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-held angle achieved by lasers w ith a specially designed structure. For an InGaAs-AlGaAs quantum-well laser with a 2.5-mu m-wide ridge waveguide, the far-field pattern has a vertical far-field angle of 13 degrees and a lateral far-field angle of 8 degrees. Meanwhile, the threshold current remains acceptably low (approximate to 36 mA for a 500-mu m-long cavity), The slope efficien cy of the L-I characteristic is high (>0.9 W/A) compared to that of th e conventional laser.