High-Power and High-Order Random Raman Fiber Lasers

High-order random Raman fiber lasers are investigated for generating high-power widely wavelength-tunable light sources. By cascaded random Raman lasing and adjusting pump laser wavelength, continuous wavelength tuning from 1 to 1.9 μm is reported. For power scaling, a high-power Yb-doped fiber laser at 1064 nm with improved temporal stability is developed as the pump source. The ninth-order cascaded random Raman fiber laser with a spectral purity of 86.6% is achieved at 1806 nm. Up to 100.1-W inband power is obtained with an optical efficiency of 38.4% from 1064 nm and 27.2% from 915 nm. The results prove that cascaded random Raman  fiber laser is a versatile technology to generate  high-power fiber laser at wavelength  outside the rare earth emission bands.

I. Introduction

Recently, random Raman fiber lasers (RRFLs) have drawn extensive attention due to their simple cavityless configuration, high efficiency and wavelength agility. As a result, they find diverse applications in the scientific research, optical communication and industrial community. Since the first demonstration of RRFL in [1], much efforts are put on the performance improvement. For the power scaling, the output power of the RRFL increased from hundreds of milliwatts [1] , [2] to hundreds of watts [3] –[7], and even to kilowatt with a master oscillator power amplification (MOPA) configuration [8], [9] . For the optical efficiency, RRFLs demonstrated pump-to-Stokes wave conversion of up to 89% [5], [10]. For the polarization characteristic, linear polarization output due to the polarization dependent Raman gain was reported with RRFLs [10], [11]. Also, different kinds of fibers, such as conventional single mode fiber [1], Raman fiber [12], phosphorus-doped fiber [6], and even tapered fiber [13] were adopt to supply the Raman gain and distributed feedback Rayleigh scattering. Besides that the performance of the RRFLs is approaching that of conventional Raman fiber lasers, new operation schemes of pulsed [14], [15] and diode pumped RRFLs [16] are developing and pave the way for more applications.