Laser and Nonlinear Optics Lab

This work presents a novel method for synthesizing graphene quantum dots (GQDs) using pulsed laser irradiation in chlorobenzene, 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 & Impact-Driven Particle Extraction

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 designed a dual-functional optomechanical device for beam chopping and steering, which is inexpensive, remotely controllable, and compatible with existing optical setups.

Further, we 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).

Figure 1: (a) Schematic depicting impact dynamics of a particle-laden droplet on a hydrophobic substrate and generation of satellite droplets, (b) Optical beam chopper developed in lab, (c) Schematic showing moving meniscus-assisted template-free optothermofluidic patterning, and (d) Cover art of Soft Matter journal depicting photo-controlled liquid flows.

Angle-Tunable Polymeric Photonic Diode with 1D-Photonic Crystal

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.

Computational Materials 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 primary focus of research is on designing materials used as electrochemical catalysts for the Oxygen Reduction Reaction (ORR), Hydrogen Evolution Reaction (HER), and N₂, CO, and CO₂ reduction. Additionally, 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 maintain a high-performance computing server (Alexandra) alongside support from the NIT Calicut computing cluster (Madhava), using VASP and Wannier90 codes.

Relativistic Astrophysics Group

Our primary research interest lies in developing and performing gravitational wave (GW) searches for compact binary systems and probing the astrophysics of GW sources. We focus on searching for gravitational lensing signatures in GW signals from binary black hole mergers in LIGO/Virgo data, as well as developing and implementing tests for General Relativity (GR).

Based on detection rates by Advanced LIGO and Virgo, we expect these detectors to observe hundreds of binary black hole mergers as they achieve design sensitivities. A fraction of them undergo gravitational lensing by intervening matter distributions, causing magnification or frequency-dependent modulations. Our group develops methods to detect and infer these lensed binary black hole signals while performing high-precision tests of Einstein's theory of general relativity.

Laboratory of Theoretical & Fundamental Physics

We focus on the dynamics of physical systems involving inherent constraints, quantizing constrained Hamiltonian theories using canonical and geometrical methods. Our research covers gauge theories, reformulating gauge non-invariant theories via symplectic methodology, symmetries/supersymmetries within the BRST framework, and Supersymmetric Quantum Mechanics (SUSY QM).

In recent works, we quantized the FLPR model via modified Faddeev-Jackiw formalism, establishing off-shell nilpotent and anti-commuting (anti-)BRST symmetries, establishing the FLPR model as a toy model for Hodge theory (Eur. Phys. J. Plus 138 (2023) 12, 1107; Mod. Phys. Lett. A 39 (2024) 02, 2350186 in collaboration with Ansha S Nair and Rohit Kumar). Additionally, we derived two- and three-parameter families of potentials for the non-linear KdV equation (Phys. Lett. A 517 (2024) 129655 in collaboration with Sreedevi Mohan S, Elsa Baby, and Aradhya Shukla).

Direct Synthesis of Cobalt Sulfide Electrocatalysts for Water Splitting

Electrochemical water splitting is a sustainable method for green hydrogen production, requiring active, low-cost alternatives to noble metal catalysts like Platinum. We developed a facile low-temperature solvothermal synthesis method for direct growth of cobalt sulfide-based nanospheres (Co_xS_y) on carbon cloth (CC) as binder-free working electrodes for Hydrogen Evolution Reaction (HER) catalysts. The synthesized electrocatalyst (Co_xS_y/CC) demonstrated strong electrocatalytic performance and stability in both acidic (0.5 M H₂SO₄) and alkaline media (1 M KOH).

Template-Assisted Sol-Gel Synthesis of BiFeO₃ Hollow Tubes

Bismuth ferrite (BiFeO₃) is a perovskite material known for multifunctional applications in photocatalysis and sensing. We introduced a facile method for synthesizing BiFeO₃ hollow tubes using kapok fiber collected from Ceiba pentandra as a bio-template for the first time. The proposed method eliminates additional extraction steps from the parent template, offering a cost-effective strategy for phase-pure BiFeO₃ hollow tube synthesis.

Photonic Materials & Devices Laboratory (PMDL)

Metamaterials and Photonic Structure Laboratory (MSPL)

We investigate electromagnetic wave phenomena in engineered structures at THz and microwave frequencies. Key achievements include Talbot metasurfaces, energy harvesting metasurfaces (2.44 GHz), cross-polarization metasurfaces, and space-coiled photonic structures. Lab features CST Studio Suite, MEEP, MPB solvers, and a UV lithography unit.

Cosmology & Epoch of Reionization

Focuses on the Epoch of Reionization—the period when early stars and galaxies formed. Recent publications in Nature Astronomy (doi:10.1038/s41550-023-02057-y) and MNRAS (doi:10.1093/mnras/stad3317) exploring early Universe radio signals and exotic dark matter models gained international media attention.

Quantitative Measurement of Atmospheric Trace Gases

Researchers at the Applied Optics and Instrumentation Laboratory (AOI) developed a high-accuracy instrument measuring tropospheric trace gases, specifically Nitrate radicals (NO₃). Deployed at Palayam Bus Terminal with Calicut Corporation's assistance, the device successfully pinpointed NO₃ radical presence formed via NO₂ and O₃ reactions, tracking vehicular exhaust pollution levels in urban settings.