Single-longitudinal-mode thulium-doped fiber laser based on the composite filtering effect of multiple types narrow-bandwidth filters

•A compound filtering process involving multiple filters within the thulium-doped laser cavity strengthens the stability of the SLM operation.•The linewidth of a 1.94 μm single-longitudinal-mode laser is significantly narrower by the multiple filters.•A reliable way to achieve the wavelength tuning from 1940.02 to 1941.12 nm by varying the temperature of the Fiber Bragg Grating. We demonstrate a single-longitudinal-mode thulium-doped fiber laser operating at 1.94 μm. Stable single-longitudinal mode operation is contingent upon the synergistic filtering effect of multiple narrow-bandwidth filters of varying types. By inserting dynamic Bragg grating with unpumped thulium-doped fiber, fiber Bragg grating and sub-ring filters into the thulium-doped laser cavity to enhance longitudinal mode selection capability, the maximum single-longitudinal-mode laser power reaches 544 mW. The time-domain root mean square (RMS) value of laser power is calculated to be 0.41 %. The wavelength tuning from 1940.02 to 1941.12 nm is also demonstrated by varying the temperature of the Fiber Bragg Grating.