Propagation of THz plasmon pulse on corrugated and flat metal surface

Terahertz Surface Waves Propagating on Metals with Sub-wavelength Structure and Grating Reliefs

“…Similar observations are made concerning the size of other couplers, for example the sharp edge [13,37]. For SP grating couplers, the agreement between calculated and experimental groove depths, which play the role of a coupling constant, is quite good, but still the excited SP shows a too-short propagation length [8,38,40]. Recently, Laman and Grischkowsky [39] have suggested that the reduced experimental conductivity of several samples of Cu and Al in the THz range can be attributed to a large amount of carrier scattering due to lattice defects within the 100 nm THz skin-depth layer.…”

“…The sensitivity of THz SP to sub-wavelength reliefs is also demonstrated through the ability of a grating with 70 μm groove depth to effectively radiate a SP as a free space wave, while the SP field localization in air is of the order of 2-5 mm! As previously explained, the THz SP localization in air is weak and the SP field distribution in air is very similar to a freely propagating plane wave, thus the out-coupling process at the metal edge is very effective [38]. Moreover, it implies that the field scattered in air remains rather well collimated.…”

“…This strange disagreement between theoretical and experimental α SP was discovered three decades ago [35]. To reach its fully evolved form, the SP must propagate over a distance of several tens of cm, considerably larger than d air [38]. This disagreement concerning the SP propagation length is also observed for the coupling parameters, which is quite expected as the coupling parameters (d air ) and the propagation length are mutually dependent values.…”

Non-Drude like behaviour of metals in the terahertz spectral range

“…This propagating mode was first predicted by Sommerfeld [38] and was studied at even lower frequencies (microwaves) in the 1950s [39][40][41]. Since then, a number of groups have shown that bound surface waves can propagate over distances up to 10-20 cm on a variety of different metals sheets and wires over a broad range of THz frequencies [42][43][44][45][46][47][48][49][50][51][52][53].…”

Terahertz subwavelength ribbon waveguide based plasmonic sensors for refractive index and thickness detection

“…General metals could, however, be considered as perfect electric conductors for THz waves, which are prohibited from penetrating into metals to excite SPPs, because the metal plasmon frequencies are located in ultraviolet or visible band to make THz radiations expand outside the metal surface 2 . Based on suitable coupling schemes, including aperture-pair 3 , prism-pair 4 and a metal parallel-plate waveguide 5 , such extended surface waves propagated on finite-conductivity metal surfaces can be supported, known as Sommerfeld-Zenneck wave 5 or THz surface plasmons 6 . It is difficult to use THz surface plasmons for sensing analytes owning small amounts or very small thicknesses based on the spectrums of intrinsic absorption 7 and dielectric constants 8 that are realized in THz broadband transmission of metal-sheet and -wire waveguides while loading analytes on the metal surfaces.…”