An ancient method of glass blowing has been applied to the fabrication of axicons, the miniature cone-shaped lenses used to shape the light from lasers. The technology could lead to the development of cheaper and more accurate OCT devices.
The technique, developed by the FTO-ST Institute in France, was recently described in The Optical Society journal Optics Letters. It is based on the process used to make large numbers of photonic and electronic circuits, and allows the researchers to make glass axicons with diameters of 0.9 and 1.8 millimetres.
The team behind the innovation have developed a method that combines gas expansion from multiple reservoirs to produce the axicon, shaping its surface from underneath and leaving a high-quality optical surface.
Silicone cavities are deposited in concentric rings that are sealed in glass. Placing this in a furnace causes in the gas trapped in the cavities to expand, creating ring-shaped bubbles that push the glass surface into the desired cone shape.
The technique allows for multiple lenses to be made at once, rather than just one at a time, at a far lower cost than the methods currently employed.
“Our technique has the potential of producing robust miniature axicons in glass at a low cost, which could be used in miniaturised imaging systems for biomedical imaging applications, such as optical coherence tomography,” Mr Nicolas Passilly, a member of the research team, said.
“Wafer-level microfabrication allows the axicons to be integrated into more complex microsystems created also at a wafer-level, leading to a system made of a wafer stack. This type of integration comes with better optical alignments, high performance vacuum packaging and much lower-costs for the final systs because a large number can be processed simultaneously.”
According to The Optical Society, the research team plans to incorporate the axicons in OCT devices that are also currently under development.
