标题：Analysis of a log periodic nano-antenna for multi-resonant broadband field enhancement and the Purcell factor
作者：Yang, Jie; Kong, Fanmin; Li, Kang; Sheng, Shiwei
作者机构：[Yang, Jie; Kong, Fanmin; Li, Kang; Sheng, Shiwei] Shandong Univ, Sch Informat Sci & Engn, Jinan 250100, Peoples R China.
通讯作者地址：[Kong, FM]Shandong Univ, Sch Informat Sci & Engn, 27 South Shanda Rd,Licheng St, Jinan 250100, Peoples R China.
关键词：Log periodic; Nano-antenna; Field enhancement; Purcell factor
摘要：Broadband nano-antennas play a central role in many areas of science and technology. However, a more intuitive understanding for rational design of nano-antennas with broadband response is desirable. A log periodic nano-antenna was studied in the paper. The finite-difference time-domain method was used to explore the spectral characteristics of the log periodic nano-antenna by the excitation mode of reception and emission. The effects of geometry on field enhancement and the Purcell factor were systematically described and investigated. The field enhancement of the nano-antenna can be tuned by geometric parameters such as the outer radius, the tooth angle, and the ratio of the radial sizes of successive teeth, which provide control over both the spectral resonance position and the field enhancement peak amplitude. The Purcell factor mainly depends on the outer radius, the tooth angle, and the bow angle. In addition, multi-resonant field enhancement was analyzed in detail by conformal transformation. Furthermore, a careful comparison of the characteristics of a bowtie nano-antenna demonstrated that the log periodic nano-antenna has considerable potential for multi-resonant field enhancement and improvement of the Purcell factor. The results provide a promising prospect for designing and optimizing the log periodic nano-antenna in a broad range of wavelengths. (C) 2015 Elsevier B.V. All rights reserved.