Analysis of Amplification Characteristics of Surface Plasmon Polaritons Based on the Rate-Equation Theory

A rate-equation theory model with the amplified spontaneous emission (ASE) effect considered for the surface plasmon polariton (SPP) waveguide amplifier is presented for analyzing the SPP amplifications with both side and SPP pumping techniques. By partitioning the cross section of the waveguide to suitable small units and introducing the overlapping integrated factor in each unit, the 3-D coupled equations of the model can be simplified to 1-D equations, which could be solved more conveniently. With our model, the gain and noise properties of a dielectric-loaded SPP waveguide amplifier are simulated. The results show that the ASE effect reduces the signal gain and deteriorates the signal-to-noise ratio of the SPP amplifier. For both the pumping schemes, the gains and noises for SPP multimode amplifications depend on the waveguide structure. By optimizing the waveguide structure, the gain-equalized amplification for different SPP modes may be achieved.