Micro-lens machining on optical fibers by direct laser ablation

Abstract

Beam shaping at the output of optical fibers is required in a variety of applications including optical sensors, telecommunication devices and medical applications. We present a laser micro-machining technique for the fabrication of micro-lenses directly upon the end face of silica fibers using a F 2 -laser processing station. Ablation is performed in a mask projection arrangement with 25x demagnification. A mask with an occluded circular beam shape is imaged perpendicular to the fiber axis. The fiber is rotated axially while the laser cuts through the fiber, yielding a spherically shaped tip with radius defined by the mask dimensions. Strong 157 nm absorption by the silica glass facilitates precise structuring without micro-crack formation. The quality of the fiber-lenses is characterized by AFM, SEM and by analysing the beam profile at the fiber output.

UV-laser ablation of fused silica mediated by solid coating absorption

“…In the case of fused silica, 157 nm seems to be appropriate to induce well defined ablation 4 5 . Sub-micron gratings 6 , pixelated diffractive elements 7 , and micro lenses 8 have been fabricated using F 2 -laser ablation at 157 nm. The third method is to use an indirect process, where the laser energy is coupled into an auxiliary material which is in close contact with the material to be ablated.…”

UV laser cutting of organic nanofibers

“…On the other hand, micro fabrication by laser ablation has become a strong and flexible tool for the generation of components or devices for a variety of applications in micro-electronics, micro-mechanics, micro-fluidics, and micro-optics. 12 In many cases the ablative removal of material is applied to fabricate holes, channels or three dimensionally shaped surfaces. Micro lenses, waveguides, and gratings are examples for optical elements, which can be fabricated this way.…”