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We theoretically investigate the simultaneous formation and stable propagation of slow optical soliton pairs in semiconductor quantum dots with a four-level biexciton-exciton cascade configuration. Owing to the destructive interference set up by two continuous wave control fields that couple to a biexciton state, the linear as well as nonlinear dispersion can be dramatically enhanced simultaneously with the absorptions of two weak probe fields being almost suppressed. These results reveal that the detrimental distortions of the two weak-pulsed probe fields due to dispersion effects can be well balanced by the self-phase modulation effect under very low input light intensity, which leads to the slow temporal optical soliton pairs with matched group velocity and amplitude. We also show that the propagation of slow optical solitons can be strongly modified by the biexciton coherence. [ABSTRACT FROM AUTHOR]

We propose and analyze an effective scheme to enhance the optical higher-order sideband generation in a three-cavity array with local parity-time (PT) symmetry. In this three-cavity configuration, a single cavity containing a quantum dot (QD) is coupled to an assisted PT-symmetric combination of two cavities. Beyond the weak-excitation approximation, we derive the analytic formulas used to determine the nonlinear coefficient of the optical second-order sideband (OSS) by employing the perturbation technique. Using experimentally achievable parameters, we identify the conditions under which the assisted PT-symmetric double-cavity system allows us to modify the transmission of the probe field and improve the efficiency of OSS generation beyond what is achievable in a loss-only QD-cavity system. We examine the influence of the PT phase transition from unbroken- to broken-PT regimes on the OSS generation. It is found that the efficiency of optical second-order sideband generation can be significantly enhanced when the assisted double-cavity system is in PT-symmetric phase, extremely in the vicinity of the transition point. The present results illustrate the potential to utilize PT-symmetric physical systems for enhancing optical higher-order sidebands and controlling optical frequency combs, as well as to guide the design of experimental implementation. [ABSTRACT FROM AUTHOR]

We propose a efficient scheme for high-precision three-dimensional (3D) atom localization via spatial interference in a generic double two-level atomic system driven by a weak probe field and three mutually perpendicular standing-wave fields. Because the spatial interference originates from the position-dependent atom-field interaction, the position information of the atom can be obtained by the measurement of the atom population. We find that the precision of 3D atom localization in volumes depends sensitively on the frequency detuning and the phase shifts associated with the standing-wave fields. Interestingly enough, we show that adjusting the frequency detuning and phase shifts can lead to a redistribution of the atoms and a significant change in the visibility of the interference pattern. As a result, the atom can be localized in volumes that are substantially smaller than a cubic optical wavelength. [ABSTRACT FROM AUTHOR]

We present a theoretical investigation of high-order-harmonic generation (HHG) via bichromatic plasmonic near fields with metal nanoparticles. Bichromatic plasmonic near fields, which depend on temporal waveform synthesis, are generated when a metallic nanoparticle subjected to a moderate-intensity (<1012W/cm²) bichromatic few-cycle pulse. By means of a windowed Fourier transform of the time-dependent acceleration, we show that the differences in energies and level crossing between the adiabatic states of a two-level Hamiltonian are responsible for the cutoff energy of harmonics. Thus, we can manipulate the adiabatic states, and consequently the HHG spectra, by means of the bichromatic plasmonic near fields. In contrast to the case of a monochromatic field alone, a significant cutoff extension can be achieved via optimization of the bichromatic few-cycle pulse. Moreover, the supercontinuum in the bichromatic field shows a higher energy spectrum along with a broader bandwidth, which is beneficial for the efficient generation of broadband-isolated ultrashort extreme ultraviolet pulses from few-cycle laser fields. [ABSTRACT FROM AUTHOR]

Considering two-level media in the array of weakly coupled nanocavities, we reveal a variety of dynamical regimes, such as diffusion, self-trapping, soliton, and breathers for the wave packets in the presence of photon tunneling processes between the next-nearest cavities. We focus our attention on the low-branch bright polariton soliton formation, due to the two-body polariton-polariton scattering processes. When detuning frequency is manipulated adiabatically, the low-branch lattice polariton localized states, i.e., soiitons and breathers evolving between photonlike and matterlike states, are shown to act as carriers for spatially distributed storage and retrieval of optical information. [ABSTRACT FROM AUTHOR]