Coherent random lasing behavior in low-dimensional active weakly scattering random systems

Abstract

We report theoretical studies of the coherent random lasing behavior in active weakly scattering random fiber lasers by using finite-difference time-domain (FDTD) method. We design and simulate a model of active weakly scattering random fiber lasers. Results show that the scattering mean free path reduces significantly with reducing the dimension of systems. For same situation, the scattering mean free path in our model is at least two orders of magnitude lower than that in high dimensional systems. We calculate the length of lasing oscillation cavity by using power Fourier transform, and we found Lc<<L (the sample size) in one-dimensional active weakly scattering random systems. We attribute this effect to the low dimension of our system. Strong evidence is presented that the well-defined pump threshold and the coherent feedback behavior is existent in one-dimensional active weakly scattering random systems. We show that there is a one-to-one correlation between laser mode and oscillation cavity. These results provide essential mechanism to realize one-dimensional active random laser, for example, active random fiber laser. We believe that our study provides an original way to access coherent random laser in weakly scattering random systems.