External-cavity semiconductor-laser array insensitive to paraxial misalignment

We report a tilted-mirror external-cavity gain-guided laser array whose output power is insensitive to small misalignments of the cavity elements. This novel configuration delivers a near-diffraction-limited (1.5 times diffraction-limited) single-lobed beam in the entire current range without the need for realignment of the cavity. The light-current characteristic is linear and kink free, with a higher efficiency compared with the free-running array. A compact graded-index lens design that can emit a collimated beam with a circular cross section is also described.