Laser printed fiber microlens for fiber-diode coupling by direct laser writing

A printable microlens on fiber end for coupling between a laser diode to a single-mode fiber (SMF) is demonstrated. The fiber microlens fabricated by the novel technique based on laser direct writing using a quasi-Bessel beam has gained high coupling efficiency, long working distance, and sufficient alignment tolerance. A coupling efficiency of 53.5% was measured for SMF coupling at a working distance of 16 μm. The tolerances for a 1-dB loss increment for translational displacements and angular deviations between the fiber microlens and the laser diode were 2.5 and 1.2 μm, and 2.0 and 5.0 degrees, respectively. The printable fabrication of a microlens on a fiber endface by laser direct writing allows for a batch process to reproduce a multiple microlens with a high consistency in a simple and fast fabrication cycle, with no need of individual fiber loading and unloading.