A design methodology for directional beaming control by metal slit–grooves structure

Abstract

A design method is proposed for directional beaming control by a subwavelength metal slit surrounded with grooves. With the approach of modulating the phases of the radiation light decoupled by the surrounding grooves from surface plasmon polariton waves, the wavefronts of the radiation light from both sides of the slit are controlled in the beam toward specific directions. The design formulae of the plasmonic structures for directional beaming are deduced based on Huygens’ principle. Besides the grating equation being derived, the design requirement for the grating positions is determined. The transmitted field distributions through the designed structures are calculated by the finite-difference time-domain method. The results show that the transmitted light can be directionally beamed efficiently and the beam angle can be controlled accurately within the region of ± 20°.

Design and experimental demonstration of a plasmonic directional beaming device

“…So the proposed design method has the applicability to adjust and control the beam direction within the beam angle of 20°. The agreement of simulation results with those in [24] provides evidence for the universality of the design method for different types of structures.…”

“…(1), the symbol λ represents the incident wavelength of 633 nm, and the dependence of phase difference ϕ x − ϕ 0 on groove position x can be obtained by investigating a simplified structure that is composed of only a pair of grooves symmetrically surrounding the central slit [24,25]. We have investigated this simplified structure, and explored the relation between the phase difference and the groove position, which is expressed in the following formula under linear approximation [8]:…”

“…However, these designs lack systematically methodological investigations and directly experimental verifications. In our recent work, a design method of plasmonic beaming devices with expected beam angles is proposed [24]. We investigated the scattering behavior of SPP by the grooves in a silver film and modulated the phase of the radiation light scattered from each groove based on Huygens's principle.…”

“…To beam the transmitted light at a specific beam angle of θ, the wave front should have an angle of θ with respect to the device surface, as shown in Fig. 1, so the phase from the slit (denoted as ϕ 0 ) and the phase from the groove with the position of x (denoted as ϕ x ) should satisfy the following equation, which is discussed in detail in [24].…”

Direction-tunable enhanced emission from a subwavelength metallic double-nanoslit structure

“…The diffraction problem also greatly limits integration and miniaturization of conventional optical components. Over the past few decades, advances have allowed metals to be structured and characterized on the nanometer scale, as a result, great efforts have been made to overcome the diffraction limitation with the help of surface plasmon polaritons (SPPs) on metallic surfaces [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. The pioneering work of unusually high transmission through subwavelength periodic hole arrays in metal films was report by Ebbesen et al [2].…”