Efficient coupling between laser diodes with a highly elliptic field and single-mode fibers by means of GIO fibers

A new configuration is proposed for efficient coupling between laser diodes (LDs) with a highly elliptic field and single-mode fibers (SMFs). Graded-index oval-core (GIO) fibers were employed to match the LD and SMF field profiles. Experiments show that the coupling loss between the LD, operating at a wavelength of 980 nm with a field profile aspect ratio of 5.9, and SMF is effectively 0.6 dB. The tolerances for lateral displacements are roughly an order of magnitude larger than those in the conventional wedge-shaped lensed-fiber coupling scheme.