Influence of interdiffusion on multilayered gradient refractive index (GRIN) lens materials

• Published in: Polymer (Guilford) 2012-03, Vol.53 (6), p.1393-1403
• Main Authors: Lai, Chuan-Yar, Ponting, Michael T., Baer, Eric
• Format: Article
• Language: English
• Subjects: Applied sciences; atomic force microscopy; diffusivity; Exact sciences and technology; Forms of application and semi-finished materials; Interdiffusion; Multilayer; Polymer industry, paints, wood; polymers; Refractive index; Sheets and films; Technology of polymers
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2012.01.036

The interdiffusion of two materials used to fabricate polymeric gradient refractive index (GRIN) lenses was examined by varying contact time during multilayer films co-extrusion composed of alternating poly(methylmethacrylate) (PMMA) and poly(styrene-co-acrylonitrile) with 17mol% acrylonitrile (SAN17). The model applied successfully described their interdiffusion, and a reasonable mutual diffusion coefficient of 7.0×10−13m2/s was determined. Atomic force microscopy confirmed good agreement between modeled profiles and actual layer structure, and optical properties were investigated. Films with contact times of ≤160s exhibited multiple refractive indices, while films with longer contact times, showed single refractive indices that followed an additive line. Though a single additive value requires layers ≤ a quarter-wavelength of light, these films exhibit such behavior with thicknesses 5× greater than expected, though layer resolution is still present. Using the model profiles, it was determined that only a 1% reduction in material purity is required to reduce the effective layer thickness. [Display omitted]