IR GRIN lenses prepared by ionic exchange in chalcohalide glasses

Area of Science:

• Materials Science
• Optical Engineering
• Infrared Optics

Background:

• Gradient refractive index (GRIN) lenses reduce the size and weight of optical systems.
• Traditional ion exchange for GRIN lenses is challenging with chalcogenide glasses due to low glass transition temperatures and mechanical weakness.
• Infrared waveband applications require specialized GRIN elements.

Purpose of the Study:

• To develop novel chalco-halide glasses for creating infrared GRIN lenses via ion exchange.
• To overcome the limitations of ion exchange in chalcogenide glasses for GRIN lens fabrication.
• To demonstrate the feasibility of producing GRIN lenses with significant refractive index changes for thermal imaging.

Main Methods:

• Development of chalco-halide glasses using alkali halide (NaI) addition in a GeSe2-Ga2Se3 matrix.
• Application of ion exchange process (K+ for Na+) to induce a permanent change in refractive index.
• Characterization of optical and structural properties, including diffusion length and refractive index gradient.

Main Results:

• Achieved a significant permanent change in refractive index (Δn of 4.5 x 10^-2) via K+/Na+ ion exchange.
• Demonstrated a diffusion length exceeding 2 mm, suitable for GRIN lens fabrication.
• Obtained GRIN lenses exhibit excellent transmission in the 3-5 µm and 8-12 µm atmospheric windows.

Conclusions:

• The developed chalco-halide glasses are suitable for fabricating infrared GRIN lenses using ion exchange.
• This advancement facilitates the creation of lighter and more compact thermal imaging devices.
• The method offers a viable route for producing high-performance infrared optical components.