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.