Single-step precision manufacturing of ZnSe lenses for FLIR thermal imaging: From atomic insights to lab-scale fabrication and integration

Abstract

Zinc selenide (ZnSe) is widely used in optical components, including lenses, mirrors and thermal imaging systems, owing to its medium refractive index and broad infrared transmission range (0.6 to 21 μm). However, its soft-brittle nature presents challenges in achieving the nanometric smooth finishes required for precision manufacturing. This study introduces a single-step precision manufacturing process for ZnSe and demonstrates its application in a plano-convex lens integrated into FLIR thermal imaging systems for heat detection in integrated circuits.

To explore ZnSe's ductile plasticity, we developed a molecular dynamics (MD) model. Generalized Stacking Fault Energy (GSFE) calculations revealed that ZnSe favours slip on the Shuffle set ⟨110⟩ (111), unlike harder, brittle materials like silicon and silicon carbide, which favour the Glide set ⟨11–2⟩ (111) explaining the soft and brittle nature of ZnSe. The model predicted that a Peierls stress of approximately 0.027 GPa initiates the motion of ½ ⟨110⟩ perfect dislocations along the (111) slip planes, leading to plasticity and dislocation dissociation into 1/6 ⟨112⟩ (Shockley) partial dislocations. Analysis of the cutting region revealed phase transformation from zinc-blende to a hexagonal structure and defects, including intrinsic stacking faults and ∑3 coherent twin boundaries. Additionally, simulations indicated that the (100) orientation requires the least stress for plastic deformation, while the (110) orientation requires the most.

By shedding light on these mechanisms, this research aims to enhance our understanding of the precision machining of ZnSe, guiding the development of optimised cutting strategies to minimise defects and improve manufacturing outcomes. In sum, it introduces a “Design-to-Manufacture” approach, linking atomic-level insights with the practical integration of ZnSe lenses into thermal imaging applications.