Photonic Band Gap Materials: Light Control at Will




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Modulating excitonic spin and energy transfer in semiconductor QDs by using exciton-plasmon interaction and exciton-Mn2+ exchange



Qu-Quan Wang*

Department of Physics, Wuhan University, Wuhan 430072, P. R. China,

* Email: qqwang@whu.edu.cn


Abstract


We theoretically investigated exciton coherent dynamics in the hybrid complex composed of a semiconductor quantum dot (SQD) and an Au nanorod (NR). For the anisotropic SQD, in the resonance of longitudinal SP of Au NR, the polarization ratio P(t) = [ρyy(t) - ρxx(t)] / [ρyy(t) + ρxx(t)] increases from 0.22 to 0.99 during the excitation due to the efficient enhancement of Rabi frequency of the transition between |y and vacuum states, and decreases from 0.02 to -0.92 after the excitation pulse due to the enhancement of decay rate of the |y state. This offers an approach to modulate the dynamic polarization ratio of radiative emissions of SQDs [1].

We experimentally investigated the exciton-plasmon interactions between SQDs and silver nanoparticle antenna. Strong enhancement of PL and highly efficient plasmon-assisted Förster resonant energy transfer (FRET) between CdSe/ZnS QDs are demonstrated. The optimized PL ratio of acceptor-to-donor increases to as high as 13.6 and the PL enhancement of acceptor QDs reaches 21.2 [2].

Silver nanorings that possess singly twinned crystals and a circular cross section were fabricated via a reductive reaction solution. By lighting up the multipolar dark plasmons with slanted illumination, the silver nanoring exhibits unique focused scattering and large local-field enhancement. Strong exciton-plasmon interactions occurred between a monolayer of CdSe/ZnS SQDs and a single silver nanoring antenna at the “hot spots” located at the cross points of the incident plane and nanoring; the position of these spots are tunable by adjusting the incidence angle of illumination [3]. Theoretical analysis shows that the Ag nanoring could be used to amplify propagating surface plasmons [4].


References

(1) M. T. Cheng, S. D. Liu, and Q. Q. Wang, “Modulating emission polarization of semiconductor quantum dots through surface plasmon of metal nanorod” Appl. Phys. Lett. 92, 162107 (2008).

(2) “Multipole-Plasmon-Enhanced Förster Energy Transfer between Semiconductor Quantum Dots via Dual-Resonance Nanoantenna Effects”. Submitted to ACS Nano.

(3) H. M. Gong, L. Zhou, X. R. Su, S. Xiao, S. D. Liu, and Q. Q. Wang, “Lighting dark plasmons of silver nanoantenna rings to enhance exciton-plasmon interactions” Adv. Funct. Mater. 19, 298 (2009).

(4) “Surface plasmons amplification in single Ag nanorings”. Submitted to Opt. Lett.


Micro-fabrication and micro-manipulation with holographic imaging



Jianying Zhou

State Key Laboratory of optoelectronic materials and technologies, School of Physics and Engineering, Sun Yat-Sen University


Abstract


Deterministic and self-adaptive algorithms with a spatial light modulator based system are applied to the generation of optical imaging with micro and sub-micro resolution. The applications of the pattern generation in optical engineering are discussed, with the fabrication of functional photonic structures presented as an example.



Dynamic and Steady Control of Quantum Coherence in Photonic Crystals via Zeeman Effect


Lu-Zhou Chen, Yong-Gang Huang, Chong-Jun Jin, Xue-Hua Wang


State Key Laboratory of optoelectronic materials and technologies, School of Physics and Engineering, Sun Yat-Sen University


The dynamic evolution of an multi-levels atom in three-dimensional photonic crystals under an applied magnetic filed is investigated. By combining Zeeman effect with photonic band gap effect, the dynamic quantum superposition states and steady quantum coherent trapping states of the atom can be flexibly controlled. This pave an effective way to coherent manipulation of quantum states in solid-state systems that has important application in quantum information processing.


Fabrication of metamaterials via inverted hemispherical lithography


Mingkai Liu, Xuhai Xia, Yang Shen, Xuehua Wang, Chongjun Jin


State Key Laboratory of optoelectronic materials and technologies, School of Physics and Engineering, Sun Yat-Sen University


A cost-effective nanofabrication method for forming large area and high coverage two-dimensional metal nanostructures in the flat and curved surfaces is proposed. This method starts with a periodic array of hemi-spherical dimples on polystyrene (PS) film prepared by colloidal lithography with a sacrificial layer of polyacrylic acid (PAA) underneath. After the removal of PAA in water solution, the PS layer is turned over and attached to the substrate to be patterned. A down air-hemispherical mask is formed after oxygen plasma etching. As the holes at the bottom is much larger than that on the surface, the mask is especially suitable for a standard lift-off process. Based on this mask, metal disc and pair of metal disc arrays, as well as two-dimensional nanostructures on a curved surface, have been fabricated. Optical measurement shows that a surface plasmon resonant exists in a periodic disc array. This method is valuable for the fabrication of a magnifying metamaterial hyperlens in order to eliminate the limitation of optical diffraction. We also developed a method to form a periodic dimple with metal layer. The localization of the light in this structure is analyzed and measured.


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