Long-term atomic resonator-based stabilisation system of ultrafast laser with small physics package

A long-term miniaturised stabilisation scheme for a mode-locked laser based on a rubidium coherent population trapping atomic resonator is demonstrated. By directly locking the repetition rate of a mode-locked laser to the ⁸⁵Rb 3.035 GHz coherent population trapping resonance, a miniaturised stabilisation system for the mode-locked laser is achieved. The stabilised laser shows a frequency instability of 5 ?? 10^-11 (1 s) and a long-term instability of ˜3 ?? 10^-12. This scheme avoids the extra stability loss in the electronic connection between the mode-locked laser and the frequency reference. The whole stabilisation system occupies only a physics package of 5 ?? 5 ?? 2.2 cm, which provides a compact and portable approach for mode-locked laser repetition rate stabilisation.