Wavelength Tunability of a Coupler and Air-Gap Etalon Controlled High-Efficiency $L$ -Band Mode-Locked Erbium-Doped Fiber Laser

Mode-locked erbium-doped fiber laser with a full L-band wavelength tunability from 1567 to 1612 nm by controlling the ratio of its output coupler is demonstrated, which exhibits intracavity gain of 34 dB and maximum output power of 91 mW. The dual-wavelength (980 and 1480 nm) bidirectional pumping scheme enhances quantum efficiency and power conversion ratio to 42% and 37%, respectively. Continuous-wave lasing linewidth of 0.02 nm is obtained with the introduction of an intracavity air-gap Fabry-Peacuterot filter made by polishing the fiber connector end. A 45-nm wavelength tunablility with pulsewidth of 2.4 ps and linewidth of 6.8 nm are observed under mode-locking regime. Tuning resolution of 0.3 nm and wavelength-dependent power variation of <1.2 dB are also reported