Single-quantum emitters emit only one photon at a time, but the properties of the photon depend on how the emitter is excited. Incoherent excitation is simple and broadly used with solid-state ...emitters such as quantum dots, but does not allow direct manipulation of the quantum state. Coherent, resonant excitation on the other hand is used in pump-probe techniques to examine the quantum state of the emitter, but does not permit collection of the single-photon emission. Coherent control with simultaneous generation of photons has been an elusive goal in solid-state approaches, where, because of strong laser scattering at the detection wavelength, measurement of resonant emission has been limited to cross-polarized detection or Stokes-shift techniques. Here we demonstrate that a semiconductor quantum dot in a microcavity can be resonantly driven and its single-photon emission extracted background free. Under strong continuous-wave excitation, the dot undergoes several Rabi oscillations before emitting, which are visible as oscillations in the second-order correlation function. The quantum-dot states are therefore 'dressed', resulting in a Mollow-triplet emission spectrum. Such coherent control will be necessary for future high-efficiency sources of indistinguishable single photons, which can be used for quantum key distribution or through post-selection to generate entangled photon pairs.
The electric-field-induced evolution of the recently discovered periodic 180 degree nanostripe domain structure is predicted in epitaxial Pb(Zr0.5Ti0.5)O3 ultrathin films from first principles. This ...evolution involves (1) the lateral growth of majority dipole domains at the expense of minority domains with the overall stripe periodicity remaining unchanged, (2) the creation of surface-avoiding nanobubbles, and (3) the formation of a single monodomain state. Analogies and differences (i) with ferroelectric thin films made of BaTiO3 and (ii) with ferromagnetic thin films under magnetic field are discussed.
We show that resonance fluorescence, i.e., the resonant emission of a coherently driven two-level system, can be realized with a semiconductor quantum dot. The dot is embedded in a planar optical ...microcavity and excited in a waveguide mode so as to discriminate its emission from residual laser scattering. The transition from the weak to the strong excitation regime is characterized by the emergence of oscillations in the first-order correlation function of the fluorescence, g(tau), as measured by interferometry. The measurements correspond to a Mollow triplet with a Rabi splitting of up to 13.3 microeV. Second-order correlation measurements further confirm nonclassical light emission.
We report a comprehensive discussion of quantum interference effects due to the finite structure of neutral excitons in quantum rings and their first experimental corroboration observed in the ...optical recombinations. The signatures of built-in electric fields and temperature on quantum interference are demonstrated by theoretical models that describe the modulation of the interference pattern and confirmed by complementary experimental procedures.
•Excess barium self-limits the stoichiometry of barium titanate.•Barium titanate self-assembles when grown using co-deposition with excess barium.•Higher piezoelectric coefficients of barium after ...surface cleaning.
The growth of stoichiometric barium titanate using molecular beam epitaxy was investigated by providing excess barium during co-deposition of barium, titanium, and oxygen. X-ray photoelectron spectroscopy confirmed that excess barium accumulated at the surface as barium oxide, and that post methanol cleaning removed the barium oxide and resulted in the stoichiometry of all grown films to be that of bulk stoichiometric barium titanate. Piezoforce microscopy was used to determine the ferroelectric properties of the thin films. Results demonstrated the d33 values were equal to or better than bulk values. These results indicate that the excess barium self-limited the growth to the stoichiometry of barium titanate by transferring the excess barium to the surface as barium oxide, creating a new growth approach for barium titanate.
•Observation of the hybrid plasmon emission from the double metallic structure.•Explanation of the hybrid plasmonic effect based on the numerical simulation.•Hybrid plasmonic intensity depends on the ...excitation position and the geometry.•Plasmonic emission of the double metallic structure is wavelength dependent.
Bullseye nanostructures with different central disk diameters and numbers of concentric rings have been fabricated in Au/Ag metallic films on glass substrates by focused ion beam milling. The Au/Ag bimetallic nanoresonator is expected to provide chemical stability and outstanding plasmonic property. A novel hybrid plasmonic emission has been observed by cathodoluminescence in the scanning electron microscope. It is found that the hybrid plasmon amplitude of the bullseye structure highly depends on the excitation position. The plasmonic intensity is the maximum when the beam is located at the edge of the central disk, and it can be tuned by selecting the disk size and the number of grooves. Additionally, the finite element simulation reveals that the bimetallic bullseye structure strongly confines the optical radiation, and the electric field distribution directly relates to the emission wavelength.
We report room-temperature Raman scattering studies of nominally undoped (100) GaAs1−xBix epitaxial layers exhibiting Bi-induced (p-type) longitudinal-optical-plasmon-coupled (LOPC) modes for 0.018 ≤ ...x ≤ 0.048. Redshifts in the GaAs-like optical modes due to alloying are evaluated and are paralleled by strong damping of the LOPC. The relative integrated Raman intensities of LO(Γ) and LOPC ALO/ALOPC are characteristic of heavily doped p-GaAs, with a remarkable near total screening of the LO(Γ) phonon (ALO/ALOPC → 0) for larger Bi concentrations. A method of spectral analysis is set out which yields estimates of hole concentrations in excess of 5×1017cm−3 and correlates with the Bi molar fraction. These findings are in general agreement with recent electrical transport measurements performed on the alloy, and while the absolute size of the hole concentrations differ, likely origins for the discrepancy are discussed. We conclude that the damped LO-phonon-hole-plasmon coupling phenomena plays a dominant role in Raman scattering from unpassivated nominally undoped GaAsBi.
A high-performance 1.3 μm InAs/GaAs quantum-dot laser directly grown on Si substrates has been achieved by using InAlAs/GaAs strained-layer superlattice serving as dislocation filter layers (DFLs). ...The Si-based laser achieves lasing operation up to 111°C with a threshold current density of 200 A/cm2 and an output power exceeding 100 mW at room temperature.
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