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Boosting third-harmonic generation by a mirror-enhanced anapole resonator

: Xu, L.; Rahmani, M.; Kamali, K.Z.; Lamprianidis, A.; Ghirardini, L.; Sautter, J.; Camacho-Morales, R.; Chen, H.; Parry, M.; Staude, I.; Zhang, G.; Neshev, D.; Miroshnichenko, A.E.

Fulltext ()

Light. Online resource 7 (2018), Art. 44, 8 pp.
ISSN: 2047-7538
ISSN: 2095-5545
Journal Article, Electronic Publication
Fraunhofer IOF ()

We demonstrate that a dielectric anapole resonator on a metallic mirror can enhance the third harmonic emission by two orders of magnitude compared to a typical anapole resonator on an insulator substrate. By employing a gold mirror under a silicon nanodisk, we introduce a novel characteristic of the anapole mode through the spatial overlap of resonantly excited Cartesian electric and toroidal dipole modes. This is a remarkable improvement on the early demonstrations of the anapole mode in which the electric and toroidal modes interfere off-resonantly. Therefore, our system produces a significant near-field enhancement, facilitating the nonlinear process. Moreover, the mirror surface boosts the nonlinear emission via the free-charge oscillations within the interface, equivalent to producing a mirror image of the nonlinear source and the pump beneath the interface. We found that these improvements result in an extremely high experimentally obtained efficiency of 0.01%.