The near-IR to mid-IR spectral range (specifically bands ranging from 1 – 10 µm) is of particular interest not only for molecular spectroscopy but also for telecommunications in space. Many functional groups and typical bonds of organic molecules exhibit fingerprint optical absorptions in this specific part of the optical spectrum. Furthermore, for space applications, specific optical bands in the mid-IR are transmitted with low losses through Earth’s atmosphere.

One of the main challenges in this context is to fabricate suitable optical components such as waveguides or other free-form optics components. Glass with transmission spectra in the mid-IR, such as chalcogenide or tellurite glass have unfortunately poor manufacturability and mechanical properties, making them difficult to form into arbitrary shapes with robust enough mechanical properties.

Here, we explore a novel manufacturing process for the fabrication of glass-in-glass composites made of mid-IR glass, such as chalcogenide (As2S3) embedded within an arbitrarily shaped fused silica substrate.

The production process involves femtosecond laser-assisted chemical etching to carve out three-dimensional volumes that are subsequently pressure-infiltrated with molten mid-IR glass. This approach offers an interesting pathway for forming mid-IR waveguides and other free-form miniature optical components embedded in silica, thus enabling the fabrication of 3D micro-optical components forming a hybrid composite with broadband optically transparent mid-IR elements embedded in a mechanically strong and chemically stable fused silica support frame.