The spatial coherence properties of the spontaneous emission in the one-dimensional strong random system with gain

By using the finite difference time domain method, the spatial coherence properties of the spontaneous emission in the one-dimensional strong random system with gain are investigated in detail. Results show that the coherence properties improve slowly with the increase of the system length at low pump rates. And at high pump rates the coherence properties obviously become better after a certain system length. While at very high pump rates it is a non-monotonic function of the system length, there exists the best coherence at a certain system length. These behaviors are explained by Lamb theory and scaling theory. Our study may be helpful to the designing of random lasers.