Abstract
Amplitude enhancement in a group front of continuous wave (CW) Gaussian beam refracted at the boundary of right- and left-handed media is observed. Behind the interface plane in a high dispersion double negative medium the individual Fourier components of the beam diffract at different angles and have diversified phase speeds. This results in the group front build-up that propagates on with the beam and moves sideways with respect to the group velocity direction, where energy is transported. The enhancement is illustrated with 2-D simulations using finite difference time domain (FDTD) method.
Highlights
After Zhang and Park [20], we accept that a group front moves with group front velocity, which is parallel to group velocity when a wave packet propagates in nondispersive medium, or when it incidents normally at the interface between righthanded material (RHM) and dispersive left-handed medium (LHM)
To avoid misinterpretation we indicate that when continuous wave (CW) Gaussian beam propagating from RHM enters a normal dispersion LHM its group velocity has the same direction as the energy velocity
From the above simulation we find that the envelope of a transient sinusoidal Gaussian beam with steady state angular frequency ω = 2πf0 = 3.77 × 1015 rad/s propagates in the LHM with the group velocity vg = (0.19±0.02)c that is close to that assessed in the normal incidence case
Summary
Negative refraction of electromagnetic waves at the interface between a nondispersive righthanded material (RHM) and a strongly dispersive lossy left-handed medium (LHM) has received much attention in the literature of the last few years [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23]. In 2004, Zhang and Park [20] made a clear distinction between group and group front velocity directions connected with propagation of spectral components of a Gaussian wave packet negatively refracted in a normal dispersion DNG medium. They confirmed the result of Smith et al [6] that positively refracted group fronts move in a different direction than negatively refracted energy flow. After Zhang and Park [20], we accept that a group front moves with group front velocity, which is parallel to group velocity when a wave packet propagates in nondispersive medium, or when it incidents normally at the interface between RHM and dispersive LHM.
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