High-brightness PT-symmetric laser bars with exceptional point modulation via spectral beam combining.

PT-symmetric semiconductor laser bars are fabricated and experimentally harnessed via spectral beam combining. A 22.20% reduction in the PT-symmetry-breaking threshold current is observed, compared to that of free-running operation, which is justified by the numerical analysis, based on a three-mirror equivalent model and the gain-clamping effect. At 26 A, the measured M2 values of spectral beam combining are 1.83 and 1.86 for the slow and the fast axes, respectively. Calculated peak brightness reaches 411 MW·cm-2·sr-1 with 13.16 W output power. This work achieves flexible exceptional-point control via external cavity feedback, with brightness enhanced.