arXiv subjects

Jaydeep K. Basu

Publications and source records attributed to Jaydeep K. Basu.

8 recordsLinked to original sources

arXiv2026

Cavity-Enhanced Activation of Radiatively Suppressed Light-Hole Exciton Emission in Colloidal Nanoplatelets

Light-hole (LH) excitons provide access to well-defined polarization and spin degrees of freedom that are central to quantum photonics and chiral light-matter interactions. Achieving LH emission is challenging because LH states are energetically unfavoured and typically relax non-radiatively. Existing strategies to access LH excitons rely on modifying the electronic band structure through strain, shape anisotropy, or piezoelectric fields, approaches that are material-specific and offer limited post-synthesis tunability. Here we demonstrate an all-photonic route to activate LH exciton emission in colloidal CdSe-CdS nanoplatelets (NPLs) using a distributed Bragg reflector (DBR) cavity, without altering the underlying band structure. In the absence of a cavity mode, the system exhibits amplified spontaneous emission from heavy-hole (HH) states without detectable LH emission at low excitation powers. By spectrally matching a cavity resonance to the LH exciton, cavity-coupled LH emission emerges at significantly lower excitation powers. Temperature-dependent spectroscopy reveals reversible switching between LH- and HH-coupled emission through exciton-cavity detuning, while polarization-resolved and spectrally resolved time-resolved photoluminescence measurements provide independent evidence distinguishing the cavity-coupled LH and HH emission channels. These findings establish cavity engineering as a general materials-level approach for accessing radiatively suppressed optical states.

physics.optics↗

arXiv2025

Origin of the Fano interference and its tunability with near-field interactions in a guided mode-resonant metasurface

Asymmetric resonances emerging from the Fano interference are a well-known phenomenon in fields like atomic physics and grating optics, and they have recently started to gain interest in artificially engineered dielectric, metallic, or composite metasurfaces and metamaterials. The guided mode-resonant metasurface belongs to this class with grating-waveguide responses and shows asymmetric resonances. Here, we have theoretically studied the origin of the resonance, finding out the root of the Fano interference. We have followed the ab initio theory derived from the Feshbach formalism for the electromagnetic scattering. We have numerically simulated the metasurface to obtain different field parameters required for the ab initio theory; in this regard, we have used the multipole decomposition of the scattering fields for the induced moments. Motivated by our recent experiments, we have used a planewave and polarized dipole sources to excite the metasurface, and studied subsequent effects, like the resonance redshift and the resonance linewidth narrowing for the metasurface. These happened due to the change of the excitation, and we have numerically quantified them. The change of the excitation source bears the novelty of the work. Thus, it helps comprehend the experimental observations qualitatively. This work could help explain and explore possibilities to observe asymmetric resonances in metasurfaces for various excitation conditions, and the key results of resonance shift and linewidth narrowing could be significant for precision applications and fundamental optical studies.

physics.optics↗

arXiv2025

Non-monotonic temperature dependence of light-matter interaction in hyperbolic metamaterial due to interplay of electron-phonon scattering

Hyperbolic metamaterials (HMM) are artificially engineered materials that are congenial for light-matter interaction studies and nanophotonic applications with the hyperbolic dispersion of light propagating through them, which offers a large photonic density of states. We have explored HMM's broadband cavity-like modes and ultrasmall mode volumes, even though the system has lossy plasmonic constituents. The light-matter interaction properties of plasmonic materials strongly depend on different internal damping mechanisms. Temperature is a macroscopic parameter that controls these internal mechanisms and is reflected in their corresponding interaction behaviors. In this work, we investigated the light-matter interaction properties of the HMM system with temperature. We studied the HMM system weakly coupled to quantum emitters. This weakly coupled system shows a non-monotonicity in its broadband absorption and the emission from near-field coupling with quantum emitters. This is determined by the interplay between the electron-phonon and the phonon-phonon scatterings occurring in the metal nanowire array, effectively providing the damping with temperature. Theoretically, we confirmed the increased presence of the phonon-phonon scattering in nanowires compared to bulk metals, which plays an instrumental role in the observed light-matter interaction effects. This study could efficiently predict the use of the HMM in optics and photonics applications, with precise tuning and availability of control parameters with temperature. Also, this study could help identify the effect of increased phonon-phonon scattering in nanostructures and explore the possibility of quantifying and applying it by optical measurements.

physics.optics↗

arXiv2025

Unraveling cavity-like modes of two-dimensional broad band hyperbolic metamaterial and their coupling to quantum emitters

Hyperbolic metamaterials (HMM) are artificially engineered materials that exhibit hyperbolic dispersion of light propagating through them. These have been extensively studied for tailoring light propagation. Most studies use an effective medium approach that is extremely useful, though it misses out on properties that can arise from the microscopic details of the HMM. In particular, the HMM can have cavity-like modes, and it is important to understand such modes and their relevance in light propagation and coupling of HMM to quantum emitters. In this work, we bring out the cavity-like modes of the silver nanowire-alumina two-dimensional HMM, which remain on top of the broad response of the HMM. These modes define the characteristic reflection spectra. The observed resonances and their widths are in good agreement with our simulations. These well-defined modes occur even though the metallic part of the HMM has Ohmic losses. Then, we present experimental results on the coupling of quantum emitters to the cavity-like modes of the HMM. We present results for both steady-state and time-resolved photoluminescence. Using these, we extract the corresponding Purcell factors for radiative rate enhancement. Theoretical analyses of the experimental data allow the determination of the cavity coupling parameters and mode volumes. These experimental results are confirmed by the FDTD calculations for the HMM mode volume. This work elucidates the pathway to precise engineering for future applications of HMM modes in strong light-matter interactions.

