Spin defects in hexagonal boron nitride, and specifically the negatively charged boron vacancy (VB‐) centers, are emerging candidates for quantum sensing. However, the VB‐ defects suffer from low quantum efficiency and, as a result, exhibit weak photoluminescence. In this work, a scalable approach is demonstrated to dramatically enhance the VB‐ emission by coupling to a plasmonic gap cavity. The plasmonic cavity is composed of a flat gold surface and a silver cube, with few‐layer hBN flakes positioned in between. Employing these plasmonic cavities, two orders of magnitude are extracted in photoluminescence enhancement associated with a corresponding twofold enhancement in optically detected magnetic resonance contrast. The work will be pivotal to progress in quantum sensing employing 2D materials, and in realization of nanophotonic devices with spin defects in hexagonal boron nitride.

Light carries both spin angular momentum (SAM) and orbital angular momentum (OAM), which can be used as potential degrees of freedom for quantum information processing. Quantum emitters are ideal candidates towards on-chip control and manipulation of the full SAM–OAM state space. Here, we show coupling of a spin-polarized quantum emitter in a monolayer W S e 2 with the whispering gallery mode of a S i 3 N 4 ring resonator. The cavity mode carries a transverse SAM of σ = ± 1 in the evanescent regions, with the sign depending on the orbital power flow direction of the light. By tailoring the cavity–emitter interaction, we couple the intrinsic spin state of the quantum emitter to the SAM and propagation direction of the cavity mode, which leads to spin–orbit locking and subsequent chiral single-photon emission. Furthermore, by engineering how light is scattered from the WGM, we create a high-order Bessel beam which opens up the possibility to generate optical vortex carrying OAM states.

The emergence of interlayer excitons (IEs) from atomic layered transition metal dichalcogenides (TMDCs) heterostructures has drawn tremendous attention due to their unique and exotic optoelectronic properties. Coupling the IEs into optical cavities provides distinctive electromagnetic environments which plays an important role in controlling multiple optical processes such as optical nonlinear generation or photoluminescence enhancement. Here, the integration of IEs in TMDCs into plasmonic nanocavities based on a nanocube on a metallic mirror is reported. Spectroscopic studies reveal an order of magnitude enhancement of the IE at room temperature and a 5‐time enhancement in fluorescence at cryogenic temperatures. Cavity modeling reveals that the enhancement of the emission is attributed to both increased excitation efficiency and Purcell effect from the cavity. The results show a novel method to control the excitonic processes in TMDC heterostructures to build high performance photonics and optoelectronics devices.

Surface plasmons in graphene have great potential for molecular sensing applications thanks to their exceedingly high sensitivity to environmental changes. Here, we demonstrate a type of hybrid graphene–metal metasurface that supports strong graphene plasmonic resonances in the terahertz range. Each unit cell of such a hybrid metasurface consists of a graphene antidot enclosing a metal disk realized using a self-aligned photolithography process. This hybrid design combines the advantages of both graphene- and metal-based photonic structures, leading to ∼3 times stronger tunable plasmonic resonances and an order of magnitude larger near-field intensity enhancement with respect to those of bare graphene antidot metasurfaces.

Chiral single photons are highly sought to enhance encoding capacities or enable propagation-dependent routing in nonreciprocal devices. Unfortunately, most semiconductor quantum emitters (QE) produce only linear polarized photons unless external magnets are applied. Magnetic proximity coupling utilizing 2D ferromagnets promises to make bulky external fields obsolete. Here we directly grow Fe-doped MoS2 (Fe:MoS2) via CVD that displays pronounced hard ferromagnetic properties even in monolayer form. This approach with monolayer ferromagnets enabled us to fully utilize the strain from the pillar stressor on the substrate to form QE in WSe2 deterministically. The Fe:MoS2/WSe2 heterostructures display strong hysteretic magneto-response and high-purity chiral single photons with a circular polarization degree of 92±1% without external magnetic fields. Furthermore, the chiral single photons are robust against uncontrolled external stray fields. This ability to manipulate quantum states and transform linear polarized photons into high-purity chiral photons on-chip enables nonreciprocal device integration in quantum photonics.