Near-field visualization of focal depth modulation by step corrugated plasmonic slits

Abstract

Nanometric plasmonic slits with stepped corrugations have been designed and fabricated to achieve plasmonic focusing and focal depth modulation. A scanning near-field optical microscope is employed to directly visualize the transmitted light from the slits. The near-field and far-field two-dimensional images taken at different planes parallel to the slit surface unambiguously demonstrated the focusing effect of the nanoslits. Furthermore, by forming stepped corrugations with either a concave or a convex profile on both sides of the slits, the phase of the transmitted beam can be effectively manipulated, thus allowing an accurate tuning of the focal depth.

Plasmonic Lenses: A Review

“…Depth-tuned structures Three types of plasmonic slits (convex, concave, and flat/constant groove depth) with different stepped grooves have been designed and fabricat- to achieve efficient plasmonic focusing and focal depth modulation of the transmitted beam. Figure 5 shows the fabricated depth-tuned plasmonic lens using focused ion beam milling [27]. The general design of the plasmonic slit is shown in Fig.…”

Experimental Investigation of Focusing of Gold Planar Plasmonic Lenses

“…A depth-tuned plasmonic lens was reported based on simulation [14,15] and experiment [16]. The modeling of reflection coefficient in periodic grooves shows the reflection as a function of the grooves' structural and material parameters [17].…”

Recent Progress in Far-Field Optical Metalenses

“…Since the diffracted beams are modulated by the nanometric grooves, through adjusting the parameters of the grooves such as their width, depth, period and number, the diffracted beams can be fully manipulated resulting in a tailored ultracompact lens [28]. The architecture can exhibit radial symmetry, so the plasmonic lens would consist of an annular slit and concentric grooves which, under radially polarized illumination, produces a focus spot.…”