(a) Grating structure (1D array of grooves: the width and the depth separated by a distance ) for comparison. (b) GW structure with a tapered input port. [(c)–(e)] Three different GGWs for light trapping: (c) depth-varying structure, (d) gap-varying structure, and (e) both-varying structure (gap and depth both vary).
Band structures in the GW with , , , and . As shown above, the axis is the propagation constant in a unit of .
(a) E field intensity distribution of the -like plasmon mode in the GW with , , , and . (b) Transverse E field intensity distributions of the -like plasmon modes for three different depths , 50, and . [(c) and (d)] Snapshots of the phase of the magnetic field (Hy): -like plasmon mode in the GW with gap (c), and -like oscillating mode in the GW with gap (d).
(a) Dispersion curves of the spoof SPPs for , , and and different gaps , 40, 60, and . Inset: cutoff frequency vs gap. (b) Dispersion curves of the spoof SPPs for , , and and different depths , 40, 50, and . Inset: cutoff frequency vs depth.
(a) Transfer efficiency vs gap at 1 THz for , , and . (b) Transfer efficiency vs depth at 1 THz for , , and . (c) Transfer efficiency vs wavelength for , , , and .
(a) E field intensity distribution in the GW with , , , and at 1.2 THz after the propagation time of (c is the light velocity in vacuum). The scale of the intensity is indicated by logarithmic scale color bar. (b) The distributions of E intensity at a plane in the center of the GW after three different propagation times of 5000, , and (50 ps).
E field intensity distributions in three different GGWs at 1 THz after the propagation time of 25 ps for (a) the gap-varying structure with and decreasing from 80 to , (b) the depth-varying structure with and increasing from 17 to , and (c) the both-varying structure with decreasing from 80 to and increasing from 17 to , over along the x direction. Insets: schematic structures of the GGWs. The scale of the intensity is indicated by the logarithmic scale color bar.
The distributions of E intensity at a plane in the center of the both-varying GGW (dashed line in the insets) for (a) different propagation times of 25 and 50 ps, and (b) different excitation frequencies of 1, 1.5, and 2 THz.
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