Gain-Enhanced Propagation of Surface Plasmons in V-Groove Metallic Waveguides

Oren Lotan Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel Cameron Smith Department of Micro- and Nanotechnology, Technical University of Denmark, ., Denmark Jonathan Bar-David Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel Anders Kristensen Department of Micro- and Nanotechnology, Technical University of Denmark, ., Denmark Uriel Levy Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel

Surface Plasmon Polaritons (SPP’s) are electromagnetic waves coupled to surface charge density oscillations which propagate on metallic interfaces. Due to their unique dispersive relation and strong light confinement, Plasmonic based devices are showing promise in the attempt to manipulate light at the nano-scale. This can be of importance in the fields of optical communications, optical computing, sensing and more [1].

However, Plasmonic devices suffer from high losses which limit the propagation length and therefore present an obstacle for integrating plasmonic devices into photonic circuits or lab-on-Chip devices. A proposed solution to this problem is introducing a gain medium into plasmonic devices, thus amplifying the plasmonic signal and compensating for the high losses [2].

In this work, we shall examine a plasmonic waveguide, which is a V-shaped groove made of gold (Au) layer deposited on a Silicon substrate [3]. Above the gold layer we fabricate a flow cell and stream through a dye solution which will act as the gain medium, interacting evanescently with the plasmonic mode.

Our device is designed to support a probe beam around the wavelength of . This beam is coupled into the waveguide through a nano-mirror on one end of the device and coupled out of the waveguide in a similar fashion. At the same time, a second beam ( is directed to the center of the waveguide serving as a pump for the gain medium excitation. By measuring the output signal versus the input signal for waveguides of various lengths, with different types of gain media and varying pump beam intensities, we should be able to obtain the gain efficiency and the propagation loss in these structures.

[1] “Ozbay, Ekmel. 2006. “Plasmonics: Merging Photonics and Electronics at Nanoscale Dimensions.” Science 311 (5758): 189–93. doi:10.1126/science.1114849.

[2] Nezhad, Maziar P., Kevin Tetz, and Yeshaiahu Fainman. 2004. “Gain Assisted Propagation of Surface Plasmon Polaritons on Planar Metallic Waveguides.” Optics Express 12 (17): 4072. doi:10.1364/OPEX.12.004072.

[3] Smith, Cameron L. C., Anil H. Thilsted, Cesar E. Garcia-Ortiz, Ilya P. Radko, Rodolphe Marie, Claus Jeppesen, Christoph Vannahme, Sergey I. Bozhevolnyi, and Anders Kristensen. 2014. “Efficient Excitation of Channel Plasmons in Tailored, UV-Lithography-Defined V-Grooves.” Nano Letters, February. doi:10.1021/nl5002058.









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