Minor lobe suppression in semiconductor injection lasers

Claim 1

A semiconductor injection laser device comprising a region of first conductivity-type material, a region of second conductivity-type material contiguous to said region of first conductivity-type material and forming a planar p-n junction therebetween, said device having a pair of oppositely facing reflecting surfaces forming an optical cavity resonator for sustaining oscillations of coherent radiation, means for generating stimulated coherent radiation in a major intensity lobe comprising means for forward biasing said junction and for applying thereto current in excess of the lasing threshold, means for extracting a portion of said radiation from said resonator, said device disadvantageously tending to produce radiation in at least a first minor lobe, said major and minor lobes constituting transverse modes perpendicular to the plane of said junction, and means for attenuating radiation in said minor lobe characterized in that said attenuating means comprises an absorbing region located interior to said device at and beyond the plane between said major and minor lobes, said minor lobes normally exist in said second conductivity-type region and said absorbing region comprises a region of the same conductivity type as said second region, but of smaller bandgap, thereby forming a phase boundary between said second region and said absorbing region.