Time-dependent diffusion model of lasing in a random amplifying medium

We study the dynamics of lasing from photonic paints using a time-dependent diffusion model [1]. Solving the time-dependent diffusion equation for the light intensity in the medium with nonlinear gain and loss provides us with all the information on the spectral, spatial and temporal properties of the emitted intensity and of the gain coefficient inside the sample. Our model recaptures the narrowing effects of scatters on the emission spectral linewidth [2,3] and the emitted pulse duration [4], observable in disordered media with gain, at a specific threshold pump intensity. The dependence of the threshold intensity on scatterer density and excitation spot diameter is studied and found to be in qualitative agreement with experiment [2-5].


References:

[1] The diffusion model presented here represents a generalization of
the time-independent model by S. John and G. Pang (see S. John and G. Pang, Phys. Rev. A, 54, 3642 (1996) ); L. Florescu and S. John, to be submitted to Phys. Rev. E.
[2] N. M. Lawandy et al., Nature, 368, 436 (1994).
[3] W.L Sha, C.-H. Liu, and R. R. Alfano, Opt. Lett. 19, 1922 (1994).
[4] M. Siddique, and R. R. Alfano, G. A. Berger, M. Kempe and A. Z. Genack, Opt. Lett. 21, 450 (1996).
[5] G. van Soest, Makoto Tomita, and A. Lagendijk, Opt. Lett. 24, 306 (1999).