Phase-locking and brightness enhancement of a broad-area blue laser diode array

Phase-locking of a QCW-operated broad-area blue laser diode array is demonstrated with 18.8 W peak power and 87.7% visibility via a compact external cavity that uses a partially reflective output coupler (no wavelength selection). The resulting "in-phase" far-field pattern is stable with injection current. We further propose and validate a method of brightness enhancement by increasing the effective optical fill-factor of a quasi-near-field image of the phase-locked laser array through a cylindrical Fresnel lens array on a reflective Spatial Light Modulator (SLM). The increased optical fill-factor is shown to enhance brightness by reducing the far-field divergence angle by a factor of 2.37, thereby quenching far-field satellite peaks and concentrating power into a central lobe.