A ring-shaped random laser in momentum space
A ring-shaped random laser in momentum space is designed through directly coupling random laser with a commercial optical fiber. By using a simple approach of selectively coating the random gain layer on the surface of fiber, the red and yellow random lasers are respectively achieved with low threshold and good emission direction due to the guiding role of optical fibers. The unique coupling mechanism leads to the random lasing with ring-shape in momentum space, indicating an excellent illuminating source for high-quality imaging with an extremely low speckle noise. More importantly, triple-state color-switchable random lasing with yellow, red and yellow-red dual-color can be flexible obtained by simply moving the pump position. The results may promote random lasers’ practical applications in the fields of sensing, in vivo biologic imaging, high brightness full-field illuminating.