Single-Mode 2.05 μm Narrow Linewidth Bidirectional Pumped Tm/Ho-Doped Hybrid Pulsed Fiber Amplifier

In this paper, we propose a novel approach for a high peak-power single-mode 2.05 μm narrow linewidth bidirectional pumped Tm-doped fiber (TDF)/Ho-doped fiber (HDF) hybrid fiber laser amplifier. By utilizing the different frequency shifts of TDF and HDF, which effectively improves the threshold of stimulated Brillouin scattering (SBS). Compared to a 2.2 m TDF amplifier, the bidirectional pumped 1.1 m TDF&1.4 m HDF hybrid amplifier eliminates SBS and amplified spontaneous emission (ASE), improving the signal-to-noise ratio (SNR) from 39 dB to 48 dB. At a pulse repetition frequency (PRF) of 10 kHz, limited by gain saturation, the pulse energy and peak power are 17.5 μJ and 116 W, respectively. In addition, compared to a 2.8 m TDF amplifier, the bidirectional pumped 1.4 m TDF&1.4 m HDF hybrid amplifier increases pulse energy from 10.4 μJ to 34 μJ and peak power from 69 W to 226 W at the pulse widths of 150 ns, raising the SBS threshold by 3.2 times. The linewidth of the narrow linewidth light is about 5.12 MHz, which is close to the Fourier transform limit. The polarization extinction ratio (PER) and beam quality factor M2 are estimated to be about ∼15.6 dB and ∼1.08.