Abstract
We theoretically study the gain-assisted double plasmonic resonances to enhance second harmonic generation (SHG) in a centrosymmetric multilayered silver-dielectric-gold-dielectric (SDGD) nanostructure. Introducing gain media into the dielectric layers can not only compensate the dissipation and lead to giant amplification of surface plasmons (SPs), but also excite local quadrupolar plasmon which can boost SHG by mode matching. Specifically, as the quadrupolar mode dominates SHG in our nanostructure, under the mode matching condition, the intensity of second harmonic near-field can be enhanced by 4.43 × 102 and 1.21 × 105 times when the super-resonance is matched only at the second harmonic (SH) frequency or fundamental frequency, respectively. Moreover, the intensity of SHG near-field is enhanced by as high as 6.55 × 107 times when the nanostructure is tuned to double super-resonances at both fundamental and SH frequencies. The findings in this work have potential applications in the design of nanosensors and nanolasers.
Highlights
We design a spherical SDGD multi-layered nanostructure and investigate the plasmon-enhanced second harmonic generation (SHG) through gain-assisted double-plasmonic resonances
We show that the dark quadrupolar mode can be excited by
The intensity of SH near-field is enhanced by 6.55 × 107 times when the super-resonances at SH and fundamental frequency are both excited by gain media (Fig. 5d)
Summary
We theoretically study the gain-assisted double plasmonic resonances to enhance second harmonic generation (SHG) in a centrosymmetric multilayered silver-dielectric-gold-dielectric (SDGD) nanostructure. The intensity of SHG near-field is enhanced by as high as 6.55 × 107 times when the nanostructure is tuned to double super-resonances at both fundamental and SH frequencies. When two plasmonic resonance modes are properly matched to both the fundamental and SH frequencies, the SH emission can be further enhanced[16, 24, 25] On another front, introducing active materials (such as dye molecules, rare earth ions, or semiconductor nanocrystals) is an effective method to reduce or compensate the intrinsic losses in plasmonic structures[26,27,28,29,30,31]. The mode-matched double-resonant plasmonic nanoshells can serve as an ideal candidate for SHG enhancement
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