Atomically thin two-dimensional transition metal dichalcogenides have garnered tremendous attention from researchers owing to their distinct electrical and optical properties. Improving the photoluminescence of these two-dimensional atomic semiconductors is imperative for their seamless integration into photonic and optoelectronic devices. Concurrently, the advent of two-dimensional materials such as graphene and transition metal dichalcogenides has ushered in opportunities within the realm of valleytronics. Valleytronics endeavors to exploit valley degrees of freedom for information processing, mirroring the principles of spin-based spintronics and charge-based electronics. Notably, these materials demonstrate a unique spin-valley locking mechanism, thereby enabling modulation of the electronic valley degree of freedom through light. In the present study, we fabricated cost-effective nanocone structures via colloidal lithography and subsequently integrated them with a monolayer of WSe2. Through this methodology, we amplified both the photoluminescence and valley polarization enhancement of the WSe2 monolayer by harnessing plasmonic hotspots.
Radiative losses in nanophotonic devices are a fundamental challenge in their miniaturization. Plasmonic metals overcome the radiation losses, but high ohmic losses hinder the optical performance. Supercavity modes, also known as quasi-bound states in the continuum (BIC), help circumvent this problem. In this work, we propose a low refractive index 2D-periodic array of slotted disk that supports symmetry protected BIC and accidental BIC at off-gamma point. This BIC point is very fascinating to study the exciton-cavity interaction. To study the exciton-cavity, TMDCs have the great potential to generate the exciton. This exciton is coupled with BIC mode to generate the polariton state in a strong coupling region.
The presence of a vertical component to the transition dipole moment in interlayer excitons, which suppresses electron-hole overlap, results in longer radiative lifetimes as compared to intralayer excitons. Such tightly bound interlayer excitons well-suited candidates for valley-based quantum information processing applications. Their optical accessibility is, however, limited due to their out-of-plane transition dipole moment. We first design a system to strengthen the coupling of interlayer excitons in two-dimensional (2D) material heterostructures with Purcell enhanced out-of-plane resonant modes of a Whispering Gallery Mode (WGM) resonator at room temperature. The high quantum confinement of light in a small modal volume and high Q-factor allow a much stronger coupling of these excitons to the electromagnetic field. We then discuss how to engineer an asymmetric transmission of light from these excitons, which facilitates readout from such systems. We also present our attempts to experimentally demonstrate the valley selective separation and routing of interlayer excitons in the MoSe2/WSe2 heterobilayer stack of TMDCs material by integrating on a planar silicon nitride (SiN) bus-waveguide coupled with a microring resonator (MRR).
Non-Hermitian systems with varying loss-gain profiles are receiving significant attention due to their exotic behavior at a certain point called the exceptional point (EP). EPs are singularities of non-Hermitian systems where the eigenfrequencies as well as the associated eigenstates coalesce. These EP singularities are ultrasensitive to small perturbations. A conventional system follows a linear relation with perturbation whereas these singularities follow a square root dependence for small perturbations.
Atomically thin two-dimensional transition metal dichalcogenides have fascinated researchers due to their unique electronic and optical properties. The control of exciton-trion dynamics in two-dimensional semiconductors is critical for their application in optoelectronic devices. One way to engineer the exciton-trion dynamics is by applying strain in the monolayers of these two-dimensional materials using nanostructured substrates. Here we demonstrate a versatile route to engineering the exciton-trion dynamics in monolayer WSe2 by applying biaxial strain. A polytetrafluoroethylene (PTFE) nanocone array decorated by thin gold film and fabricated via colloidal lithography is used to create the strain in the superposed monolayer. To distinguish the effect of strain and plasmonics, we compare our results on the nanocone surface with the one for monolayer WSe2 on a plane gold film.
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