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(a) Schematic diagram of the plasmonic waveguide system: w, the width of the waveguide and stubs; p, theperiod of the grating; h, the grating depth. (b) Dispersion curves calculated using transmission line theory (red dashed line). The results are shown for a waveguide structure with a constant grating depth of h = 500 nm, w = 50 nm, and p = 200 nm. Also shown are the dispersion curves for lossless metal (black solid line). (c) Evolution of propagation constant β at different frequencies with the grating depth of w = 50 nm and p = 200 nm. (d) Group index of SP wave as a function of frequency for h = 320 nm. The cutoff frequency f cutoff is about 193.5 THz (i.e., λ cutoff ≈ 1.55 μm). The inset shows group index versus the grating depth for the incident frequency of 193.5 THz.
(a) Time-dependent field intensity (|H z|2) in the stubs. Inset: arrival time of SP wave at different spatial positions. (b) Intensity evolution of SP wave at different spatial positions of the proposed structure. In calculations, the incident light is a TM-polarized Gaussian pulse with a width of 100 fs and central frequency of 160 THz. The grating depth of the structure changes from 150 nm to 500 nm linearly in a 16 μm region. The period and width of the grating structure are 200 nm and 50 nm, respectively.
Field distributions of the trapped waves with the frequencies of (a) 193.5 THz, (b) 163.5 THz, (c) 133.5 THz, and (d) 103.5 THz. The incident light is TM-polarized Gaussian pulses with the duration of 100 fs. The grating depth of the plasmonic waveguide system is linearly increased from the left-hand side (h = 150 nm) to the right-hand side (h = 500 nm) (enhanced online). [URL: http://dx.doi.org/10.1063/1.4733477.1]10.1063/1.4733477.1
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