Breaking the mid-infrared interconnection barrier: a robust bonding for high-power optics based on liquid-like chalcogenide glass

Achieving low-loss optical interfaces between high-refractive-index (n > 2) components is critical for mid-infrared photonic systems, yet hindered by the trade-off between refractive index matching, IR transparency and thermal stability. Here, we introduce a groundbreaking solution-bonding the optical lenses and fibers with a liquid-like chalcogenide glass, which possesses an ultra-low glass transition temperature below room temperature, high refractive index and exceptional mid-infrared transparency. The basic performances of the liquid glass are characterized and proved by detailed viscosity distribution, mechanical shear and bonding tensile strength measurements. Most of all, the optical transmission and laser delivery of these bonded chalcogenide glass fiber devices demonstrate a significant improvement, with transmission efficiency increasing from 36% to 91%, and laser power delivery from several hundred mW rising to 14.5 W at a wavelength near 4 µm. Additionally, the system demonstrates long-term stability, maintaining performance over at least 3 months and more than 206 heating-cooling cycles when utilizing this liquid-like glass adhesive. This research not only addresses the challenge of bonding mid-infrared optical components but also holds immense promise for advancing integrated mid-infrared optics applications, including spectroscopy, sensing, and imaging.