All-fiber high-energy pulsed laser at 1572  nm for coherent detection of atmospheric CO₂ concentration

We developed a high-energy pulsed laser at 1572 nm based on an all-fiber master oscillator power amplifier (MOPA) for coherent lidar detection of carbon dioxide profiles. By applying two acoustic-optic modulators (AOMs), the signal-to-noise ratio of the output signal is greater than 50 dB. Near-Gaussian pulses are realized by modulating the first AOM with a specifically designed asymmetric triangular wave. The optical-to-optical conversion efficiency of the main amplifier is improved to 7.2% with water cooling and is nearly doubled compared to that under air cooling conditions. The efficiency reaches a high level in 1572 nm amplification with erbium-ytterbium co-doped fibers pumped by 976 nm laser diodes. The system delivers 140 µJ pulses at a 10 kHz repetition rate with a 400 ns pulse width and a peak power of 350 W. The output pulse exhibits a 2 MHz linewidth and stable energy with a root-mean-square (RMS) energy deviation of only 2.2% in 90 min. The laser generates pulses with beam quality factors (M²) of 1.63 in the x direction and 1.68 in the y direction. The overall performance of the laser system meets the requirements for high-precision carbon dioxide coherent lidar detection.