The ammonium fluoroborate crystal developed by Pan Shilie's team at the Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, was recently published in the journal Nature. Using the ammonium fluoroborate crystal, the team achieved the first direct frequency-doubling output of 158.9-nanometer vacuum ultraviolet laser light, setting a new output wavelength record for this band. This achievement provides a novel core material for the field of deep ultraviolet nonlinear optics.

In 2007, after completing his postdoctoral work at Northwestern University in the United States, Pan Shilie returned to China and established a team at the Xinjiang Technical Institute of Physics and Chemistry. Their goal was to develop a new generation of deep ultraviolet nonlinear optical crystals possessing a combination of large band gap, strong nonlinear optical effect, high birefringence, and ease of growth. Through computer simulations, the team discovered that fluorine atoms could play a unique balancing role in ammonium borate materials, thereby defining ammonium fluoroborate crystal as the core research direction. Lacking reference literature and established processes, the team independently designed reaction vessels and developed a vapor deposition method, first synthesizing millimeter-scale ammonium fluoroborate crystals in 2016, which pushed the wavelength breakthrough for deep ultraviolet crystals past 200 nanometers. Subsequently, based on years of accumulated experimental data, the team continuously optimized the process, screened advantageous crystal nuclei, and overcame the technical challenge of layered crystal growth. In 2024, centimeter-scale ammonium fluoroborate single crystals were successfully created, and the team also independently developed a complete device processing technique tailored for this crystal, completing the leap from material to practical device.

During testing, when a specific laser beam was incident on the ammonium fluoroborate crystal, the output of 158.9-nanometer vacuum ultraviolet laser light was successfully achieved. Pan Shilie said, "It worked, the new crystal is a success!" Rooted in the frontier region for nearly two decades, the ammonium fluoroborate crystal has moved from concept to reality, and Pan Shilie has fulfilled his scientific research commitment.