Long-Range Hybrid Plasmonic Waveguide of Graded-Index InGaAsP Active Layer Based on InP

Abstract

A hybrid plasmonic waveguide based on indium phosphide (InP) was proposed for nanoscale optical confinement and long-range propagation at a wavelength of 1.55 µm. The waveguide consists of an InGaAsP layer designed as a ridge with a gold cap. The InGaAsP materials are suitable for InP substrates. The refractive index of In_1−xGa_xAs_yP_1−y was graded by changing the mole fraction to improve the confinement and propagation length compared with the conventional one. Changing only the y parameter with constant x results in a propagation length increase compared to the inverse case, changing only the parameter x. This parallels good results in the mode effective area ( ) and figure-of-merit (FoM) for the exact condition of changing y, expressing a good confinement condition. A propagation length of 40 µm is achieved with better confinement than the standard hybrid case. The designs proposed in this paper were simulated using COMSOL Multiphysics.