Dual-wavelength thulium-doped fiber laser with separate wavelengths selection based on a two mmi filters configuration

Dual-wavelength laser emission of a ring cavity Tm-doped fiber laser with a separate wavelength selection of the simultaneously generated laser lines is experimentally demonstrated. A dual-wavelength laser operation is obtained by using two homemade multimode interference (MMI) filters with transmission peaks at the wavelengths of 1814.23 and 1872.15 nm, which are placed in a Mach Zehnder interferometer configuration for independent selection of the dual-wavelength generated laser lines. The selection of the shorter laser wavelength is achieved by submerging the MMI filter in different ethylene glycol/water mixtures, reaching a wavelength selection in the broad range of ~24 nm. The stability results of the simultaneously generated laser lines are also shown. The use of the proposed MMI filters as reliable spectral filters for dual-wavelength generation in all-fiber Tm-doped fiber laser systems is experimentally demonstrated.