Properties of TM resonances on metallic slit gratings

Abstract

Electromagnetic resonances on metallic slit gratings induced by TM polarized incident light have been investigated and physically interpreted. We have developed an electromagnetic model imposing surface impedance boundary conditions on the metallic grating surface from which we derive simple formulas explaining all physical properties of these resonances. It is demonstrated that Fabry-Perot (or cavity) resonances are generated by the zeroth slit mode yielding extraordinary transmission. For very narrow slits, the resonant H-field is squeezed to the slit walls and causes enhanced power losses. The excitation of surface plasmon polaritons (SPPs), however, is generated by two mode coupling. SPPs are linked to sharp absorption peaks and dips in transmittance. It is shown that these phenomena are primarily caused by the interaction of the electromagnetic fields with the finite conducting slit walls. These findings have been confirmed by measured transmittance data of gold gratings with periods of 0.5 μm, 1 μm, and 2 μm.

Unified Theory of Surface-Plasmonic Enhancement and Extinction of Light Transmission through Metallic Nanoslit Arrays

“…For example, at ε M ′ ≈ −15 where many previous analyses have been performed2, |λ AR − λ SPF | ≈ 4 × 10 −4 Λ and |λ R − λ Rayleigh | ≈ 1.5 × 10 −3 Λ. In this situation, it is likely to form a hasty conclusion that the SPP plays only a negative role15163031 and that the actual SPP-associated effects, such as the abrupt shift of the CM resonance condition, are confused with the effect of Rayleigh anomaly28. In [15,16] for example, the authors analyzed Au slit arrays in the near- and mid-infrared spectral domains where ε M ′ < −30.…”

“…A widely accepted enhancement mechanism for slit arrays is based on Fabry-Pérot resonances of slit-guided modes789101112131415161718, i.e., cavity modes (CMs). Many recent papers conclude that CMs provide the enhancement mechanism while SPPs play only a negative role13141516. In this view that deters SPPs, spectral location of the transmission minimum corresponds to the SPP resonance condition and the associated field pattern shows typical SPP character with its null at the aperture opening.…”

“…In this view that deters SPPs, spectral location of the transmission minimum corresponds to the SPP resonance condition and the associated field pattern shows typical SPP character with its null at the aperture opening. Strong surface-plasmonic absorption1516, excitation of a nonresonant SPP13, and the surface-plasmonic bandgap effect1718 have been suggested explanations for these negative effects of SPPs. The negative effect of an SPP has also been reported for hole arrays, and different viewpoints based on the nonresonant SPP excitation19 and destructive interference between transmission pathways via surface modes and hole-guided modes20 have been published as suggested explanations.…”

Finite gratings of many thin silver nanostrips: Optical resonances and role of periodicity

“…waveguide-mode) resonances or "vertical plasmons" observable on the thick strip metal gratings. 11,[33][34][35][36] In the reminder of this paper, Section II presents concise summary of the formulation and method of treatment. Section III deals with numerical study of resonances in the case of H-polarization.…”

On-chip near-infrared spectroscopy of CO2 using high resolution plasmonic filter array

“…Besides, at certain thickness, the cavity resonance in the nano-slit and the surface plasmon polariton on Au surface will have deconstructive interference, which will cause the discontinuity shown in the Figure 1(e). [25][26][27][28][29] Finally, the three parameters are chosen to be G ¼ 100 nm, H ¼ 40 nm and T ¼ 1.2 lm (dashed line). Although the FWHM at T ¼ 1.2 lm is slightly larger than that at T ¼ 1.3 lm (<1 nm), the side-band effect is less at T ¼ 1.2 lm.…”