Surface Plasmon Propagation in Gold Nanowires Fabricated by an Improved Lithography Method

Long Gao Nanoscale Physics and Devices Laboratory, Institute of Physics, Chinese Academy of Sciences and Beijing National Laboratory for Condensed Matter Physics, Beijing, China Hong Wei Nanoscale Physics and Devices Laboratory, Institute of Physics, Chinese Academy of Sciences and Beijing National Laboratory for Condensed Matter Physics, Beijing, China Deng Pan Nanoscale Physics and Devices Laboratory, Institute of Physics, Chinese Academy of Sciences and Beijing National Laboratory for Condensed Matter Physics, Beijing, China Hongxing Xu Center for Nanoscience and Nanotechnology, School of Physics and Technology, Wuhan University, Wuhan, China

Noble metal nanowires with subwavelength cross-sections can support propagating surface plasmons (SPs) with highly confined electromagnetic field, and thus are suitable for photonic nanodevices and nanocircuits [1]. Among the various fabrication methods, lithographic fabrication can produce highly controllable nanostructures, which are especially required for practical applications. However, SPs in the nanowaveguides fabricated by lithography method usually suffer serious loss, which limits the SP propagation length and their further applications [2].

Here we report some improvements on the fabrication process of preparing gold nanowires. By removing the adhesion layer that damps the SP resonance [3], we can largely suppress the SP propagation loss in gold nanowires. Instead of using adhesion layer, the nanowires can be immobilized and protected by coating a dielectric (Al₂O₃) layer. This dielectric layer also changes the refractive index of surrounding medium and tunes the propagating SPs on the nanowires [4]. With these improvements, we can obtain gold nanowires with reproducible physical geometry, high SP propagation efficiency and tunable propagating SPs. Furthermore, a controllable router can be realized on a Y-shaped nanobranch fabricated by this method. These results show a promising application future of lithographically fabricated metal nanostructures on plasmonic nanocircuitry.

References

[1] Wei, H.; Xu, H. X. Nanophotonics 2012, 1, 155−169.

[2] Kusar, P.; Gruber, C.; Hohenau, A.; Krenn, J.R. Nano Lett. 2012, 12, 661-665.

[3] Huang, J. S.; Callegari, V.; Grisler, P.; Brüning, C.; Kern, J.; Prangsma, J.C.; Wu, X.; Feichtner, T.; Ziegler, J.; Weinmann, P.; Kamp, M.; Forchel, A.; Biagioni, P.; Senngauser, U.; Hecht, B. Nat. Commun. 2010, 1, 150-157

[4] Wei, H.; Zhang, S. P.; Tian, X. R.; Xu, H. X. Proc. Natl. Acad. Sci. USA 2013, 110, 4494-4499

dragontall@iphy.ac.cn