Research On 2-?m Pulsed Laser Performances Of Sol-gel-fabricated Tm-doped Silica Fiber

Pulsed lasers operating at 2 ?m wavelength have attracted wide interest due to their application potentiality in material processing,remote sensing,free-space optical communication,military application,and pumping sources for mid-infrared super-continuum generation.Tm-doped silica fiber laser is an ideal ways to generate pulsed lasers at 2 ?m wavelength.On the one hand,it has the intrinsic advantages of fiber lasers: efficient heat dissipation,compactness,good beam quality and high doping capability;On the other hand,it simultaneously possesses the inherent merits of general Tm-doped gain media: The quantum efficiency can be beyond 100% due to the existence of cross relaxation(CR)while pumping by 790-nm LD.Furthermore,the wide emission spectrum of Tm-doped fiber allows generation and amplification of ultrashort pulses near 2 ?m wavelength.However,the most ever-reported Tm-doped fiber laser pulses demonstrated a lower energy for adopting gain fiber with small core diameter.In this dissertation,adopting large-core sol-gel-fabricated Tm-doped silica(SGTS)fiber as gain fiber,we studied its laser performances including continuous-wavelength(CW)laser,Q-switching laser and mode-locking laser performances.The main works are included as follows:1.Firstly,CW laser performances with 2 m,3 m,and 4 m-length SGTS fiber were tested,and the 4 m-length SGTS fiber demonstrated the best laser performance with a slope efficiency of 18.85% and a maximum output power of 1.6 W.2.Secondly,with the 4 m-length SGTS fiber as gain fiber,the SESAM Q-switched and the BP SAM Q-switched fiber oscillators generated high-energy pulsed lasers operating at the wavelength of 1955 nm.The maximum average output power,the shortest pulse duration and the maximum pulse energy are 1024 mW,2.04 ?s,21.36 ?J and 615 mW,660 s,11.72 ?J,respectively.3.At last,adopting the 4 m-length SGTS fiber as gain fiber and SESAM as the mode-locker,we have demonstrated high-power mode-locked pulses operating at the wavelength of 1954 nm.The mode-locked laser had a maximum average output power of 1.0 W,repetition rate of 23.2 MHz and pulse width of 23.9 ps,corresponding to pulse energy of 43.1 nJ,peak power of 1.8 kW.Large-core Tm-doped fiber fabricated via sol-gel method has a high doping homogeneity,preventing the cluster of rare-earth ions and the fluorescence quench effect,indicating that SGTS fiber can generate 2 ?m pulsed laser with high pulse energy and high beam quality.Compared with the ever-reported Tm-doped fiber lasers,all experimental results demonstrated in this dissertation shows that the large-core Tm-doped fiber fabricated via sol-gel method has the potentiality for generating laser pulses with high power and high energy at the wavelength of 2 ?m.