Continuously-tunable light-matter coupling in optical microcavities with 2D semiconductors.

A theoretical variation between the two distinct light-matter coupling regimes, namely weak and strong coupling, becomes uniquely feasible in open optical Fabry-Pérot microcavities with low mode volume, as discussed here. In combination with monolayers of transition-metal dichalcogenides (TMDCs) such as WS, which exhibits a large exciton oscillator strength and binding energy, the room-temperature observation of hybrid bosonic quasiparticles, referred to as exciton-polaritons and characterized by a Rabi splitting, comes into reach. In this context, our simulations using the transfer-matrix method show how to tailor and alter the coupling strength actively by varying the relative field strength at the excitons' position - exploiting a tunable cavity length, a transparent PMMA spacer layer and angle-dependencies of optical resonances.

Direct Measurement of the Radiative Pattern of Bright and Dark Excitons and Exciton Complexes in Encapsulated Tungsten Diselenide.

The optical properties of particularly the tungsten-based transition-metal dichalcogenides are strongly influenced by the presence of dark excitons. Recently, theoretical predictions as well as indirect experimental insights have shown that two different dark excitons exist within the light cone. While one is completely dark, the other one is only dipole forbidden out-of-plane, hence referred to as grey exciton.

Shedding light on exciton's nature in monolayer quantum material by optical dispersion measurements.

Strong light-matter interactions based on two-dimensional excitons formed in quantum materials such as monolayer transition-metal dichalcogenides have become a major subject of research in recent years. Particularly attractive is the extraordinarily large oscillator strength as well as binding energy of the excitonic quasiparticles in these atomically-thin crystal lattices. Numerous theoretical studies and experiments have been devoted to the exploration of the excitonic systems that could be exploited in future nano-scaled optoelectronic devices.

Enhancement of the Monolayer Tungsten Disulfide Exciton Photoluminescence with a Two-Dimensional Material/Air/Gallium Phosphide In-Plane Microcavity.

Light-matter interactions with two-dimensional materials gained significant attention in recent years, leading to the reporting of weak and strong coupling regimes and effective nanolaser operation with various structures. Particularly, future applications involving monolayer materials in waveguide-coupled on-chip-integrated circuitry and valleytronic nanophotonics require controlling, directing, and optimizing photoluminescence. In this context, photoluminescence enhancement from monolayer transition-metal dichalcogenides on patterned semiconducting substrates becomes attractive.

Gate Tuning of Förster Resonance Energy Transfer in a Graphene - Quantum Dot FET Photo-Detector.

Graphene photo-detectors functionalized by colloidal quantum dots (cQDs) have been demonstrated to show effective photo-detection. Although the transfer of charge carriers or energy from the cQDs to graphene is not sufficiently understood, it is clear that the mechanism and efficiency of the transfer depends on the morphology of the interface between cQDs and graphene, which is determined by the shell of the cQDs in combination with its ligands. Here, we present a study of a graphene field-effect transistor (FET), which is functionalized by long-ligand CdSe/ZnS core/shell cQDs.

Particle-based optical sensing of intracellular ions at the example of calcium - what are the experimental pitfalls?

Colloidal particles with fluorescence read-out are commonly used as sensors for the quantitative determination of ions. Calcium, for example, is a biologically highly relevant ion in signaling, and thus knowledge of its spatio-temporal distribution inside cells would offer important experimental data. However, the use of particle-based intracellular sensors for ion detection is not straightforward.