High-power continuous-wave Raman frequency conversion from 1.06 µm to 1.49 µm in diamond

We report continuous-wave beam conversion from 1.06 to 1.49 µm in a diamond Raman laser operating on the second Stokes shift. High power (114 W) and high conversion efficiency (44%) is achieved using a single cavity that is highly resonant at the first Stokes wavelength but has high output coupling at the second Stokes wavelength (89%). An analytical model was developed for external-cavity Raman lasers operating in steady-state, revealing that optimization of second Stokes output is markedly different to first Stokes and that there is a direct and proportional relationship between the second Stokes output coupling and the pump depletion in the diamond, which we have confirmed by experiment. This technology shows promise for power scaling beyond the capabilities of current fiber lasers operating in the applications-rich 1.5-1.6 µm wavelength range.