Tunable Negative Group Delay in a Birefringent Fabry–Pérot-Like Cavity With High Fractional Advancement Induced by Cross-Interference Effect

Yao, Hsin-Yu; Chen, N. C.; Chang, Tsun-Hsu; Winful, Herbert G.

doi:10.1109/tmtt.2016.2600318

Cited by 13 publications

(9 citation statements)

References 25 publications

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“…Although propagating in a dispersive medium, we note that after reaching section #50, the pulse preserves its Gaussian shape, although attenuated by the factor of 1.14 × 10 2 due to losses imparted by the line. Similarly at node #80, the time delay calculated from (8) gives t c, 80 − t 0 = 3.234 μs, in good agreement with time delay determined from the group velocity, namely 80 sections/v g = 3.261 μs. However, at section # 80, the pulse is greatly attenuated by the factor 1.15 × 10 5 , albeit maintaining the Gaussian profile.…”

Section: Resultssupporting

confidence: 75%

“…Moreover, strong birefringence with broadband negative group delay (NGD) in the millimetre-wave region was achieved in a circular waveguide loaded with an asymmetric cross-shaped slotted structure [8]. In addition, anomalous negative group dispersion without absorption and reflection was reported in coupled-line structures [9], enabling such structures for applications in pulse shaping, delay control, constant phase shifters [10], and in the reduction in beam squinting in series-fed antenna arrays [11].…”

Section: Introductionmentioning

confidence: 99%

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Negative group velocity in resistive lossy left‐handed transmission lines

Barroso

Oliveira

Coutinho

et al. 2017

IET Microwaves, Antennas & Propagation

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This study reports on negative group velocities in a lumped transmission line, where capacitors and inductors connected to resistors are placed in the series and shunt branches of the periodic line, respectively. The propagation characteristics of the left‐handed transmission line are examined along with two methods. The first method consists of analysing the lumped‐element ladder network by solving in the time domain a system of differential equations derived from the Kirchhoff's voltage and current laws. In the second method, transmission matrix of the unit cell is applied to obtain the dispersion diagram from which the time group delay induced by the periodic network is derived as a function of frequency. Also, non‐analytical input signals are considered, whereby transient effects occur at both ends of modulated half‐sine wave packets propagating under negative group delay (NGD) regime of the left‐handed line. NGD effects arise from ohmic dissipation due to the resistors which establish a frequency range in which NGD propagation is allowed. This finding is numerically demonstrated by injecting into the line modulated Gaussian wave packets, for which the negative time delays determined from the numerical solution of circuit equations and from the dispersion relation are in good agreement.

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Section: Resultssupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Negative group velocity in resistive lossy left‐handed transmission lines

Barroso

Oliveira

Coutinho

et al. 2017

IET Microwaves, Antennas & Propagation

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“…In analogy with electron tunneling through a barrier in quantum mechanics [23], several theoretical and experimental works have treated the problem of optical tunneling time, optical clock, Hartmann effect, group delay, and superluminal phenomena [24] in (i) a single layer sandwiched between two media under total internal reflection [25,26], (ii) 1D photonic Bragg reflector (superlattice) made of isotropic and/or anisotropic layers [27][28][29][30][31], (iii) microwave waveguide under cutoff frequency or with a birefringent Fabry-Perot cavity [32][33][34], (iv) optical fiber at the cutoff wavelength [35], (v) metamaterials and microresonators [36,37], and (vi) coaxial photonic crystals [38][39][40][41][42]. (vii) Also, a large amount of work has been performed on electromagnetic periodic structures called frequency selective surface (FSS) [43].…”

Section: Introductionmentioning

confidence: 99%

Comparison of density of states and scattering parameters in coaxial photonic crystals: Theory and experiment

et al. 2020

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We present an analytical and experimental study of the scattering parameters in a one dimensional (1D) symmetric photonic crystal and their relation to the density of states (DOS). The 1D photonic crystal is constituted by N alternating wires and loops that are either inserted horizontally or attached vertically between the source and load on a transmission line. The complete knowledge of the scattering matrix coefficients (S i j ) allows us to access the DOS and eigenvalues of the finite periodic structure as well as the DOS and dispersion curves of an infinite periodic system. We show the usefulness of the transmission and reflection delay times and highlight their similarities and differences with respect to the DOS, in particular as a function of the absorption strength in the system. For both horizontal and vertical geometries, we show analytically that in a lossless structure, the DOS is proportional to the Friedel phase, namely the derivative of the argument of the determinant of the scattering matrix S. For a low loss system, this proportionality remains still valid with a good approximation and can be used as a practical tool to derive the DOS and therefore the dispersion curves from experimental data. Also, the absorption can be accurately extracted from the measurement of the modulus of the determinant of S. However, for increasing strength of dissipation, we show how and why these relationships cease to be valid. Still, the transmission delay time can remain an efficient tool to derive DOS even at relatively high dissipation strength. Additionally, we show that in the vertical geometry the transmission and reflection delay times exhibit negative delta peaks which are related directly to the eigenmodes of the finite system with different boundary conditions on its extremities. Our theoretical results are obtained by means of the Green's function approach, whereas the experimental demonstrations are performed using standard coaxial cables in the radio-frequency domain.

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“…In terms of experiments, Longhi et al 12 proposed a double Lorentzian fiber Bragg grating to observe the reflected group delay of optical pulses. Yao et al 13 demonstrated that the large and broadband negative group delay can be obtained using a circular waveguide with an asymmetric crossshaped slotted structure. However, because of the restraints of materials and mechanisms, the optical pulse group delay induced by traditional materials and structures exhibits relatively small value, and the controllable performances are not sufficiently flexible.…”

Section: Introductionmentioning

confidence: 99%

Enhanced and tunable transmitted group delays based on epsilon-near-zero response of Weyl semimetal

Zeng

2022

Opt. Eng.

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.We theoretically discuss the group delays induced by the transverse-magnetic polarized light penetrating a Weyl semimetal (WSM) film. It is shown that the transmitted group delay τps emerges because of the nonzero off-diagonal components of the dielectric constant tensor. In particular, the transmitted group delays τpp and τps are enlarged significantly at the epsilon-near-zero (ENZ) frequency, where steep phase changes occur due to the sharp changes of the transmission coefficients | tpp | and | tps | . More importantly, the tunable ENZ effect can be effectively obtained with Fermi energy, so the giant enhanced group delays at various frequencies can be readily realized. The enhanced group delays also show the adjustability of WSM thickness, incident angle, and Weyl node separation. Our findings supply easy and available methods to realize the adjustable enhanced group delays with a WSM.

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Tunable Negative Group Delay in a Birefringent Fabry–Pérot-Like Cavity With High Fractional Advancement Induced by Cross-Interference Effect

Cited by 13 publications

References 25 publications

Negative group velocity in resistive lossy left‐handed transmission lines

Negative group velocity in resistive lossy left‐handed transmission lines

Comparison of density of states and scattering parameters in coaxial photonic crystals: Theory and experiment

Enhanced and tunable transmitted group delays based on epsilon-near-zero response of Weyl semimetal

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