  The ability to manipulate cavity resonant modes is of critical importance in
laser physics and applications. By exploiting the parity time (PT) symmetry, we
propose and experimentally realize a single-mode FP laser with improved output
power and high-speed modulation have been demonstrated. The proposed PT
symmetric laser consists of two coupled structurally identical FP resonators.
The gain and loss in two FP resonators can be manipulated independently by
changing the injection currents. In the PT symmetric FP laser, single-mode
operation is accomplished by selectively breaking of PT symmetry depending
solely on the relation between gain-loss and coupling. Single-mode lasing with
output power of 1.7 dBm and a sidemode suppression ratio (SMSR) exceeding 24 dB
is demonstrated. The 3 dB bandwidth of 7.9 GHz is achieved and clear
eye-openings were obtained for 2.5 Gbps and 10Gbps NRZ operation over 10 km
single-mode fibers. Furthermore, the PT symmetry breaking is experimentally
confirmed with measured loss and coupling coefficient of two FP resonators. The
influence of cavity length, facet reflectivity, and electrical isolation
between two P-side electrodes on the side mode suppression ratio and output
optical power is also been demonstrated, paving the way for further improvement
of the PT symmetric FP laser.
