Synthesis and manufacturing the mirrors for ultrafast optics

Abstract

Properties of 3 types of multilayer dielectric chirped mirrors manufactured with Helios Leybold system (magnetron sputtering with plasma/ion assisted technology) are discussed. The first type includes mirrors providing negative group delay dispersion (GDD) and high reflectance in a wavelength range 650-1150 nm. Such mirrors are used in a broadband Ti:Sapphire oscillator for generating sub-6 femtosecond pulses. The second type of mirrors has extremely low both GDD oscillations and losses in a range 740-840 nm. Such mirrors are of interest for both long-cavity high-energy Ti:Sapphire oscillators and so-called external cavities for storing energy from femtosecond oscillators. The lowest residual GDD fluctuations achieved for this type of mirrors are 5 fs². The third type is high reflectors with very high reflectivity. Different coating materials: Nb<inf>2</inf>O<inf>5</inf>, TiO<inf>2</inf>, Ta<inf>2</inf>O <inf>5</inf> together with SiO<inf>2</inf> are compared for these 2 types of mirrors. The results of reproducibility of such mirrors and their characterization in terms of reflectivity, losses, surface quality are presented. Comparison of the design with the manufactured mirror is also done.