Theory and design of double-cavity Raman fiber lasers

We introduce the concept of the double-cavity Raman fiber laser (DC-RFL) with three Bragg gratings at the laser wavelength. In such RFLs, the threshold pump power and the conversion efficiency at large pump powers can be designed independently of each other, whereas in ordinary single-cavity RFLs these two optimization criteria collide. The particular behavior of DC-RFLs is interpreted, and a simple technique for the numerical simulation and an analytical relation for the threshold pump power of these devices are presented.