Dual-wavelength all-fiber Q-switched fiber laser using bismuth-doped fiber as saturable absorber

A passively Q-switched all-fiber laser is demonstrated using a 10-cm-long bismuth-doped fiber (BDF) as a saturable absorber (SA). The dual-wavelength operation was obtained due to the nonlinear effect inside the fabricated BDF, which has a high germanium content. Stable Q-switched pulses were obtained at the dual synchronous wavelengths of 1 530.1 nm and 1 531.1 nm. When the pump power is tuned from 105.3 mW to 191.0 mW, the repetition rate can be varied from 82.6 kMz to 117.6 kHz. The maximum pulse energy and average output power were 83.4 nJ and 9.8 mW, respectively while the minimum pulse width was 8.5 µs at the maximum pump power of 191.0 mW. Our results indicate that BDF could be a promising alternative optical modulator for pulsed fiber laser application.