Moldable infrared optics with gradient index of refraction based on chalcogenide glasses – IRGRIN

The objective of this project is to develop infrared gradient refractive index (GRIN) optics based on chalcogenide glasses for thermal imaging in the 8-12 µm atmospheric window. A handheld infrared imaging demonstrator will be developed to evaluate the performance of these optics and two applications, a civilian one and a military one will be proposed. This project is clearly in the scope of "thématique 5 (photonique)" and especially "le sous-thème 6.5.3 (composants optiques : optiques moulables) of this call for projects. "Chalcogenides for glasses and fibers" are among the priorities of this theme.

Combining the GRIN effect with the geometric power of curved surfaces offers exciting new possibilities for optical design. For example, it is possible to design an optical system with a high focusing power, a large field of view and well-corrected aberrations while having a small thickness, a small curvature and a reduced number of lenses compared to conventional optical systems. The high transparency of GRIN optics from the visible to thermal infrared would make it possible to combine several spectral bands. Thus, the use of GRIN lenses can significantly reduce the size, weight and cost of optical systems, which is increasingly required for both military and civil applications.

Visible GRIN optics are generally fabricated through ion exchange in oxide glasses but right now, there is no GRIN optic that can be used in the thermal infrared range of 3-5 or 8-12 µm.

In this project, we propose to develop moldable chalcogenide glass optics having gradient refractive index compatible with the targeted thermal imaging applications.

The originality and the ambitious nature of this project are as follows:
- Use of patented chalcogenide glasses for efficient ion exchange or controlled crystallization to obtain a refractive index gradient.
- Development of a method for manufacturing GRIN IR optics by combining ion exchange and molding.
- Development of a handheld LWIR prototype thermal camera to demonstrate the effectiveness of IR GRIN optics.

To achieve the ambitious objectives, the consortium consists of three partners: an academic laboratory with thirty years of experience in infrared glasses, a public industrial laboratory that has long-term expertise in optical instrumentation to anticipate the evolution of future optronic systems and a leading multinational industrial group in infrared materials and optics. These partners have a long history of successful collaborations.

Technological and scientific challenges are clearly identified. The solutions to address these challenges, validated by convincing preliminary results, are detailed in the proposal.