title: Broadband Metallic Planar Microlenses in an Array: the Focusing Coupling Effect.
abstract: The microlens arrays (MLAs) are widely utilized for various applications. However, when the lens size and the spacing between two adjacent microlenses are of the length scale of the working wavelength, the diffraction effect plays a vital role in the final focusing performance. We suggest a kind of broadband metallic planar microlenses, based on which the ultra-compact microlens arrays are also constructed. The focusing coupling effect revealing for such devices is then investigated in detail by using the finite-difference time-domain (FDTD) method, with the emphasis on the changing spacing between adjacent microlenses, the working wavelength, the diameter of microlenses, and the array size. The results show that a larger spacing, a larger lens size, a shorter wavelength, or a smaller array scale can lead to a weaker focusing coupling effect. This research provides an important technological reference to design an array of metallic planar microlenses with the well-controlled focusing performance.
authors.affiliation: Key Laboratory of Micro/Nano Systems for Aerospace, Ministry of Education, Northwestern Polytechnical University, Xi'an, 710072, China. yyt@nwpu.edu.cn.|Key Laboratory of Micro- and Nano-Electro-Mechanical Systems of Shaanxi Province, Northwestern Polytechnical University, Xi'an, 710072, China. yyt@nwpu.edu.cn.
authors.forename: Yiting
authors.initials: Y
authors.lastname: Yu
authors.affiliation: Key Laboratory of Micro/Nano Systems for Aerospace, Ministry of Education, Northwestern Polytechnical University, Xi'an, 710072, China. 1179033676@qq.com.|Key Laboratory of Micro- and Nano-Electro-Mechanical Systems of Shaanxi Province, Northwestern Polytechnical University, Xi'an, 710072, China. 1179033676@qq.com.
authors.forename: Ping
authors.initials: P
authors.lastname: Wang
authors.affiliation: Key Laboratory of Micro/Nano Systems for Aerospace, Ministry of Education, Northwestern Polytechnical University, Xi'an, 710072, China. yechuanzhu_30@hotmail.de.|Key Laboratory of Micro- and Nano-Electro-Mechanical Systems of Shaanxi Province, Northwestern Polytechnical University, Xi'an, 710072, China. yechuanzhu_30@hotmail.de.
authors.forename: Yechuan
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Key Laboratory of Micro/Nano Systems for Aerospace, Ministry of Education, Northwestern Polytechnical University, Xi'an, 710072, China. jsd@mail.nwpu.edu.cn.|Key Laboratory of Micro- and Nano-Electro-Mechanical Systems of Shaanxi Province, Northwestern Polytechnical University, Xi'an, 710072, China. jsd@mail.nwpu.edu.cn.
authors.forename: Jinshuai
authors.initials: J
authors.lastname: Diao
keywords: Focusing coupling; Metallic planar microlenses; Microlens arrays; Nanosphere lithography