Carbide-bonded graphene-based Joule heating for embossing fine microstructures on optical glass

This paper reports the fabrication of high-quality microstructures on optical glass via hot embossing using carbide-bonded graphene (CBG) based Joule heating for the first time. In this study, a tailor-made micro hot embossing tool equipped with a modified CBG-based Joule heating system was designed and developed for transferring microstructures (e.g., microlens arrays, MLAs for short) from the CBG-coated silicon mold insert into the optical glass (P-SK57). Initially, the surface topographies of a typical 3x3 MLA from a bare silicon mold to an embossed glass replica were compared for evaluating form errors brought in during different preparation stages. The feasibility of the CBG-based Joule heating technique for the non-equilibrium thermal imprinting of optical glass was evaluated by the surface integrity and replication fidelity of the embossed MLA features. Thermally induced residual stress and imaging performance of the embossed glass lens were assessed as well. Experimental results indicate that the proposed CBG-assisted hot embossing technique, in combination with single point diamond turning technology, has the capability of producing high-quality glass MLAs. Moreover, this technique allows notably fine replication of surface shapes at the microscale, as well as roughness information at the nanoscale. Consequently, the embossed MLA replica shows satisfactory imaging performance.