In developing micro- and nanodevices, stiction between their parts is a well-known problem. It is caused by the finite-temperature analogue of the quantum electrodynamical Casimir–Lifshitz forces, which are normally attractive. Repulsive Casimir–Lifshitz forces have been realized experimentally, but their reliance on specialized materials severely limits their applicability and prevents their dynamic control. Here we demonstrate that repulsive critical Casimir forces, which emerge in a critical binary liquid mixture upon approaching the critical temperature, can be used to counteract stiction due to Casimir–Lifshitz forces and actively control microscopic and nanoscopic objects with nanometre precision.
The perfect absorption of light has been traditionally achieved by layered structures whose thickness is at least λ/4n. To achieve electromagnetically thin perfect absorbers, research has focused on metallic metasurfaces which require complex nanofabrication. MoS2 is a promising material for ultra-thin perfect absorbers due to the high oscillator strength of its excitonic transitions and layered nature. However previous efforts to increase MoS2 absorption involve intricate fabrication. Our work shows enhanced absorption in monolayers, perfect absorption and exciton-polaritons in MoS2 slabs. This work simultaneously presents a simple approach to achieve perfect absorption in ultra-thin non-metallic structures and to observe cavity-free exciton-polaritons.
In this talk, I will discuss strong light-matter interactions achieved by using transition metal dichalcogenides (TMDs) as the resonant material in both plasmonic nanocavities and Mie resonance sustained by the high-refractive index of the material itself. As a result of this interaction, one observes the emergence of new polaritonic eigenstates. These states are of hybrid nature and possess both light and matter characteristics, which is reflected in vacuum Rabi splitting, observed in the absorption or transmission spectra.
Strongly coupled material excitations to optical modes has shown potential to modify the material’s chemistry. The optical modes are usually given by an external cavity, such as Fabry-Pérot cavities, which may limit the scope of applications. Here we highlight the possibility of self-coupling electronic or vibrational resonances to optical modes sustained by the materials themselves. We show electronic and vibrational cavity-free polaritons in concrete examples, such as a slab of excitonic material and a spherical water droplet in vacuum. The abundance of cavity-free polaritons in simple structures points at their practical importance for polaritonic chemistry, exciton transport, and modified material properties.
In this talk I will discuss strong light-matter interactions achieved by using transition metal dichalcogenides (TMDCs) as the resonant material in both plasmonic nanocavities and Mie resonance sustained by the high-refractive index of the material itself. As a result of this interaction, one typically observes the emergence of new polaritonic eigenstates. These states are of hybrid nature and possess both light and matter characteristics, which is reflected in vacuum Rabi splitting, observed in the absorption or transmission spectra. Because of the hybrid nature of these states, the excited state temporal dynamics can be significantly altered in comparison to the uncoupled system dynamics. This, in turn, can have profound effects on the emission and photochemical processes. I will show that TMDCs are a particularly interesting polaritonic system in this sense."
Surface plasmon resonances in metal nanostructures can lead to novel optical properties. The greatly enhanced
electromagnetic field makes surface-enhanced Raman scattering (SERS) a highly sensitive spectroscopic technique. We
employed Ag nanowires as plasmonic waveguide and achieved
remote-excitation SERS at a few molecules level. The
junctions between metal nanowires and nanoparticles offer hot spots for SERS, while the enhancement strongly depends
on the laser polarization. We studied the polarization dependence in Au nanowire-nanoparticle systems of different
geometry. The polarization of Raman-scattered light in SERS is a rarely studied topic. We found nanoantennas
composed of a few nanoparticles can manipulate the polarization of emission light. A nanoparticle trimer is the simplest
nanoantenna to realize the polarization control. By tuning the position and size of the third particle, emission polarization
can be modified in a controllable way. In addition, the refractivity of the surrounding media also plays a crucial role for
the emission polarization.
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