Single-mode positive-index guided cw constricted double-heterojunction large-optical-cavity AlGaAs lasers with low threshold-current temperature sensitivity

A new type of constricted double-heterojunction large-optical-cavity (CDH-LOC) laser is obtained by growing relatively thick (0.2–0.3 μm) convex-lens-shaped active layers above concave-lens-shaped guide layers. By using the effective-index method it is shown that the resultant lateral waveguide is of the positive-index type. The device reproducibly provides single-mode cw laser operation (10 mW cw and 20 mW pulsed) in narrow single-lobed beams (ϑ∥ = 8°; ϑ⊥ = 30°), and displays very high threshold-current temperature coefficients, (T0≅135 °C, pulsed and cw) for LOC-type structures. The cw threshold currents and differential quantum efficiencies (one facet) are between 60–70 mA and 30–35%, respectively. The performance of the ’’positive-index’’ CDH-LOC laser is discussed in view of results from the previously reported ’’leaky-cavity’’ CDH-LOC laser.