Amplified spontaneous emission of surface plasmon polaritons (SPPs) at the interface of a resonant gain medium has been observed. The amplification is accompanied by significant spectral narrowing and limits the gain available for compensation of SPP propagation losses. The effect is similar to the deteriorating influence of amplified spontaneous emission in laser resonators.
Bolger, P. M., Dickson, W., Krasavin, A. V., Liebscher, L., Hickey, S. G., Skryabin, D. V., & Zayats, A. V. (2010). Amplified spontaneous emission of surface plasmon polaritons and limitations on the increase of their propagation length. Optics Letters, 35(8), 1197-1199. https://doi.org/10.1364/OL.35.001197