Laser and nonlinear optics lab

Impact of Tamm Plasmon Structures on Fluorescence and Optical Nonlinearity of Graphene Quantum Dots  by Hasana Jahan Elamkulavan, Nikhil Puthiya Purayil, Sanjay Subramaniam, and Chandrasekharan Keloth, 

This paper was published in Nature Scientific Reports in 2024. 

This work presents a novel method for synthesizing graphene quantum dots (GQDs) using pulsed laser irradiation in chlorobenzene, which is highlighted as a significant advancement in the field. The study also presents novel insights into how Tamm plasmon structures can modulate the optical properties of GQDs, focusing on tuning and enhancing fluorescence and optical nonlinearity. This work provides a promising approach for developing advanced photonic devices and sensors through tailored light-matter interactions, opening up new possibilities for improving the performance of quantum dot-based systems via engineered plasmonic structures.

Figure 1: a) Laser Ablation Synthesis of GQDs, b) Fabricated Photonic Crystal Structures, c) Cross-section SEM image of the TPC, d) Reflectance Spectra of DBR and TPC, e) Angular Dispersion of the TPC, f) Simulated Electric Field Distribution in the TPC, g) NLO Properties Showing Enhancement and Optical limiting and h) PL Properties Showing the Tuning of Fluorescence.

Optically Directed Colloidal Assembly and Impact-Driven Particle Extraction from Droplet-Based Systems

Optically controlled assembly of suspended particles from evaporating sessile droplets is an emerging method for on-demand particle patterning on solid substrates. We demonstrated a simple light-directed patterning of gold (Au) nanoparticles using thermoplasmonically controlled liquid flow. We successfully applied the developed strategy for realizing a closely packed hybrid particle assembly with Au and polystyrene (PS) particles, enhancing evaporative lithography for programmable nanoparticle patterning (Langmuir 38, 2003-2013, 2022). Additionally, we introduced a novel approach that combines light-induced Marangoni flow and vertical lifting for precise Au nanoparticle patterning without photomasks or templates (Langmuir 40, 12276–12287, 2024). We demonstrated the applicability of the developed plasmonically active surface for the large-area parallel manipulation of non absorbing microparticles based on optothermoconvective flow. Next, we have designed a dual-functional optomechanical device for beam chopping and steering, which is inexpensive, remotely controllable, and compatible with existing optical setups.

Further, we have introduced a simple and efficient strategy for producing both pristine liquid marbles (LMs) and Janus liquid marbles (JLMs) in the volume range of 200 nL to 18 μL (Langmuir 36, 15396-15402, 2020). The method is based on the impact of a liquid drop on a particle bed at a Weber number of ∼55, which generates two daughter droplets that are converted into LMs/JLMs within a few tens of milliseconds (∼50 ms). The process allows the simultaneous production of JLMs and LMs with volume control. We extend this approach for the continuous and fast production of nearly identical JLMs with ultra-low volume and enhanced mechanical stability, which could improve the capabilities of open-surface microfluidic applications (Langmuir 38, 11743-11752, 2022). Furthermore, we created an isothermal, additive-free particle extraction method using droplet impact-driven flows, achieving 90% extraction efficiency in milliseconds (Physics of Fluids 36, 012014, 2024).

The above research works were conducted by Farzeena C, Ragisha C M, Lekshmi B S, and B Suryasaradhi under the guidance of Dr. Subramanyan Namboodiri Varanakkottu at the Department of Physics, NIT Calicut.

Figure 1: (a) Schematic depicting the impact dynamics of a particle-laden droplet on a hydrophobic substrate and the generation of particle-enriched satellite droplet, (b) the optical beam chopper developed in our lab, (c) schematic showing the moving meniscus-assisted template-free optothermofluidic nanoparticle patterning and (d) cover art of the Soft Matter journal depicting the photo-controlled liquid flows in colloidal dispersions.

Angle-tunable polymeric photonic diode with 1D-photonic crystal for enhanced light control

Integrated optical circuits depend on optical diodes for passive nonreciprocal light transmission. The realization of optical diode action remains a significant challenge in nanophotonics, with conventional approaches often relying on non-compact and expensive magneto and electro-optic isolators. We have made an angle-tunable polymeric photonic diode with enhanced light control by integrating it with a 1D photonic crystal. The diode's non-reciprocity can be controlled by changing the incident light angle. In contrast to earlier diodes employing this principle, this diode architecture offers a simplified fabrication process, exhibits a compact footprint, and eliminates the need for a liquid phase. Our structure exhibits a nonreciprocity factor of ∼12.5 dB, achieved through a facile and cost-effective fabrication method. This promising combination makes this system a potential candidate for developing compact photonic integrated devices. The work is recently published in Journal of Materials Chemistry C. The work was carried out under the guidance of Dr. C. S. Suchand Sangeeth and Prof. Chandrasekharan K.

