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

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 7.0×10−13 m2/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.

通过改变由交替的聚甲基丙烯酸甲酯（PMMA）和含17mol%丙烯腈的苯乙烯 - 丙烯腈共聚物（SAN17）组成的多层膜共挤出过程中的接触时间，对用于制造聚合物梯度折射率（GRIN）透镜的两种材料的相互扩散进行了研究。所应用的模型成功地描述了它们的相互扩散，并确定了合理的互扩散系数为7.0×10⁻¹³ m²/s。原子力显微镜证实了模拟轮廓与实际层结构之间良好的一致性，并且对光学性能进行了研究。接触时间≤160秒的薄膜呈现出多个折射率，而接触时间较长的薄膜则显示出遵循加和线的单一折射率。尽管单一加和值要求层厚≤光的四分之一波长，但这些薄膜在厚度比预期大5倍的情况下仍表现出这种行为，不过层分辨率仍然存在。利用模型轮廓确定，只需材料纯度降低1%就可降低有效层厚度。