Shape analysis and coupling loss of microlenses on single-mode fiber tips

By geometrical ray tracing the wavefront aberration of microlenses on single-mode fiber tips, the shape of which is evaluated from microphotos, is calculated. Using the thus obtained wave aberration, the coupling efficiency from a laser diode into the lensed fiber is computed. The validity of this method is checked for drawn taper lenses, which were found to be nearly hemispherical, and for strongly aspherical microlenses. Calculated coupling efficiencies agree well with measurements.