Enhanced random laser by metal surface-plasmon channel waveguide.

Compared with conventional lasers, the random laser is realized through strong multiple scatterings in disordered gain system. In this paper, random lasing (RL) in one-dimensional metal surface plasmon (SP) waveguide with gold-plated self-formed silicon pyramids was investigated comprehensively. Consequently, the emission intensity of RL was enhanced dramatically and the RL threshold was reduced significantly through Au-coated Si spiky tips. Meanwhile, one-dimensional metal SP channel waveguides confined the emitting light in a certain direction with a small divergence angle. Using FDTD simulations, it was found that the enhancement effect for RL is likely attributed to the localized surface plasmon (LSP) field. In addition, the LSP field nearby the spiky tips can enhance field-molecule interaction, which was benefit for lasing in small scale. The results in this letter supplied a feasible method to realize the application of RL in subwavelength optical elements.