Research Highlights

Ref: “Direct writing of room temperature polariton condensate lattice ” Ravindra Kumar Yadav, Sitakanta Satapathy, Prathmesh Deshmukh, Biswajit Datta, Addhyaya Sharma, Junsheng Chen, Matthew Y. Sfeir, Andrew Olsson, Amar H. Flood, Vinod M.Menon,NanoLetters,2024,24,16,4945-4950.URL:https://pubs.acs.org/doi/full/10.1021/acs.nanolett.4c00586

Room temperature polariton condensate lattice

Realizing lattices of exciton polariton condensates has been of much interestowing to the potential of such systems to realize analogue Hamiltonian simulators and physicalcomputing architectures. Here, we report the realization of a room temperature polaritoncondensate lattice using a direct-write approach. Polariton condensation is achieved in amicrocavity embedded with host−guest Frenkel excitons of an organic dye (rhodamine) in asmall-molecule ionic isolation lattice (SMILES). The microcavity is patterned using focused ionbeam etching to realize arbitrary lattice geometries, including defect sites on demand. The bandstructure of the lattice and the emergence of condensation are imaged using momentum-resolved spectroscopy. The introduction of defect sites is shown to lower the condensationthreshold and result in the formation of a defect band in the condensation spectrum. Thepresent approach allows us to study periodic, quasiperiodic, and disordered polaritoncondensate lattices at room temperature using a direct-write approach.

Room Temperature Weak-to-Strong Coupling and the Emergence of Collective Emission from Quantum Dots Coupled to PlasmonicArrays

Colloidal quantum dot (CQD) assemblies exhibit interesting optoelectronic properties when coupled to optical resonators ranging from Purcell-enhanced emission to the emergence of hybrid electronic and photonic polariton states in the weak and strong coupling limits, respectively. Here, experiments exploring the weak-to-strong coupling transition in CQD–plasmonic lattice hybrid devices at room temperature are presented for varying CQD concentrations. To interpret these results, generalized retarded Fano–Anderson and effective medium models are developed. Individual CQDs are found to interact locally with the lattice yielding Purcell-enhanced emission. At high CQD densities, polariton states emerge as two-peak structures in the photoluminescence, with a third polariton peak, due to collective CQD emission, appearing at still higher CQD concentrations. Our results demonstrate that CQD–lattice plasmon devices represent a highly flexible platform for the manipulation of collective spontaneous emission using lattice plasmons, which could find applications in optoelectronics, ultrafast optical switches, and quantum information science.

Ref: “Room temperature tunable coupling of single photon emitting quantum dots to localized and delocalized modes in plasmonic nanocavity array” Ravindra Kumar Yadav,Wenxiao Liu,Ran Li, Teri W. Odom, Girish S. Agarwal, and Jaydeep Kumar Basu. ACS Photonics ,2021, 8, 2, 576–584.URL: https://pubs.acs.org/doi/abs/10.1021/acsphotonics.0c01635.

Room-Temperature Coupling of Single Photon Emitting Quantum Dots to Localized and Delocalized Modes in a Plasmonic Nanocavity Array

Single photon sources, especially those based on solid state quantum emitters, are key elements in future quantum technologies. What is required is the development of broadband, high quantum efficiency, room temperature, single photon sources, which can also be tunably coupled to optical cavities, which could lead to the development of all-optical quantum communication platforms. In this regard, the deterministic coupling of single photon sources to plasmonic nanocavity arrays has a great advantage due to a long propagation length and delocalized nature of surface lattice resonances. Guided by these considerations, we report experiments on the room temperature tunable coupling of single photon emitting colloidal quantum dots (CQDs) to localized surface plasmon and surface lattice resonance modes in plasmonic nanocavity arrays. Using a time-resolved photoluminescence measurement on isolated CQD, we report the significant advantage of surface lattice resonances in realizing a much higher Purcell effect, despite the large dephasing of CQDs. We present measurements on the antibunching of CQDs coupled to these modes with g(2)(0) values in the quantum domain, providing evidence for effective cooperative behavior. We present a density matrix treatment of the coupling of CQDs to plasmonic and lattice modes enabling us to model the experimental results on Purcell factors as well as on the antibunching. We also provide experimental evidence of indirect excitation of remote CQDs mediated by the lattice modes and propose a model to explain these observations. Our study demonstrates the possibility of developing nanophotonic platforms for single photon operations and communications with broadband quantum emitters and plasmonic nanocavity arrays since these arrays can generate entanglement between spatially separated quantum emitters.

Ref: “Strongly Coupled Exciton-Surface Lattice Resonances engineer Long-Range Energy Propagation” Ravindra Kumar Yadav, Matthew Otten, Weijia Wang, Cristian L. Cortes, David J. Gosztola, Gary P. Wiederrecht, Stephen K. Gray, Teri W. Odom, and Jaydeep Kumar Basu. Nano Letters, 2020, 20, 5043-5049.URL: https://pubs.acs.org/doi/abs/10.1021/acs.nanolett.0c01236

Strongly coupled exciton–surface lattice resonances engineer long-range energy propagation

Achieving propagation lengths in hybrid plasmonic systems beyond typical values of tens of micrometers is important for quantum plasmonics applications. We report long-range optical energy propagation due to excitons in semiconductor quantum dots (SQDs) being strongly coupled to surface lattice resonance (SLRs) in silver nanoparticle arrays. Photoluminescence (PL) measurements provide evidence of an exciton-SLR (ESLR) mode extending at least 600 μm from the excitation region. We also observe additional energy propagation with range well beyond the ESLR mode and with dependency on the coupling strength, g, between SQDs and SLR. Cavity quantum electrodynamics calculations capture the nature of the PL spectra for consistent g values, while coupled dipole calculations show a SQD number-dependent electric field decay profile consistent with the experimental spatial PL profile. Our results suggest an exciting direction wherein SLRs mediate long-range interactions between SQDs, having possible applications in optoelectronics, sensing, and quantum information science.

Ref: “Observation of photonic spin-momentum locking due to coupling of achiral metamaterials and quantum dots” Ravindra Kumar Yadav, Wenxiao Liu, SRK Chaitanya Indukuri, Adarsh B. Vasista, G. V. Pavan Kumar, Girish S. Agarwal, and Jaydeep Kumar Basu. Journal of Physics: Condensed Matter, 2020, 33, 015701.

Observation of photonic spin-momentum locking due to coupling of achiral metamaterials and quantum dots

Chiral interfaces provide a new platform to execute quantum control of light-matter interactions. One phenomenon which has emerged from engineering such nanophotonic interfaces is spin-momentum locking akin to similar reports in electronic topological materials and phases. While there are reports of spin-momentum locking with combination of chiral emitters and/or chiral metamaterials with directional far field excitation it is not readily observable with both achiral emitters and metamaterials. Here, we report the observation of photonic spin-momentum locking in the form of directional and chiral emission from achiral quantum dots (QDs) evanescently coupled to achiral hyperbolic metamaterials (HMM). Efficient coupling between QDs and the metamaterial leads to emergence of these photonic topological modes which can be detected in the far field. We provide theoretical explanation for the emergence of spin-momentum locking through rigorous modeling based on photon Green's function where pseudo spin of light arises from coupling of QDs to evanescent modes of HMM.

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