Title: Nano-optical imaging of exciton-plasmon polaritons in WSe2/Au heterostructures
Abstract: Two-dimensional heterostructures have the ability to enhance the processes involving light-matter interactions that have various applications in various nanophotonics and optoelectronics. In particular, polaritons, formed by coupling between light and other quasiparticles, are important interactions that form building blocks of nanophotonics as they enable confinement in mid- to far- infrared regimes. This work investigates exciton-plasmon polaritons (EPPs) in WSe2/Au heterostructures with scattering-type scanning near-field optical microscopy (s-SNOM). With the nano-optical imaging technique, we map the interference fringes of EPPs at various excitation energies and construct the dispersion diagram of the EPPs, which shows a strong exciton-plasmon coupling with a sizable Rabi splitting energy (~0.19 eV). Further, we investigate the dependence of polariton wavelength on the WSe2 thickness (d). We find that when d is below 40 nm, the polariton wavelength decreases rapidly with increasing d, whereas, as d reaches 50 nm and above, the wavelength drops to about 210 nm, which is over 4 times smaller than free-space photons. Our simulations suggest that the high spatial confinement of EPPs is due to the strong localization of the polariton field inside WSe2. This work uncovers the potential for EPPs for future applications of highly confined polaritons in two-dimensional heterostructures.
Bio: Raghunandan B. Iyer got his M. Tech degree in 2015 from the Indian Institute of Technology Kanpur, India. He is currently working towards his Ph.D. in Electrical Engineering with a specialization in Microelectronics and Photonics. His area of interest is light-matter interactions in optoelectronic heterostructures. In particular, his focus is on 2-d heterostructures and organic bulk heterojunctions. He was a presidential scholar from Aug 2017 to Aug 2019 at ECpE.
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