Achieving efficient localization of white light at the nanoscale is a major challenge due to the diffraction limit, and nanoscale emitters generating light with a broadband spectrum require ...complicated engineering. Here we suggest a simple, yet highly efficient, nanoscale white-light source based on a hybrid Si/Au nanoparticle with ultrabroadband (1.3–3.4 eV) spectral characteristics. We incorporate this novel source into a scanning-probe microscope and observe broadband spectrum of photoluminescence that allows fast mapping of local optical response of advanced nanophotonic structures with submicron resolution, thus realizing ultrabroadband near-field nanospectroscopy.
In this report, we study influence of the Si (111) substrate surface preparation on the growth, electronic and optical properties of the GaN nanowires (NWs) obtained via plasma-assisted molecular ...beam epitaxy. The substrate preparation varied from bare Si (111) surface and its deliberately nitridated counterpart to growth on AlN and Ga2O3 buffer layers and Ga droplets seeding layers. Statistical data on the morphology of the synthesized arrays was obtained and analyzed. The most homogeneous NW array in terms of length distribution was obtained on AlN buffer layer. It was demonstrated that the NWs surface density drastically depends on the surface preparation method. Electrical properties of the arrays were studied via analysis of volt-ampere characteristics and optical properties were investigated with photoluminescence. The highest conductivity and optical response were obtained with AlN buffer layer.
Analytic solution of semiclassical dynamics equations of the Dicke model in a superradiant state is presented. The time dependences of the amplitudes of superradiant photonic condensate and coherent ...population of two-level atomic array in the microwave cavity prove to be expressed via Jacobi elliptic functions of real time and manifest existence of an adiabatic invariant of motion in the strongly coupled system. The periodic beatings of the photonic and atomic coherent state amplitudes are shifted in time revealing an effect of “bound luminosity,” when energy stored in the two-level system during “darkness” in the cavity is suddenly converted into photonic condensate that “illuminates” the cavity for half a period, before it plunges into “darkness” again.
We report on comparative optical studies of InAs/Al
Ga
As quantum dots (QDs) grown by molecular beam epitaxy either with or without a thin GaAs interlayer inserted between the AlGaAs barrier and InAs ...QDs. Emission properties of individual QDs are investigated by micro-photoluminescence spectroscopy using 500-nm-size etched cylindric mesa structures. The single-photon statistics of the QDs of both types, emitting in the red spectral range between 636 and 750 nm, is confirmed by the measurements of the second-order correlation function. A negligibly small exciton fine structure splitting is detected in the majority of the QDs grown with the GaAs interlayer that implies the possibility of generating pairs of entangled photons with high entanglement fidelity.
Spontaneous break down of translational invariance of Fermi-system along Matsubara's time axis may lead to emergency of a new kind of "hidden order". An exact solution is found that minimizes ...Landau-Ginzburg-Wilson (LGW) action of the fermionic system close to a usual spin density wave (SOW) instability. The solution has the form of SDW with amplitude that is analytic double-periodic function of the Matsubara and real time. This kind of order parameter behaves like a "hidden order", since, e.g. in the limit of zero temperature, T = 0 K, the state is characterized by a bound state of two antiferromagnetic SDW's propagating in the opposite directions in real space and forming "standing wave" with zero expectation value for the magnetization. There is finite energy gap between this state and lowest excited states corresponding to SDW's propagating in the opposite directions with slightly different amplitudes. Green's function of the hidden order field (HOF) is finite and periodic along Matsubara's axis, but Wick-rotated to the axis of real frequencies, it reveals periodic "chain" of second order poles. Hence, the scattering cross section of the HOF is zero in the lowest order approximation and, therefore, HOF is indeed "invisible". Despite this, HOF induces a gap in the fermionic quasiparticle spectrum at Fermi-level, and also possesses several "visible" spin-modes with discrete frequencies above a finite gap. Relevance of the picture to high-T sub()c"hidden order" and pseudo-gap state is briefly discussed.
The problem on a fluid flow in a pulsating vessel is considered in the framework of the quasi-one-dimensional hemodynamic equations. The fluid viscosity is assumed to be anisotropic; i.e., the ...viscosity coefficient depends on the flow direction. The possible solutions are studied analytically and numerically.
In this paper we demonstrate the results on selective area growth of GaP nanowires via self-catalyzed growth method using molecular beam epitaxy (MBE) technique on patterned Si(111) substrates. The ...pattern fabrication method on a base of the photolithography process over an array of microspherical lenses has been studied theoretically and then optimized in order to obtain the nanostructures with controlled morphology. It was found that the positive resist thickness corresponding to the best achievable resolution in the subwavelength region is 250 nm in case of 1.5 μm silica spheres and excitation with 365 nm LED. The silica growth mask for selective epitaxy was fabricated. The ordered array of GaP nanowires was synthesized with MBE. Large scale ordering and selectivity of the growth technique is demonstrated.
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