Computational Material Science Lab

In the Computational Materials Science Lab, we focus on understanding and predicting the properties of materials through first principles based atomistic modeling using Density Functional Theory (DFT). The main focus of research is on designing materials used as electrochemical catalysts for the Oxygen Reduction Reaction (ORR), Hydrogen Evolution Reaction (HER), and N­_2, CO, CO₂ reduction. Along with that we have recently started investigating novel quantum materials like Heusler alloys, topological insulators, Weyl and Dirac semimetals, for spintronic applications, using tight binding models. We have a high performance computing server Alexandra in our research group for our computations, besides support from the NIT Calicut computing cluster Madhava. Computations are performed using VASP and Wannier90 codes. Currently, five research scholars, one principal investigator (WISE-KIRAN project) and one TARE fellow are members of this research group, which is led by Prof. Raghu Chatanathodi.

Relativistic Astrophysics Group (PI: Haris M K)

Our primary research interest is in developing and performing gravitational wave (GW) searches for compact binary systems and probing the astrophysics of the GW sources.  At present we are focusing on two wide areas of gravitational wave astronomy; searching for gravitational lensing signatures in GW signals from binary black hole mergers in LIGO/Virgo data and development and implementation of tests of  general theory of relativity.

Based on the rate of detections by Advanced LIGO and Virgo, we expect these detectors to observe hundreds of binary black hole mergers as they achieve their design sensitivities. A small fraction of them can undergo gravitational lensing by intervening matter distributions, resulting in lensing signatures in the signal. If the size of the lenses are big enough, the lensing process magnifies/de-magnifies these GW signals without affecting their frequency profiles. Smaller lenses cause frequency dependent modulations in the signal.  We work on developing  methods for the detection and inference of such lensed binary black hole signals.

The detection of gravitational waves (GW) by the LIGO-Virgo network marked a turning point in astronomy, offering a new way to study the universe through the ripples in spacetime. These observations, particularly those from merging black holes and neutron stars, provided unprecedented opportunities to test Einstein’s general theory of relativity (GR) with great precision. While GR has consistently held up under scrutiny, researchers are always searching for potential deviations. Being part of LIGO-Virgo collaboration, our group is actively involved in developing and performing tests of general relativity using gravitational wave data.

Laboratory of Theoretical & Fundamental Physics

We focus on the study of the dynamics of physical systems involving inherent constraints. Our investigations entail quantizing the constraint Hamiltonian theories by utilizing canonical and geometrical methods. We primarily focus on the investigation of gauge theories. We are also interested in the reformulation of gauge non-invariant theories into gauge theories through the symplectic methodology. The other themes of research comprise the studies of (i)- various aspects of symmetries and supersymmetries of field theories within the BRST framework - which enables the analysis of physical systems at the quantum level and (ii)- Supersymmetric Quantum Mechanics (SUSY QM).

In our recent works, we have quantized the FLPR model in the framework of modified Faddeev-Jackiw formalism. We also deduced gauge symmetries and established the off-shell nilpotent and absolutely anti-commuting (anti-)BRST symmetries. Further, we employed supervariable approach to derive and elucidate the geometrical origin and interpretation of (anti-)BRST and (anti-)co-BRST symmetries. Moreover, by unfolding all the hidden symmetries, we established the FLPR model as a toy model for the Hodge theory. These works (Eur. Phys. J. Plus 138 (2023) 12, 1107 and Mod. Phys. Lett. A 39 (2024) 02, 2350186) are done in collaboration with Ansha S Nair and Rohit Kumar.

We found the two- and three-parameter dependent isospectral deformation of the reflectionless potential using scaling methodology. We have also illustrated that the scaling deformation ends up in translation deformation and explicitly pointed out how these two methods converge. Further, we have shown that the generated two- and three-parameter families of potential are the solutions to the non-linear KdV equation. This work (Phys. Lett. A 517 (2024) 129655) is done in collaboration with Sreedevi Mohan S, Elsa Baby and Aradhya Shukla. This group is led by Dr. Saurabh Gupta.

