The quest for an integrated quantum optics platform has motivated the field of semiconductor quantum dot research for two decades. Demonstrations of quantum light sources, single photon switches, ...transistors and spin-photon interfaces have become very advanced. Yet the fundamental problem that every quantum dot is different prevents integration and scaling beyond a few quantum dots. Here, we address this challenge by patterning strain via local phase transitions to selectively tune individual quantum dots that are embedded in a photonic architecture. The patterning is implemented with in operando laser crystallization of a thin HfO
film 'sheath' on the surface of a GaAs waveguide. Using this approach, we tune InAs quantum dot emission energies over the full inhomogeneous distribution with a step size down to the homogeneous linewidth and a spatial resolution better than 1 µm. Using these capabilities, we tune multiple quantum dots into resonance within the same waveguide and demonstrate a quantum interaction via superradiant emission from three quantum dots.
Commonly observed variations in photoluminescence (PL) spectra of crystalline organic semiconductors, including the appearance or enhancement of certain PL bands, are shown to originate from a small ...amount of structural disorder (e.g., amorphous inclusions embedded in a crystal), rather than be necessarily related to chemical impurities or material oxidation. For instance, in rubrene, a minute amount of such disorder can lead to the appearance of a dominant PL band at 650 nm as a result of triplet excitons captured and fused at these sites, with a subsequent emission from the amorphous phase.
Kelvin probe force microscopy measurements on rubrene single crystals partially coated with fluorinated and non‐fluorinated SAM derivatives are employed to determine the SAM‐induced surface ...potentials caused by an interfacial charge‐transfer doping process resulting in an interface dipole. The surface potential and topographic information in turn allow calculation of the effective intramolecular electric fields and carrier densities due to doping in the SAM‐modified rubrene crystals.
We demonstrate strong exciton–plasmon coupling in silver nanodisk arrays integrated with monolayer MoS2 via angle-resolved reflectance microscopy spectra of the coupled system. Strong exciton–plasmon ...coupling is observed with the exciton–plasmon coupling strength up to 58 meV at 77 K, which also survives at room temperature. The strong coupling involves three types of resonances: MoS2 excitons, localized surface plasmon resonances (LSPRs) of individual silver nanodisks and plasmonic lattice resonances of the nanodisk array. We show that the exciton–plasmon coupling strength, polariton composition, and dispersion can be effectively engineered by tuning the geometry of the plasmonic lattice, which makes the system promising for realizing novel two-dimensional plasmonic polaritonic devices.
The manipulation of light-matter interactions in two-dimensional atomically thin crystals is critical for obtaining new optoelectronic functionalities in these strongly confined materials. Here, by ...integrating chemically grown monolayers of MoS2 with a silver-bowtie nanoantenna array supporting narrow surface-lattice plasmonic resonances, a unique two-dimensional optical system has been achieved. The enhanced exciton–plasmon coupling enables profound changes in the emission and excitation processes leading to spectrally tunable, large photoluminescence enhancement as well as surface-enhanced Raman scattering at room temperature. Furthermore, due to the decreased damping of MoS2 excitons interacting with the plasmonic resonances of the bowtie array at low temperatures stronger exciton–plasmon coupling is achieved resulting in a Fano line shape in the reflection spectrum. The Fano line shape, which is due to the interference between the pathways involving the excitation of the exciton and plasmon, can be tuned by altering the coupling strengths between the two systems via changing the design of the bowties lattice. The ability to manipulate the optical properties of two-dimensional systems with tunable plasmonic resonators offers a new platform for the design of novel optical devices with precisely tailored responses.
Active control of light-matter interactions in semiconductors is critical for realizing next generation optoelectronic devices with real-time control of the system’s optical properties and hence ...functionalities via external fields. The ability to dynamically manipulate optical interactions by applied fields in active materials coupled to cavities with fixed geometrical parameters opens up possibilities of controlling the lifetimes, oscillator strengths, effective mass, and relaxation properties of a coupled exciton–photon (or plasmon) system. Here, we demonstrate electrical control of exciton–plasmon coupling strengths between strong and weak coupling limits in a two-dimensional semiconductor integrated with plasmonic nanoresonators assembled in a field-effect transistor device by electrostatic doping. As a result, the energy-momentum dispersions of such an exciton–plasmon coupled system can be altered dynamically with applied electric field by modulating the excitonic properties of monolayer MoS2 arising from many-body effects. In addition, evidence of enhanced coupling between charged excitons (trions) and plasmons was also observed upon increased carrier injection, which can be utilized for fabricating Fermionic polaritonic and magnetoplasmonic devices. The ability to dynamically control the optical properties of a coupled exciton–plasmonic system with electric fields demonstrates the versatility of the coupled system and offers a new platform for the design of optoelectronic devices with precisely tailored responses.
