A new fiber laser configuration that has great potential as a seed laser was published in Optics Letters.

We present an all-polarization-maintaining mode-locked fiber laser based on a nonlinear amplifying loop mirror utilizing a 3 × 3 coupler. A pump laser diode placed outside the cavity pumps both the oscillator and fiber amplifier. This laser configuration effectively utilizes all ports of the coupler, making the laser compact and low-cost, and has great potential as a seed laser for ultrashort pulse lasers.

Masanori Nishiura, Ryo Kageyama, and Tatsutoshi Shioda, “Efficient use of all ports of a 3 × 3 coupler in a nonlinear amplifying loop mirror-based fiber laser,” Optics Letters 48 (2023) 4312-4315.
https://doi.org/10.1364/OL.496871