Thin-film filter, wavelength-locked, multi-laser cavity for dense wavelength beam combining of broad-area laser diode bars

We report on individual wavelength locking of a multiplet of 100-μm broad-area laser diode emitters arranged on a 50% fill-factor bar by means of a single external multi-laser cavity using an ultra-narrowband thin-film filter as a dispersive optical element. The achieved wavelength-locked output power is 216 W, corresponding to an electrical-to-optical conversion efficiency of about 49.7%. The 45 emitters of the laser diode bar are stabilized within a spectral range of about 6.4 nm. Our approach is suited for killowatt-class dense wavelength beam combining of direct diode lasers.