High Efficient Far-Field Nanofocusing with Tunable Focus Under Radial Polarization Illumination

We design a new nanofocusing lens for far-field practical applications. The constructively interference of cylindrical surface plasmon launched by the subwavelength metallic structure can form a subdiffraction-limited focus, which is modulated by the dielectric grating from the near field to the far field. The principle of designing such a far-field nanofocusing lens is elucidated in details. The numerical simulations demonstrated that nanoscale focal spot (0.12λ2) can be realized with 3.6λ in depth of focus and 4.5λ in focal length by reasonably designing parameters of the grating. The focusing efficiency can be 7.335, which is much higher than that of plasmonic microzone plate-like lenses. A blocking chip can enhance the focusing efficiency further as the reflected waves at the entrance would be recollected at the focus. By controlling the number of the grooves in the grating, the focal length can be tuned easily. This design method paved the road for utilizing the plasmonic lens in high-density optical storage, nanolithography, superresolution optical microscopic imaging, optical measurement, and sensing.

[1]  C. Du,et al.  Nanopinholes-Based Optical Superlens , 2008 .

[2]  J. Pendry,et al.  Collection and concentration of light by touching spheres: a transformation optics approach. , 2010, Physical review letters.

[3]  Changtao Wang,et al.  Beam manipulating by metallic nano-slits with variant widths. , 2005, Optics express.

[4]  Kathleen S. Youngworth,et al.  Focusing of high numerical aperture cylindrical-vector beams. , 2000, Optics express.

[5]  Marvin J. Weber,et al.  Handbook of Optical Materials , 2002 .

[6]  U. Levy,et al.  Plasmonic focusing with a coaxial structure illuminated by radially polarized light. , 2009, Optics express.

[7]  Yongqi Fu,et al.  Plasmonic Lenses: A Review , 2010 .

[8]  Hyungduk Ko,et al.  Light focusing at metallic annular slit structure coated with dielectric layers. , 2010, Applied optics.

[9]  Bert Hecht,et al.  Excitation and superfocusing of surface plasmon polaritons on a silver-coated optical fiber tip , 2005 .

[10]  Liangping Xia,et al.  Three-dimensional nanoscale far-field focusing of radially polarized light by scattering the SPPs with an annular groove. , 2010, Optics express.

[11]  Uriel Levy,et al.  Demonstration of nanofocusing by the use of plasmonic lens illuminated with radially polarized light. , 2009, Nano letters.

[12]  Zhaowei Liu,et al.  Focusing surface plasmons with a plasmonic lens. , 2005, Nano letters.

[13]  J. Takahara,et al.  Superfocusing modes of surface plasmon polaritons in a wedge-shaped geometry obtained by quasi-separation of variables , 2008 .

[14]  J. Pearson,et al.  Subwavelength focusing and guiding of surface plasmons. , 2005, Nano letters.

[15]  Chih-Kung Lee,et al.  Subwavelength nondiffraction beam generated by a plasmonic lens , 2008 .

[16]  Strongly frequency dependent focusing efficiency of a concave lens based on two-dimensional photonic crystals , 2006 .

[17]  L. Lim,et al.  Plasmonic microzone plate: Superfocusing at visible regime , 2007 .

[18]  Tomasz Szoplik,et al.  Focusing radially polarized light by a concentrically corrugated silver film without a hole. , 2009, Physical review letters.

[19]  Effect of polarization on symmetry of focal spot of a plasmonic lens. , 2009, Optics express.

[20]  Qiwen Zhan,et al.  Plasmonic lens made of multiple concentric metallic rings under radially polarized illumination. , 2009, Nano letters.