Widely Tunable Watt-Level Single-Frequency Tm-Doped Fiber Ring Laser as Pump for Mid-IR Frequency Generation

We demonstrate a thulium-doped fiber ring laser (TDFRL) integrated with an amplifier, which has a watt-level single-frequency output at 2 $\mu\text{m}$ with a 120-nm wavelength tunability. The TDFRL is constructed based on a hybrid ring-linear resonator configuration. An unpumped TDF is incorporated as a self-constructed saturable absorption grating. A blazed grating aligned in a Littrow configuration is employed for broadband wavelength-selective feedback. The characteristics of the laser output mode are analyzed by using an all-fiber scanning ring resonator.