Transient fields of a horizontal electric dipole on a multilayered dielectric medium

Experimental time-domain study of THz signals from impulse excitation of a horizontal surface dipole

“…[6][7][8] Although the time and size scale of the previous theoretical GHz electromagnetic calculations are 1000 times longer than in this THz experiment, our scaled results confirm many of the observations of the theory. 4 The calculation predicts back-''reflected'' waves as well as the two ''direct'' waves, one in the substrate and one above the substrate, which is precisely what we experimentally observe. In the theory, these two direct waves exhibit several features: they decay as 1/r 2 , as is expected for the near-field component; they have a relative inversion to each other, the magnitude of the dielectric signal is several times larger than the signal through air; and they have a shape which is a time integral of the far-field back-reflected pulse.…”

“…Electromagnetic theoretical calculations have been performed for nanosecond current impulse excitations of a horizontal Hertzian dipole on a multilayered dielectric medium. 4 Although the time and size scale of the theoretical calculations are a factor of 1000 longer than in our experiment, there is a direct correspondence of these GHz microwave predictions and our THz measurements because for equivalent dielectric properties and similar wavelength/size ratios there is a one-to-one correspondence of the results. Contrary to the known far-field radiation pattern, which does not allow surface propagation, 6-8 for near-field radiation the theory predicts the existence of two ''direct'' surface pulses as well as the shape of these pulses being the time integral of the far-field ''reflected'' pulses.…”

“…3 To gain an intuitive understanding of the characteristics of the detected signal, the transient electric field of a timedependent dipole moment in an isotropic media is discussed, as well as scaled comparisons of the THz experimental results to an analogous theoretical calculation in the field of electromagnetics at GHz frequencies. 4 The experimental study also demonstrates the potential use of the far-field pulse for on-chip communication of picosecond pulses of THz radiation.…”

“…The calculated index of refraction for the first and second pulse correlate well with that of air ͑1.00͒ and the ordinary index of sapphire ͑3.07͒, respectively, thereby, confirming the predicted propagation speeds. 4 Also, with a ps impulse excitation of a short dipole, Eq. ͑1͒ shows that for a homogeneous dielectric, starting at a distance of about 100 m in sapphire, the far-field term dominates.…”

Exact Formulas for the Lateral Electromagnetic Pulses From a Horizontal Electric Dipole on the Boundary Between a Isotropic Medium and One-Dimensionally Anisotropic Medium

“…Almost half century ago, Van der Pol [12] first formulated the transient EM field of a vertical electric dipole with a delta-function excitation on the boundary between two half-spaces by invoking the Hertz potential. Lately, the same problem was visited by many investigators [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29].…”