| 摘要 |
PURPOSE:To enable a device to go into a stable single transverse mode oscillation by a method wherein the width of the waist of a rib-geometry optical waveguide in a region of a refractive index waveguide structure and the width of the waist of a rib-geometry optical waveguide in a region of a gain waveguide structure are so designed as to meet specified values. CONSTITUTION:An index difference is generated in the direction of junction for the creation of an index waveguide in the presence of an AlGaAs layer higher than an active layer 204 in energy gap and lower than a clad layer 205 in mixed crystal ratio for Al. At the middle of the resonator, the width of an index waveguide is rendered smaller than that of a current injecting layer for the effectuation of a longitudinal multiple-axis mode oscillation in a gain waveguide region. The non-focus reduction is kept extremely low for improved stability in transverse mode oscillation. In this example, the waist of a rib-geometry optical waveguide in a region of an index waveguide structure should be 0.5-10mum, the width of the waist of a rib-geometry optical waveguide in a region of a gain waveguide structure should be not less than 5mum, and the thickness of the clad layer on the active layer outside the optical waveguides should be not more than 2mum. As for the compound semiconductor layer to be buried in the sides of the optical waveguides, an AlGaAs-based compound should be used in which the mixed crystal ratio for Al is higher than the clad layer.
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