Dual-band annular-beam random laser for color speckle-free imaging

Random lasers with controllable performance are considered the ideal light source for the next generation. Here, a novel, to our knowledge, random laser is proposed, which is fabricated by drop-coating disordered structures onto the side wall of a capillary. The index distribution affects the optical transmission and shapes the emission beam, realizing annular-beam random lasing in real space and momentum space. Furthermore, dual-band random lasers are fabricated simply by integrating the different gain random systems. The colorful lasing can be switched effectively by controlling the pump positions. When the proposed random laser is used as pump source for imaging, speckle-free images with different colors are obtained within the same random laser. This work will promote the development of random lasers in the field of illumination devices and optical integration.