Direct thermal bonding of infrared optics using viscous chalcogenide glasses

The absence of reliable infrared-compatible bonding materials fundamentally constrains doublet lens implementation in thermal imaging systems, compromising both aberration correction performance and system miniaturization. This work systematically investigates the viscous chalcogenide glasses (ChGs) from As₃₂Se_48-xTe_xI₂₀ system (x = 0∼30 at%) for infrared (IR) thermal bonding applications. This material exhibits a relatively low glass transition temperature (T_g) and a wide adjustable refractive index range (Δn≈0.45), making it suitable for thermal bonding with almost all IR optical materials. The achromatic performance of the IRG22/IRG26 (Ge₃₃As₁₂Se₅₅/As₄₀Se₆₀) doublet lens was verified in Zemax, and its successful thermal bonding eliminated air-gap interfacial losses, yielding an internal transmittance of 95.7%. Adhesion testing verifies 0.25 MPa interfacial strength in thermally bonded optics sufficient for cryogenic IR reliability thresholds without chemical curing.