Highly Efficient and High-Power Raman Fiber Laser Based on Broadband Chirped Fiber Bragg Gratings

A highly efficient and high-power Raman fiber laser was developed based on the use of broadband fiber Bragg gratings (FBGs) as optical couplers. The broadening of the Stokes signal is analyzed in both cases where the laser emission is restricted or not by the FBGs bandwidth. The use of broadband FBGs with minimized cladding-mode losses allows us to overcome the problem of power leakage outside the laser cavity through the input coupler. It is shown that by carefully tailoring the intracavity spectral losses and the FBGs losses, lasing efficiencies approaching the quantum limit can be obtained. In fact, 7.8 W of Stokes power with a conversion efficiency of 93.6% has been obtained.