Electrochemical water splitting is a sustainable method for green hydrogen production, but requires highly active and low-cost alternatives to the traditional expensive noble metal-based catalysts such as Platinum. Hitherto, the search for such alternative electrocatalysts with reliable stability has not been fulfilled. Also, many state-of-the-art synthesis methods are suitable for laboratory conditions, laborious and require expensive synthesis facilities. Here, we have developed a facile low-temperature solvothermal synthesis method for the direct growth of cobalt sulfide-based nanospheres (Co_xS_y) on carbon cloth (CC) as binder-free and self-standing working electrodes for direct applications as efficient HER catalysts. The as-synthesized electrocatalyst materials (Co_xS_y/CC) showed good electrocatalytic performance with reliable stability for HER in both acidic (0.5 M H₂SO₄) and alkaline media (1 M KOH). The synthesis method followed in this work can be effectively extended to other metal sulfides as well to obtain more efficient HER catalyst materials for future needs.

Template assisted sol-gel synthesis of BiFeO₃ hollow tubes: Introducing kapok fiber as a bio-template

Bismuth ferrite (BiFeO₃) is a perovskite material well known for its multifunctional properties and related applications in photocatalysis and sensing. In this work, we introduced a facile method for the synthesis of BiFeO₃ hollow tubes using the sol-gel method, where kapok fiber collected from Ceiba pentandra is used as a biotemplate for the first time. The structural analysis was carried out using XRD and Raman analysis, whereas the formation of hollow tube morphology was confirmed with the help of FESEM analysis. The complete decomposition of the kapok fiber template during the annealing process was confirmed with the help of Fourier transform infrared spectroscopy. The XRD analysis indicated that monitoring both the annealing pathway and the final annealing temperature is pivotal in attaining the formation of phase pure BiFeO₃. The proposed method eliminates the requirement for additional procedures for extracting the synthesized hollow tubes from the parent template, in addition to providing a less expensive strategy for the synthesis of BiFeO₃ hollow tubes. The experiment was guided by Dr. Maneesh Chandran, Department of Physics, NIT Calicut. This was published in Materials Today Communications. 

Prof. Aji A. Anappara (Photonic Materials and Devices Laboratory)

Self-powered photodetectors on paper substrates for UV-vis-NIR detection

Self-powered photodetectors are devices that convert radiant energy to electrical response (voltage or current) without the need for an external power source or battery for their operation. These devices have a wide range of applications across various fields such as environmental monitoring, smart lighting, wearable technology, Internet of Things (IoT) devices, security and surveillance, biomedical devices as well as transportation; owing to their unique traits of energy autonomous operation, dark-current suppression, wide-band sensitivity and ambient-temperature operation. Recently, in the Photonic Materials and Devices Laboratory (NITC), we have designed and fabricated flexible, paper-based photodetectors which can detect wavelengths covering UV-vis-NIR ranges of electromagnetic spectrum. These devices can operate at ambient conditions of temperature and humidity, without the requirement of external biasing. This work was guided by Prof. Aji A. Anappara, and was done as a part of the doctoral thesis of Ms. Varsha Sharma (P210011PH), and was granted multiple Indian patents (Patent No.: 532661, granted on 12/04/2024; Patent No.: 529570, granted on 21/03/2024; Patent No.: 551014, granted on 25/09/2024 and, Patent No.: 541052, granted on 06/06/2024).

Event-responsive, retinomorphic sensors for light-intensity detection

Event-driven optical sensors respond to changes in light intensity and can selectively sense specific events or stimuli, much like how human eyes process visual information. These are devices designed to mimic the functionality of biological retinas. By responding to specific events, with fast-response, making them ideal for real-time monitoring or remote operations, even without the requirement of a battery or external bias. In the Photonic Materials and Devices Laboratory (NITC), we have realized event-responsive retinomorphic sensors which can operate at room-temperature. The design was developed by Prof. Aji A. Anappara and was fabricated by Ms. Varsha Sharma (P210011PH) as a part of her Ph.D. research. The work was granted an Indian Patent No.: 541052 (granted on 06/06/2024). In NITC, we have developed zero-bias, retinomorphic photodetectors exclusively using all-edible materials as well; the architecture and working are published as an Indian Patent (Appl. No.: 202441029524, published on 19/04/2024).

