We discuss the dynamics of a three-level V-type atom driven simultaneously by a cavity photon and microwave field by examining the atomic population evolution. Owing to the coupling effect of the cavity photon, periodical oscillation of the population between the two upper states and the ground state takes place, which is the well-known vacuum Rabi oscillation. Meanwhile, the population exchange between the upmost level and the middle level can occur due to the driving action of the external microwave field. The general dynamic behavior is the superposition of a fast and a slow periodical oscillation under the cooperative and competitive effect of the cavity photon and the microwave field. Numerical results demonstrate that the time evolution of the population is strongly dependent on the atom-cavity coupling coefficient g and Rabi frequency Ωe that reflects the intensity of the external microwave field. By modulating the two parameters g and Ωe, a large number of population transfer behaviors can be achieved.
We numerically demonstrate a novel ultra-broadband polarization-independent metamaterial perfect absorber in the visible and near-infrared region involving the phase-change material Ge_2Sb_2Te_5(GST).The novel perfect absorber scheme consists of an array of high-index strong-absorbance GST square resonators separated from a continuous Au substrate by a low-index lossless dielectric layer(silica)and a high-index GST planar cavity.Three absorption peaks with the maximal absorbance up to 99.94% are achieved,owing to the excitation of plasmon-like dipolar or quadrupole resonances from the high-index GST resonators and cavity resonances generated by the GST planar cavity.The intensities and positions of the absorption peaks show strong dependence on structural parameters.A heat transfer model is used to investigate the temporal variation of temperature within the GST region.The results show that the temperature of amorphous GST can reach up to 433 K of the phase transition temperature from room temperature in just 0.37 ns with a relatively low incident light intensity of 1.11×10~8W∕m^2,due to the enhanced ultra-broadband light absorbance through strong plasmon resonances and cavity resonance in the absorber.The study suggests a feasible means to lower the power requirements for photonic devices based on a thermal phase change via engineering ultra-broadband light absorbers.
High-sensitivity and broad bandwidth photo-detector devices are important for both fundamental studies and high-technology applications. Here, by using three-dimensional （3D） finite-difference time-domain simulation, we design an optimized 3D multi-layer gold nano-antenna to enhance the near-infrared （NIR） absorption of germanium nanoparticles. The key ingredient is the simultaneous presence of multiple plasmonic resonance modes with strong light-harvesting effect that encompass a broad bandwidth of germanium absorption band. The simulation results show more than two orders of magnitude enhanced absorption efficiency of gernanium around 1550 nm. The design opens up a promising way to build high-sensitivity and broad bandwidth NIR photo-detectors.
Excitation of surface plasmon polaritons（SPPs） propagating at the interface between a dielectric medium and a silver thin film by a focused Gaussian beam in a classical Kretschmann prism setup is studied theoretically. We find that the center of the transmitted Gaussian evanescent wave has a giant lateral shift relative to the incident Gaussian beam center for a wide range of incident angle and Gaussian beam wavelength to excite SPPs, which can be more than two orders of magnitude larger than the silver film thickness. The phenomenon is closely related with the conventional Goos–Hnchen effect for total internal reflection of light beam, and it is called the transmission Goos–Hnchen shift. We find that this lateral shift depends heavily on the excitation wavelength, incident angle, and the silver layer thickness. Finite-difference time-domain simulations show that this transmission Goos–Hnchen shift is induced by a unique dynamical process of excitation, transport, and leakage of SPPs.
The control and application of surface plasmons （SPs）, is introduced with particular emphasis on the manipulation of the plasmonic wavefront and light-matter interaction in metallic nanostructures. We introduce a direct design methodology called the surface wave holography method and show that it can be readily employed for wave-front shaping of near-infrared light through a subwavelength hole, it can also be used for designing holographic plasmonic lenses for SPs with complex wavefronts in the visible band. We also discuss several issues of light-matter interaction in plasmonic nanostructures. We show theoretically that amplification of SPs can be achieved in metal nanoparticles incorporated with gain media, leading to a giant reduction of surface plasmon resonance linewidth and enhancement of local electric field intensity. We present an all-analytical semiclassical theory to evaluate spaser performance in a plasmonic nanocavity incorporated with gain media described by the four-level atomic model. We experimentally demonstrate amplified spontaneous emission of SP polaritons and their amplification at the interface between a silver film and a polymer film doped with dye molecules. We discuss various aspects of microscopic and macroscopic manipulation of fluorescent radiation from gold nanorod hybrid structures in a system of either a single nanoparticle or an aligned group of nanoparticles. The findings reported and reviewed here could help others explore various approaches and schemes to manipulate plasmonic wavefront and light-matter interaction in metallic nanostructures for potential applications, such as optical displays, information integration, and energy harvesting technologies.
