## 1 Introduction  
Fiber lasers have become leading candidates in the high power regime thanks to advantages over traditional solid-state lasers such as gain efficiency, compactness, ruggedness, and flexibility. Generally, these are pumped by diode lasers, which are very efficient converters from electrical to optical energy [1]. Ytterbium-doped fiber (YDF) lasers emitting around 1 \(\upmu\)m work particularly well, and have reached 20 kW of output power with excellent beam quality [2]. However, rare-earth doped fibers emit in fixed spectral bands and require that the diode laser emission spectrum overlaps with their absorption bands. By contrast, fiber Raman lasers (FRLs) are a wavelength-agile alternative for producing gain and power with optical fiber. In these, the emission wavelength is determined by the pump wavelength and the Raman shift, which can be one or several Stokes orders, and is restricted by the transparency range of the fiber rather than by the spectral bands of stimulated emission [3,4]. In addition, FRLs possess the potential for low quantum defect. This becomes smaller at shorter wavelengths, relative to the pump photon energy [5]. Other properties that can be used to overcome limitations of rare-earth-doped fiber sources are instantaneous pump-to-Stokes conversion and immunity to self-Q-switching. Photodarkening is another problem with Yb-doped fibers [6]. This can occur also in FRLs, especially with highly germanium-doped fibers (as often used for FRLs), operating at visible wavelengths at high power densities. Thus, for example, photodarkening is known to occur in fibers used for supercontinuum generation at visible wavelengths [7]. However, at longer wavelengths and lower power densities for Raman conversion in fibers longer than 100 m, we expect photodarkening to be negligible. Furthermore, cladding-pumped Raman gain fibers, similarly to conventional rare-earth-doped fibers, can enhance the brightness when a multimode (MM) optical pump beam is transformed into an output with better beam quality [8,9]. Power-scaling of FRLs has been the subject of much research, but typically with diode-pumped rare-earth-doped fiber lasers used as pump sources [10]. As an example, a YDFL-pumped fiber Raman laser reached 1.3 kW of CW output power at 1120 nm with high overall conversion efficiency [11]. Still, the use of a two-stage pumping scheme makes the FRLs more complex and is only practical for certain wavelengths. Furthermore, the intermediate pump source is often diffraction-limited. Further conversion in a FRL will then degrade the brightness, and is therefore counter-productive when brightness is our primary concern. It is also possible to pump the FRL directly with diodes. This eliminates the intermediate conversion stage, and furthermore benefits from the wide wavelength coverage available from diodes. This includes wavelengths not covered by alternative practical pump sources, e.g., in the 800-1000 nm range. However, despite these attractions, power-scaling of diode-pumped FRLs has been held back by the high pump densities and low fiber propagation losses that are needed to reach laser threshold, since stimulated Raman scattering (SRS) is a weak process. Diode-pumping has been restricted to single-mode devices operating at around 1.5 \(\upmu\)m [12]. These benefit from the high brightness of single-mode laser diodes and low fiber loss. However, the power of single-mode diodes is limited to the watt-level or less, and multimode diodes in this wavelength range lack in brightness and are much lower in power and efficiency than what is possible at shorter wavelengths. While FRLs pumped by MM diodes have been demonstrated recently at wavelengths as short as 0.8 \(\upmu\)m [13], the high fiber loss meant that the required pump brightness could only be reached in pulsed mode, which restricted the average power.