Abstract
Single photon emitters in atomically-thin semiconductors can be deterministically positioned using strain induced by underlying nano-structures. Here, we couple monolayer WSe2 to high-refractive-index gallium phosphide dielectric nano-antennas providing both optical enhancement and monolayer deformation. For single photon emitters formed on such nano-antennas, we find very low (femto-Joule) saturation pulse energies and up to 104 times brighter photoluminescence than in WSe2 placed on low-refractive-index SiO2 pillars. We show that the key to these observations is the increase on average by a factor of 5 of the quantum efficiency of the emitters coupled to the nano-antennas. This further allows us to gain new insights into their photoluminescence dynamics, revealing the roles of the dark exciton reservoir and Auger processes. We also find that the coherence time of such emitters is limited by intrinsic dephasing processes. Our work establishes dielectric nano-antennas as a platform for high-efficiency quantum light generation in monolayer semiconductors.
Highlights
Single photon emitters in atomically-thin semiconductors can be deterministically positioned using strain induced by underlying nano-structures
We find that the PL fullwidth at half maximum (FWHM) of ≈ 450 μeV corresponds to T2 = 2.9 ps (FWHM = 2Γ = 2ħ/T2) close to the observed T2 values, indicating that the coherence of the studied SPE is limited by pure dephasing, which we attribute to interactions with phonons during the exciton relaxation[39], as for the excitation power < 20 nW used in the experiment the contribution of the Auger annihilation can be excluded
We have demonstrated that high-refractive-index GaP nanoantennas offer an efficient approach for nano-scale positioning and quantum efficiency (QE) enhancement in strain-induced SPEs in monolayer WSe2
Summary
Single photon emitters in atomically-thin semiconductors can be deterministically positioned using strain induced by underlying nano-structures. For SPEs coupled to GaP nanoantennas, we observe from two to four orders of magnitude higher power-normalized PL intensity, compared to SPEs found on SiO2 nanopillars.
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