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 85 Rb 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.