arXiv subjects

Arda Gulucu

Publications and source records attributed to Arda Gulucu.

4 recordsLinked to original sources

arXiv2026

Toroidal Plasmonic Nanodimers for Enhanced Near-Infrared Emission in Heterostructured InP Quantum Dots

Near-infrared (NIR) emitters operating in the 650-900 nm range are highly attractive for imaging and sensing in turbid media; however, cadmium-free InP-based quantum dots (QDs) often suffer from limited brightness due to nonradiative pathways and inefficient photon outcoupling. In particular, heterostructured InP QDs can exhibit band alignments that induce partial spatial separation of charge carriers, leading to reduced electron-hole wavefunction overlap. This modifies intrinsic recombination dynamics and enhances the sensitivity of their emission to the surrounding photonic environment. Here, we investigate silver toroidal plasmonic nanoantenna dimers (Ag TPNDs) through finite-difference-time-domain (FDTD) simulations as a geometry-tunable platform for enhancing NIR emission of heterostructured InP-based QDs. The coupled toroidal geometry supports strongly confined bonding modes that generate intense nanogap hotspots, while its resonance can be systematically tuned through the toroid aspect ratio. By spectrally aligning the antenna response with QD emission bands (675-845 nm), we achieve large Purcell enhancements together with high quantum efficiencies, demonstrating efficient conversion of enhanced decay rates into radiative emission. We further show that nanometer-scale variations in emitter-antenna separation strongly modulate the radiative rates and spectral response. These results establish toroidal plasmonic nanodimers as a topology-driven platform for controlling emission in NIR quantum emitters and for advancing NIR nanophotonic applications.

physics.optics↗

arXiv2025

Programmable Quantum Mode Switches via Plasmonic Toroidal Nanoantennae

The ability to switch and program the spectral response of quantum modes via deterministically located plasmonic nanoantennae presents opportunities for wide spectrum of applications from biosensors to quantum computing. Due to its topology, toroidal nanoantenna (TNA) focuses immense amount of three-dimensional (3D) local electric field by toroidal moment while allowing pre and post positioning around quantum emitters (QEs). Here, within local-response finite difference time domain (FDTD) simulations, we demonstrate high-contrast spectral switching of the radiative decay channel of a dipolar QE coupled to a TNA by introducing effective Lorentzian quantum objects (QOs). At optimized TNA geometries, Fano interference between the broadband plasmonic continuum and narrow quantum transitions of QOs suppresses both radiative and non-radiative decay channels near 850 nm, yielding an observable full switching that traps energy within the hybrid mode instead of re-emitting it. To show the promises of the concept, we further demonstrate systems with multiple QOs where spectral degeneracy enhances the transparency bandwidth, while detuning generates distinct minima, enabling individually addressable spectral responses. These results establish plasmonic TNAs as promising architectures for spectral detection and individual mode switching of single- or multi-QO configurations and empowers the user for the implementation of photonic processing of continuous photon sources.

physics.optics↗

arXiv2025

Optically Switchable Fluorescence Enhancement at Critical Interparticle Distances

Plasmonic nanostructures provide electric field localization to be used as a fluorescence enhancement tool for the closely located fluorophores. However, metallic structures exhibit non-radiative energy transfer at close proximity, which suppresses the boost in the photoluminescence spectrum due to inhomogeneous medium. Compensation to non-radiative losses is fundamentally restricted, therefore defining the critical interparticle distances, where the fluorescence enhancement is detectable hold utmost importance for device applications. In this work, we numerically identified the critical interparticle distances of a metal nanoparticle (MNP) and quantum emitters (QEs) with angstrom resolution by analyzing the interplay between quantum yield and non-radiative decay. By engaging a collimated light application on silver nanoparticle (AgNP) placed at a critical distance, we simulated an active fluorescence enhancement switch yielding observable 7-fold increase in fluorescence intensity. The provided free space simulation includes the complete response of AgNP with retardation and higher order multi-polar effects for which the previous analytical works fall short. While the model bridges the absorption and emission spectra via corresponding Stokes shift values and presents a general approach for the interaction of QEs and MNPs in Rayleigh regime, it can be extended to Mie regime for larger QEs and can be modified for dielectric device environment.

physics.optics↗

arXiv2024

Thickness-dependent Characteristics and Oxidation of Cadmium

In this study, the structural, electronic and vibrational properties of thinnest possible Cadmium crystal are investigated by performing first-principle calculations. Total energy optimization and dynamic stability calculations reveal that the thinnest possible crystal structure is a double-layered structure consisting of alternating layers formed by trigonal arrangements of Cd atoms. Excessive softening of optical phonons occurs as a result of structural relaxation when going from a bulk to a single layer (SL) structure. It is also shown that thinnest structure obtained from bulk Cd crystals maintains its metallic feature despite the dimensional crossover. In addition, it is predicted through calculations that the SL Cd crystal strongly interacts with oxygen and that the oxidized regions even undergo chemical transformation to form the CdO crystal. In the double-layer CdO crystal resulting from the oxidation of individual Cd layers, the layers are connected to each other with strong covalent bonds, and this structure is a semiconductor with a band gap of 2.10 eV. While the robust metallic structure of the thinnest possible Cd crystal provides flexibility in terms of its use in nanoscale applications, on the other hand, the fact that its electronic properties can be changed by oxidation is important for optoelectronic device applications.

cond-mat.mtrl-sci↗