Large energy, narrow bandwidth 1550 nm picosecond polarization-maintaining fiber laser.

A large energy, narrow bandwidth picosecond polarization-maintaining fiber laser operating at 1550 nm has been demonstrated. The seed laser is a self-starting Er-doped fiber oscillator based on a Figure-9 configuration, generating pulses with a duration of 48 ps and a repetition rate of 15 MHz. To reduce spectral broadening during subsequent amplification, the pulse spectrum is reshaped into a near-Gaussian profile using a narrowband uniform fiber Bragg grating (FBG). By employing an erbium-ytterbium co-doped double-clad fiber (EYDCF) amplifier with a core diameter of 25 μm, the pulse energy is boosted to 546 nJ (corresponding to the peak power of 11 kW) at a repetition rate of 1.5 MHz with a narrow spectral bandwidth of 0.2 nm. Furthermore, the amplified pulsed laser exhibits a good beam quality (M≈1.23) and minimal power fluctuation (RMS = 0.14%@2hrs). The as-designed laser is well-suited for applications such as lidar and frequency conversion.