The Study Of Thulium Doped Silica Fiber And All-fiber Continuous Lasers With A Wavelength Of 2 Microns

Compared with conventional lasers,fiber laser has many advantages such as high efficiency,low threshold,good beam quality,simple and compact structure,wide wavelength tunable range,being able to work in harsh environments,etc.more and more people began to pay attention to it.In addition to the common advantages of the fiber laser,thulium-doped fiber laser(TDFL)— its output at 2?m,has some characteristics such as human-eye-safety,water absorption peak and in the "atmospheric window",in biomedical,laser detection,remote sensing,optical communications,materials handling,military and other fields has a special superiority.However,due to involving military,political and other sensitive areas,high-performance thulium-doped fiber is strictly controlled and prohibited export to China.Therefore,to achieve high-performance thulium-doped fiber and high-power 2?m thulium-doped fiber laser localization is of great significance.The main work of this paper was respectively from technical theory and experiment two parts,detailed the research of thulium-doped fiber and thulium-doped fiber laser.The study began with the basic principle of thulium-doped fiber,such as energy-level structure,spectrum,pump modes of thulium ion,and the interaction between thulium ions in silica fiber.The preparation of double-clad thulium-doped fiber had been learned,which was based on modified chemical vapor deposition(MCVD).The key techniques of thulium-doped fiber laser were studied: basic structure,cladding pump technique,fiber bragg grating(FBG)technique,coupling technique,high attenuation cladding power stripping technique and fiber end-cap designing technique.Detailed analyzed the reasons of the double-clad fiber can efficiently convert the low-beam-quality pump light emitted by the laser diode(LD)into a fundamental-mode laser.In the section of experiment,based on the fiber preparation technique,homemade thulium-doped fiber was being tested,compared and screened.The fiber with best performance could be used in the construction of high-power thulium-doped fiber laser.The laser mode optimization and end-cap preparation was completed,and the experimental results were displayed.The focus was on the 793 nm pumped high-power continuous thulium-doped all-fiber lasers.We realized a straight cavity thulium-doped fiber laser by using a homemade double-clad thulium-doped fiber with core and cladding ratio of 25/250,the laser output power was 121 W,the center wavelength was 1915 nm and the slope efficiency was 51%.We also built another fiber laser by using 25/400 homemade double-clad thulium-doped fiber with master oscillator power-amplifier(MOPA)structure,this fiber laser system achieved a output power of 295 W,which was a new record among China at the time the experiment finished,and the center wavelength was 1981 nm,the slope efficiency was 49.61%.A tandem-pumping thulium-doped fiber laser was achieved,in order to verify the possibility of non-793 nm pumped thulium-doped fiber laser,and to compare the advantages and disadvantages of the two pump modes.The tandem-pumping fiber laser was pumped with a 1915 nm TDFL pump source,resulting in a 1980 nm laser output with an output power of 63 W and a slope efficiency of 79%.