Fabrication and molecular beam epitaxy regrowth of first-order, high contrast AlGaAs∕GaAs gratings

We present a fabrication technique and molecular beam epitaxy (MBE) regrowth of first-order, high contrast AlGaAs∕GaAs diffraction gratings for laser emitting at 980nm. An immersion holography technique is used to uniformly pattern first-order gratings with a pitch of 155nm. MBE is used to overgrow Al0.75Ga0.25As on etched GaAs gratings. It is found that slow growth rates with optimum arsenic overpressure are necessary to overgrow gratings with low pitting defect densities. These first-order, high contrast gratings are integrated as distributed Bragg reflectors in an edge-emitting laser structure. Single-mode emission at 1μm with a side mode suppression ratio greater than 30dB is demonstrated.