Abstract
Unique structural and optical properties of atomically thin two-dimensional semiconducting transition metal dichalcogenides enable in principle their efficient coupling to photonic cavities having the optical mode volume close to or below the diffraction limit. Recently, it has become possible to make all-dielectric nano-cavities with reduced mode volumes and negligible non-radiative losses. Here, we realise low-loss high-refractive-index dielectric gallium phosphide (GaP) nano-antennas with small mode volumes coupled to atomic mono- and bilayers of WSe{}_{2}. We observe a photoluminescence enhancement exceeding 10{}^{4} compared with WSe{}_{2} placed on planar GaP, and trace its origin to a combination of enhancement of the spontaneous emission rate, favourable modification of the photoluminescence directionality and enhanced optical excitation efficiency. A further effect of the coupling is observed in the photoluminescence polarisation dependence and in the Raman scattering signal enhancement exceeding 10{}^{3}. Our findings reveal dielectric nano-antennas as a promising platform for engineering light-matter coupling in two-dimensional semiconductors.
Highlights
Unique structural and optical properties of atomically thin two-dimensional semiconducting transition metal dichalcogenides enable in principle their efficient coupling to photonic cavities having the optical mode volume close to or below the diffraction limit
The strong light–matter interaction regime has been realised in optical microcavities[9,10,11,12] and photonic crystals[5], where atomic layers of two-dimensional (2D) transition metal dichalcogenides (TMDs) were placed at the anti-node of the photonic mode
It has been shown that high-refractive-index dielectric nano-antennas can provide confined optical modes with strongly reduced mode volumes[28,30,31,32,33,34]
Summary
Unique structural and optical properties of atomically thin two-dimensional semiconducting transition metal dichalcogenides enable in principle their efficient coupling to photonic cavities having the optical mode volume close to or below the diffraction limit. By coupling semiconducting TMDs to such plasmonic structures, large photoluminescence (PL) enhancements[16,17,18,19,20,21], strong light–matter coupling[22,23,24], brightening of the dark excitonic states[25], and modification of optical properties of quantum light emitters[26,27] have been observed In some of these reports, special care had to be taken to overcome optical losses in metallic plasmonic structures by introducing a few nm dielectric spacer separating the TMD layer[20,21,29]. Multilayer TMDs themselves were used to fabricate high-index nanodisks, whose resonant response could be tuned over the visible and near-infrared (near-IR) ranges[35]
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