Laser micromachining of periodic surface radius change on the optical fiber circumference

In this paper, we are showing that holes and marking spots with sizes that are comparable to the wavelength of a CO₂ laser at λ=10.6  μm can be achieved reproducibly on a conventional optical fiber SMF28 when it is positioned at the focal point. Some theory on Gaussian beam propagation is briefly reviewed and readily applied to drill a fiber on its axis near the focal point. As the fiber was moved from the focal point, it was found that some features, such as ridges along the fiber circumference, were also micromachined by the laser. It was demonstrated that the fabrication of surface nanoaxial photonic fibers, long-pitch grating fibers, and pump laser strippers can be envisaged on a conventional SMF28 with a cladding diameter of 125 μm.