All-fiber, linearly polarized 2.8 μm laser based upon a tilted ZBLAN fiber Bragg grating

An all-fiberized, linearly polarized laser operating in the mid-infrared spectral region of 2.8 μm is demonstrated. The laser is realized via inscribing a 45° tilted fiber Bragg grating (TFBG) on the active fiber of an erbium (Er³⁺) doped ZBLAN fiber laser. Robust linearly polarized operation is achieved. The laser delivers a maximum output power of 612 mW with a polarization extinction ratio (PER) of 20 dB, and its long-term stability is excellent (RMS < 0.75%). This is the first, to our knowledge, effort to realize a linearly polarized mid-infrared laser with all-fiber architecture. Our work is informative for developing high-performance linearly polarized mid-infrared lasers, which are desired in a range of areas such as precision measurement, nonlinear frequency conversion, and coherent beam combining.