3D printing gives laser waveguides a ceramic upgrade for higher power

What if the tiny structures that guide laser light could handle far more power than today’s glass fibers? Researchers at Lawrence Livermore National Laboratory (LLNL) may have found a way to make this possible—by 3D-printing the waveguide itself from ceramic. This process is based on the same light-guiding technology that carries data across the world’s oceans. The material they used is yttrium aluminum garnet (YAG), which conducts heat far better than silica and is less prone to stimulated Brillouin scattering, a phenomenon that can limit laser power. However, until now, making precise ceramic waveguides without defects has been difficult. The LLNL team overcame this challenge by 3D-printing the light-guiding core and its surrounding cladding together. “We developed a direct ink writing additive-manufacturing technique for fabricating ceramics with highly tailored structures,” Ross Osborne, lead researcher and a scientist at LLNL, said. Printing a new path for laser light A waveguide is essentially a carefully designed path for light. It has a central core surrounded by cladding. Differences between the two materials keep light confined to the core as it travels through the structure. Similar microscopic light-guiding structures are also becoming central to new chip-scale laser technology. The researchers used transparent YAG ceramic, with ytterbium added to the core to create Yb, while the surrounding cladding remained undoped YAG. The ytterbium ions provide the optical gain needed for lasing. The key manufacturing trick was direct ink writing, a form of 3D printing. The team extruded a nanoparticle-loaded Yb paste as thin filaments into undoped YAG, creating the laser-guiding channels and their surrounding cladding in one process. “The process begins with a nanoparticle paste that is extruded into a three-dimensional shape. The printed structure is then dried, sintered, and hot isostatically pressed to produce a transparent ceramic,” Osborne added. The researchers created three waveguides inside a single ceramic block. Since the core and cladding are made together, the method can achieve high fabrication yield while minimizing defects at the interface. A tiny ceramic block starts lasing The experiment produced working laser waveguides. Their cladding scatter loss was below 1.3% per centimeter at 1.3 micrometers. When pumped with a 940-nanometer Ti laser, the waveguides produced laser light at 1,030 nanometers. The best-performing waveguide had an elliptical cross-section measuring 100 × 60 micrometers and was 1.4 centimeters long. It achieved a 61 percent slope efficiency and a 12.4 percent round-trip loss. The result follows earlier work on 3D-printed ceramic laser structures. In 2021, researchers demonstrated ink-jet-printed Yb planar waveguides, reporting guide thicknesses of 25–350 micrometers and a 23.6 percent slope efficiency. The new work differs by using direct ink writing to create three-dimensional channel waveguides, rather than a planar structure. The broader importance of controlling light through tiny structures can also be seen in optical sensors built directly on fiber, where miniature devices use the same general ability to manipulate light inside extremely small structures. From milliwatts to kilowatts The researchers have not yet demonstrated the huge power increase they envision. Their current devices operate at the hundreds-of-milliwatts scale, but the team ultimately wants to reach kilowatt-level output. LLNL scientist Ross Osborne says the crystalline architecture could potentially provide more than 10 times the output power of glass fibers while retaining a compact footprint. If that goal is achieved, the technology could be useful for high-power laser machining and defense applications, including counter-drone and missile-defense systems. The push toward more powerful and compact laser systems is already visible in areas ranging from high-power ultrafast lasers to photonic systems designed for next-generation communications. However, a lot of work remains. The team must improve the fabrication process, scale up the laser power, and determine whether the ceramic waveguides can maintain their optical performance under much higher loads. For now, the research work does not propose a replacement for glass fiber lasers. Instead, it demonstrates a new way to manufacture the tiny structures that control laser light—and one that could make the power advantages of crystalline ceramics much easier to exploit. The study is published in the journal Optics Letters. Get the latest in engineering, tech, space & science - delivered daily to your inbox.Rupendra Brahambhatt is an experienced writer, researcher, journalist, and filmmaker. With a B.Sc (Hons.) in Science and PGJMC in Mass Communications, he has been actively working with some of the most innovative brands, news agencies, digital magazines, documentary filmmakers, and nonprofits from different parts of the globe. As an author, he works with a vision to bring forward the right information and encourage a constructive mindset among the masses.