Diffractive optical element for coupling semiconductor laser diode to single-mode fiber

摘要

An integrated scheme is proposed for low-loss coupling between a semiconductor laser diode (LD) and a single-mode fiber (SMF) by using a diffractive optical element (DOE). The DOE is designed based on diffractive optics principle, which phase distribution is optimization result of iterative phase retrieval algorithm. A new far-field amplitude constraint is introduced into the iteration to provide very high mode conversion quality. The scheme is applicable to realize high efficient coupling to SMF for any semiconductor LD. Coupling losses lower than 0.02dB have been reached for all the discussed LDs with aspect ratios of the elliptical fields from 1 to 9. The requirements on axial displacement and rotation angle have been removed. The tolerance for 1-dB loss increment for lateral misalignment is 0.9 μm. And the coupling loss is insensitive to tilt angle.