Tunable Yb-doped fiber laser with single longitudinal mode (SLM) operation based on subring cavities

1064 nm band Ytterbium doped fiber (YDF) laser is proposed and investigated. Using 70 cm YDF and FBG parameter optimization reflectivity and pumping scheme, a high slope efficiency of 50% and low threshold power are obtained. The power variation is less than 0.1 dB in 13 nm tuning span. Using the Vernier effect, near single frequency lasing is realized for the whole tuning range in 2dBm output power.