Single mode broad area distributed Bragg reflector ring oscillators

A large aperture, spatially coherent, single frequency semiconductor ring laser is demonstrated for the first time. Two diffraction gratings oriented orthogonally to each other are used to uniquely select a single broad area mode which oscillates at a single wavelength. Spatial coherence across a 411 μm output aperture is observed, giving a diffraction limited output beam measuring 0.2°×0.135°. The surface emitting ring oscillators contain strained InGaAs/GaAs quantum well active regions and operate at 1012 nm to pulsed output powers exceeding 500 mW with threshold current densities under 300 A/cm².