Abstract

The carrier-envelope phase (CEP) of mode-locked lasers plays a decisive role for frequency metrology and attosecond science. A transition from the current microwave-based frequency standards to optical clockworks appears imminent. The precision of these clockworks enables residual jitters between carrier and envelope of a pulse of less than 10 attoseconds [1]. Such a tight lock has only been enabled by the feed-forward stabilization technique [2]. With an ever increasing precision of frequency metrology, it is currently still unclear at which level fundamental physical limitations, e.g., from quantum noise, set in. This aspect is of particular importance for the observation of a possible drift of elementary physical constants, e.g., the fine-structure constant. Here, we discuss a white frequency noise contribution that is apparently caused by amplified spontaneous emission inside a mode-locked laser oscillator. Our measurements indicate that, in particular, fiber lasers are strongly affected by this previously unreported mechanism.

© 2015 IEEE