Laser micromachining of efficient fiber microlenses

We present results of the use of a CO(2) waveguide laser for the reproducible fabrication of efficient microlenses on single-mode optical fibers. Short intense laser pulses are used both to melt microlens tips to specific radii and to micromachine microlenses by ablative removal of small (~1-mum(2)) areas of glass from the fiber surface. CO(2) laser heating of fiber tips results in more consistent lens curvature than the electric arc commonly used in microlens fabrication. The microlenses formed using a laser microlathe, in which spinning fibers are shaped by simultaneous cutting and heating in the pulsed CO(2) laser beam, show excellent laser-fiber coupling with losses in the 1.5-3-dB range, an improvement of more than 2 dB over coupling with standard microlenses made by the etch and melt technique.