Effect of lens size on the focusing performance of plasmonic lenses and suggestions for the design

Abstract

We present a detailed investigation of the effect of lens size on the focusing performance of plasmonic lenses based on metallic nanoslit arrays with variable widths. The performance parameters considered include the focal length, depth of focus (DOF), full-width half-maximum (FWHM) and the maximum intensity of the focal point. 2D FDTD simulation was utilized. The results show that all the lens parameters are greatly affected by the lens size. A larger lens size, with a total phase difference of at least 2π, will produce a better focusing behavior and a closer agreement with the design. The Fresnel number and diffraction theory can be used to explain the effect of lens size. Suggestions are provided for realization of a practical plasmonic lens using the existing nanofabrication techniques.

Robustly Efficient Superfocusing of Immersion Plasmonic Lenses Based on Coupled Nanoslits

“…Moreover, the light focusing with a FWHM of 176 nm, i.e., λ/3.69, is achieved using the oil immersion lens, which is much smaller than the reported superfocusing of λ/2.60 realized by the non-immersion lens. In addition, according to our previous investigation of the size effect on the focusing performance [11], the superfocusing capability of the oil immersion lens can be further enhanced by increasing the aperture size. The oil immersion lenses with different apertures are designed and validated using the FDTD method.…”

“…k is the free-space wavevector. ε m and ε d are the permittivity of the metal and dielectric material inside the nanoslits, [11].…”

“…Allowing the easy integration for on-chip applications, planar plasmonic lenses based on metallic nanoslits have been extensively studied both numerically [11][12][13] and experimentally [14][15][16]. This type of metallic nanostructured lens can realize focusing at an anticipated distance from the lens via the proper structural design.…”

Subwavelength beam focusing via multiple-metal slits arranged along a triangle surface

“…Plasmonic lenses, with the ability to focus SPPs into a spot beyond the diffraction limit, which enables various applications such as super-resolution imaging, high density optical data storage, and integrated optical circuit, have attracted an increasing research interest in recent years [9][10][11][12][13][14][15][16]. Various geometries, including circular holes with concentric grooves [9], slits flanked by linear arrays of grooves [10], metal slits with variant depths [11] or widths [13][14][15][16][17], and single metallic slit surrounded with grooves [17][18][19], have been considered to implement the focusing capability of plasmonic lenses. However, although a few excellent designs of them are capable of focusing light beyond the diffraction limit [13,14], complex structure and sophisticated parameters make them especially difficult to fabricate by using the present techniques.…”

Active Focusing of Light in Plasmonic Lens via Kerr Effect

“…Surface-plasmon based lenses or plasmonic lenses as an alternative to the ordinary refractive lenses are capable of super focusing beyond the diffraction limit and have great applications in optical data storage, nanofabrication, single molecular biosensing, circular polarizer analyzer and etc [7,[25][26][27]. Single subwavelength slit surrounded by surface corrugation [28] or by chirped dielectric surface gratings [29], chirped circular slits corrugated on metallic film [30], quasiperiodic array of nanoholes [31] and nanometric cross-shaped aperture arrays [32] in a metal screen are some of the reported design principles to implement the focusing capability of plasmonic lenses.…”