  A color-switchable random laser 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. Moreover, 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, random lasing
with different colors can be flexible obtained by simply moving the pump
position.
