Quantitative analysis and near-field observation of strong coupling between plasmonic nanogap and silicon waveguides

We present a near field optical study of a plasmonic gap waveguide vertically integrated on silicon. The experimental study is based on a near field scanning optical microscope configured in perturbation mode. This operation mode is described and modeled to give a physical insight into the measured signal. A high spatial resolution allows for the characteristics of the plasmonic gap modes, such as near field distributions, effective indices, direction of propagation, and coupling between perpendicularly polarized modes, to be imaged and analyzed with accuracy. This experimental work is supported by numerical simulations based on finite element optical mode solvers and by the application of the strongly coupled-mode theory to the device. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4725511]