Coherent summation of the radiation of a single-mode laser diode array

We report the phase-locked lasing of an array of 25 singlemode laser diodes in an external resonator with the use of a waveguide grating mirror providing angular and spectral selectivity. The laser array was found to generate on the out-of-phase supermode with a stabilised wavelength of 930.8 nm and an output power up to 0.75 W. The output beam exhibited a near diffraction-limited quality (M² ≈ 1.2) in both directions.