Researchs On Thulium-doped Fiber Laser At 2.05 ?m

Recently,the thulium-doped fiber laser operating at 2 ?m have attracted a lot of attentions.It is worth mentioning that 2050 nm located at the atmosphere window.There are plenty of application in the field of remote sensing and laser communication.Besides,2050 nm was at the low absorption band of ZGP crystal,so it is also useful in the optical parameter oscillator based on ZGP.This paper carried out comprehensive reseaches on the high quality thulium doped fiber laser at 2050 nm.Firstly,we attained pulsed output at ps or ns level by mode-locking,acousto-optical modulation and gain-switch.After that,we got the high power pulses and single-frequency laser with master oscillator power amplification system.The primary contents are shown as follows:1.The research background of the fiber laser at 2050 nm.According to the output characteristic of different laser,the development of continuous wave,ultrashort pulse and nanosecond pulse fiber laser are reviewed.2.We design and achieve an experimental scheme of an all-fiber high power single frequency TDFL at 2050 nm.A DFB laser was used as the seed of the system,and it was amplified to 75 W with three stage amplifiers.Pulsed single-frequency seed laser was achieved by AOM.The repitition rate and the pulse width are all tunable.After amplification,the peak power of the pulse was boosted to 0.6 kW,reaching to the threshold of SBS.3.We design and achieve an experimental scheme of an all-fiber high peak power picosecond pulsed TDFL at 2050 nm.A mode-locking TDFL based on SESAM was built as the seed laser.The pulse width of the seed was 31.9 ps,the repitition rate was 13.68 MHz.The signal power was raised to 23.5 W with two stages amplifiers.The according peak power was above 54 kW.4.We design and achieve an experimental scheme of an all-fiber high pulse energy nanosecond pulsed TDFL at 2050 nm.The seed laser was built based on gain-switch.The pump source was a pulse fiber laser at 1550 nm.The repitition rate of the pulse from seed laser was tunable,and the pulse width was controllable.The nanosecond pulse was amplified with the MOPA system.After the optimization of the amplifier,it is the first time that the nanosecond pulse with pulse energy of 1 mJ,peak power of 10 kW was obtained in the all-fiber format laser.We also investigated the characteristic of the gainswitched seed laser with different pump repitition rate.The results shows that with higher repitition rate of the pump laser,the threshold of the oscillator would be higher,and the pulse width of the output would be narrower.