60-nm-Wide Tunable Single-Longitudinal-Mode Ytterbium Fiber Laser With Passive Multiple-Ring Cavity

A broadband tunable, single-longitudinal-mode (SLM) ytterbium fiber laser based on a passive multiple-ring cavity (MRC) technique is proposed and demonstrated experimentally for the first time to our knowledge. Two different short ring cavities are inserted into the main ring cavity and serve as wideband mode filters to ensure SLM oscillation. With 1-m ytterbium-doped fiber as the gain medium, the SLM operation is achieved with over 60-nm wavelength tuning range at 100-mW pump power. The laser is very stable with output power of 6 dBm and an optical signal-to-noise ratio of higher than 53 dB in all the 60-nm tuning range.