Experimental study on spectral beam combining for two fiber lasers in external cavity

Experimental results of spectral beam combining for two fiber lasers in an external cavity have been reported,which used largemode-area Er3+/Yb3+ co-doped doublecladding fiber as the gain medium. The maximal output power of 0.80 W with combining efficiency more than 82.5% was obtained. The effect of changing fiber-end distance from the system axis, as well as rotation of the grating on spectral output and combining efficiency was demonstrated and analyzed, which shows that one of the spectra is multimoded when the distance of fiber end from the system axis is beyond a certain range, and combining efficiency increases when the angle of the grating decreases with respect to horizontal plane．