A strong modification of the electronic properties of solution‐processable conjugated polythiophenes by self‐assembled silane molecules is reported. Upon bulk doping with hydrolized fluoroalkyl ...trichlorosilane, the electrical conductivity of ultrathin polythiophene films increases by up to six orders of magnitude, reaching record values for polythiophenes: (1.1 ± 0.1) × 103 S cm−1 for poly(2,5‐bis(3‐tetradecylthiophen ‐2‐yl)thieno3,2‐bthiophene) (PBTTT) and 50 ± 20 S cm−1 for poly(3‐hexyl)thiophene (P3HT). Interband optical absorption of the polymers in the doped state is drastically reduced, making these highly conductive films transparent in the visible range. The dopants within the porous polymer matrix are partially crosslinked via a silane self‐polymerization mechanism that makes the samples very stable in vacuum and nonpolar environments. The mechanism of SAM‐induced conductivity is believed to be based on protonic doping by the free silanol groups available within the partially crosslinked SAM network incorporated in the polythiophene structure. The SAM‐doped polythiophenes exhibit an intrinsic sensing effect: a drastic and reversible change in conductivity in response to ambient polar molecules, which is believed to be due to the interaction of the silanol groups with polar analytes. The reported electronic effects point to a new attractive route for doping conjugated polymers with potential applications in transparent conductors and molecular sensors.
Doping conjugated polythiophenes with silane‐based molecules capable of forming self‐assembled monolayers results in an increase in the electrical conductivity by up to six orders of magnitude. Additionally, the interband optical absorption becomes significantly reduced, making the polymer films transparent in the visible range. These results point to a new attractive route for doping conjugated polymers with potential applications in transparent conductors and molecular sensors.
The interaction of quantum systems with mechanical resonators is of practical interest for applications in quantum information and sensing and also of fundamental interest as hybrid quantum systems. ...Achieving a large and tunable interaction strength is of great importance in this field as it enables controlled access to the quantum limit of motion and coherent interactions between different quantum systems. This has been challenging with solid state spins, where typically the coupling is weak and cannot be tuned. Here we use pairs of coupled quantum dots embedded within cantilevers to achieve a high coupling strength of the singlet–triplet spin system to mechanical motion through strain. Two methods of achieving strong, tunable coupling are demonstrated. The first is through different strain-induced energy shifts for the two QDs when the cantilever vibrates, resulting in changes to the exchange interaction. The second is through a laser-driven AC Stark shift that is sensitive to strain-induced shifts of the optical transitions. Both of these mechanisms can be tuned to zero with electrical bias or laser power, respectively, and give large spin-mechanical coupling strengths.
We study exciton–plasmon coupling in two-dimensional semiconductors coupled with Ag plasmonic lattices via angle-resolved reflectance spectroscopy and by solving the equations of motion (EOM) in a ...coupled oscillator model accounting for all the resonances of the system. Five resonances are considered in the EOM model: semiconductor A and B excitons, localized surface plasmon resonances (LSPRs) of plasmonic nanostructures, and the lattice diffraction modes of the plasmonic array. We investigated the exciton–plasmon coupling in different 2D semiconductors and plasmonic lattice geometries, including monolayer MoS2 and WS2 coupled with Ag nanodisk and bowtie arrays and examined the dispersion and line shape evolution in the coupled systems via the EOM model with different exciton–plasmon coupling parameters. The EOM approach provides a unified description of the exciton–plasmon interaction in the weak, intermediate, and strong coupling cases with correctly explaining the dispersion and lineshapes of the complex system. This study provides a much deeper understanding of light–matter interactions in multilevel systems in general and will be useful to instruct the design of novel two-dimensional exciton–plasmonic devices for a variety of optoelectronic applications with precisely tailored responses.
We demonstrate strong exciton-plasmon coupling in silver nanodisk arrays integrated with monolayer MoS sub(2) via angle-resolved reflectance microscopy spectra of the coupled system. Strong ...exciton-plasmon coupling is observed with the exciton-plasmon coupling strength up to 58 meV at 77 K, which also survives at room temperature. The strong coupling involves three types of resonances: MoS sub(2) excitons, localized surface plasmon resonances (LSPRs) of individual silver nanodisks and plasmonic lattice resonances of the nanodisk array. We show that the exciton-plasmon coupling strength, polariton composition, and dispersion can be effectively engineered by tuning the geometry of the plasmonic lattice, which makes the system promising for realizing novel two-dimensional plasmonic polaritonic devices. Keywords: MoS sub(2); plasmonic lattice; strong coupling; polariton; plexciton
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