1. Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. Cross section schematic of the three types of PL structure. (a) Equivalent insulator-metal-insulator (IMI) model, (b) phase difference by different grooves, (c) CG type of PL structure, (d) CGP type of PL structure, and (e) CGH type of PL structure. Figure Legend: From: Optimization of structure parameters of concentric plasmonic lens for 355 nm radially polarized illumination J. Nanophoton. 2015;9(1):093794. doi:10.1117/1.JNP.9.093794

2. Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. The simulation results of CG type of PL. Red line is the trend of field enhancement intensity, blue line is the trend of FWHM. (a) The intensity strength changes periodic with increasing the width of the first ring. (b) Field enhancement intensity achieved its optimal value with increasing the groove width. (c) Coupled intensity by the two surface plasmon polariton (SPPs) results in strong confinement and short-ranging. (d) The intensity increases with increasing the groove number. Figure Legend: From: Optimization of structure parameters of concentric plasmonic lens for 355 nm radially polarized illumination J. Nanophoton. 2015;9(1):093794. doi:10.1117/1.JNP.9.093794

3. Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. The simulation results of the CGP type of PL. Red line is the trend of the field intensity, blue line is the trend of the FWHM. (a) The field intensity achieved its optimal value with increasing the aspect ratio (film thickness/pillar diameter) of the nanorod. (b) FWHM achieved its optimal value when aspect ratio is equal to 3.7. (c) The first groove width reveals its importance as the demarcation part of LSPs and SPPs. (d) Field enhancement intensity and FWHM shows periodic rule in the change with the distance between axis and the first ring-groove edge. (e) The intensity achieved its optimal value when the groove width was between 100 nm to 150 nm. (f) The growth trend of the intensity increasing with the groove number. Figure Legend: From: Optimization of structure parameters of concentric plasmonic lens for 355 nm radially polarized illumination J. Nanophoton. 2015;9(1):093794. doi:10.1117/1.JNP.9.093794

4. Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. The simulation results of the CGH type of PL. (a) Transmission efficiencies will increase rapidly when the feature size is bigger than 5 nm. (b) The field intensity and FWHM have a periodical change with the width of the ring. (c) The intensity achieved its optimal value with changing the groove width. (d) The intensity changed to be steady with the groove number is bigger than 9. Figure Legend: From: Optimization of structure parameters of concentric plasmonic lens for 355 nm radially polarized illumination J. Nanophoton. 2015;9(1):093794. doi:10.1117/1.JNP.9.093794

5. Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. Intensity distributions in the condition of CG, CGP, and CGH types of PL. Figure Legend: From: Optimization of structure parameters of concentric plasmonic lens for 355 nm radially polarized illumination J. Nanophoton. 2015;9(1):093794. doi:10.1117/1.JNP.9.093794

6. Date of download: 6/21/2016 Copyright © 2016 SPIE. All rights reserved. SEM photos of the fabricated three types of PL structures by FIB: (a) CG-type PL, (b) CGP-type PL, (c) CGH-type PL, (d) enlarged photo of CG type, (e) enlarged photo of CGP type, and (f) enlarged photo of CGH type. Figure Legend: From: Optimization of structure parameters of concentric plasmonic lens for 355 nm radially polarized illumination J. Nanophoton. 2015;9(1):093794. doi:10.1117/1.JNP.9.093794