Modes and Airy distribution of a non-distributed feedback-based random cavity

Light confinement in a disordered medium by multiple scattering processes plays a crucial role in the development of a random laser (RL). Modes of an RL are complex and emit in all directions due to the absence of a well-defined cavity. In a non-distributed feedback random laser (NDFRL), cavity formation has a close similarity with the Fabry-Pérot cavity (FPC) of a conventional laser. Hence, the investigation of an NDFRL is advantageous to understand the RL modes. In this regard, a detailed analysis of its passive cavity resonance modes is essential. However, these resonance modes are fundamentally different from the spectral intensity distribution, namely the Airy distribution of the cavity. The Airy distribution has periodic peaks due to constructive interference of light and its peaks appear similar to the resonance modes. For a cavity with a high quality factor (Q-factor), the Airy distribution and the resonance modes are exactly the same and indistinguishable, but they differ significantly when the cavity becomes lossy (i.e., low Q). The random passive cavity of an NDFRL has a low Q-factor as the system is inherently open and lossy. We investigate the mode profiles and the Airy distribution of a passive cavity of NDFRL and observe that their relation is similar to that of a conventional passive FPC.