Zhang Jingjing
Technical University of Denmark, Department of Photonics Engineering - DTU Fotonik, DK-2800 Kgs. Lyngby, Denmark.
Sci Rep. 2015 May 28;5:10083. doi: 10.1038/srep10083.
The resolution of conventional optical lenses is limited by diffraction. For decades researchers have made various attempts to beat the diffraction limit and realize subwavelength imaging. Here we present the approach to design modified solid immersion lenses that deliver the subwavelength information of objects into the far field, yielding magnified images. The lens is composed of an isotropic dielectric core and anisotropic or isotropic dielectric matching layers. It is designed by combining a transformation optics forward design with an inverse design scheme, where an evolutionary optimization procedure is applied to find the material parameters for the matching layers. Notably, the total radius of the lens is only 2.5 wavelengths and the resolution can reach λ/6. Compared to previous approaches based on the simple discretized approximation of a coordinate transformation design, our method allows for much more precise recovery of the information of objects, especially for those with asymmetric shapes. It allows for the far-field subwavelength imaging at optical frequencies with compact dielectric devices.
传统光学透镜的分辨率受衍射限制。几十年来，研究人员进行了各种尝试，以突破衍射极限并实现亚波长成像。在此，我们提出了一种设计改进型固体浸没透镜的方法，该方法可将物体的亚波长信息传输到远场，从而产生放大图像。该透镜由各向同性的电介质核心和各向异性或各向同性的电介质匹配层组成。它是通过将变换光学正向设计与逆向设计方案相结合来设计的，其中应用了进化优化程序来寻找匹配层的材料参数。值得注意的是，该透镜的总半径仅为2.5个波长，分辨率可达λ/6。与以前基于坐标变换设计的简单离散近似方法相比，我们的方法能够更精确地恢复物体信息，特别是对于那些形状不对称的物体。它允许使用紧凑的电介质器件在光频下进行远场亚波长成像。
