Fiber laser cavity with dynamically transformable topology for switchable bidirectional pulse generation

Abstract

We propose and study a novel type of fiber laser cavities which features dynamically transformable topology and enables pulse-to-pulse directional switching of the intracavity laser power flow. The key element of the proposed fiber cavity configuration is a fast 2 × 2 waveguide electrooptic switch (WEOS) which links a Sagnac-like (bidirectional) passive fiber loop with a unidirectional fiber loop incorporating an optical amplifier (OA) (rare-earth- or semiconductor-based). Electronic control of the WEOS port-to-port transmittance enables reversable gradual transformation of the laser cavity topology. This transformation results in directional switching of the laser radiation circulation in the Sagnac fiber loop. Proper dynamics of such transformation allows obtaining of complementary pulse trains from the counter-directional outputs in the Sagnac fiber loop. We validated this capability in a proof-of-concept transformable fiber cavity employing a semiconductor OA. The proposed cavity configuration enables switchable bidirectional pulse generation in various regimes including mode-locked ones.