Abstract

Rapid advances in ultrashort pulse generation resulted in sub-10 fs pulses from a Ti:sapphire laser in 1994. It became evident that the main limitation for further reduction of the pulse duration is given by the higher order dispersion in the laser. Chirped mirrors [1] provide a powerful and compact technique for dispersion compensation. Additionally, they exhibit a broader high reflectivity range in comparison to standard quarter-wave Bragg mirrors. In ref. [1], chirping means that the Bragg wavelength is gradually increased along the mirror, producing a negative group delay dispersion (ODD). However, an analytic explanation of the unwanted oscillations typically observed in the group delay and GDD of such a simple chirped mirror does not exist in standard theories of optical interference coatings. Therefore, these oscillations are very often minimized purely by computer optimization.

© 1998 Optical Society of America