New Conference Aims At Know-How Transfer For Laser-Based Optics Manufacturing

The Fraunhofer Institute for Laser Technology ILT is supplementing its established Aachen "6th Conference on Laser Polishing LaP" on October 15 and 16, 2024 for the first time with a new conference that takes up the growing global interest in photonic process chains for the optics industry. The "1st Conference on Laser-based Optics Manufacturing LOM" focuses on the laser-based production of complex optics and is intended to stimulate the transfer of knowledge from research to industry. Laser-based optics manufacturing promises competitive advantages because it is cost-effective, digitally controllable and, on top of that, free of grinding dust and polishing agents.

The vision of purely photonic process chains in optics manufacturing is becoming a reality. "It is now foreseeable that lasers will develop their potential along the entire process chain, from shaping to polishing to shape correction," says Dr. Edgar Willenborg, polishing group leader at Fraunhofer ILT in Aachen. In the first industrial applications, laser-based processes would complement already established mechanical processes. The driver of this development is the increasing demand for complex aspheres and freeform optics designed specifically for individual applications. Their production pushes mechanical manufacturing processes to their limits. This is because they are usually optimized for the processing of spherical - i.e. semi-circular - lenses.

Mechanically forming, polishing and correcting the more complex aspheres is time-consuming and costly. This is where freely programmable, contactless laser processes have an advantage. The use of forming tools and polishing agents is no longer necessary. In addition, the laser processes leave behind chemically clean surfaces. "And thanks to the numerically controlled processes without forming tools, the processing times are no longer dependent on the lens shape," explains Willenborg.

New conference focuses on laser-based optics manufacturing
There are still a number of challenges to be overcome on the way to the widespread use of laser-based manufacturing processes for optics. In particular, the required dimensional accuracy and the wide range of materials for glass and polymer optics pose unsolved questions. In order to address these issues in a targeted and timely manner with an international specialist community from research and industry, the Fraunhofer ILT is launching a new conference: The "1 st Conference on Laser-based Optics Manufacturing LOM" will take place on October 15 and 16 in combination with the "6th h Conference on Laser Polishing LaP" in the premises of the Aachen institute. In addition to 20 lectures, the combined conference offers an extensive laboratory tour, a showcase and poster exhibition and various discussion and networking formats. "Because we expect a highly specialized international community from research and industry, both conferences will be held in English," explains Willenborg. Since the focus is on the transfer of know-how to industrial application, the majority of the presentations come from researchers.

In technical terms, the LOM focuses on photonic process chains, the shaping of which is based on removal using ultrashort pulse (USP) lasers and selective laser-induced etching (SLE). CO2 lasers are used for polishing . Their beam melts the surface of the glass or plastic lenses at a depth of just a few 10 µm. In this zone, the material changes into a honey-like state and then automatically smooths out as it cools due to the surface tension. "This remelting of the edge layer, together with the surface smoothing through the interfacial tension, results in outstanding surface qualities," emphasizes the Fraunhofer ILT expert. The roughness in the sub-nanometer range sets new standards and predestines the laser processes for applications that require the highest optical performance. Laser processes are already in use to remove micro-roughnesses where light scatters and makes surfaces appear cloudy, complementing process chains that have previously been dominated by mechanical means.

Laser polishing as an enabler in the future market of laser inertial fusion
One focus of the new conference is on optical surfaces with high damage thresholds. Four lectures will shed light on the potential of laser processes for increasing optical damage thresholds. This includes a specialist lecture from California's Lawrence Livermore National Laboratory (LLNL), in whose National Ignition Facility (NIF) in December 2022 it was possible for the first time in human history to ignite a plasma under laboratory conditions and thus trigger the fusion of the hydrogen isotopes deuterium and tritium. This released more energy than was required for laser ignition. The NIF operates the world's largest, most energetic laser system with 192 beam paths, over two megajoules of pulse energy and 500 terawatts of peak power. The high-energy UV laser pulses regularly bring optical components to the edge of the damage threshold - and beyond. A promising approach to making them more robust is laser polishing. Unlike mechanical processes, it does not leave any micro-defects in the lens surface.

The "6th Conference on Laser Polishing LaP" focuses on laser polishing of metals, glass, plastics and other materials. It is about functional and design surfaces as well as the post-treatment of complex additively manufactured components. Here too, non-contact laser processes have advantages over mechanical processes due to the often complex component geometries.

"With their respective range of topics, both conferences are unique worldwide," emphasises Willenborg. There are no separate specialist conferences on either laser-based optics manufacturing or laser polishing. It is precisely because these young fields of technology are developing very dynamically that the Fraunhofer ILT is focusing on early knowledge transfer. "Companies that are already taking advantage of the benefits of modern laser polishing processes can gain real competitive advantages," he says. In addition, networking within the scientific community is important in order to recognise synergies in research and to jointly exploit them in the interests of rapid progress.