Direct generation of noise-like rectangular pulses with 5.2 µJ and 2 W from a linear all-fiber laser system at 1565 nm

The first demonstration of noise-like rectangular pulses (NLRPs) with a record pulse energy of 5.2 µ J and a peak power of 160 W at 1565 nm is presented. This is achieved through a linear-cavity fiber laser system with a power-symmetric nonlinear optical loop mirror as the mode locking element. Stable and highly energetic pulses are generated by extending the cavity length and carefully choosing the coupling ratio of the fiber loop mirror. The laser self-starts at a pump threshold of 1.12 W, and as the pump power increases to 10.5 W, the pulse duration extends from 2.2 to 32.2 ns, while the average output power increases from 0.14 to 2 W, yielding a high slope efficiency of 19.1%. Operating at a fundamental repetition rate of 392 kHz, this laser system delivers the highest reported pulse energy and peak power for NLRPs at a wavelength of 1565 nm in a linear cavity. Its cost-effectiveness, stability, and high performance make it a promising tool for applications such as LIDAR, supercontinuum generation, laser materials processing, and nonlinear spectroscopy.