Extremely small vertical far-field angle of InGaAs-AlGaAs quantum-well lasers with specially designed cladding structure

We report on a very small vertical far-field angle achieved by lasers with a specially designed structure. For an InGaAs-AlGaAs quantum-well laser with a 2.5-μm-wide ridge waveguide, the far-field pattern has a vertical far-field angle of 13/spl deg/ and a lateral far-field angle of 8/spl deg/. Meanwhile, the threshold current remains acceptably low (/spl ap/36 mA for a 500-μm-long cavity). The slope efficiency of the L-I characteristic is high (>0.9 W/A) compared to that of the conventional laser.