Wavelength-tunable passively mode-locked lasers

• Main Authors: Yuh-Fwu Chou, 周裕福
• Other Authors: Jyhpyng Wang
• Format: Others
• Language: zh-TW
• Published: 1994
• Online Access: http://ndltd.ncl.edu.tw/handle/81924725886360260274

博士 === 國立臺灣大學 === 電機工程研究所 === 82 === In the past five years, there has been a series of dramatic advances in ultrashort-pulses laser technology. The inventions of additive-pulse mode-locking (APM) and Kerr-lens mode-locking (KLM)make it possible to obtain stable femtosecond pulses in a broad wavelength region from an oscillator. Both the APM and KLM result from the nonresonant nonlinearity of intracavity Kerr medium, in contrary to the colliding-pulse mode-locking, which makes use of the resonant nonlinearity. It is the reason why all the APM or KLM lasers with broadband gain medium have excellent wavelength tunability. In this dissertation, we present our developments of Kerr-lens mode locking in dye lasers, from which near-transform-limited femtosecond pulses with wavelength tunability over 33 nm are obtained. Our research provides a new approach to generate wavelength-tunable mode locking in dye lasers, which are widely used in scientific research. The self-starting of the mode locking is achieved with a dilute dye-saturable-absorber jet. The threshold of self- starting of mode locking is measured and compared with simulated results from theoretical models of intracavity pulse broadening effect. The measurements of self-starting threshold are also carried out for a Kerr-lens mode-locked Ti:sapphire laser. Both results enable us to conclude that the phase diffusion effect is the major barrier to the self-starting of mode locking. According to the phase diffusion model which is confirmed by these experiments, we can figure out the minimum strength of intracavity pulse shortening effect required to start mode locking.