title: Near-field engineering of Fano resonances in a plasmonic assembly for maximizing CARS enhancements.
abstract: Surface enhanced coherent anti-Stokes Raman scattering (SECARS) is a sensitive tool and promising for single molecular detection and chemical selective imaging. However, the enhancement factors (EF) were only 10~100 for colloidal silver and gold nanoparticles usually used as SECARS substrates. In this paper, we present a design of SECARS substrate consisting of three asymmetric gold disks and strategies for maximizing the EF by engineering near-field properties of the plasmonic Fano nanoassembly. It is found that the E-field "hot spots" corresponding to three different frequencies involved in SECARS process can be brought to the same spatial locations by tuning incident orientations, giving rise to highly confined SECARS "hot spots" with the EF reaching single-molecule sensitivity. Besides, an even higher EF of SECARS is achieved by introducing double Fano resonances in this plasmonic nanoassembly via further enlarging the sizes of the constituent disks. These findings put an important step forward to the plasmonic substrate design for SECARS as well as for other nonlinear optical processes.
authors: School of Physical Science &Engineering and Key Laboratory of Materials Physics of Ministry of Education of China, Zhengzhou University, Zhengzhou 450052, China.|College of Electric and Information Engineering, Pingdingshan University, Pingdingshan, 467000, China.
authors: Jinna
authors: J
authors: He
authors: School of Physical Science &Engineering and Key Laboratory of Materials Physics of Ministry of Education of China, Zhengzhou University, Zhengzhou 450052, China.
authors: Chunzhen
authors: C
authors: Fan
authors: Department of Mathematics &Physics, Zhengzhou Institute of Aeronautical Industry Management, Zhengzhou 450015, China.
authors: Pei
authors: P
authors: Ding
authors: School of Physical Science &Engineering and Key Laboratory of Materials Physics of Ministry of Education of China, Zhengzhou University, Zhengzhou 450052, China.
authors: Shuangmei
authors: S
authors: Zhu
authors: School of Physical Science &Engineering and Key Laboratory of Materials Physics of Ministry of Education of China, Zhengzhou University, Zhengzhou 450052, China.
authors: Erjun
authors: E
authors: Liang