Mid-infrared all-fiber superfluorescent source in Er3+-doped fluoride fiber

•All-fiber MIR superfluorescence generation and amplification in Er3+-doped fluoride fiber has been demonstrated for the first time.•Two home-made MIR side pump combiners based on evanescent wave side-coupling theory are fabricated directly on two sections of gain fiber.•The total power of MIR superfluorescent fiber source has been amplified to 0.55 W with spectral range of 2680–2880 nm. We report, to the best of our knowledge, the first mid-infrared (MIR) all-fiber superfluorescent source based on a superfluorescent seed and a single-stage amplifier. A 7.8-m-long section of highly-Er3+-doped fluoride fiber is used in the superfluorescent seed and a 4.3-m-long section of lightly-Er3+-doped fluoride fiber acts as the amplifier. Two home-made MIR pump-signal combiners based on side-pumping technology are fabricated directly on two sections of gain fiber. By direct-low-loss fusion splicing of two kinds gain fiber, the power of MIR superfluoresescence main output is amplified to 0.35 W and the power of rear output is amplified to 0.2 W. The output spectrum under maximum power spans from 2680 nm to 2880 nm with 20 dB bandwidth of 60 nm. The measured time domain and output beam profile show that this superfluorescent source keeps relatively stable in microsecond time scale without self-pulsing effect occurrence and has near single-mode gaussian characteristic. This works provides a new way for MIR superfluorescent source, which is of practical interest in a range of applications.