Ultranarrow Second-Harmonic Resonances in Hybrid Plasmon-Fiber Cavities
Research output: Contribution to journal › Research article › Contributed › peer-review
Contributors
Abstract
We demonstrate second-harmonic generation with ultranarrow resonances in hybrid plasmon-fiber cavities, formed by depositing single-crystalline gold nanorods onto the surface of tapered microfibers with diameters in the range of 1.7-1.8 μm. The localized surface plasmon mode of the single gold nanorod efficiently couples with a whispering gallery mode of the fiber, resulting in a very narrow hybrid plasmon-fiber resonance with a high quality factor Q of up to 250. When illuminated with a tunable 100 fs laser, a sharp SHG peak narrower than half of the spectral width of the impinging laser emerges, superimposed on a broad multiphoton photoluminescence background. The enhancement of the SHG peak of the hybrid system is typically 1000-fold when compared to that of a single gold nanorod alone. Tuning the laser over the hybrid resonance enables second-harmonic spectroscopy and yields an ultranarrow line width as small as 6.4 nm. We determine the second-harmonic signal to rise with the square of the laser power, while the multiphoton photoluminescence background rises with powers between 4 and 6, indicating a very efficient higher-order process. A coupled anharmonic oscillator model is able to describe the linear as well as second-harmonic resonances very well. Our work will open the door to the simultaneous utilization of narrow whispering gallery resonances together with high plasmonic near-field enhancement and should allow for nonlinear sensing and extremely efficient nonlinear light generation from ultrasmall volumes.
Details
Original language | English |
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Pages (from-to) | 5576-5582 |
Number of pages | 7 |
Journal | Nano letters |
Volume | 18 |
Issue number | 9 |
Publication status | Published - 12 Sept 2018 |
Peer-reviewed | Yes |
External IDs
PubMed | 30075631 |
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Keywords
ASJC Scopus subject areas
Keywords
- gold nanorods, nanooptics, narrow linewidth, Nonlinear plasmonics, second-harmonic generation, whispering gallery mode