Example of new method of glass-in-glass fabrication. Photo credit: Torun GözdenResearchers in Switzerland have developed a new method for glass-in-glass fabrication that can create complex 3D miniature infrared (IR) optics, a breakthrough that could find applications in infrared sensing and spectroscopy,broadband telecommunications and imaging. The technique allows IR glass to be combined with another glass and then formed into miniature shapes, is effective for a wide range of glasses, and could lead to new concepts in robust sensors that can fit in miniature volumes, as well as being a platform for making complex broadband composite optics.
Although glass that can transmit IR wavelengths is already used in spectroscopy to identify various materials and substances, it is problematic to produce, and the glass can be fragile and easily degradable when wet. As reported inOptics Express [Casamenti et al. Opt. Express (2022) DOI: 10.1364/OE.451026], a collaboration between laboratories at the EPFL and the Institute for Quantum Electronics at ETH Zurich showed how the process could lead to complex infrared optics that make IR imaging and sensing more accessible.
The process embedded IR glasses inside a durable silica matrix, which can create nearly any interconnected 3D shape with features of a micron or less in size, and demonstrates an innovative way to fine-tune the properties of 3D optics with subtle combinations of glass. The fabrication involved combining chalcogenide IR glass with fused silica glass, including a set of pillars with different dimensions. The glass host provided not just the mold for shaping the fragile mid-IR glass down to the microscale, but also forms a glass composite that is useful for its optical properties.
An arbitrarily shaped 3D cavity was first made inside the fused silica glass substrate by femtosecond laser-assisted chemical etching, a process that changed the glass structure to allow the exposed areas to be removed with a chemical. Then, the cavity was filled with another material to produce a composite structure. This second material is melted and pressurized to flow and solidify within the network of carved silica cavities.
The technique could be used to make infrared optical circuits and arbitrarily shaped IR micro-optics not previously possible due to the poor manufacturability of IR glass. As team leader Yves Bellouard told Materials Today, “Our fabrication method can be used to protect IR glass, opening new avenues for micro-scale infrared optical circuits that are fully integrated in another glass substrate”.
The work is still in the early stages, but the process in this proof-of-concept is comparatively generic, and the team are investigating its capabilities for combining different glasses, and hope to test the composite parts in spectroscopy and other applications.
“Our fabrication method can be used to protect IR glass, opening new avenues for micro-scale infrared optical circuits that are fully integrated in another glass substrate”Yves Bellouard