Dods S R, Zhang Z, Ogura M
School of Electrical and Electronic Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, UK.
Appl Opt. 1999 Jul 20;38(21):4711-9. doi: 10.1364/ao.38.004711.
A highly dispersive mirror for dispersion compensation in femtosecond lasers is designed by inverse spectral theory. The design of a simple quarter-wave Bragg reflector can be modified by moving the poles in the optical impedance found in the photonic stop band. These spectral quantities are used as independent variables in the numerical optimization because they have no effect on the location of the photonic stop band, and so the design requirements to obtain a high reflectivity and a specific delay spectrum are decoupled. The design was fabricated by ion-beam sputtering. A group delay dispersion of -300 fs(2) was measured over a bandwidth of 28 nm, with a remaining reflectivity of greater than 99% in this range. The mirrors were used to make two Ti:sapphire lasers with 10- and 4-mm-long crystals, both of which generated near-transform-limited pulses of 35-fs duration. Because of the high dispersion of the mirrors, the laser cavities needed only five and three bounces from the mirrors, thus keeping reflection losses to a minimum.
利用逆谱理论设计了一种用于飞秒激光色散补偿的高色散镜。通过移动光子禁带中光学阻抗的极点，可以对简单的四分之一波长布拉格反射器的设计进行修改。这些光谱量在数值优化中用作自变量，因为它们对光子禁带的位置没有影响，因此获得高反射率和特定延迟谱的设计要求得以解耦。该设计通过离子束溅射制备。在28nm带宽上测得的群延迟色散为-300fs²，在此范围内剩余反射率大于99%。这些镜子被用于制作两台钛宝石激光器，晶体长度分别为10mm和4mm，两台激光器均产生了持续时间为35fs的近变换极限脉冲。由于镜子的高色散，激光腔仅需从镜子反射五次和三次，从而将反射损耗降至最低。
