Dynamically manipulating third-harmonic generation of phase change material with gap-plasmon resonators.

Here we theoretically demonstrate a dynamic third-harmonic generation (THG) device by incorporating chalcogenide phase change material (Ge2Sb2Te5) into ultra-small cavities of gap-plasmon resonators. Through coupling to plasmonic resonances, the THG efficiency of Ge2Sb2Te5 is increased up to five orders of magnitude due to the greatly enhanced electromagnetic fields within the ultra-small cavities. More interestingly, the THG signals of the proposed device can be dynamically switched on and off by tuning the phase states of Ge2Sb2Te5 between amorphous and crystalline. Our proposed dynamic THG nanostructures are beneficial to developing dynamic nonlinear nanophotonic devices.

Weak plasmon-exciton coupling between monolayer molybdenum disulfide and aluminum disks.

Manipulation of the photoluminescence (PL) of monolayer (ML) molybdenum disulfide (MoS2) with metallic plasmonic nanostructures has attracted much more attention for potential applications in optoelectronic devices. However, due to the limitation of resonance wavelength and oxidation properties, gold and silver are not the best selections for manipulating PL of MoS2. Here, we employ aluminum (Al) disks to tune the PL of ML MoS2. We have found that PL enhancement reaches the maximum when plasmonic resonances of Al disks overlap with the absorption peaks of ML MoS2. Near-field simulations show that PL enhancement is due to weak plasmon-exciton coupling.