Influence of gain localization in one-dimensional random media

Based on the transfer matrix method, we studied the effects of gain distribution on the performance of light localization in one-dimensional completely random systems. Due to the scattering of the pump light, the gain can also be localized. Compared with homogenous gain distribution, the localized gain can induce light confinement more efficiently. The overlapping between the laser modes and the localized gain brings on the high-Q modes that are amplified preferentially, and reduces the lasing threshold. The threshold can be hundreds times lowered in some special cases. With increase of the random system size, the localization position goes deeper into the media first, and then saturates when the system is thicker than 550 layers. For a given kind of random laser systems, an optimal system size exists, for which the mode intensity is significantly enhanced. The influence of the system structure on the lasing intensity and localization position is also discussed.