In this work, we discovered the possibility of greatly relaxing requirements to the speed and dynamic range of pump power variation and, thus, of reducing synchronous pumping of ytterbium (Yb)-based fiber lasers to a very simple pump modulation yielding a mode-locked pulsed output. We show that even slow (microsecond-scale) low-index (≤0.5) sine-wave synchronous modulation of the pump power can result in shaping of a regular train of nanosecond laser pulses. It is revealed that the energy-conservative process of laser pulse shortening against the pump modulation period can take place in the quasi–two-level laser active medium owing to mistiming-induced gain discrimination of the temporal laser pulse profile. Thus, nanosecond pulses with energy up to 50 nJ were obtained in our experimental all-fiber Yb-based laser configuration. Our theoretical modeling reveals routes to much stronger pulse shortening through tunable pump modulation parameters. This discovery allows the establishment of more reliable and easy-to-implement high-efficiency alternatives to other types of high-energy ultralong mode-locked fiber lasers.
|Журнал||Journal of the Optical Society of America B: Optical Physics|
|Состояние||Опубликовано - 1 окт 2020|