Passive repetition-rate stabilization for a mode-locked fiber laser by electro-optic modulation
Tingting Yu, Shuhong Jiang, Jianan Fang, Tingting Liu, Xiuqi Wu, Ming Yan, Kun Huang, Heping Zeng
Abstract
We report a passive stabilization of the repetition rate for a mode-locked fiber laser by using an electro-optic modulator in a phase-biased nonlinear amplifying loop mirror. The underlying mechanism, in contrast to active feedback operations, lies in the cross-phase modulation between electrical and optical pulses within an electro-optic crystal. The resulting spectral shift can automatically compensate for the cavity-length drift via the group velocity dispersion. Consequently, the artificial actuator enables a capture range up to 2.3 mm, much longer than that achieved by index changes of the modulator. A robust and tight locking for the repetition rate is then realized with a standard deviation as low as 9 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi>μ</mml:mi> </mml:mrow> </mml:math> Hz with a 1-s sample time over 11 hours, corresponding to a fractional instability of 4.3 × 10 −13 . Furthermore, a dynamic optical sampling by repetition-rate tuning has been manifested with a fast refresh rate at 100 kHz and a broad scanning range over 305 ps. The demonstrated passive servo action may provide a simple yet effective way to stabilize the repetition rate with high precision, large bandwidth, and wide tunability.