中文摘要：

为了实现轻量化的大数值孔径红外透镜,基于模式耦合理论,建立了金属薄膜上方形孔对入射光场相位调制与方孔边长尺寸、深度的关系,在此基础上,提出了一种可实现大数值孔径的亚波长金属结构薄膜透镜。采用数值模拟方法对此透镜的聚焦特性进行了模拟仿真,结果表明：对于10.6μm的入射波长,口径尺寸为300μm的透镜可实现半高全宽仅为4μm的聚焦光斑,其等效的数值孔径高达3.3,充分证明了这类透镜在实现大数值孔径方面的优势,为设计轻量化的高分辨红外光学元件提供了新的方法。

英文摘要：

To realize infrared lens with light weight and large numerical aperture,the dependence of the phase modulation of the transmitted light filed through a square hole perforated into a metal film on its side length and depth was studied using model coupling theory.Based on this,a kind of subwavelength structured metal film lens,which had large realizable numerical aperture,was brought forward.Then,its focusing characteristics was simulated with numerical method.The results show that when the aperture of this kind of lens is 300 μm,the full width of half maximum（FWHM） of its focus can be as small as 4 μm for 10.6 μm of incident light wavelength and its equivalent relative aperture is as high as 3.3,which proves its advantages in achieving large numerical aperture lens and provides a new way for designing infrared elements with light weight and high resolution.