Negative group velocity and group delay in left-handed media

Abstract

The dynamics of wave propagation in media with negative index of refraction is analyzed through analytical calculations, simulations, and experiments. Using a free space setup, the transmission characteristics of two split ring resonator and strip wire left-handed media (LHM), designed for operation at K -band frequencies (18-26 GHz), are measured. The first LHM, which is 3 unit cells long in the propagation direction, exhibits a maximum negative group delay of -0.9 ns . The second LHM (4 unit cells long) exhibits a maximum negative group delay of -1.2 ns . For both LHM the bandwidth of the negative group delay (and hence the negative group velocity) region was approximately 250 MHz.

Neutralization of LC- and RC-Disturbances with Left-Handed and NGD Effects

“…Several experiments confirmed the physical existence of the superluminal and NGD phenomena with negative refractive index media [32][33][34][35][36][37]. In the presence of losses, the NGD generated by NGD passive media is accompanied by excessive losses [15][16][38][39][40]. So, the applications are still limited in low frequencies.…”

“…The first experimental verification of this NGV phenomenon was performed in 1982, by Chu and Wong by using laser pulses propagating a GaP:N sample as shown in [8]. To verify the existence and illustrate the significance of this extraordinary phenomenon, many theoretical and experimental demonstrations were performed [8][9][10][11][12][13][14][15][16]. This counterintuitive phenomenon was explained from the pulse reshaping because of constructive and destructive interferences in the frequency band of anomalous dispersion.…”

“…This counterintuitive phenomenon was explained from the pulse reshaping because of constructive and destructive interferences in the frequency band of anomalous dispersion. In this region, it was shown several times, that the group refractive index ) (ω g n can become negative [12][13][14][15][16][17][18]. In this case, the group velocity, which is defined as:…”

“…It was stated that the NGD effect does not contradict the causality principle [19][20][21][22][23][24][25][26]. In addition, the left-handed (LH) lumped passive circuit capable to generate NGD effect for microwave signals up to GHz has been introduced by the group of Mojahedi [15][16]. The topology of this circuit was established from the 1D metamaterials modelling of the array split ring resonators having simultaneously negative permittivity and negative permeability.…”

Two-stage radio-frequency interferometer sensors

“…Thus, through the summation of two traveling waves, i.e., an interference process, an RF interferometer exhibits unique dispersion characteristics with minimal reflections occurring only in the summation device. Other NGD electrical structures and circuits, such as the electromagnetic structures of a backward wave oscillator (BWO), 16 the distributed transmission line filter, 17 left-handed media, 12,18 and the active circuits, 13,19 involve complicated wave reflection and propagation processes. …”