The invention provides a random
fiber laser system and belongs to the novel
laser device field. In the
system, a traditional single-mode
fiber is taken as a
laser medium, and a cascaded
semiconductor laser is taken as pump light which is coupled to the
fiber along an opposite direction from a middle point of the fiber.
Photon is in propagation in the fiber, scattering is generated because of nonuniform random
refractive index, and distributed
Rayleigh scattering is formed. The pump light provides distributed
Raman gain along the fiber. When total
gain is greater than total loss, backward scattered
photon is amplified to generate laser. Frequency of
random laser is a result of frequency of last grade pump light shifting downward with 13 THz. By properly selecting pump light, output of the
random laser in a whole fiber transparent window is realized. By using cascaded
semiconductor laser as the pump light, not only is
Raman gain spectrum bandwidth increased, but also
Raman gain form is controlled. Thereby the
random laser in the invention has the characteristics of controllable mode, super-long transmission, low threshold, high output power and the like.