The purpose of this thesis is to fabricate l = 1.55mm ridge waveguide spot size converter lasers for high laser-to-fiber coupling. The laser structure design includes the lateral and vertical directions. In the vertical aspect, we use six asymmetric InGaAsP/InP quantum wells of 50, 50, 100, 100, 150, 150Å. The asymmetric multi-quantum-well structure is designed to gather the optical field in the 150Å-wide quantum wells. Besides, we add a passive waveguide near the 150Å-wide quantum wells to expand optical field profile. In the lateral aspect, we use tapered ridge waveguides which have two different fashions: one is tapered down from 2.5mm to 1mm, and the other is tapered up from 2.5mm to 4mm.
The results show that the tapered-up ridge waveguide laser has a CW operation with Ith = 34mA and diverge angles of 14°×36° (q//×q^) at room temperature. The tapered-down ridge waveguide laser exhibits only a pulsed operation at room temperature. At lower temperature T = 13°C, the tapered-down laser has a CW operation of Ith = 36mA and diverge angles of 14°×36°(q//×q^). From I-V and C-V measurements, we attribute the heating problem to the large series resistance caused by the incorrect n-type doping profile in the epitaxy process.