Review of random laser research ( Invited )

Due to its unique structure and low coherence, random lasers are widely used in fields such as speckle-free imaging, sensing, and light therapy. The feedback mechanism of random lasers is light scattering introduced by disordered media. High threshold and non-directionality are its main disadvantages. In order to solve these problems, researchers used the one-dimensional confinement of optical fibers to obtain random fiber lasers with a low threshold and a certain directionality. In the past ten years, the development of random lasers has experienced a process from incoherent feedback to coherent feedback, from complete disorder to controllable output parameters. A large number of studies have tried to explain the physical nature of random lasers using quantum theory, chaotic laser theory, and numerical analysis. The origin and development history of random lasers and random fiber lasers were reviewed, the classification and related principles of random lasers were introduced, the methods of controlling random laser output parameters were summarized, the recent typical applications of random lasers were demonstrated, fiber random lasers feedback types and gain mechanisms were analyzed, and finally the future of random lasers development was prospected.