Excitation and propagation of surface electromagnetic waves studied by terahertz spectrochronography

Abstract

We show the spectrochronography as an efficient tool to extend the THz time domain technique. Assuming that all the information is contained in the time-dependent electric field we apply a windowed transfer technique to measure the instantaneous spectra evolution. As an example, surface electromagnetic waves on the metal grating are considered. Dynamics of surface wave spectral component is measured.

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

“…For a sine-like groove shape, we observed as expected only the first order (N=±1) of SP excitation/reflection while, for rectangular grooves, SP are excited through many orders of diffraction ( Fig. 3(b)) [47].…”

“…In fact, the groove depth serves as a coupling constant which controls the shape of the SP resonances, in particular the minimum of the dips in the reflection spectra and thus the coupling efficiency. There exists an optimum groove depth for which the coupling efficiency is maximum [47,48], observed when diffraction and absorption losses contribute equally. The overall shapes of the calculated curves are comparable to the measured ones, and the coupling efficiency optimization is clearly observed.…”

“…SP lifetime and propagation length on the grating are several times smaller than on a flat surface due to the out-coupling processes and diffraction losses, which make the SP dips easily seen in the reflection spectrum [39]. The bandwidth of the excited SP is determined by the number of illuminated grooves, the divergence of the incident radiation, and the losses (diffraction and absorption) related to the studied grating [47]. Typically, SP resonances exhibit a 30-GHz bandwidth.…”

“…A shallow diffraction grating engraved in metal constitutes an effective and convenient device for tunable excitation of narrowband THz SPs, as demonstrated in [46,47]. Let us first consider here the case of collinear excitation, i.e.…”

Visualizing the results of a mathematical information system for identification of materials by interaction with a short-period terahertz pulse

“…It has been proposed in [18][19][20][21][22][23][24][25][26] and it is free from the above mentioned shortcomings. The SDA-method provides information about the dynamics of the entire spectrum using a single series of response measurements of the medium (or measurements of its integral characteristics).…”