Passively mode-locked quantum dot laser subject to dual long cavity time-delayed optical feedback

In this contribution, we study experimentally the impact of two long external passive optical cavities on the repetition rate and timing jitter of a monolithic passively mode-locked InAs/InGaAs quantum dot laser. The dual cavity scheme allows to fully suppress feedback induced sidebands in the radio-frequency spectrum. By fine delay control of the optical self-feedback delay lengths, a repetition rate tunability of 9.4 MHz is achieved. The lowest repetition rate line width amounts to less than 50 Hz, corresponding to a timing jitter of 1.7 fs. We explain the experimentally observed timing jitter and repetition rate trends qualitatively by adapting a versatile simple time-domain model. Both experiment and simulations indicate the strongest pulse train timing jitter reduction at feedback lengths that yield the lowest repetition rate frequency deviation