分类： 光学 >> 量子光学 提交时间： 2023-02-19
Yuan Zhang
Yuxin Niu
Shunping Zhang
Yao Zhang
Shi-Lei Su
Guangchao Zheng
Luxia Wang
Gang Chen
Hongxing Xu
Chongxin Shan
摘要： Plasmon-mediated superradiance for molecules around metallic nanospheres was proposed ten years ago. However, its demonstration has not been achieved yet due to the experimental difficulty of positioning molecules, and the theoretical limitation to the enhanced collective rate of low excited molecules. In this Letter, we propose that the ultrafast plasmon-mediated superradiant pulses can be observed with strongly excited methylene blue molecules standing vertically inside gold nanoparticle-on-mirror nanocavities. Our simulations indicate that in this system the molecules could interact with each other via plasmon- and free-space mediated coherent and dissipative coupling. More importantly, the coherent coupling mediated by short-ranged propagating surface plasmons cancel largely the direct dipole-dipole coupling mediated by the free-space field, and the dominated dissipative coupling mediated by relatively long-ranged gap plasmons enables the ultrafast superradiant pulses within picosecond scale. Our study opens up the possibility of studying the rich superradiant effects from the quantum emitters in a sub-wavelength volumn by engineering the plasmonic environments.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Fei Chen
Hang Zhou
Hui Li
Song Luo
Zheng Sun
Zhe Zhang
Fenghao Sun
Beier Zhou
Hongxing Dong
Huailiang Xu
Hongxing Xu
Alexey Kavokin
Zhanghai Chen
Jian Wu
摘要： Whispering gallery modes in a microwire are characterized by a nearly equidistant energy spectrum. In the strong exciton-photon coupling regime, this system represents a bosonic cascade: a ladder of discrete energy levels that sustains stimulated transitions between neighboring steps. In this work, by using femtosecond angle-resolved spectroscopic imaging technique, the ultrafast dynamics of polaritons in a bosonic cascade based on a one-dimensional ZnO whispering gallery microcavity is explicitly visualized. Clear ladder-form build-up process from higher to lower energy branches of the polariton condensates are observed, which are well reproduced by modeling using rate equations. Moreover, the polariton parametric scattering dynamics are distinguished on a timescale of hundreds of femtoseconds. Our understanding of the femtosecond condensation and scattering dynamics paves the way towards ultrafast coherent control of polaritons at room temperature, which will make it promising for high-speed all-optical integrated applications.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Manipulating the spin polarization of electron beams using light is highly desirable but exceedingly challenging, as the approaches proposed in previous studies using free-space light usually require enormous laser intensities. Here, we propose the use of a transverse electric optical near field, extended on nanostructures, to efficiently induce spin flips of an adjacent electron beam by exploiting the strong inelastic electron scattering in phase-matched optical near fields. Our calculations show that the use of a dramatically reduced laser intensity ($\sim 10^{12}\,$W/cm$^2$) with a short interaction length ($16\,\mu$m) achieves an electron spin-flip probability of approximately $12\%$. Intriguingly, the two spin components of an unpolarized incident electron beam -- parallel and antiparallel to the electric field -- are spin-flipped and inelastically scattered to different energy states, providing an analog of the Stern--Gerlach experiment in the energy dimension. Our findings are important for optical control of free-electron spins, preparation of spin-polarized electron beams, and applications as varied as in material science and high-energy physics.
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