physics.optics↗

arXiv2023

Inhibited spontaneous emission of quantum dots weakly coupled to off resonant silver nanoplatelets and silver nanowires

Spontaneous emission (SE) rate of any light emitters directly scales with the locally available modes for photons. The emission rate can be modified, by changing the dielectric environment of light emitters. Generally cavities with modes in resonance to light emission frequency, are used to amplify the light emission rate. The Fermi golden rule predicts that if the cavity modes are offresonant to the emission frequency, then the SE rate is suppressed. In this study, we demonstrate that the SE of colloidal alloyed quantum dots is inhibited by coupling them to chemically synthesized Silver nanowires and Silver nanoplatelet systems. The silver nanoplatelet and silver nanowire plasmonic resonance modes are in ultraviolet and infrared regions of the electromagnetic spectrum. The quantum dots emit in visible region of light. This off-resonant weak coupling of emitters and cavities results in emission rate suppression and is quantified by time resolved photoluminescence (TRPL) measurements. TRPL decay profiles show that the emission rate can be suppressed by coupling self assembled quantum dot monolayers to a single silver nanoplatelet and a single silver nanowire respectively.

physics.optics↗

arXiv2022

Evaluating the transition dipole moment of quantum dots with absorption and angle resolved photo-luminescence spectroscopy

In this manuscript, the evaluation procedure of transition dipole moment (TDM) is discussed. Semiconducting Cd_{x}Zn_{1-x}Se_{y}S_{1-y} alloyed quantum dots (AQDs) are used as the two level emitting system. The AQDs are then self-assembled into monolayers by the Langmuir-Schaefer method. The TDM magnitude and orientation of AQDs are extracted from the absorption spectrum and the angle resolved Photo-luminescence emission spectrum measurements respectively. The TDM of AQDs in vacuum is evaluated as 9.07 D and the anisotropy coefficient shows that the AQD emission is isotropic.

physics.optics↗

arXiv2022

Selectively strong coupling MoS$_2$ excitons to a metamaterial at room temperature

Light emitters in vicinity of a hyperbolic metamaterial (HMM) show a range of quantum optical phenomena from spontaneous decay rate enhancement to strong coupling. In this study, we integrate monolayer Molybdenum disulfide (MoS$_2$) emitter in near field region of HMM. The MoS$_2$ monolayer has A and B excitons, which emit in the red region of visible spectrum. We find that the B excitons couple to HMM differently compared to A excitons. The fabricated HMM transforms to a hyperbolic dispersive medium at 2.13 eV, from an elliptical dispersive medium. The selective coupling of B Excitons to the HMM modes is attributed to the inbuilt field gradient of the transition. The B exciton energy lies close to the transition point of the HMM, relative to A Exciton. So, the HMM modes couple more to the B excitons and the metamaterial functions as selective coupler. The coupling strength calculations show that coupling is 2.5 times stronger for B excitons relative to A excitons. High near field of HMM, large magnitude and the in-plane transition dipole moment of MoS$_2$ Excitons, result in strong coupling of B excitons and formation of hybrid light-matter states. The measured differential Reflection and Photoluminescence spectra indicate the presence of hybrid light-matter states i.e. Exciton-Polaritons. Rabi splitting of at least 129 meV at room temperature is observed. The low temperature Photoluminescence measurement shows mode anticrossing, which is characteristic feature of hybrid states. Our results show that the HMM works as a energy selective coupler for multi-excitonic systems as MoS$_2$.

physics.optics↗

arXiv2021

Spontaneous emission dynamics of $Eu^{ 3+}$ ions coupled to hyperbolic metamaterials

Sub-wavelength nanostructured systems with tunable electromagnetic properties, such as hyperbolic metamaterials (HMMs), provide a useful platform to tailor spontaneous emission processes. Here, we investigate a system comprising $Eu^{ 3+}(NO_{3})_{3}6H_{2}O$ nanocrystals on an HMM structure featuring a hexagonal array of Ag-nanowires in a porous $Al_{2}O_{3}$ matrix. The HMM-coupled $Eu^{ 3+}$ ions exhibit up to a 2.4-fold increase of their decay rate, accompanied by an enhancement of the emission rate of the $^{ 5}D_{0}\rightarrow$ $^{ 7}F_{2}$ transition. Using finite-difference time-domain modeling, we corroborate these observations with the increase in the photonic density of states seen by the $Eu^{ 3+}$ ions in the proximity of the HMM. Our results indicate HMMs can serve as a valuable tool to control the emission from weak transitions, and hence hint at a route towards more practical applications of rare-earth ions in nanoscale optoelectronics and quantum devices.

physics.optics↗