Grating-coupled double-heterostructure AlGaAs diode lasers

Abstract

Corrugated AlGaAs waveguide devices have been fabricated which emit low-divergence ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\sim1\deg</tex> by 15°) laser beams nearly normal to the waveguide plane when pulsed electrically at room temperature. The devices are fabricated from material which is essentially the same as that used to fabricate CW room-temperature lasers, differing only in that the two top layers of AlGaAs and GaAs are very thin ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\sim0.4 \mu</tex> m and 0.1 μm, respectively). Threshold current densities of 3000-4000 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> are typical in these devices even though ∼20 percent of the resonator length is unpumped. The far-field pattern produced by the TE polarized leaky-wave laser beams emanating from the unpumped region is usually composed of two mode lines. A theory is outlined which describes how these mode lines are generated. The possibility of obtaining distributed-feedback (DFB) oscillation in devices of this type is also discussed.