Abstract

We demonstrate for the first time, we believe, a broadband low-finesse A-FPSA that starts KLM mode-locking of a Ti:sapphire laser and supports 10-fs pulses (Fig. 1). A similar absorber structure supports pulses as short as 12 fs with soliton mode-locking¹ over the full cavity stability regime without KLM. Previously, rapid progress in ultrashort pulse generation using Ti:sapphire lasers has led to pulses as short as 8-fs based on Kerr lens mode-locking (KLM) and proper dispersion compensation.² However, these pulses are not self-starting. Recently, we demonstrated pulses as short as 19 fs using a high-finesse antiresonant Fabry-Perot saturable absorber (A-FPSA)³ to start KLM and pulses as short as 34 fs with an AR-coated thin saturable absorber mirror⁴ that started and stabilized soliton mode-locking over the full range of the cavity stability regime. In both cases, the main limitation for further pulse-width reduction was the bandwidth of the bottom AlGaAs/AlAs Bragg mirror on which the absorber was grown. We eliminated this bandwidth limitation by replacing the Bragg mirror by a silver mirror. This process has been applied to several saturable absorber designs.

© 1996 Optical Society of America