Square nanosecond mode-locked Er-fiber laser synchronized to a picosecond Yb-fiber laser

A mode-locked Er-doped fiber laser was triggered to synchronize with a separate ultrashort picosecond Yb-doped fiber laser by cross phase modulation. Square nanosecond pulses were generated in the long-cavity Er-fiber laser by the peak intensity clamp effect while the synchronization maintained. At the maximum pump power of 450 mW, a synchronous laser pulse duration of 5.5 ns has been achieved. This synchronous nanosecond and picosecond system has shown a large length mismatch tolerance of 2.6 mm and can work stably for days.