Negative dispersion mirrors for dispersion control in femtosecond lasers: chirped dielectric mirrors and multi-cavity Gires-Tournois interferometers

Chirped dielectric laser mirrors have been known for years as useful devices for broadband feedback and dispersion control in femtosecond pulse lasers. First we present a novel design technique referred to as frequency domain synthesis of chirped mirrors. These mirrors exhibit high reflectivity and nearly constant group delay over 150 THz supporting generation of sub-5-fs pulses in the visible. Afterwards, multi-cavity thin-film Gires-Tournois interferometers are introduced for the first time as an alternative approach to realize "negative dispersion mirrors". These novel dielectric high reflectors exhibit reflectivities R>99.97% and a negative group delay dispersion of ⫆ǃ fs² over a bandwidth of 56 THz. Dispersive properties originate from coupled resonances in multiple 5/2 cavities embedded in the layer structure. The general structure and performance of multi-cavity Gires-Tournois interferometers are compared to that of chirped dielectic mirrors and their distinct applications are discussed.