Traversal of pulses through negative (ε\varepsilon, μ\mu) materials

We study the traversal times of electromagnetic pulses across dispersive media with negative dielectric permittivity ($\varepsilon$) and magnetic permeability ($\mu$) parameters. First we investigate the transport of optical pulses through an electrical plasma and a negative refractive index medium (NRM) of infinite and semi-infinite extents where no resonant effects come into play. The total delay time of the pulse constitutes of the group delay time and the reshaping delay time as analyzed by Peatross et al \cite{peatross}. For evanescent waves, even with broadband width, the total delay time is negative for an infinite medium whereas it is positive for the semi-infinite case. Evidence of the Hartman effect is seen for small propagation distance compared to the free space pulse length. The reshaping delay mostly dominates the total delay time in NRM whereas it vanishes when $\varepsilon(\omega)=\mu(\omega)$. Next we present results on the propagation times through a dispersive slab. While both large bandwidth and large dissipation have similar effects in smoothening out the resonant features that appear due to Fabry-P\'{e}rot resonances, large dissipation can result in very small or even negative traversal times near the resonant frequencies. We investigate the traversal and the Wigner delay times for obliquely incident pulses. The coupling of evanescent waves to slab plasmon polariton modes results in large traversal times at the resonant conditions. We also find that the group velocity mainly contributes to the delay time for pulse propagating across a slab with refractive index (n) = -1. The traversal times are positive and subluminal for pulses with sufficiently large bandwidths.Comment: 12 pages,9 figure

Time for pulse traversal through slabs of dispersive and negative (ϵ\epsilon, μ\mu) materials

The traversal times for an electromagnetic pulse traversing a slab of dispersive and dissipative material with negative dielectric permittivity ($\epsilon$) and magnetic permeability ($\mu$) have been calculated by using the average flow of electromagnetic energy in the medium. The effects of bandwidth of the pulse and dissipation in the medium have been investigated. While both large bandwidth and large dissipation have similar effects in smoothening out the resonant features that appear due to Fabry-P\'{e}rot resonances, large dissipation can result in very small or even negative traversal times near the resonant frequencies. We have also investigated the traversal times and Wigner delay times for obliquely incident pulses and evanescent pulses. The coupling to slab plasmon polariton modes in frequency ranges with negative $\epsilon$ or $\mu$ is shown to result in large traversal times at the resonant conditions. We also find that the group velocity mainly contributes to the delay times for pulse propagating across a slab with n=-1. We have checked that the traversal times are positive and subluminal for pulses with sufficiently large bandwidths.Comment: 9 pages, 9 figures, Submitted to Phys. Rev.

Exact solutions of optical pulse propagation in nonlinear meta-materials

An analytical and simulation based method has been used to exactly solve the nonlinear wave propagation in bulk media exhibiting frequency dependent dielectric susceptibility and magnetic permeability. The method has been further extended to investigate the intensity distribution in a nonlinear meta-material with negative refractive index where both ε and μ are dispersive and negative in nature

Delay times and detector times for optical pulses traversing plasmas and negative refractive media

We show that arrival times for electromagnetic pulses measured through the rate of absorption in an ideal impedance matched detector are equivalent to the arrival times using the average flow of optical energy as proposed by Peatross {\it et al.} [ Phys. Rev. Lett. {\bf 84}, 2370 (2000)]. We then investigate the transport of optical pulses through dispersive media with negative dielectric permittivity and negative refractive index choosing the geometry such that no resonant effects come into play. For evanescent waves, the definitions of the group delay and the reshaping delay get interchanged in comparison to propagating waves. The total delay times for the evanescent waves can be negative in an infinite plasma medium even for broad-band pulses. The total time is, however, positive for broad band pulses in the presence of an interface when the radiation is detected outside the plasma. We find evidence of the Hartman effect for pulses when the distance traversed in the plasma is much smaller than the free space pulse length. We also show that for a negative refractive index medium(NRM) with $\epsilon(\omega)$ = $\mu(\omega)$ the reshaping delay for propagating waves is identically zero. The total delay time in NRM is otherwise dominated by the reshaping delay time, and for broad band pulses in NRM the total delay time is subluminal

Kendrapada Sheep: An Insight Into Productivity and Genetic Potential of this Prolific Breed

Kendrapada sheep of Odisha is a prolific, medium stature meat type breed. The Kendrapada sheep is the second prolific sheep of India after Garrole of West Bengal, which carries FecB mutation, responsible for prolificacy. The reproductive traits of this sheep is the major attribute where the ewe of this sheep comes to heat at around 10–11 months and drops its first lamb at around 15–16 months of age. The average lambing interval in these sheep is 8 months with gestation period of 150 days. The reproductive performance of these sheep is the uniqueness of this sheep population with more than 70% multiple births; 62.8% twinning, 2.3% triplet and 1% quadruplets. Thus research should be undertaken to conserve the valuable germplasm of Kendrapada sheep to improve the other breeds of India which are good in context of weight gain but lack prolificacy. As sheep are well adapted to diverse climatic conditions they can easily thrive on wide variety of grasses and crop residues thus fits well in zero input free grazing system of rearing by rural poor. However the potentiality of this Kendrapada sheep in terms of meat quality and prolificacy and resistance to diseases has been the simulating force to take up base line survey along with variety of trials to conserve this breed. Keeping the above mentioned points in mind the present study was carried out to highlight the baseline details of this neglected breed as it is one of the first review articles on Kendrapada sheep