth by integrating multiple microring resonators in a cascaded configuration. This is critical for distinguishing small changes in the refractive index (RI) associated with different VOCs. Finite element method (FEM) simulations demonstrate the superior sensing performance of a proposed device, showing a spectral sensitivity of 469.5 nm/RIU and a quality factor (QF) of 518.75. The compact design and high sensitivity make this sensor an excellent candidate for on-chip VOC monitoring in industrial safety, as well as portable breath sensors to detect VOC biomarkers for early disease diagnosis. © IEEE. 1973-2012 IEEE.