Coupling-sensitivity comparison of hemispheric and hyperbolic microlenses

We investigate the effects of translational displacements and angular misalignments of semiconductor laser-fiber systems coupled to tapered, hemispheric and laser-machined, hyperbolic microlenses. Hyperbolic lenses, which typically couple 2 dB more optical power into a single-mode fiber than do hemispheric lenses, are more sensitive to translational offsets, although they are less sensitive to angular misalignments. We demonstrate that increased coupling can be permanently realized in a system through the use of the hyperbolic lens if the laser package can confine the position of the lens to within a 1.6-microm region. Angular misalignments can be as large as 10 degrees for a 0.5-dB power penalty for the hyperbolic microlens.