Direct Near-Field Observation of Surface Plasmon Polaritons on Silver Nanowires.

Matthias M Wiecha,Andrey Bogdanov,Shihab Al-Daffaie,Amin Soltani,Hartmut G Roskos,Mark D Thomson,Franko Küppers,Oktay Yilmazoglu

doi:10.1021/acsomega.9b03036

Abstract

Surface plasmon polaritons on (silver) nanowires are promising components for future photonic technologies. Here, we study near-field patterns on silver nanowires with a scattering-type scanning near-field optical microscope that enables the direct mapping of surface waves. We analyze the spatial pattern of the plasmon signatures for different excitation geometries and polarization and observe a plasmon wave pattern that is canted relative to the nanowire axis, which we show is due to a superposition of two different plasmon modes, as supported by electromagnetic simulations including the influence of the substrate. These findings yield new insights into the excitation and propagation of plasmon polaritons for applications in nanoplasmonic devices.

Highlights

Silver nanowires (Ag-NWs) have attracted a great deal of attention over the last few years. Due to their ability to carry subwavelength plasmon modes,[1,2] they are promising tools for future optoelectronic and nanophotonic applications, which aim at benefiting from the advantages of light in photonic on-chip devices.[3−6] Recently, terahertz (THz) photomixers equipped with Ag NWs in their active region have shown an enhanced emission especially at higher frequencies (>1 THz) compared to the state-of-the-art interdigital photomixer design.[7]
The contribution of different plasmon modes has been investigated in the far field by quantum-dot fluorescence,[4,8] whereas near-field measurements by means of scanning near-field optical microscopy (SNOM)[9] just reported a single mode so far
We have mapped out the field patterns of surface plasmon polaritons on a silver nanowire in an inhomogeneous environment

Summary

INTRODUCTION

Silver nanowires (Ag-NWs) have attracted a great deal of attention over the last few years Due to their ability to carry subwavelength plasmon modes,[1,2] they are promising tools for future optoelectronic and nanophotonic applications, which aim at benefiting from the advantages of light (e.g., its speed) in photonic on-chip devices.[3−6] Recently, terahertz (THz) photomixers equipped with Ag NWs in their active region have shown an enhanced emission especially at higher frequencies (>1 THz) compared to the state-of-the-art interdigital photomixer design.[7] The incorporation of Ag NWs into photomixers leads to a significant reduction of the device capacitance of around 1 order of magnitude and increases the photocurrent by up to 32 times as compared to conventional photomixers.

RESULTS AND DISCUSSION

CONCLUSIONS

EXPERIMENTAL SECTION

■ ACKNOWLEDGMENTS

■ REFERENCES