1121 nm resonator properties and impact on the design of a 1178 nm sodium guidestar laser

A dual seeded (pump at 1069 nm and second Stokes at 1178 nm) Raman laser system involving amplification of the second Stokes in a Raman resonator having high reflector Bragg gratings tuned to the first Stokes at 1121 nm is proposed. This system has the potential of generating 50 W of output power at 1178 nm. Because the laser is seeded with the desired output wavelength (second Stokes), outputs having narrow or broad linewidths can be achieved. Highly efficient Raman conversion is achieved in a short Raman fiber (< 20 m) due to high 1121 nm circulating power levels in the Raman resonator. Stimulated Brillouin Scattering, the 1121 nm circulating power level, and the effects of modal instability are constraints on the design of a narrow linewidth system. Length of the resonator cavity, power level of the 1069 nm pump, and power level of the 1178 nm seed are parameters that can be adjusted to optimize the design. Usage of germanosilicate fiber improves the performance of the system. Finally, because of the low power level of available 1178 nm seeds, a two stage system (low and high power stages) is necessary to achieve 50 W of 1178 nm output power.