@misc{oai:uec.repo.nii.ac.jp:00001094,
 author = {戸倉川, 正樹 and Tokurakawa, Masaki},
 month = {2016-09-16},
 note = {2009, In this thesis, ultrashort pulse lasers based on Yb3+-doped materials havebeen developed. Yb3+-doped mode-locked lasers have several advantagesover other mode-locked lasers in a high power operation. They can bedirectly pumped by a high power InGaAs laser diode. The uniqueenergy-level scheme of Yb3+ ion leads to very small quantum defects(<10%) and high quantum efficiency (~1), and thus highly efficient highpower laser operations under less heat loads are possible. The mechanicaland thermal properties of Yb3+-doped materials depend on their hostmaterials, and therefore various kinds of Yb3+-doped materials have beenstudied. Recently, sub 60-fs mode-locked laser operations based onYb3+-doped crystals having inhomogeneous broadened gain bandwidthsand high Q cavities have been reported, but such crystals tend to show poorthermal properties, poor mechanical properties and/or anisotropy structureso that high power laser operation is difficult with them. In addition, theirhigh Q cavities tend to be not suitable for highly efficient laser operations,because their output coupling efficiencies tend to be lower than optimizedvalues for highly efficient laser operation. In general cases, the efficiencyand output power were limited to less than 10 % and 100 mW, respectively.In this thesis, direct LD pumped highly efficient high power ultrashortpulse lasers based on the techniques of Kerr-lens mode locking andmulti-gain media oscillator have been developed. For power scalability,gain media having good thermal and mechanical properties such asYb:sesquioxide materials were used.In case of the SESAM mode locking, the available pulse durations werelimited to be ~200 fs by a transition to multi-pulsed operations. To achievemuch short pulse duration, the Kerr-lens mode-locked laser cavity wasconstructed. The fast and large gain modulation of Kerr lens enablesultrashort pulse operation with cavities having proper output couplingefficiencies. To achieve large soft aperture Kerr-lens effect withxbroad-stripe LD (BLD) pumping, the cavity was aligned nearly unstable atfast axis of pumping BLD. Generations of sub 80-fs pulses with above 1-Waverage powers have been successfully achieved with the help pf Kerr-lenseffect. Additionally the ultrashort pulse operation based on a multi-gainmedia oscillator has been also demonstrated to achieve further short pulseduration by an artificially broadened gain bandwidth. From the oscillator,pulses as short as 53 fs with above 1-W average power have been obtained.The influence of the Kerr-lens effect inside the cavity and its dependenceon cavity state was numerically estimated. The necessary equationsultrashort-pulsed laser operations were calculated based on competition ofgain saturation effect and the importance of Kerr-lens effect was explained.The power scalability is also discussed based on above calculations forfuture works. The usability of ceramic gain media in the femtosecond laseroperation was also proved in this thesis.},
 title = {Kerr-lens mode locked lasers based on Yb 3+ -doped materials},
 year = {},
 yomi = {トクラカワ, マサキ}
}