"Nonlinear infrared plasmonic waveguide arrays" by Alessandro Salandrino, Yuan Wang et al.

Article Title

Nonlinear infrared plasmonic waveguide arrays

Authors

Alessandro Salandrino, NSF Nanoscale Science and Engineering Center (NSEC), University of California, Berkeley, CA 94720, USA
Yuan Wang, NSF Nanoscale Science and Engineering Center (NSEC), University of California, Berkeley, CA 94720, USA
Xiang Zhang, NSF Nanoscale Science and Engineering Center (NSEC), University of California, Berkeley, CA 94720, USA Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA

Keywords

infrared plasmonics, plasmonic waveguides, nonlinear plasmonics, waveguide theory, waveguide arrays

Abstract

The large negative permittivity of noble metals in the infrared region prevents the possibility of highly confined plasmons in simple waveguide structures such as thin films or rods. This is a critical obstacle to applications of nonlinear plasmonics in the telecommunication wavelength region. We theoretically propose and numerically demonstrate that such limitation can be overcome by exploiting inter-element coupling effects in a plasmonic waveguide array. The supermodes of a plasmonic array span a large range of effective indices, making these structures ideal for broadband mode-multiplexed interconnects for integrated photonic devices. We show such plasmonic waveguide arrays can significantly enhance nonlinear optical interactions when operating in a high-index, tightly bound supermode. For example, a third-order nonlinear coefficient in such a waveguide can be more than three orders of magnitude larger compared to silicon waveguides of similar dimensions. These findings open new design possibilities towards the application of plasmonics in integrated optical devices in the telecommunications spectral region.