Manipulating Laser Modes in Diffusive Disordered Systems by Precisely Designing the Boundary of the Local Pump

Abstract Manipulating laser modes in diffusive random systems is crucial to understanding the optical physics of disordered structures. However, the laser modes in diffusive random lasers are highly extended and correlated, making their manipulation difficult. Herein, this work reveals the critical role of the pump boundary on the governing mode interaction and emission characteristics of diffusive random lasers (RLs). By increasing the ratio between the square root of the pump area and the circumference of the pump region, the strongly correlated nonresonant laser mode with a continuous spectral distribution is transformed into an independent resonant laser mode with a discrete frequency distribution. A critical ratio of 5.76 is demonstrated as the transition point for pump spots with arbitrary shapes. This pump strategy provides a universal guideline for regulating laser modes in diffusive RL systems that can be applied to multifunctional lasers to clarify the behavior of light in disordered structures.