Coherent combining of fiber lasers

It seems straightforward to combine the latest high power fiber lasers together to scale up power. Yet every approach, including HRL´s self-organization architecture, has proved more challenging than expected at high power. In practice power scaling elicits several undesirable phenomena whose consequences inhibit coherent combining. Stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS), for example, can together turn the relatively benign power fluctuations associated with mode beating into fiber-damaging pulses. Coherence and polarization integrity are inevitably impaired by glass-related nonlinear index changes (n₂). HRL has demonstrated two to four lasers coherently combined to the 200 Watt level, using free space coupling with beamsplitters. In addition, nine independent lasers were locked in an all-fiber coupler