Single-mode 230  W output power 1018  nm fiber laser and ASE competition suppression

We present a high-power single-mode (SM) monolithic fiber laser centered at 1018 nm, producing 230 W CW, with an M2 of 1.17 and light to light efficiency of 75%. To the best of our knowledge this is the highest power described in the open literature from a SM fiber laser at this wavelength. Careful simulations were employed taking into account the various wavelength-dependent parameters, such as the doped fiber absorption, emission, saturation effects, and the cavity mirrors’ reflection, in addition to the fiber geometrical parameters. Parameters that were found to be most critical for suppressing the amplified spontaneous emission at higher wavelengths were the fiber length and the extinction ratio of the fiber Bragg grating reflectivity between 1018 nm and above 1030 nm.