Laser creates cheaper free-form optics

Ashley N. Paddock, ashley.paddock@photonics.com

A new process for fabricating small batches of nonspherical glass optical components will allow manufacturers to produce high-quality, customizable optical components of any geometry quickly and inexpensively.

High-speed laser ablation of fused silica. The laser controls how much silicon it removes and what shape it makes to produce virtually any surface form. Images ©Fraunhofer Institute for Laser Technology ILT, Aachen.

Researchers at Fraunhofer Institute for Laser Technology used a computer-controlled CO₂ laser to heat a square-shaped piece of fused silicon to its evaporation temperature (2230 °C), carving away at the silicon much as a sculptor would cut away sections of marble to create a statue.

The laser uses custom inputs to control how much silicon it removes and what shape it makes so that virtually any surface form can be produced. Once the silicon is shaped, it is reheated to near the evaporation point to reduce roughness; the material stays polished while it cools. Further imperfections can be buffed out afterward using the same ablative process.

The components take various forms after individual steps of the laser-based fabrication process.

As the laser process is controlled by computer data, the inputs can easily be changed to create optical components to order. The new process also is estimated to speed up manufacturing time by a factor of 10, which could drastically increase production and drive down the cost of manufacturing. However, before it can be applied in industry, the technique must be optimized by increasing the precision of the laser ablation and the quality of the polishing process.

The researchers presented their process at AKL, the International Laser Technology Congress, on the Fraunhofer campus.