Weak-disorder-induced reduction of the lasing threshold in periodic systems

Abstract

We report numerical and experimental results on a finite-size, weakly disordered, amplifying multilayer with underlying periodicity. Computed transmission spectra evidence the simultaneous existence of perturbed band-edge modes and random lasing modes in exclusive configurations of disorder. A larger energy is seen to outcouple through the random lasing modes as compared to the band-edge lasing modes. With the gain being uniform across the band gap, this phenomenon originates from the increased quality factor of modes by the addition of disorder. Experiments carried out on a linear array of weakly disordered microresonators exhibit excellent agreement with the numerical observations, demonstrating threshold reduction by the addition of disorder in a periodic system.