Fabrication, characterisation, and optimisation of optical fibre lenses and efficient wave-guide coupling using an iterative approach

Abstract

The coupling efficiency of a pigtailed optical fiber lens is often a critical parameter in the manufacture of optical devices. For example, efficient coupling from high power semiconductor lasers to optical fiber pigtails with fiber lenses is of great importance as the uncoupled power can affect the lifetime of the device through thermal degradation of the pigtail or its welding point; for optical amplifiers, the coupling efficiency determines the overall gain. Generally, mass-produced optical fiber lenses do not have a consistent enough quality and it is often necessary to discard lenses that exhibit poor coupling. We previously demonstrated a method for digitally modifying optical fiber lenses. We have now developed a scheme whereby we are able to produce high quality optical fibre lenses with a given lens radius and then to iteratively alter it to achieve the required divergence and spot size in a repeatable fashion for efficient coupling to a variety of devices such as semiconductor optical amplifiers, lasers and wave-guides. We have consistently demonstrated 75% coupling efficiency to angled facet semiconductor optical amplifiers at 1550nm with only three-axis adjustment, and believe the true coupling efficiency to be close to 90%. Our powerful scheme allows the use of nearly all of the lenses for a given application.