Passively mode-locked fiber laser based on GeTe as a saturable absorber

In this work, we fabricate a saturable absorber based on GeTe with saturation intensity and modulation depth of 12.6M W/c m ² and 7%, respectively. We obtain stable conventional soliton and stretched soliton mode-locking operation. For the conventional soliton state, the average output power increased from 0.93 to 8.70 mW with the increase of pump power, and the fundamental repetition rate was 7.8351 MHz. Its central wavelength and 3 dB bandwidth were 1564.72 and 4.78 nm, respectively. For the stretched soliton state, when the pump power was increased from 87.4 to 420.3 mW, the average output power increased from 2.05 to 10.46 mW. When the maximum average output power reached 10.46 mW, the maximum average single-pulse energy was 0.86 nJ. The experimental results show that GeTe nanosheets will have broad application potential in the field of ultrafast photonics.