Bidirectional operation of a mode-locked fiber laser based on a four-port circulator and two SESAMs

We demonstrate a novel bidirectional fiber laser mode-locked with two semiconductor saturable absorber mirrors (SESAMs) incorporated into the laser cavity through a four-port circulator. The laser allows the generation of two independent countercirculating mode-locked pulse trains, each with individual fundamental repetition. In the experiment, two countercirculating pulse trains, with repetition rate of 21.3 MHz and 15.2 MHz, respectively, are obtained simultaneously. By controlling the intracavity loss imposed on these two pulse trains, either one of the two pulse trains can be switched on or off.