High Power2μm Fiber Laser And Applications

High-power solid-state lasers operating in the eye-safe2mm spectral region areof great interest for numerous applications such as atmospheric monitoring, remotesensing, LIDAR and medicine. Cladding pumped Tm-doped fiber lasers offer apromising route to higher output power owing to their great advantages such asrelative thermal immunity, high efficiency, and outstanding beam quality. In order tocontrol the spectral and temporal characteristics of the Tm-doped fiber lasers, thisdissertation present theoretical and experimental study on double clad Tm-doped fiberlasers. The fiber-bulk hybrid laser is also the main concerned work in this dissertation.For theoretical study, the energy structure and spectral characteristics of Tm3+inthe fiber host silica are investigated. Light propagating characteristics in the fiber arediscussed. The properties of relevant materials are analyzed. Based on the rateequation and light propagation equation, the dynamic characteristics of Tm-dopedfiber laser were analyzed. The thermal limit for the fiber used in this work wasestimated by solving the steady-state heat equation.For experimental study, we mainly investigated the spectral and temporal controlof Tm-doped fiber lasers. A fiber-bulk hybrid laser was studied to overcome thelimitation of pulse energy.Firstly, we did an experiment without spectral control, a maximum output powerof152W was generated, corresponding to a slope efficiency of54%with respect tolaunched pump power. We found that the output spectrum is quite broad (>20nm), thespectrum was also not stable, a red-shift of the spectrum was observed with theincrease of launched pump power. Then, a diffraction grating was used to select theoperating wavelength, a maximum output power of62W was obtained, with over200nm tuning range. The output spectrum is quite stable, with a linewidth of <1nm.We also studied the MOPA laser system, more than100W of tunable laser wasgenerated.Secondly, by employing a SESAM as mode lock devices, we observed stablemode lock pulses with a pulse width of about150ps and pulse energy of about11nJ,the repetition rate is about35MHZ. The fiber we used is a LMA fiber, which maysupport pulses with a higher energy.Finally, we studied the fiber bulk hybrid laser, a Tm-doped fiber laser at1933nm was employed as pump power to in-band pump Ho:YAG crystal, a maximum outputpower of18.4W was obtained at2124nm, corresponding to a slope efficiency of~60%.