Compact plasmonic dichroic splitting with high splitting ratio based on a cascaded-grating structure

A compact dichroic surface plasmon polariton (SPP) splitting scheme composed of two cascaded subgratings of different dimensions is proposed and investigated. The normal incident photons illuminated on the dichroic splitting structure are converted to surface plasmons traveling to the left or right depending on the wavelength. The operation principle is clarified and a coupled-mode model is developed to facilitate structure design. The generated SPPs propagating to the left and right directions on the metal surface can be manipulated nearly independently by altering the left and right subgrating, respectively. Proof-of-principle demonstrations show that a remarkable property of high splitting ratios is achieved with 43.0 dB at wavelength 1310 nm (left: right power contrast) and 35.7 dB at wavelength 1550 nm (right: left power contrast). The proposed splitting concept has general applicability across other operating wavelengths, such as the visible and near-infrared range. (C) 2014 Optical Society of America