FDTD modeling of lasing and photon localization in microcavities formed by random material

Anderson localization of photons in disordered media and photonic bandgap are closely related. Both inhibit light propagation due to interference (not absorption). There are three regimes for photon transport in random material, diffusion, weak localization, and strong localization. We have developed a methodology using the finite difference time domain method to simulate the lasing and the photon transport behavior of all three scattering regimes in random material. FDTD is a full-vector-wave time domain solution of the Maxwell equation. It can be used to solve Maxwell equations for a complete electromagnetic analysis of arbitrary linear and nonlinear structure. The FDTD method has the advantage in its inherent time domain ability to count for the nonlinear effect in the random lasing material, To simulate the randomized material, the grain size and the refraction index of the grain particles are assigned by a random number generator with either uniform or gaussian distribution. The shape of the grain size is assigned randomly to count for additional randomness. For closer comparison with the experiments, the SEM photo of the random material is imported to the FDTD grid to specify the real geometry of grain distribution. The Lorentzian gain model with nonlinear saturation effect is used for active media