Spatiotemporal mode-locked intelligent fiber laser based on cascaded photonic lanterns

An intelligent controlled spatiotemporal mode-locked (STML) fiber laser based on a photonic lantern (PL) is proposed and experimentally demonstrated. A pair of in-house developed PLs is spliced into the cavity in a back-to-back structure. This PL-based structure functions as a mode multiplexer/demultiplexer to generate higher-order spatial modes. Owing to the strong polarization-dependent loss structural characteristics, the structure also serves as an equivalent saturable absorber based on nonlinear polarization rotation. The STML fiber laser delivers pulsed high-order modes at a center wavelength of 1555.4 nm with a pulse duration of 6.99 ps. With the deployment of a motorized polarization controller and a time-domain signal feedback system, the laser enables intelligent control via a stochastic global polarization search algorithm. Experimental results indicate that the proposed laser can effectively evade disturbances from complex intracavity states and accurately lock onto the fundamental mode-locking state within only 2 min.