We study experimentally as well as numerically the transport andgeneration of light in multiple scattering media with optical gain. Byimaging the spatial distribution of light escaping from the side of thesample, the propagation depth is analyzed. Far below and far aboverandom laser threshold, the spatial profile of emission light isindependent of pump intensity, while around threshold, the spatialdistribution of emission light changes profoundly. The experimentalresults are explained by interpreting the numerical solutions to a setof coupled time-dependent diffusion equations on a nonuniform spatialgrid. Our studies provide a new and easily accessible method forobserving the random laser threshold.

R. G. S. El-Dardiry, A. P. Mosk, A. Lagendijk

2010

09/2010

Opt. Lett.

35

3063-3065