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

## TL;DR

A new liquid-like chalcogenide glass adhesive improves mid-infrared optical bonding, enabling efficient laser delivery and stable performance for advanced IR applications.

## Contribution

Introduces a liquid-like chalcogenide glass adhesive that overcomes refractive index mismatch and enables high-power mid-IR optical bonding.

## Key findings

- Bonded devices achieved 91% transmission efficiency and 14.5 W laser power delivery at 4 µm.
- The adhesive maintained performance over 3 months and 206 heating-cooling cycles.
- Eliminated organic absorption and refractive index mismatch in mid-IR optical systems.

## Abstract

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.

Liquid-like chalcogenide adhesive enables robust mid-IR fiber bonding, eliminating refractive index mismatch and organic absorption, achieving efficient 11.7 W laser power delivery at 4.7 µm with record performance.