The Study of Kerr Lens Mode-Locking in Nd:YLF Laser

• Main Authors: Chih-Chung Kang, 康志聰
• Other Authors: Sheng-Lung Huang
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/57657831004833964000

碩士 === 國立中山大學 === 光電工程研究所 === 87 === We have utilized semiconductor laser diode longitudinal-pump Nd:YLF solid-state crystal with the acoustooptic modulator produced actively mode-locked ultrafast optic pulse in our laboratory. Taking advantage of Nd:YLF crystal (linewidth 375 GHz) with high conversion efficiency, longer fluorescent life time(480μs) and better thermal con-ductivity, and producing stable optic pulse to 8.5ps. For Nd:YLF active mode-locked laser technology, it is a very narrow pulse width. Comparing to active mode-locked laser, passive mode-locked laser will have the ability to make narrower pulse width. In general, utilizing kerr effect to produce kerr-lens mode-locked. At present, using Argon laser pumped Ti:sapphire crystal with kerr-lens effect has already been able to produce 10fs passively mode-locked pulse. In this thesis, takeing Nd:YLF crystal as kerr medium and simulating the abilities and conditions for producing kerr-lens mode-locked in a fold laser cavity, and discovering that kerr-lens mode-locked is taking place in the edge of stable laser cavity. In experiment, utilizing semiconductor laser diode longitudinal-pump Nd:YLF solid-state crystal, and utilizing the sim-ulation result as laser cavity experimental configuration, when pumped power achieves 3.5W and intracavity average power achieves 11W, we can get 600ps mode-locked optic pulse. This consequence is rather reasonable compared with the literature which is used kerr medium's(SF10) nonlinear refractive index, ten times larger then Nd:YLF, and will produce 3ps pulse width when its intracavity average power achevies 10W. It will cause the result of pulse width less than 10ps as intracavity average power achieves 20W above. In addition, we know that the thermal lensing effect will affect the stabi-lity and reliability of the laser when high power semiconductor laser pumps solid-state crystal. In this thesis, we will also utilize "Mode Master" to observe the thermal lensing phenomenon in the high power pump Nd:YLF crystal.