Dr. Natesan Yogesh: Metamaterials and Photonic Structure Laboratory (MSPL)

The metamaterials and photonic structure laboratory (MSPL) was established in 2023 based on the SERB-SRG research grant at the Department of Physics, NIT Calicut. We investigate the electromagnetic wave phenomena in artificially engineered structures such as metamaterials and photonic crystals at terahertz (THz) and microwave frequencies. Some of our research interests include 3-D THz metamaterials, metasurfaces for energy harvesting, polarization and confinement applications. Our lab is equipped with various electromagnetic solvers (CST Studio Suite, MPB and MEEP (Open sources)) and a UV lithography unit (under procurement) for metasurface fabrication. We actively collaborate with the Delhi light source facility (IUAC), Microwave and THz substrate-making groups, IIT Madras and Shenzhen University.

Some of the significant results of our lab include the realization of Talbot metasurface for polarization-assisted focusing functionality, Electromagnetic energy harvesting metasurface at 2.44 GHz, Cross-polarization metasurface for dielectric sensing, light-confinement space-coiled photonic structures, Asymmetric reflection in tri-layered metasurface and coded metasurface for dark field creations. Our group participated in the PIERS Chengdu China Conference and published a total of 10 conference proceedings technical papers.

Research Scholars: 1. R. Meena (zero-refractive index metamaterials) 2. Rishin Chandran (chiral spatial-modulated chiral metasurfaces)

M.Sc Project Students: Gopika (Fano metasurface-2023), Priyankar (3D Metamaterials-2023), Vincent Shanto (Asymmetric Reflection-2024), Aravind (Coded Metasurface for dark field trap-2024), Jerin(THz Biosensor-on going), Gopika(Perovskites Metamaterials-On going), Febina (Non-Hermitian Metasurface-On going), Aneena(Bio-inspired Metasurface-On going)

B.Tech Students: Abijith K Reju (Talbot Metasurface-2023), Abhishek (Graphene Photonics-2023), Aditya (Metasurface cross-polarizers-2023), Akshay (Metasurface cross-polarizers and Non-Moire Tiles-2023), Abdual Varis, Amogh Suseelan and Arjun (Electromagnetic Energy Harvesting Metasurface-2023 SIP)

Dr. Rajesh Mondal's research focuses on the Epoch of Reionization, the period when the first stars and galaxies formed. He builds models to understand these early objects and the surrounding medium and explores how a specific radio signal can be used to probe them. This research has the potential to unlock mysteries in astrophysics, cosmology, and even fundamental physics. His recent Nature Astronomy paper on the Dark Ages (https://doi.org/10.1038/s41550-023-02057-y) and a paper on exotic dark matter models (https://doi.org/10.1093/mnras/stad3317) have gained significant media attention. • Jerusalem Post • Phys.org • EurekAlert • ts2.space • Universe Today • Mirage News • News Beezer • Bharat Times • Tel Aviv University • israeleconomico • heise online • News Space • Ynet News • HaYadAn • Twitter: Nature Astronomy"

Quantitative measurement of atmospheric trace gases with high accuracy.

Researchers of Applied Optics and Instrumentation laboratory (AOI), Department of Physics, NIT- Calicut developed an instrument that can measure the tropospheric trace gases, especially Nitrate radical (NO3 radical) with high accuracy. The instrument was designed and developed in AOI lab and was deployed in the heart of Calicut city at Palayam Bus terminal, with the help of Calicut Corporation. The experiment's success was marked by pin pointing the presence of NO3 radical in Calicut city, which is formed in the atmosphere by the chemical reaction of tropospheric Nitrogen dioxide (NO2) and O3 (Ozone). The key source of NO2 in the city is from vehicle exhaust and the presence of NO3 indicates that the pollution from the vehicle exhaust is high in the city. By deploying the instrument in the urban area, the researchers proved that the technique used behind the instrument could be used efficiently for the accurate monitoring of other trace gas species too, that have far reaching impact on both climate and human health. The experiment was carried out under the guidance of Prof.M.K.RaviVarma, Department of Physics, NIT Calicut. Arun R., Suhail Kuttoth, Sherya Joshy, Shebin John, Aishwarya S. and Anoop P. were the researchers who worked behind the development and deployment of this instrument.

The specific field measurement and the results appeared in the regional newspaper Mathurbhumi, Dt. 21-12-2018. Please refer to the following link for online version of the news.
https://www.mathrubhumi.com/technology/news/new-spectroscope-system-to-measure-pollution--1.3412111