Design of negative dispersion mirrors used for the femtosecond-pulse laser

阐述了用光学薄膜进行色散补偿的基本原理，介绍了设计的基本过程．根据Ti：Sapphire飞秒激光器中腔内色散补偿的要求，设定了色散补偿目标，通过计算机优化，得到了一种40层的Ta2O5／SiO2介质膜系．该膜系能在720～870am范围获得大于99．5％的反射率，在510～550nm获得大于90％的透射率，在740～850nm提供较平滑的-40fs^2的群延迟色散．这样的结果经过7次反射后，可以补偿5-mm Ti：sapphire晶体产生的绝大部分群延迟色散。The basic theory of dispersion compensation of the thin film is discussed. The optimized multiplayer mirrors used for a femtosecond mode-locked Ti∶Sapphire laser is reported. The mirrors exhibit high reflectivity (>99.5%) over a wavelength range from 720 to 870 nm, high transmittance (>90%) from 510 to 550 nm and smooth variation of group delay dispersion from 740 to 850 nm. Most GDD of a 5-mm Ti∶Sapphire crystal can be compensated by seven bounces